57Gxi Fuel Pump Nightmare

"Having read the previous post

"Having read the previous posts regarding fuel issues with the 5.7 Gxi, I have decided I have a unique problem and need some advice. My engine is the "A" model from 2002 with less than 250 hours and is in a Cobalt 227. In the past 2 years, I have replaced the fuel pumps 4 times. These babies run from $700 - $1000 installed. All of the issues have been addressed, such as the anti-siphon valve, fuel filters, water separator, etc. to no avail. Symptoms are: rough idle and when gas is applied, the engine stumbles and even backfires, on occassion. EVERYTHING has been replaced, from the throttle body, injectors, water pump, distributor cap, wires, etc. Anything that could be bolted to the engine has been replaced except the ECM and the Volvo-Penta mechanics have all checked it and there are no trouble codes. Voltages to the pumps have been checked, as well, and are OK. There has been some small amounts of water in the fuel, but normal for where I am in Mexico, and attributed to condensation.

Has anyone had major fuel pump problems with this engine or is it just me? Needless to say, its driving me crazy, not to mention the cost."

a little water will run these

a little water will run these pumps

"From what I've seen, its

"From what I've seen, its not unusual to have a small amount of water in the gas due to condensation and the water separator, if its doing its job, should take care of it. The mechanics who have worked on the boat tell me that what I have is in the "normal" range and shouldn't be causing the problem.

If water IS the problem, where could it be coming from other than condensation? The vent line has a loop in it, which should prevent water from coming in that way and since the gas tank is attached to the hull and is virtually inaccessible, I can't see if it has a crack in it, which would allow water in. There is no gas in the bilge, so I've kind of ruled out the leaky tank.

So, bottom line, if water is the culprit, what steps do I need to take I haven't already done?"

"Steven, I am familiar with yo

"Steven, I am familiar with your problem having had a fuel cell fail. There are many threads on this subject, most boil down to clogged filters, too many filters before the pump and bad fuel. I have a 2005 Volvo shop manual and they state that the vast majority of the pumps fail due to old gas. They (volvo) say that even treated gas will only last 6 months. Volvo now makes the fuel cell in two parts meaning you can order the high pressure pump by itself. If you need the low pressure pump you have to buy the entire fuel cell. I would isolate the fuel first by disconecting the fuel line and placing it in a fuel container. That will address all of the potential problems of your fuel line, filters, tank and vent. If it still runs poorly place a fuel pressure gauge on the low pressure pump (I think it should run about 15lbs) next test your high pressure pump - it should put out about 50-60lbs. If that tests good and you have 12 volts at both pumps, it is not your pump. You may also want to invest in the shop manual, it has a whole section on fuel injection problems."