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Old 01-16-2019, 11:03 PM   #11
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Join Date: Oct 2008
Location: Wentworth, NH
Posts: 3,606
Re: GMT400 Wiring Woes

If you're getting a 2 sec pulse at key on then the ECM and fuel pump relay are working the way they should.

Here's the 1992 GM CK Wiring manual.

The rest of the 1992 service manuals from my library are in my signature.

Sounds like you have it pretty well nailed down to an open in the fuel pump power wire between the relay and the fuel pump. Start looking for damage along those wires. Look at the pump ground too. It'd be obnoxious to get the pump power fixed and have a dodgy ground hang you up.
1959 M35A2 LDT465-1D SOLD
1967 Dodge W200 B383, NP420/NP201 SOLD
1969 Dodge Polara 500 B383, A833 SOLD
1972 Ford F250 FE390, NP435/NP205 SOLD
1976 Chevy K20, 6.5L, NV4500/NP208 SOLD
1986 M1008 CUCV SOLD
2000 GMC C2500, TD6.5L, NV4500
2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263
2009 Impala SS LS4 V8

RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials...Please include at least the year and model in your threads. It'll be easier to answer your questions.
And please let us know if and how your repairs were successful.

Last edited by hatzie; 01-16-2019 at 11:09 PM.
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