95 GMC Jimmy 4.2L V-6

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  #1  
Old 09-04-08, 11:54 PM
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95 GMC Jimmy 4.2L V-6

Ok, so my truck periodically decides that it wants to start jerking on the highway and then lost all power and die. Pressing the gas pedal doesnt seem to work, and sometimes it wont start back up again for about 20+mins. It cranks just fine, and sometimes will start for a second but wont idle, then dies..sometimes it starts and then will die again a few miles down the road. As of last nite, it wont start at all, but it will still crank over like it wants to start. I have a full tank of gas btw so Im not outta gas.....
I had dagnostics ran on it and was told it was the fuel pump...so I had a friend change that, and it ran for a ways then now im having the same problem again.

Someone at the repair shop (who btw wanted to charge $650 to fix a fuel pump), told my dad that Jimmy's have to have a certain fuel pump brand (OM I think it was??) or the pump will not work?? If thats the case then why would autopart stores sell different brands??
So is it that? maybe the fuel filter? Someother sensor? Could the diagnostic tests they ran be wrong?? HELP ME!!!!
 
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Old 09-05-08, 03:42 AM
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The symptoms you have point towards the fuel system. Usually diagnostics for that condition is a pressure check on the fuel rail. That testing will look for problems in the pump and the pressure regulator. Along with some other things you can use that test to look for leaky injectors.

The brand you heard was probably OEM which refers to Original Equipment Manufacturer. It implies you would have to put the same pump back on it which the vehicle came out with. Sometimes that's true, but there's a little wiggle room. When the OEM part specs are met in aftermarket parts, they usually perform as well.

In your case, if the pump is supplying the volume of fuel at the pressure required for the engine, while not blowing fuses or tripping relays, it should work. That's pretty much the extent of what a fuel pump has to accomplish.

The performance of what you had installed can be checked by the same tests that determined the pump was at fault at the start. That is a good place to begin.

If we use as a starting point that you have a good pump, though, the next place to look would be the fuel filter (which would be the first thing to change as maintenance), then the pressure regulator. If you can get the pressure up, but it bleeds down quickly, the regulator is where I would go. A dirty filter will impact the running pressure of an engine, but typically only in a load demand condition. If the flow restriction allows the fuel system to meet the fuel demands (relative to load) of the engine you won't have problems until the demands go up (loaded condition). All this means it may idle, but won't run past the idle if the filter is plugged.
 

Last edited by marbobj; 09-05-08 at 05:51 AM.
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