Question about 1999 Chevrolet Silverado 1500

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1998 chevy pickup 1500 V6

I am loosing my prime after truck sits . Any suggestions?


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In my experience, if the fuel system is loosing pressure after sitting, then the internal check valve in the fuel pump is to blame. This essentially can only be remedied by replacing the fuel pump. Your pump is an in-tank unit that can only be serviced by dropping the tank and replacing the pump. My recommendation would be to replace the complete fuel pump module. (one piece unit including pump and fuel level sending unit) You may consider purchasing only the electric pump motor to replace within the module, but that typically involves taking the module apart, splicing wires, and risking damage to the housing and level sender unit in the process. I have found that replacing the whole module and the "sock" on the pump, although more pricey, is the best answer due to said issues and usually a better parts warranty coverage. You should also replace the fuel filter at that time or shortly thereafter. The reason being, that when you drop the tank to service the pump, you can stir up sediments that may have settled in the tank over time. They'll collect in the filter and may stop up the system if in excessive amounts. I hope this helps.

Posted on Nov 14, 2008

  • dc don Dec 10, 2010

    Understanding this has been awhile since Debbie posted, here is what I have found.

    Over time most of General Motors tend to lose primes for various reasons. The primary reason seems to be fuel formulas and processing. Also, keeping a vehicle "less than full" helps exacerbate the problems with additional moisture in the tank and rust that builds over time. Also, there are the regulator problems usually due to electrical contact problems including and the key switch itself. In most cases it seems to be the ground for the regulator that also will cause the pump to labor and fail.

    To start, with the loss of prime, I suggest each time you start allow a few seconds to pressure up the system before turning the key from "on" to "start". If you have no other problems, you probably can help the check valve by running a system cleaner like Berryman Chemtool B-12 through the system and then change the fuel filter. In the next tank run a half pint of top oil like Marvel Mystery Oil through it. And keep the tank as full as possible to keep the moisture out.

    I replaced two OEM pumps in less than a year. Found that the contacts in the key switch didn't make contact correctly all of the time, causing the pump and/or the regulator to not work correctly. I took the switch apart cleaned it with contact cleaner, wire brushed, a little conductive lube like silver lube, and I used a little Lock Ease in the key cylinder before reinstalling. Has worked great since.

    Hope this helps.




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