North American Turbocoupe Organization

Fuel Pump Troubles
Entropy1988 Offline
Junior Member
Well thanks to Jeff K for the very informative Fuel pump trouble shooting guide in the Tech section. I trouble shot the problem back to a defective Chinese fuel pump Undecided . However, I discovered that there is a continuous 5.5 volts always present at the pump electrical connector. If I disconnect the connector from the ICM box which has the fuel relay it goes away. According the circuit diagram there shouldn't be anything there if the key is not in the run position etc. With the key off the circuit shows 5.5 volts. Has anyone else had this happen. I tried new ICM and it does the same thing. So, I'm thinking wiring cause what else is left? Also, where might I find the grommets and gaskets for the fuel tank for the filler neck and for the vacuum canister check valve etc?

Entropy1988 Offline
Junior Member
Wiring harness from the ECC4 back to the pump is good. Apparently, the issue must be from the rt side where the EEC4 is to the ICM. I could run a wire for the time being and dead head the other wires just to get it running again but I'm going to pull the dash and get a good look at the harness.

Jeff K Offline
NEVER use a DMM to check power circuits!!!!!! ALWAYS use a test light. A DMM has 11 Megohm input impedance meaning that it will register small voltages in power circuits that are off due to typical Megohm open circuit resistances in switches, relays, etc. In other words, a quick calculation shows your pump relay has an open circuit resistance of around 15 Megohms which = open circuit...... I have seen this situation many many times over the last 40+ years of working as a physicist and electrical engineer.

Google the voltage divider equation for more info.

In other words, you do not have a problem!
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized

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