Mechanics

FUEL PROBLEMS

1987 GMC Sierra

Electrical problem
1987 GMC Sierra V8 Four Wheel Drive Manual 175000 miles

I cant get my truck running. Ive replaced the Fuel Filter, Fuel pump relay, Fuel selector valve, Oil pressure switch, Fuel tank Switch, MAP sensor. What should I do next
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BU113TZ
December 13, 2009.



I cant get my truck running.

When you turn key to run do you hear the fuel pump? If so check the fuel pressure with a gauge if its within specs and also for an injection pulses.

Rasmataz
Dec 13, 2009.
When I turn the key on I cant hear the pump come on but it has a fuel tank switch on the dash and you have to depress it full when switching tanks. And if I hold the switch down then turn the key on I can hear it prime but as soon as I release it the truck stops getting fuel

Tiny
BU113TZ
Dec 14, 2009.
Test the transfer switch

Rasmataz
Dec 14, 2009.
What is the transfer switch and how do you test it

Tiny
BU113TZ
Dec 16, 2009.
Fuel tank switch same as the transfer switch-check and test the fuel pump relay. When you trun ket to run you should be able to hear the fuel pump come on for 2secs-its not happening

Rasmataz
Dec 16, 2009.
I can only hear it come on for a couple seconds when I hold the switch down and turn the key on but if im not holding it down it doesnt come on at all do you think both the fuel pumps are bad?

Tiny
BU113TZ
Dec 16, 2009.
You need to determine which pump is coming on and its fuel pressure if its within specs

Rasmataz
Dec 16, 2009.
If I hold the switch on either side I can hear them come on but if I turn the key on without holding the switch down they dont come on at all I dont know if I have the switch wired up wrong or what

Tiny
BU113TZ
Dec 19, 2009.
Open up the switch and tell me how many wires are going to the switch

Rasmataz
Dec 19, 2009.
There are 4 wires going to the switch I have a test light and only 1 of the wires is hot and its only hot for a few seconds when I turn the key on. None of the other 3 wires ever make the test light come on I think there is 1 black wire, 1 red with white stripe, 1 solid red, and 1 grey wire, And the one wire that is hot for a few seconds is the red with white stripe.

Tiny
BU113TZ
Dec 19, 2009.