I have an '89 740 GL I hadn't driven in awhile, but she cranked up and ran fine, no problem, for a couple of days; charged the AC one evening and the next day it would not start. So I'm following the procedures outlined in another thread here to see if I can figure out what's going on. After going through several steps I was led to the point of attaching 12V directly to the fuel pump to see if it powered up. It did not. After removing the fuel pump, I checked again. This time it did.

Anyway, while I've got the pump off I started wondering. My question is: if while the pump is off I jumper the fuel pump relay connections (what is it, 30 and 87/2?), what would be the correct way to test power at the two leads that attach to the fuel pump? I took my ohmmeter and set it to DC 20V, took the red lead and put it to the yellow wire, put black to black and I get nothing. What am I missing?

I should add I know there is power at the relay because the relay gives the "two-clicks" when tested in place.

 

yeah, hooking a DC volt meter across the wires to the fuel pump should do it, or even a 12V light bulb.

also verify there's 12V at the pin 30 of the fuel pump relay socket, with the other meter lead on a ground.

 

I'll check pin 30 to make sure. If not, what then? Assuming there is power there, so far all I can find online at this point is to "check the wiring between the relay and the pump", but I haven't found a description of where that wiring goes.

 

On my 740 I had found that the most suspect parts that are a problem is the FP relay , Radio suppression relay and the crank position sensor. I always have a spare one available. When you pull the FP relay look at the bottom pins and see if one is burned. It is possible that the internal part of the relay is bad and even though you hear/feel it click it doesn't mean it is good. Also check the yellow wire to a different ground at the pump. Oh I assume you checked the fuses. Do you have the wiring diagram .

 

With the relay bypassed with a jumper from 30 to 87/2 and 12V now verified at 30, there is no power at the fuel pump leads under the car. I've checked fuses 1, 4, 6 and 11. I do not have a wiring diagram I feel I can trust (Haynes manual).

 

As I think about it, something happened while I was charging the AC system that I'm beginning to wonder if it might have some bearing. While attaching the gauge on the low side port (car running) the car all of a sudden almost died. I stopped what I was doing and it went back to running fine. But I think the metal gauge connector may have touched the body of the coil while also touching the accumulator, and that's what caused it to almost stop running. ? Could that have caused something that would not have been apparent immediately?

 

Could be you did something but I would assume if you shorted the coil or something else the engine would have shut down. Here is a quick fuel system check. Get some starter fluid and spray it into the small vacuum hose/hole on the downstream side of the throttle body. See if the car starts up.

 

Yes, it will crank with starter fluid. But, as indicated, with power verified at 30 pin, and with the recommended jump from 30 to 87/2, there is still no power at the fuel pump. leads. Does this car have an "in-line fuse to control unit" I see mentioned in other places (here: http://www.volvotips.com/service-man...ir-manual.html ) If so, where would it be?

 

12V at pin 30 verified. Still, with relay connections 30 & 87/2 jumpered, there is no power at pump leads.

 

If you don't have continuity from 87/2 to the FP yellow wire then there is a break in the line. Either at the bottom of the FP relay connector or the connector in line. Run a wire from hot side of fuse no. 1 (hot 12v) directly to the + position on the fuel pump. It should turn the pump on unless the pump went bad. If the pump will run start the car. The FPR coil gets grounded in the ECU at pin #20 and 21. I had a similar problem for a month and finally found that the ECU was not going to ground . I bought a rebuilt on #951 . Plugged it in and the car just purrs even with 376K miles.

 

Mystery solved! I finally yanked the fuse/relay bank out and the mount for the fuel pump relay was not snugged in. I had noticed it was way too easy to put and remove the relay, but I did not see the base moving, and it was obviously making SOME contact, but that completely explains why I was getting inconsistent results. I jumpered it for real this time and now have power at the leads. So I stuck the relay base snugly into the tray and made sure the relay was good and tight. Now all I have to do is put it back together and start trying to figure out how to keep water from getting in around the sunroof.

 

OK good . On the water problem clean out the 4 drains for the sunroof. It is not a sealed unit so usually the drain tubes plug and then it leaks inside.

 

yeah, drains at all 4 corners, front two go down the A pillars, rear two go down the C pillars, all 4 end up peeking out under the chassis. I use a bicycle brake cable to poke the debris out of those drains.

 

I checked the drains and convinced myself they are clear but to be sure I'll go back and check with a garden hose.
If the drains ARE clear, I'll just have to start another thread

 

Well, I might have spoken too soon. The pump is running and delivering fuel to the rail, I have good spark at the plugs, it will start with starter fluid, but it won't run otherwise. It was running fine before, and even though the gas in it is a little old, I don't see how a couple of days could make that much difference ??

 

ok, get or borrow a set of 'noid lights' with bosch compatible plugs, and plug them into the injectors, then have someone crank over the engine and verify they all blink. they should blink twice per full turn of the crankshaft.

if they don't blink, either your injectors aren't getting power, or the ECU isn't firing them on a 740, injector power comes through the socalled 'radio supression relay' on the left fender wall, this relay should turn on with the ignition key, and stays on. the ECU fires the injectors by intermittently grounding them, all 4 at once. to test the injector power, unplug one of the injectors, turn on the ignition, and take a volt meter, and measure the power from chassis ground (like the ground bar that the fuel rail is mounted on), to one of the injector plug pins, that should be 12V (the other pin should be floating and will give erratic results). if you don't see 12V, take a look at the RS relay.

 

I'm getting about .5 volts on either pin on two different injectors. By "left" do you mean driver's side?

 

left == US drivers side, yes. I always refer to the side of the car as seen from the drivers seat...

and no, thats the diagnostic connector, pull the cover off, and there's a jumper pin plugged into the side of the cover, unplug that, and you stick it in #2 or #6 to read error codes from your fuel injector or ignition control units. you follow procedure "DTM 1" as outlined here, https://www.volvoclub.org.uk/faq/Eng...agnosticCodesi

the fault codes are down below on that page...

the RSR is farther forward, just behind the left headlight IIRC.

 

I'm not seeing it. There is a relay mounted to the coolant fill tank. Wires are: red, red/green, blue/yellow, and black.
On my 1990 740 wagon, the relay mounted to the coolant fill tank has wires that are: re, red/gray, blue/black, and blue/green.

Just in case that is the right part, I switched them out because I know the wagon is running. Still no go.

While I'm at it, what is all this dried up waxy stuff I keep finding at relay connections, gas pump connections, etc. Is that just old dielectric grease?

I do see something mounted to the fender, but it looks pretty heavy duty to be a simple relay. I don't see anything else.

 

ok, I guess the RSR relay IS on the right side on non-turbos, sorry, my 740 was a turbo and thats on the left.

per the parts diagrams, its just forward of the spring tower. and my wiring diagrams app just crashed, and will require rebooting the VM, ugh.