Poor Idle and Hot Start Problem ('89 740)
#1
08-16-2013, 12:42 PM
Poor Idle and Hot Start Problem ('89 740)
1989 740GL non-turbo, auto trans, 110k total miles
A few weeks ago I transported the car to our AZ condo. It was running like a Swiss watch in all aspects, but started to get hard to start when hot, now requiring half throttle to start it after being driven. Cold start is still instantaneous.
Then it started stumbling (with low idle speed for as few seconds) when put into, or taken out of gear. At that point, once it regained its idle speed after a few seconds, it idled smoothly at 700-750rpm.
Now the idle speed varies (wanders) even established in neutral, or in drive while stopped. It still runs fine on the highway under load, but my wife (who is alone in AZ using the car) is concerned about having it strand her. Unfortunately, I am in TX 1000mi away, and because of pending surgery can't get out there to look at it.
I've done a LOT of reading (FAQs, Forum posts), and am guessing it's probably the Idle Air Control valve (idle stabilization circuit), or remotely, a bad engine temp sensor (under #3 intake runner), but can't be sure, of course. Another possibility is the TPS, throttle position sensor not switching to idle mode.
We see that it is SUPPOSED to have a start injector, but can't find any installed. Anyone know for sure if there IS one on the LH2.4?
The engine doesn't act like it's an ignition or injector problem, as it never has a "hard" miss even under load.
Our son is there and is willing to do some troubleshooting if I can get him data.
From what I understand from extensive reading (and see), the car has the Bosch LH 2.4 Jetronic system, with a TWO terminal IAC. I read the resistance of the IAC motor should be 14-18ohms. Not sure if applying 12v to the terminals momentarily to check operation is permissible. Son already flushed the IAC w/ brake cleaner, but read that it could take several flushes w/ carb cleaner, though he says he can reach in and the vane appears free. Because of age, we're reluctant to pinch off the IAC hose tightly as a diagnostic procedure, but maybe we could plug the ends or something.
The car has a "Check Engine" light installed, but while it has occasionally started coming on during start (it didn't use to), it always extinguishes quickly in a second or so and doesn't leave a trace.
Any personal experiences with such symptoms, or suggestions would be most helpful.
Thanks,
Bob
A few weeks ago I transported the car to our AZ condo. It was running like a Swiss watch in all aspects, but started to get hard to start when hot, now requiring half throttle to start it after being driven. Cold start is still instantaneous.
Then it started stumbling (with low idle speed for as few seconds) when put into, or taken out of gear. At that point, once it regained its idle speed after a few seconds, it idled smoothly at 700-750rpm.
Now the idle speed varies (wanders) even established in neutral, or in drive while stopped. It still runs fine on the highway under load, but my wife (who is alone in AZ using the car) is concerned about having it strand her. Unfortunately, I am in TX 1000mi away, and because of pending surgery can't get out there to look at it.
I've done a LOT of reading (FAQs, Forum posts), and am guessing it's probably the Idle Air Control valve (idle stabilization circuit), or remotely, a bad engine temp sensor (under #3 intake runner), but can't be sure, of course. Another possibility is the TPS, throttle position sensor not switching to idle mode.
We see that it is SUPPOSED to have a start injector, but can't find any installed. Anyone know for sure if there IS one on the LH2.4?
The engine doesn't act like it's an ignition or injector problem, as it never has a "hard" miss even under load.
Our son is there and is willing to do some troubleshooting if I can get him data.
From what I understand from extensive reading (and see), the car has the Bosch LH 2.4 Jetronic system, with a TWO terminal IAC. I read the resistance of the IAC motor should be 14-18ohms. Not sure if applying 12v to the terminals momentarily to check operation is permissible. Son already flushed the IAC w/ brake cleaner, but read that it could take several flushes w/ carb cleaner, though he says he can reach in and the vane appears free. Because of age, we're reluctant to pinch off the IAC hose tightly as a diagnostic procedure, but maybe we could plug the ends or something.
The car has a "Check Engine" light installed, but while it has occasionally started coming on during start (it didn't use to), it always extinguishes quickly in a second or so and doesn't leave a trace.
Any personal experiences with such symptoms, or suggestions would be most helpful.
Thanks,
Bob
#2
08-16-2013, 02:09 PM
LH 2.4 came with and without cold start injectors. they figured out they could just inject more gas with the main injectors and not need the extra one.
LH2.4 has a very clever thing, 'DTM 3' aka Diagnostic Test Mode 3. this will actuate all the little mechanisms associated with the fuel injection one after the other, while the engine is off (but switched on). the IAC will click/clack open/close a few times, the injectors will click-click a few times, if you have the electric fan (post 1992, I think), it will start/stop, and so forth. See DTM 3 here -> Engine and OBD Diagnostic Codes
I would disconnect the rubber tube from either end of the IAC< and hook up a clean hose, blow or suck gently through that hose and see if you feel the air going ON/OFF/ON/OFF during the IAC part of the test. if you do, your IAC is working perfectly and you can move on to worrying about something else.
also, perform DTM-1 and read any codes on pins 2 and 6 (no tools required for this, see above URL).
here's something completely different... your car has two fuel pumps. there is a booster pump inside the gas tank, and a main pump under the back seat. if the main pump is out, the car flat doesn't run. if the booster pump is out, the main pump has to work too hard, and the car will be prone to hot start problems due to vapor-lock, also you may experience more problems with less than a half tank of gas, including performance stuttering under full load (heavy throttle, upper middle RPM, taller gear, like accelerating hard or climbing a grade at freeway speeds).
LH2.4 has a very clever thing, 'DTM 3' aka Diagnostic Test Mode 3. this will actuate all the little mechanisms associated with the fuel injection one after the other, while the engine is off (but switched on). the IAC will click/clack open/close a few times, the injectors will click-click a few times, if you have the electric fan (post 1992, I think), it will start/stop, and so forth. See DTM 3 here -> Engine and OBD Diagnostic Codes
I would disconnect the rubber tube from either end of the IAC< and hook up a clean hose, blow or suck gently through that hose and see if you feel the air going ON/OFF/ON/OFF during the IAC part of the test. if you do, your IAC is working perfectly and you can move on to worrying about something else.
also, perform DTM-1 and read any codes on pins 2 and 6 (no tools required for this, see above URL).
here's something completely different... your car has two fuel pumps. there is a booster pump inside the gas tank, and a main pump under the back seat. if the main pump is out, the car flat doesn't run. if the booster pump is out, the main pump has to work too hard, and the car will be prone to hot start problems due to vapor-lock, also you may experience more problems with less than a half tank of gas, including performance stuttering under full load (heavy throttle, upper middle RPM, taller gear, like accelerating hard or climbing a grade at freeway speeds).
#3
08-16-2013, 02:56 PM
LH 2.4 came with and without cold start injectors. they figured out they could just inject more gas with the main injectors and not need the extra one.
That was the possibility I was expecting, like the Motronic system deleted it.
LH2.4 has a very clever thing, 'DTM 3' aka Diagnostic Test Mode 3. this will actuate all the little mechanisms associated with the fuel injection one after the other, while the engine is off (but switched on). the IAC will click/clack open/close a few times, the injectors will click-click a few times, if you have the electric fan (post 1992, I think), it will start/stop, and so forth. See DTM 3 here -> Engine and OBD Diagnostic Codes
Yes, I read about that, with the procedure to do it. Unfortunately, hard to hear in a noisy environment, but by sound or "feel" should help.
I would disconnect the rubber tube from either end of the IAC< and hook up a clean hose, blow or suck gently through that hose and see if you feel the air going ON/OFF/ON/OFF during the IAC part of the test. if you do, your IAC is working perfectly and you can move on to worrying about something else.
Good point. I was wondering, beside checking the IAC resistance at 14-18 ohms how to test that. Wasn't sure if putting 12v to it was a dumb thing to do. This way (using OBD to activate components), we know if the ECU is capable of sending a signal, and the IAC of responding to one. Also, I wasn't sure how much air it would pass when closed, and you answered that question for me (none).
also, perform DTM-1 and read any codes on pins 2 and 6 (no tools required for this, see above URL).
Yes, I did establish the box is there from a pix my wife sent-hopefully it works (read a lot have failed).
WILL any old codes be retained even if the Check Engine Light is NOT illuminated? No codes show, but the CEL never stays on (it may come on for a second or two after start now, but goes out-BEFORE, it NEVER ever came on at all).
here's something completely different... your car has two fuel pumps. there is a booster pump inside the gas tank, and a main pump under the back seat. if the main pump is out, the car flat doesn't run. if the booster pump is out, the main pump has to work too hard, and the car will be prone to hot start problems due to vapor-lock, also you may experience more problems with less than a half tank of gas, including performance stuttering under full load (heavy throttle, upper middle RPM, taller gear, like accelerating hard or climbing a grade at freeway speeds).
That was the possibility I was expecting, like the Motronic system deleted it.
LH2.4 has a very clever thing, 'DTM 3' aka Diagnostic Test Mode 3. this will actuate all the little mechanisms associated with the fuel injection one after the other, while the engine is off (but switched on). the IAC will click/clack open/close a few times, the injectors will click-click a few times, if you have the electric fan (post 1992, I think), it will start/stop, and so forth. See DTM 3 here -> Engine and OBD Diagnostic Codes
Yes, I read about that, with the procedure to do it. Unfortunately, hard to hear in a noisy environment, but by sound or "feel" should help.
I would disconnect the rubber tube from either end of the IAC< and hook up a clean hose, blow or suck gently through that hose and see if you feel the air going ON/OFF/ON/OFF during the IAC part of the test. if you do, your IAC is working perfectly and you can move on to worrying about something else.
Good point. I was wondering, beside checking the IAC resistance at 14-18 ohms how to test that. Wasn't sure if putting 12v to it was a dumb thing to do. This way (using OBD to activate components), we know if the ECU is capable of sending a signal, and the IAC of responding to one. Also, I wasn't sure how much air it would pass when closed, and you answered that question for me (none).
also, perform DTM-1 and read any codes on pins 2 and 6 (no tools required for this, see above URL).
Yes, I did establish the box is there from a pix my wife sent-hopefully it works (read a lot have failed).
WILL any old codes be retained even if the Check Engine Light is NOT illuminated? No codes show, but the CEL never stays on (it may come on for a second or two after start now, but goes out-BEFORE, it NEVER ever came on at all).
here's something completely different... your car has two fuel pumps. there is a booster pump inside the gas tank, and a main pump under the back seat. if the main pump is out, the car flat doesn't run. if the booster pump is out, the main pump has to work too hard, and the car will be prone to hot start problems due to vapor-lock, also you may experience more problems with less than a half tank of gas, including performance stuttering under full load (heavy throttle, upper middle RPM, taller gear, like accelerating hard or climbing a grade at freeway speeds).
I sent son a long list of things to work his way with in my absence. Fiddling w/ the OBD is one of them, assuming the LED is still working. These are the only faults I saw listed (link to chart)- 2013-08-15_1944 - bobinyelm's library
Thanks for suggestions. I wish I had a connector w/ long pigtails to check ECT w/ ohm meter w/out removing it. I know you can check at ECU pins, but not sure I want him maybe buggering the connector.
Someone on another Forum suggested seeing how the car idles w/ AAM disconnected, then someone else said that can destroy AAM or ECU. Do you know?
Thanks, Bob
#4
08-16-2013, 03:20 PM
the CEL (check engine light) should light up when you turn the car on and go out right after it starts.
not all engine codes show a CEL, only smog related ones do. if there are no stored codes, the OBD would blink 1-1-1 so you know the LED works. frankly, I've not seen one with a broken LED, sample size of 4-5 cars. the circuit is actually really simple, you could attach a 12V test LED to the battery + and connect its its ground clip to a pin stuck in the appropriate hole, that would do the same thing. the button grounds the jumper wire, so grounding your probe's ground clip would do the same thing.
not all engine codes show a CEL, only smog related ones do. if there are no stored codes, the OBD would blink 1-1-1 so you know the LED works. frankly, I've not seen one with a broken LED, sample size of 4-5 cars. the circuit is actually really simple, you could attach a 12V test LED to the battery + and connect its its ground clip to a pin stuck in the appropriate hole, that would do the same thing. the button grounds the jumper wire, so grounding your probe's ground clip would do the same thing.
#5
08-16-2013, 04:03 PM
the CEL (check engine light) should light up when you turn the car on and go out right after it starts.
Hmmm...
It used to be on in the run position (to check the light), but as soon as the key got to "Start" the light was never seen again.
Now it sometimes stays on for a second or two with the engine running, but never stays on.
not all engine codes show a CEL, only smog related ones do. if there are no stored codes, the OBD would blink 1-1-1 so you know the LED works.
OK-Good point!
frankly, I've not seen one with a broken LED, sample size of 4-5 cars. the circuit is actually really simple, you could attach a 12V test LED to the battery + and connect its its ground clip to a pin stuck in the appropriate hole, that would do the same thing. the button grounds the jumper wire, so grounding your probe's ground clip would do the same thing.
You're saying that the boxes black jumper wire is grounded when the switch is pushed, which actually in turn grounds whatever pin the jumper is plugged into on the test box?
But you say hooking an external LED to the Battery Positive terminal, and the LED's ground to the appropriate terminal and pushing the button would give the same result?
Did I read wrong?
Hopefully the LED is good like yours were, though.
I will pass these suggestions to our son.
BTW, Do you tend to agree that if the car runs well on the highway under load, it's probably not insufficient fuel delivery?
I wonder if a sticking (open) fuel injector could cause too-rich idle, and rpm wander, but not supply enough extra fuel to screw up above-idle performance?
I have a fuel injector tester here at home. You plug the connector into the injector and either push for button one spritz of fuel, or another for a series of activations while the injector is connected to a pressurized fuel source (I have a test canister I fill w/ Techron and pressurize to 35psi, then use w/ the device-I think it's called "The Injector Detector" I bought 20 years ago when working w/ Bosch injectors a lot). I used this to clean and test the injectors on this car when I got it a few years back (2 were clogged and had poor spray patterns, but Techron cleaned them right up).
In a couple of months when I heal up and I get back to the car (assuming son can't fix it) I'll take those w/ me, along w/ my Noid lights to check at cranking speed for good injector signals.
No one has mentioned the TPS, but maybe it's dirty, or not telling the ECU to go into the closed-loop idle mode? Would I be correct to think if it's no longer putting the system into idle mode, the symptoms I have could be because of THAT? (The TPS one thing I am asking son to check over the week-end).
Just looking for confirmation on some ideas.
It's frustrating trying to guess at things from 1000 miles.
Hmmm...
It used to be on in the run position (to check the light), but as soon as the key got to "Start" the light was never seen again.
Now it sometimes stays on for a second or two with the engine running, but never stays on.
not all engine codes show a CEL, only smog related ones do. if there are no stored codes, the OBD would blink 1-1-1 so you know the LED works.
OK-Good point!
frankly, I've not seen one with a broken LED, sample size of 4-5 cars. the circuit is actually really simple, you could attach a 12V test LED to the battery + and connect its its ground clip to a pin stuck in the appropriate hole, that would do the same thing. the button grounds the jumper wire, so grounding your probe's ground clip would do the same thing.
You're saying that the boxes black jumper wire is grounded when the switch is pushed, which actually in turn grounds whatever pin the jumper is plugged into on the test box?
But you say hooking an external LED to the Battery Positive terminal, and the LED's ground to the appropriate terminal and pushing the button would give the same result?
Did I read wrong?
Hopefully the LED is good like yours were, though.
I will pass these suggestions to our son.
BTW, Do you tend to agree that if the car runs well on the highway under load, it's probably not insufficient fuel delivery?
I wonder if a sticking (open) fuel injector could cause too-rich idle, and rpm wander, but not supply enough extra fuel to screw up above-idle performance?
I have a fuel injector tester here at home. You plug the connector into the injector and either push for button one spritz of fuel, or another for a series of activations while the injector is connected to a pressurized fuel source (I have a test canister I fill w/ Techron and pressurize to 35psi, then use w/ the device-I think it's called "The Injector Detector" I bought 20 years ago when working w/ Bosch injectors a lot). I used this to clean and test the injectors on this car when I got it a few years back (2 were clogged and had poor spray patterns, but Techron cleaned them right up).
In a couple of months when I heal up and I get back to the car (assuming son can't fix it) I'll take those w/ me, along w/ my Noid lights to check at cranking speed for good injector signals.
No one has mentioned the TPS, but maybe it's dirty, or not telling the ECU to go into the closed-loop idle mode? Would I be correct to think if it's no longer putting the system into idle mode, the symptoms I have could be because of THAT? (The TPS one thing I am asking son to check over the week-end).
Just looking for confirmation on some ideas.
It's frustrating trying to guess at things from 1000 miles.
#6
08-16-2013, 04:28 PM
LH 2.4 doesn't actually have a throttle position sensor, just a idle switch (and maybe full throttle but thats less important).
the idle switch should make a distinctly audible albeit faint click when you manually turn the throttle drum just off idle. to really test it, you'd disconnect it and put a ohm meter across it, should be 0 ohms at idle and infinite (open circuit) just off idle.
another thing that can mess up idle behavior is a gummed up throttle body.
oh, you mentioned the MAF back there... never plug or unplug it when the ignition is switched on, but yes, you can disconnect it, and see if the car starts and idles. it will run VERY poorly without it, essentially in limp-home-mode (and undoubtably throw a check engine light fault). power off, reconnect it, then clear any ODB codes after testing this.
the idle switch should make a distinctly audible albeit faint click when you manually turn the throttle drum just off idle. to really test it, you'd disconnect it and put a ohm meter across it, should be 0 ohms at idle and infinite (open circuit) just off idle.
another thing that can mess up idle behavior is a gummed up throttle body.
oh, you mentioned the MAF back there... never plug or unplug it when the ignition is switched on, but yes, you can disconnect it, and see if the car starts and idles. it will run VERY poorly without it, essentially in limp-home-mode (and undoubtably throw a check engine light fault). power off, reconnect it, then clear any ODB codes after testing this.
#7
08-16-2013, 06:07 PM
LH 2.4 doesn't actually have a throttle position sensor, just a idle switch (and maybe full throttle but thats less important).
the idle switch should make a distinctly audible albeit faint click when you manually turn the throttle drum just off idle. to really test it, you'd disconnect it and put a ohm meter across it, should be 0 ohms at idle and infinite (open circuit) just off idle.
Yes, I understand-just a microswitch that senses closed throttle.
another thing that can mess up idle behavior is a gummed up throttle body.
That was on son's list of things to clean.
I remember my Volvo 965 was very sensitive to that and would stall after every cold-start until I cleaned the throttle body.
God, that was a great car!
oh, you mentioned the MAF back there... never plug or unplug it when the ignition is switched on, but yes, you can disconnect it, and see if the car starts and idles. it will run VERY poorly without it, essentially in limp-home-mode (and undoubtably throw a check engine light fault). power off, reconnect it, then clear any ODB codes after testing this.
Good point to only disconnect/re-connect while not switched on.
I did that before transporting it, and I remember it idled like crap w/ it disconnected. We'll repeat to see how it does now.
the idle switch should make a distinctly audible albeit faint click when you manually turn the throttle drum just off idle. to really test it, you'd disconnect it and put a ohm meter across it, should be 0 ohms at idle and infinite (open circuit) just off idle.
Yes, I understand-just a microswitch that senses closed throttle.
another thing that can mess up idle behavior is a gummed up throttle body.
That was on son's list of things to clean.
I remember my Volvo 965 was very sensitive to that and would stall after every cold-start until I cleaned the throttle body.
God, that was a great car!
oh, you mentioned the MAF back there... never plug or unplug it when the ignition is switched on, but yes, you can disconnect it, and see if the car starts and idles. it will run VERY poorly without it, essentially in limp-home-mode (and undoubtably throw a check engine light fault). power off, reconnect it, then clear any ODB codes after testing this.
Good point to only disconnect/re-connect while not switched on.
I did that before transporting it, and I remember it idled like crap w/ it disconnected. We'll repeat to see how it does now.
I'll post with a follow up when we get it fixed-maybe it might be useful to someone!
#8
08-17-2013, 07:46 PM
We have an 89 740GL with 335,000 miles on it. I would do the easy things now and replace the fuel pump relay and the radio suppression relay. If that doesn't clear up the problem I would clean the throttle body and reset the TPS. Adjust the idle with the IAC hose disconnected and plugged. Idle should be around 500 rpm . When you reattach the IAC it will go back to 750RPM and should be steady. If you have a new main FP and the car runs OK on the road with less then 1/2 a tank of gas then the in tank pump should be OK. Just listen in the tank fill pipe and you can hear it running. Like I mentioned I would replace both relays.
#9
08-17-2013, 09:32 PM
We have an 89 740GL with 335,000 miles on it. I would do the easy things now and replace the fuel pump relay and the radio suppression relay.
OK, so you confirm that the Fuel Pump Relay and Radio Suppression Relay can affect only hot-start and idle, yet allow the car to run perfectly otherwise?
I was hesitant to spent the money for new ones until knowing they don't affect normal operating conditions (cold-start and cruise above idle speed).
If that doesn't clear up the problem I would clean the throttle body and reset the TPS. Adjust the idle with the IAC hose disconnected and plugged. Idle should be around 500 rpm . When you reattach the IAC it will go back to 750RPM and should be steady. If you have a new main FP and the car runs OK on the road with less then 1/2 a tank of gas then the in tank pump should be OK. Just listen in the tank fill pipe and you can hear it running. Like I mentioned I would replace both relays.
I didn't try listening through the filler pipe-I figured the fuel would damp the sound. That's a great hint! I haven't tried starting the car since the hot-start started getting worse, but 50mi ago it started fine even with less than 1/4th tank.
We have not run the tank down since the last fill (which makes me wonder if the condition started after getting that tank of fuel-Hmmm).
Given that cleaning the throttle body is free (and probably should be done anyway); same with the TPS testing and adjustment, I will do those first (being a tightwad).
What symptoms did yours give with bad FP Relay and Radio Suppression Relay? Did you have poor hot start and poor idle speed regulation with load changes?
I am putting together a list of stuff for our son to do on the car (as he lives a few miles from where the car is located) in our absence, BTW.
I am eager to get it running right again-I chose to place this low mileage (110k) car at our "away" house (after I refinished it, rebuilt the entire A/C system w/ new everything and R-134, and lots of other stuff) because I BELIEVE in the reliability of the 700 to last as yours has even when left for weeks between uses*, but now my wife doesn't trust it at ALL, and on the recent visit she returned home from today, sadly didn't even want to drive it for fear it would strand her.
OK, so you confirm that the Fuel Pump Relay and Radio Suppression Relay can affect only hot-start and idle, yet allow the car to run perfectly otherwise?
I was hesitant to spent the money for new ones until knowing they don't affect normal operating conditions (cold-start and cruise above idle speed).
If that doesn't clear up the problem I would clean the throttle body and reset the TPS. Adjust the idle with the IAC hose disconnected and plugged. Idle should be around 500 rpm . When you reattach the IAC it will go back to 750RPM and should be steady. If you have a new main FP and the car runs OK on the road with less then 1/2 a tank of gas then the in tank pump should be OK. Just listen in the tank fill pipe and you can hear it running. Like I mentioned I would replace both relays.
I didn't try listening through the filler pipe-I figured the fuel would damp the sound. That's a great hint! I haven't tried starting the car since the hot-start started getting worse, but 50mi ago it started fine even with less than 1/4th tank.
We have not run the tank down since the last fill (which makes me wonder if the condition started after getting that tank of fuel-Hmmm).
Given that cleaning the throttle body is free (and probably should be done anyway); same with the TPS testing and adjustment, I will do those first (being a tightwad).
What symptoms did yours give with bad FP Relay and Radio Suppression Relay? Did you have poor hot start and poor idle speed regulation with load changes?
I am putting together a list of stuff for our son to do on the car (as he lives a few miles from where the car is located) in our absence, BTW.
I am eager to get it running right again-I chose to place this low mileage (110k) car at our "away" house (after I refinished it, rebuilt the entire A/C system w/ new everything and R-134, and lots of other stuff) because I BELIEVE in the reliability of the 700 to last as yours has even when left for weeks between uses*, but now my wife doesn't trust it at ALL, and on the recent visit she returned home from today, sadly didn't even want to drive it for fear it would strand her.
*The car has lived at our place for 4+ years and even when left for MONTHS, would start instantly, even with a low battery and old fuel (the reason I flushed the fuel system, cleaned the injectors, and replaced the old fuel filter and the pump that sometimes liked to be poked w/ a broom handle to get started the last 6mo).
Last edited by bobinyelm; 08-17-2013 at 09:42 PM.
#10
08-17-2013, 10:14 PM
#11
08-18-2013, 07:43 AM
Somewhat agree but you can't get the hot start condition with a cold relay. As we know the FP relay get fairly hot during normal use and at times the problem will occur. After having this hot start problem every few years I have started to replace both of these relays as normal preventive maintenance. It's only a few bucks to make my bride comfortable. I recall the first time it happened and it left my wife stranded in a questionable neighborhood while she was delivering for meals on wheels. It was a 90* day and local city driving. She turned it off and it just cranked but wouldn't start. Had to flat bed it home and after pushing it into the garage it started right up. A Volvo mechanic friend told me to replace either or both relays. It also happened a few years later and having a spare set in the car I just replaced (took 3-5 mins to replace) them and it started right up. Seemed to work for me. Oh I also didn't have any codes.
#13
08-18-2013, 11:41 AM
Somewhat agree but you can't get the hot start condition with a cold relay. As we know the FP relay get fairly hot during normal use and at times the problem will occur. After having this hot start problem every few years I have started to replace both of these relays as normal preventive maintenance.
I see what you're saying-that the relay may not be closing fully, or making good contact when physically hot.
With regard to the Radio Suppression Relay, it WOULD stay hot with the hot engine supplying the heat for many hours.
With the FP Relay, not so much, because even after sitting 4 hours, the car gets hard to start, when the engine compartment stays hot, but the FP relay would have cooled off completely.
Since these parts are reasonably priced, it is probably not unreasonable to replace 24 year old parts as a preventative measure, since they can be retained as spares if marooned somewhere.
Thanks for sharing your reasoning-it made sense of your point.
It's only a few bucks to make my bride comfortable. I recall the first time it happened and it left my wife stranded in a questionable neighborhood while she was delivering for meals on wheels. It was a 90* day and local city driving. She turned it off and it just cranked but wouldn't start. Had to flat bed it home and after pushing it into the garage it started right up. A Volvo mechanic friend told me to replace either or both relays. It also happened a few years later and having a spare set in the car I just replaced (took 3-5 mins to replace) them and it started right up. Seemed to work for me. Oh I also didn't have any codes.
Good point.
In this case it will start quite easily hot, and so far reliably, IF (and only if) the throttle is held open, so I suspect the relays are working, (since either would be a no-start if inoperative), but for peace of mind for my wife who will be w/ the car while I will be 1000mi away, it may be reassuring. With them in-hand, our son can pop one in for her.
I see what you're saying-that the relay may not be closing fully, or making good contact when physically hot.
With regard to the Radio Suppression Relay, it WOULD stay hot with the hot engine supplying the heat for many hours.
With the FP Relay, not so much, because even after sitting 4 hours, the car gets hard to start, when the engine compartment stays hot, but the FP relay would have cooled off completely.
Since these parts are reasonably priced, it is probably not unreasonable to replace 24 year old parts as a preventative measure, since they can be retained as spares if marooned somewhere.
Thanks for sharing your reasoning-it made sense of your point.
It's only a few bucks to make my bride comfortable. I recall the first time it happened and it left my wife stranded in a questionable neighborhood while she was delivering for meals on wheels. It was a 90* day and local city driving. She turned it off and it just cranked but wouldn't start. Had to flat bed it home and after pushing it into the garage it started right up. A Volvo mechanic friend told me to replace either or both relays. It also happened a few years later and having a spare set in the car I just replaced (took 3-5 mins to replace) them and it started right up. Seemed to work for me. Oh I also didn't have any codes.
Good point.
In this case it will start quite easily hot, and so far reliably, IF (and only if) the throttle is held open, so I suspect the relays are working, (since either would be a no-start if inoperative), but for peace of mind for my wife who will be w/ the car while I will be 1000mi away, it may be reassuring. With them in-hand, our son can pop one in for her.
#14
08-18-2013, 09:08 PM
#15
08-18-2013, 09:17 PM
again, you can test the RSR with a volt meter or test light, unplug one of the injectors, and with the ignition switched on, there should be juice between one of the injector plug pins, and engine ground. the other pin will not have juice, it doesn't matter which one does, just that one has power.
if there's no power at the injectors, they can't fire.
if there's no power at the injectors, they can't fire.
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