First off, the car was wired like this when I purchased it and I just haven't changed it. The previous old man owner said it was for "security reasons" but now I have my doubts.

I am currently bypassing the fuel pump relay with a toggle switch (my kill switch) that is connected to the fuel pump fuse post (the other end grounded). I want to take this bad wiring out but the fuel pump does not turn on when I turn the ignition.

The fuel pumps are good, the fuse is good, the fuel pump relay is new (and I have three others) so somewhere between the ignition and the fuel pump relay i'm not getting power (is that correct?).

Could it be the ignition itself? Could it be the plug that the fuel pump relay fit into? I've exhausted my knowledge on the subject and it's too damn hot to think. SOS.

 

the crankshaft position sensor may be malfunctioning.i think it wont let the fuel pump relay close unless the engine is turning. i had this problem in my 240 and the computer wasn't sending a ground signal to the relay.after about an hour of poking around with a test light i wired it directly to the chassis 5 years ago (not the "BEST" repair because i cant leave the switch in the #2 position for very long be- cause the fuel pump is always on)and the car has started and run nearly every day since. (the days it didnt start were days i was on vacation or driving my other car, lol ) but i suspect my cps isn't working and i've been to lazy to replace it . if you need to see if everything else is working you could jump fuse #4 (in tank pump) to fuse #6 (main pump) TEMPORARILY. if everything else is working the car should start and run . it'll get you out of a jam, but definately not a repair.

 

I have all 940s, so not that "vintage" well one, but not for long, can you pop off the top of the relay and physically watch it close??? Or not?
Was that one of the years Volvo used the eco junk wiring harness?
And again, I don't know, I think it wasn't in your year yet or was, but the Radio Suppression Relay was also a "Check it" on my diagnosis. My problem turned out to be a bad pump and brain lesions. I'd put back in the shot relay instead of the new one.

 

'86 was right in the middle of the biodegradable wiring. You might need to trace the wiring all the way back to the pump as it may be deteriorated. As phaedrider stated in the earlier post, the ECU will not even provide the signal (I think ground) to the relay if it isn't detecting any rotations on the engine. However, your car doesn't have a crank position sensor and instead the pulses come from the distributor hall sensor. This should be checked out as well.

 

Thanks guys! Follow up question, act - do you think it's worth it to figure this out or should I just keep using this toggle switch?

 

That all depends on how persistent you are. If you have something that works for you - go with it. I'm an engineer by trade so I am always going to want to figure it out. I had a short in my wiring harness for the air conditioner and rather than slice open the harness and find the short, I simply ran a new wire. However, I had narrowed it down to a single wire and my model year is 90 so I was confident that I didn't have a whole bunch of wiring issues.

 

read up on this post. I was having f.pump problems ended up being cobbled wiring. I ran all new wiring and having had a problem since.

https://volvoforums.com/forum/volvo-...-f-pump-92887/

 

no CPS on a 1986 LH 2.2 system, those use a hall sensor in the distributor for ignition and injection timing.

the fuel pumps don't come on with the ignition on LH2.2, they come on when the engine is cranked over per the hall sensor, and they shut off about 1 second later if the timing pulses stop.

 

^^
This is the answer from someone (pierce) who actually knows what he's talking about.

 

No intention of a post high-jack, my 1992 240 Wagon, 4 cylinder, has intermittent stalls, no starts too. with the dual fuel pump relay cover off, always an open side. Is there a link to info on the biodegradable harnesses, as this is the first I have heard of this point. Is my 92 in the range?

 

mid year 1987 and newer do NOT have biodegradable harnesses. that said, these are 25+ year old cars, and wiring starts to break down in areas where its exposed to excess heat, ongoing oil spills, and so forth..

that 'fuel pump' relay, one half powers the fuel INJECTION system, and comes on with the ignition key. the OTHER half powers the fuel pumps, and comes on when the engine turns over. the pump half should come on for about 1 second when you first turn the ignition on, then stop until you crank the motor.

the ECU uses the presence of timing pulses from the crank position sensor (CPS) to know when to turn on the fuel pumps (and when ti fire the injectors, and the ICU uses it to know when to fire the spark). If the CPS is dying (often its the cable to the CPS that dies, but just replace the whole part), that can make for intermittent no-start and other erratic problems. the CPS is on the back of the engine, near the left rear corner of the head, and sticks down into the bell housing, where it reads timing pulses off the engine flywheel/flexiplate.