So, it's day 5 of trying to figure out what's wrong with my car. I was able to narrow it down to fuel delivery problem. The car will start with starting fluid with the injectors disconnected. The tach will go up to 1k and dies soon after. I then jumped 30 and 87/2 at fuel pump relay circuit. The car fired up while keeping the starter turning. Rpm hit 500 and dies. Tried to re-start but revert back to turning over and over again. I've replaced:
Coil
Power stage
Spark plugs and wires
Cap and rotor
Radio suppression relay closes at ignition on
Fuel pump relay is good
Both pumps whirring at ignition ON

So, what else can I check. FPR?

 

Do you have 12v at your injectors?

 

Yes I have 12V on all fuel injector wires. Someone on another board mentioned that my in tank fuel pump fuel hose may have deteriorated over time and may cause a no start due to fuel delivery problem. Is this a possibility? I would hate to take apart the in tank pump to find out that the hose is still intact. I hear the pump whir at ignition ON which means pump is working. Right?

 

Disable ignition so you dont start a fire, pull fuel rail, reground wires, aim injectors in the air and see if they spray when cranking. You can use a helper, or find the blue/yellow starter test wire under the hood to fire the starter.


There is a chance your ECU is dead.

Fuel pressure test wouldnt hurt. Use a guage, or pinch return line with pumps on and feel the fuel feed hose bulge at FPR.

EDIT-

If you don't feel like digging your tank pump out, there may be a shrader valve in the line coming off the tank to test the tank pump pressure. You can also do the listening test for the tank pump with a tube in your ear stuck down the fuel filler. You could also pull the hose off the fuel pump, fire the tank pump momentarily to check for fuel coming out of it.

One way to check your main pump: Fire it up, and then crawl down there and FEEL if its on.

Again, it doesn't tell you fuel pressure very well, but pull your fuel rail and spray it in the air to confirm your ECU is firing the injectors. I am suggesting the FREE ways to do tests. Using the proper tools is the better way of course.

ECU's can die and cause the injectors not to fire, but still prime the fuel pumps with the key on.

 

So, pulled the rail and the injectors are spraying fuel. I can hear the in tank fuel pump prime at the filler hole. What else can I check? Since injectors are spraying, does this mean ECU is working?

 

Which one is the output hose?

 

O'Reilly has a free fuel pressure guage for loan. It is installed at fuel filter.

Unclamp hose from main pump. Run pumps. See if fuel comes from line from tank. If so, tank pump and hose prob OK.

 

Yeah it pretty much does.

OK we can figure this out...

Any codes?

 

The fatter one. Goes directly to main fuel pump.

 

No codes. So after I disconnect the main hose coming from in tank fuel pump, should I pull fuse #1? And crank engine? Or should I jump the 30 and 87/2 pins?

 

Sounds like you are getting a fuel injector pulse only when the car is being cranked by the starter. Is there a base/closed ignition loop that is separate from the running open loop on a Volvo ECU? if its not a sensor, id say ECU.


Im wondering what controls injector pulse on these cars? Im not as familiar with volvo, but other makes get a cam or crank signal relayed to the ECU, that fires the injectors.

im just trying to throw some info out there.

 

There is a RPM sensor above flywheel for 1989+(NA)/1990+ Turbo 740/940.



That will work. just be ready for the fuel to come out.


Cranking the engine should make the fuel pump go too. Not a bad idea to check if it's keeping the fuel pumps powered up when cranking.


What did you do to test spark? Does it run better with the MAF unplugged? Take a really good look at rpm sensor wiring from top of bellhousing.


LH2.4 diagnosis!!!! do your reading and do your tests! Do yourself a favor and PLEASE READ the link below and do as many of the tests as you can!!!!:

http://www.volvowiringdiagrams.com/v...20Complete.pdf

http://www.volvowiringdiagrams.com/v...0Pin%20Out.jpg





If you are not skilled enough to read the above link and diagram and carry out the majority of the tests, break out the credit card and LOAD UP THE PARTS CANNON AND FIRE AWAAAAY!!!

 

Plenty of gas coming out of the main hose. I tested the spark by first taking coil wire and placing it at engine block to see if I get a spark when cranking. I got spark. I then took each spark plug wire and place spark plug and grounded it. I got spark. I then disconnected the fuel injector wires and sprayed starting fluid. the car started but needed to keep the starter turning. RPM went to 500 and died. I can also get the car to start by connecting 30 and 87/2, rpm went to 1000 and then died. So i'm assuming I'm getting a good spark.

About to check the readings off the ECU. Thanks for the diagram.

Just checked the RPM wire and it's all good. I unplugged the MAF and tried to start but just turned and turned. No go.

 

First a couple of pages it was showing the resistance on several components. I tested the ECT and I get 0 resistance. Does this mean this sensor is not working? Would it cause a no start?

 

Update: So I unplugged ECU to check voltage and resistance on the pin connectors. I noticed that the color of the wires doesnt match the pin # on the manual you gave me. DOes it matter or just ignore the color and go with the pin number? Also, as I was testing the RPM sensor via ECU. It involves cranking the car to activate starter motor. I did it twice and the car started right away but died after. What does that mean?

 

FIXED IT!!!! kinda, I disconnected the ECU to test voltage and resistance on several components. I got to checking the RPM sensor which involves cranking the car while checking voltage. The car started right up but quickly died. I did this three times and all 3x it started but died. I reconnected the ECU AND IT STARTED!!!! It stayed on and just came back to life. Idle good and engine sounds healthy. So, the bad part is I'm not sure what I fixed to make the car start and stay on. I'm just glad she is alive and running. My wife was begging me to take her to the CRUSHER!!! Ha!

 

I don't follow exactly how you did your tests at ecu plug, but glad you got it going! You are supposed to unplug ecu and then pull the sheath off. Car won't run with ecu unplugged so...not sure what you did there.

Double check your ect resistance. Bad connection, wire, or sensor can cause no start.


Sounds like you had a flaky connection at the ecu! If you unplugged it then replugged and now car runs that was prob the issue. Clean up pins and inspect plug for damaged connectors.


Edit- you stated your car ran with ecu unplugged. That means residual fuel or starting fluid in cylinders I guess. You could have flooded it somehow from something like a bad ect circuit. If bad, it can think its very very cold and dump fuel. Again, double check ect resistance at ecu plug. Wire colors vary, but pins are all the same on lh2.4. First article linked is better. Second link is more for reference and I honestly haven't ever used myself.

The most Important/common failures for the ecu inputs are rpm sensor, coolant temp, grounds, and maf. The article has you test everything though, but experience will tell you which steps to skip. Like throttle adjuatments and checking the AC input. We Dont care about the AC input right now!!! Car is dead!!!!

Maf resistance tests don't work really, but triple check your coolant temp sensor specs thru the temp range. Its kinda fun watching it change.

 

Yup! Hoping that was it. Just a flaky connection. Plan to clean the pins and re-check ECT resistance. Thanks for the help!!!

 

BRAND NEW UPDATE!!!!! We came back from our mini vaca and guess what?!!! The car didn't want to start!! Almost lost it.... But I remembered that while I was checking the resistance on the ECT, I accidentally left it unplugged while I opened up and unhooked the ECU. I then plugged the ECU back and tried to start the car with the ECT unplugged. She started right away. So tonight I did the same thing. I unplugged the ECT and she started right away. Now I know what part is the culprit for my no start issue. The ECT!!! I just replaced this part back in 2010. Glad I have lifetime warranty.

So can I possibly drive this car to Oreillys which is about 8 miles away from my house and be ok. Or should I leave it be and drive my wife's XC90.

 

Running too rich or lean can damage the cat. Too rich will also dilute the oil, so change that when you get it fixed too.


EDIT- you dont check ECT resistance AT the sensor. That is rookie ****. I mean, I guess you could, but why get all greeezy? And it also wont tell you if your plug connection is bad, or if the wiring is bad. You probably even took measurements wrong and measured across both pins. One pin is for ECU. one pin is for ICU.

The link I posted shows you how to measure resistance at the ECU plug with sheath pulled off. DO YOUR READING AND YOUR TESTS!!!


I still don't understand exactly what you have been doing, but something ain't right! It sounds like you are getting closer though. If your car doesn't start, but then unplugging the ECT gets it to start, that is a good sign!


Here is the link one more time for ya. Go to page 44 and make sure to test your ECT sensor resistance values.



http://www.volvowiringdiagrams.com/v...20Complete.pdf