Hi, A few wks ago we posted the problem we were having w/ a '94 850 that would intermitently not (re)start when the engine was hot.Along w/ it just quitting while driving dwn the road too. We first tried repalcing the plugs, then the distrtibutor cap/rotar w/ no luck. Along w/ the spark coil and the RPM/Impulse sensor as recomended by a couple of folks here. So we finally decided it was time for a visit to the dealer. BIG mistake,,,. We got PORKED to the tune of over $600 for a new fuel pump. Hey like the car has less than 200K mi on it,,,. The very next day,,, the SAME problem again... But the fuel pump did give me the idea to check what was CONTROLLING the pump,,. This came to mind after recalling how the fuel pump relay on my old 240 had given me fits,,. It took a few to ID exactly where the fuel pump relay/controller was located, but we found it under the cover for the fuse holders; Its the big, green, square one, marked "103". We knew we were on the right track when we got the engine to die whenever we tapped on the realy a few times,,,.
We pulled the relay and snapped off the cover. Althought the contacts of the relay itself looked ok( we gave them a quick burnishing though), I could CLEARLY see on the small printed circuit board where the relay was mounted, what would be described as "cold solder joints" on the two pins/leads from the realy's coil. At least it wasn't as burnt up as the circuit board on my 240's relay,,. We proceeded to carefully "reflow" the connections w/ some fresh solder, then reinstalled the relay. That was two weeks ago, and Im happy to report, NO further problems! While doing an oil change on my other 850( a '95), we decided to check its fuel pump relay too. Even though Ive had no problems, so far,, we DID see evidence of the SAME type of problem. So as a prventive meassure, we resoldered the relay connections there too.
For most "gear head" types(no offsense,,), I would recomend simply relacing the relay. However if you are handy w/ a soldering iron, you might also want to fix the old one and have it handy as an emergency field replacement,,. You would want to use a 40-50 watt soldring iron w/ a grounded tip as the circuit card has a 4538 logic chip on it. I suspect the chip's function is as a timer to energise the relay during initial startup.(?)
Apart from the cost, what iritates me about my experience at the dealership is how they apparently diognosed this problem by replacing the first(and most expensive) thing the mechcanic saw fail. INSTEAD of trying to further isolate the problem. Given the degree of electronics in vehicles these days(it would seem) that if mechcanics were trained to think more like electronic techs, they would be far more effective in isolating intermitent problems of this nature. I also wish that Volvo could find/use relays that didnt burn up over time; I noticed that while troubleshooting this problem that besides the fuel pump relay getting hot, the 3x "J" relays were also getting hot too. I previosuly had one of the J relays go on my 95 850 a few yrs ago. Could someone please tell me what EXACTLY the 3x "J" relays do, so I'll know what to check when this or that doesnt work,,,.
Cheers Steve