740gl fuel pump relay testing info please

Jeff Schubert · Post by **Jeff Schubert** » 12 Dec 2016, 22:47

Yes...Ive searched....a LOT.

Ive had some random intermittent drivability problems with my '89 740gl. Loss of power, backfiring, nearly stalling if I didn't feather the throttle. Then suddenly it would clear up.

Of course, after finding it was a common problem, I checked the relay. Key on..click. Start...another click. Seemed fine.

I found the "jumper test" and tried that, and could hear the pump running, BUT... the car wouldn't start. Pin 30 and 87/2, or the closest lower on the left, jumped to middle pin on the right. (Ive seen pictures that are NOT correct)

Not sure why that didn't work? Put the original relay back in.

In trying to further diagnose, I put my fingers on the relay while it was running 'well'. It seemed almost HOT and all of a sudden I could feel it clicking or buzzing as the car started to run worse. Ah HA! That's IT!.....right?

I removed the relay and took off its cover. The solder joints looked awful. I also found that people have had success reflowing the solder, so I tried that last night. In the meantime I ordered a new Stribel brand relay. I understand they were the OE manufacturer, and -must- be good. The one I have is actally dated... 1989.

Sorry, I'm babbling, I'll get to the point.

I am not 100% that my reflow was successful and don't want to fry anything...else. I may toast the computer?

My question....(finally lol)

What pins on the relay should or should not have continuity or resistance when not installed?

I think I may have overflowed the solder, and want to make -positive- before I even plug it back in.

Any (constructive) advice would be appreciated. My friends suggested I should crush and scrap it. Uh...no.

Wow, long post, sorry

Thanks!

Jeff Schubert · Post by **Jeff Schubert** » 13 Dec 2016, 00:53

If you think it looks bad now you should have seen the BEFORE.

Oxy Torch, plasma cutting, and stick and/or MIG welding..yes. However, I am not confident in my soldering ability. See why? Blah

My electronics testing is relatively limited as well, but I'm sure I could be walked through a bench test of this relay.I found a diode (I think) that only allows continuity in one direction.

I am still puzzled on why the relay bypass jumper test did not work, even though I heard the pump.

While I AM getting a NEW relay, I am curious IF I was able to repair this one...but apprehensive to even plug it in to try to see if it works. My luck lately it would result in a thermonuclear reaction and complete meltdown. Poof.

Its extremely difficult, likely impossible, to put the smoke back into electronics once its let out. That much I do know.

I would think 3 tests could be done, at least for continuity. At idle, with one relay closed, and both relays closed. Make sense? I could see that there would be resistance in the windings, but not full continuity, true?

So far what Ive tested... At 'idle' I am getting continuity between 30 and 86-1. I also get it between 85 and 86-2 unless I reverse testing polarity. (Diode?) I have not yet checked with the relay contact(s) closed.

What can I fry if I shorted anything? Off the top of my head, I'm thinking ecm, amm, O2 sensor? All considerably more expensive than a new relay...

Thanks again

lummert · Post by **lummert** » 13 Dec 2016, 10:19

The relay bypass test requires running a jumper from 30 to 87/1 and 87/2 if you want to start the car. You need pumps and injectors for the engine to run.

Jeff Schubert · Post by **Jeff Schubert** » 13 Dec 2016, 17:53

Yes, thank you very much, Lummert, that makes much more sense. I had only seen the one wire jumped and people claimed it worked until they got a new relay.

This will NOT work to start your Volvo..

Nor will this...

I will try the "correct" jumper and report my findings, and post pictures. There are many dead ends here that are not known to be resolved.

lummert · Post by **lummert** » 13 Dec 2016, 19:18

Jeff Schubert wrote:Yes, thank you very much, Lummert, that makes much more sense. I had only seen the one wire jumped and people claimed it worked until they got a new relay.

This will NOT work to start your Volvo..

Capture+_2016-12-13-19-16-10.png

Nor will this...

Capture+_2016-12-13-19-19-43.png

I will try the "correct" jumper and report my findings, and post pictures. There are many dead ends here that are not known to be resolved.

87/2 powers up the pumps. but the radio suppression relay needs to be triggered through 87/1 to power the injectors.

Jeff Schubert · Post by **Jeff Schubert** » 13 Dec 2016, 19:39

Excellent, thanks again. I just made myself a Y shaped jumper. As you explained, should jump 87-1 AND 87-2 to 30. Presumably 87-2 goes to fuel pump, 87-1 goes to radio suppression relay, and pin 30 is power.

So, viewed from the top of the relay panel would be 30 is lowest left, 87-1 is highest left, and 87-2 is middle right pin...correct?

For safety sake I think it would be best to plug in 87-1 and 87-2 FIRST, then plug in 30. Less chance of accidently shorting. Seems logical.

Jeff Schubert · Post by **Jeff Schubert** » 13 Dec 2016, 20:16

Well, yes, the jumper DID work to start the car. However, it still does not run right. I did for a few minutes then back to stumbling, backfiring,and barely idle.

Is there a bypass test for the radio suppression relay? I don't understand what could be causing such an intermittent problem.

I will check the codes again. The relays will not cause the CEL to come on, correct? The first codes I got the other day were 221 and/or 231. While it was trying to idle, a 133 code came up. The 221 is a too lean or too rich, which I had figured may be was a result of my now replaced fuel pressure regulator. I thought the 133 TPS code was from the lurching idle.

I ran the tests from OBD and everything sounded like it was working. I am not in a position to keep throwing random parts at this car.

I have a bad feeling it is the fuel pump, but have yet to make a contraption to check the fuel pressure.

Any suggestions are greatly appreciated. Its 4 degrees in Wisconsin and I am stranded at home.

Jeff Schubert · Post by **Jeff Schubert** » 13 Dec 2016, 20:45

I did find a way to bypass the radio suppression relay...

Man I hope this works.

Jeff Schubert · Post by **Jeff Schubert** » 13 Dec 2016, 23:44

Well then I may have found part of the issue. One of the connections to the RSR plug had wires exposed. It appears that a handful of female bullet connectors may be in order.

I may start a different post as to not be confusing the FPR with the RSR....

Jeff Schubert · Post by **Jeff Schubert** » 14 Dec 2016, 03:25

I'm now finding the Crank positioning sensor is a relatively common issue, but my car starts relatively well.

Since the last post, I did replace the plug at the RSR with female bullet connectors. They were a little loose to fit the relay, but I squished them a little for a better fit. Replacing them did not help, however I did not attempt to bypass it yet.

It had the same symptoms. Started and ran fine for 4-5 minutes then started loosing power, backfiring and running eye burning rich. I have to feather the throttle to keep it running. The tachometer did not appear to drop off at all, which if I recall, would be a sign of a failing crank positioning sensor.

When I (was able) to run the OBD tests, the TPS tested ok.

Then the CEL came on, again, but now, OBD slot 2 is not working but 6 is?! I started a different post on that...

I had disconnected the battery in hopes it would clear all codes and relearn. No such luck.

Now I can't even read the codes....!!!