Question about 1998 GMC Sierra

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Under load going up hill - looses power - check eng lite comes on. Narrowed down to low fuel pressure - changed filter and relay - 50PSI at throttle body - 5.7 engine - 4WD - Sierra SLE - what is the PSI supposed to be? Is it probably the fuel pump?

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Ideal psi for this vehicle is 56. So the missing 6 should not really make that huge of a difference.

However most of your problems are occurring while the truck is under stress, ie... uphill with a load. I can only assume the readings where taken without the demand the truck needed at the time of failure.

If you believe this is a fuel related issue, which I can not really diagnose with the information I have. I would start by looking at the fuel pressure regulator, then the pump.

Since you have already checked the relay and filter, the regulator and pump and the only things left in the system that control the fuel coming from the tank to the engine.

Once the fuel reaches the engine a lot of other factors come into play, such as the injector and components. But without the codes to go on, I'll just address the pressure going to the motor in this.

After you have checked the regulator and pump, if the problem persist, please feel free to come on back, and post the MIL codes as well as more info as to the conditions and demands for fuel at the time of testing compared to those at the time of failure.

Thanks for coming to FixYa, please feel free to come on back with all your automotive needs.

Posted on Sep 04, 2010


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