fuel pumps short problem
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Joined: Jul 2003
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From: so calif
fuel pumps short problem
Hey steve83 or timbarr!, or anyone with this knowledge.
My fuel pumps are only getting 6-7 volts at the connector and won't come on. They work as I have hooked another battery in the bed and ran two leads to the front pump. Truck runs fine , so I think, just have to pull leads off battery when I turn ignition off, only way 4 me to get to work till I fig this out, or I mean somebody can help. New Fuel pump relay installed still nothing. When I put test light on fuel pump leads out of FP relay it gets relly dim and when I ground fuel pmp test lead from STO the fuel pump relay clicks and test light barely lights up but pumps won't come on! ran codes and got 542 Fuel Pump circuit failure PCM to Ground. So do I have a short to ground? gonna change cable from neg batt post to block? truck will start and evthing works but have to power pumps with separate battery which I hope isn't screwing anything up? Also EEC relay gets really warm when keys on? Can't see any bad wires? Inertia switch getting same voltage as pump connector when keys on about 6.9 volts. my fuel gauges seem to work when I switch tanks but I know fuel isn't cause I only have front hooked up to extra battery but still have on both connectors while running and rear tank is still full. Appreciate anyones help! Maybe Fp relay from ATZN no good? It should click right? I couldn't get codes or anything such as my truck run at all if the EEC Relay was bad?
My fuel pumps are only getting 6-7 volts at the connector and won't come on. They work as I have hooked another battery in the bed and ran two leads to the front pump. Truck runs fine , so I think, just have to pull leads off battery when I turn ignition off, only way 4 me to get to work till I fig this out, or I mean somebody can help. New Fuel pump relay installed still nothing. When I put test light on fuel pump leads out of FP relay it gets relly dim and when I ground fuel pmp test lead from STO the fuel pump relay clicks and test light barely lights up but pumps won't come on! ran codes and got 542 Fuel Pump circuit failure PCM to Ground. So do I have a short to ground? gonna change cable from neg batt post to block? truck will start and evthing works but have to power pumps with separate battery which I hope isn't screwing anything up? Also EEC relay gets really warm when keys on? Can't see any bad wires? Inertia switch getting same voltage as pump connector when keys on about 6.9 volts. my fuel gauges seem to work when I switch tanks but I know fuel isn't cause I only have front hooked up to extra battery but still have on both connectors while running and rear tank is still full. Appreciate anyones help! Maybe Fp relay from ATZN no good? It should click right? I couldn't get codes or anything such as my truck run at all if the EEC Relay was bad?
Post Fiend
Joined: Nov 2002
Posts: 9,987
Likes: 7
From: Memphis, TN
fuel pumps short problem
ANYTHING from the zone is no good! 
Trust the computer's diagnosis and correct the open (not shorted) ground circuit. The Haynes manual shows the grounds, so trace it from the FP relay to the PCM to ground in the wiring diagrams, and then on the truck. You may just need to tighten a screw on the L inner fender.
Trust the computer's diagnosis and correct the open (not shorted) ground circuit. The Haynes manual shows the grounds, so trace it from the FP relay to the PCM to ground in the wiring diagrams, and then on the truck. You may just need to tighten a screw on the L inner fender.
