Back several weeks ago I posted a message to the board about my "89 244 surging after a long drive. You can read about it by following this link: http://www.brickboard.com/RWD/index.htm?id=929625

I think I have it narrowed down now but I would like your opinion.

I thought the car would only surge after a long drive but it seems that it will do it anytime it is hot outside and the fuel level is off full by 4 or 5 gallons. You try to accelerate from a stop and the car acts as if it is running out of fuel. It bucks and surges and then catches up and runs pretty well.

I replaced both fuel pumps, the in-tank sock and the main fuel filter less than a year ago, none of the parts have more than 3000 miles on them. I can insert a tube into the filler neck, place it to my ear, and hear the intank pump running. When the tank i s full or it is cool outside the car runs fine. As a matter of fact, if I stop the car and wait for it to cool off a bit it will run fine for a little while. As an example: it was running very badly so I stopped at a fast food place and bought dinner (about 5:00pm). When we came out it was a lot cooler (a little after 6:00pm). I started the car and drove the next 100 mile home, the car ran fine.

My thought is a problem with the in-tank pump. The car acts as if it is not getting enough fuel to keep the fuel pressure up, thus starving the main pump. The main pump never changes sound so I think it's working correctly. When the tank is full the in-tank pump does not have to work as hard so the car runs fine. When it is cooler outside the fuel is denser (if thats a word) and the pump dosn't work as hard. As the temp goes up the fuel becomes lighter and the in-tank pump has to work harder. Does any of this make sense?? Any thoughts?? I really do need your input.

Thanks for your help.

Tony T
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Tony Turner 89 Volvo 240DL 257K, 92 Jeep Cherokee 250K, 93 Jeep Grand Cherokee 215K, 1980 Mercedes 240D 360K

I agree, it is the in-tank that is suspect. Often a sub-par fuel hose patched into the in-tank comes loose and causes the symptoms you have. Or, the original Volvo hose just split.

Thank's for your reply. The pump I have on there now is of unknown quality. I bought an in-tank pump of the "noname"variety from someone on ebay ------ never again. I'll get a good pump and hose from FCP and see if that takes care of it.

Thanks for your help.

Tony T
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Tony Turner 89 Volvo 240DL 257K, 92 Jeep Cherokee 250K, 93 Jeep Grand Cherokee 215K, 1980 Mercedes 240D 360K

While you're at it why not install a fuel pressure gauge at the engine end of the system to see what the pumps are really putting out?

Also, I've had the same symptoms ftom the opposite problem - too much fuel pressure overfilling the carbs and choking out the engine. Of course, if this was your problem you'd have noticed the black smoke before now! ;-)

Good luck!

I've found that the fuel line for the in tank fuel pump doesn't last as long as the other fuel lines. you could very well have a break there.
this is just a theory, but I wonder if your in-tank line is leaking, and your main pump check valve is not holding pressure, and you're getting a vapor lock in the fuel line.

Sounds reasonable, but the fact that it runs okay after cooling off makes me think it could be a problem in the electrical circuit to the in-tank pump somewhere, if there is a bad connection it could get hot, making a bad connection worse. Just to rule that out, I'd check the connections, and if possible, check the current draw of the pump when it's a problem.
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'81 GLT 245 @ 259K; '83 DL 175K