I suspect a bad lift pump on my 98 12v 170k miles but would like confirmation before I go spending $150. I installed a fuel gauge and Tork Tek adjustable OFV, and when cold the gauge will show 30 PSI when warm the truck will go down to 20 PSI and drops when I accelerate. I only had 15 psi till I closed the Tork Tek OFV all the way down.

 

When was the last time you replaced the fuel filter/cleaned strainer?

 

The filter is new and the strainer was cleaned about 1 month ago.

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What kind of pressure should I have on my fuel gauge?

 

Should be 22 at idle and 25-30 at 2500 RPM. Do you have any mods?

 

The mods were all done by a previous owner - schwitzer turbo, 5 hold injectors, #6 fuel plate, 4.11 gears w/315's and a built trans. You say the fuel pressure should go up with the RPM but mine goes down. I have to completely shut the OFV to get up to 30 psi cold and still it goes down to 20 psi when the engine warms up. Bad P pump or lift pump? With my current mods should I invest in a fass setup or am I good with a stock lift pump?

 

pretty tough for a mechanical pump to go bad without tattle tale signs...ie fuel in the oil or fuel on the ground. Have you noticed either of these?

Chris

 

No - no fuel in the oil or on the ground. Just low fuel pressure.

 

The lift pumps do go bad over time. You can try pinching off the return line from the overflow valve and see if your pressure goes up. If so, you got a faulty overflow valve. If it's still low, check for restrictions from the tank to the lift pump (kinks, pinched points, etc). If that all looks good, then it probably is your lift pump.