I trying to help a friend with a fuel problem on his 1990 240. He recently had his entire exhaust system replaced. After this, the check engine light went on, he had hard starting and absolutely terrible gas mileage. I had him turn the ignition to the start position to read the diagnostic code, when I heard a constant hissing noise (like gas flowing) in the fuel injection rail - most prominently at the fuel pressure regulator. This occurs as soon as the key is put in the start position (right before crank position). I suspected the pressure regulator, so I replaced it with a new one. However, the symptom remained. I swapped the fuel pump relay with a known good one, but the symptom remained. I've determined that all the fuel injectors are continuously spraying gas. I pulled the plugs and they were all soaked with gas. The car has good spark, but the fuel is flooding out the plugs making it hard to start. He tells me this only started happening after he had the exhaust replaced. I read in my manual that the O2 sensor controls the duration of the injection, so I was wondered if that could be the problem. I disconnected the O2 sensor cable but still constant injecting. I'm not sure what to do next. All the injectors are constantly running, so I am assuming that the problem is before the injectors. I disconnected the battery and reconnected it to see if something electrical was "stuck" but nothing seems to stop the problem. I even took the fuel pump relay out and tried jumping fuse 4 to fuse 6 to see if the car would start and run, but this did not affect the symptom. I'm not sure what to do next. Any tips would be greatly appreciated.

 

When my dad first got the 745. there was a problem similar to this. Turned out that the injectors where grounding themselves. inspect the ground cables.
though it is funny that it happened after they messed with the exhasut/ O2 sensor...

wait for the experts to get on.

 

Could be the RSR relay which supplies grounds to the injectors. Just a thought.

 

Thanks for responding. I have to believe the exhaust system change has something to do with this. The car ran fine, although a little noisy. No check Engine light. As soon as my friend picked up the car from the shop, he started getting terrible gas mileage, maybe 5 MPG and the check engine light. He drove it for a few days, went through $150 worth of gas, which should have been maybe $20 worth of driving, before he came to me. I just don't understand how the injectors could suddenly become grounded. However, I;m convinced it's definitely an electrical problem, since the fuel injectors run like a hoses as soon as the key is turned on. If it's a grounding problem I was wondering if it could be a fuel injection relay. I don't know where it is located on a 1990 240 or if it is even separate from the fuel pump relay. I've already swapped out for testing the fuel pump relay (passenger side under glovebox) with 2 others I took out of two different perfectly running '92 240's which I own. This is so strange to me. I've never had a problem like this. Usually it's a lack of fuel (bad relay, fuel pump, filter. etc.) - never too much fuel!!!

 

Jagtoes, this sounds like a real possibility. Can you tell me where I would find the RSR relay on a '90 240?

 

You can find the various relays here http://www.swedishautoparts.com/240/...40-relays.html

If you scroll down to the PDF's you can find the locations here http://www.davebarton.com/volvorelays.html

Good luck and let us know how you do.

 

@jagtoes - it turns out this 1990 240 doesn't have a RSR relay set up. All I could find is an inline fuse, which neither of my '92 240's have. It turned out that I could not get the diagnostics code function to work either. My friend gfot a little frustrated and brought the car back to the shop who did the exhaust work. The first thing the mechanic did was swap out the computer. He claimed that this year (1990) had defective computers. He mentioned something about computers identified with a pink stripe or something like that. Anyway, once he changed the computer, the diagnostic functions began to work (fuel injector test, etc). Although I had already cleared the check engine the day before and it didn't trigger again. He was able to get a 1-1-1 code. He could trigger the injectors to fire in sequence, etc. The dig is, the fuel injectors STILL RAN CONTINUOUSLY as soon as the key was in the start position!!! He began to suspect the fuel pump relay, even though I told him I already tried 2 others that were known good. His retort was I did this when the car had a bad computer. Okay, but he was never able to find the problem while I was there. He kept the car overnight and I'm hugely curious about what he discovers, since apparently no-one on this forum has experienced this with a 240 before. As soon as the problem is diagnosed and resolved, I'll report the results, as this might happen to someone else.