1991 f150 truck will not start


Old 12-20-13, 12:59 PM
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Join Date: Dec 2013
Location: United States
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1991 f150 truck will not start

motor will crank, changed fuel pump, ignition switch, will not start. fuel pump will not turn on from key. fuel pump will run if I ground it with test lead. so I have a ground problem that affects fuel pump and power to coil.
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Old 12-20-13, 09:07 PM
Join Date: Aug 2006
Location: santa fe /texas
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possible "inertia" switch has tripped ?

I think it is inside the truck, under the glove box, it has a 'reset' button on top.

possible fuel pump relay is bad?

possible that the PCM is not energizing the relay ?
Old 12-23-13, 09:21 AM
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Join Date: Dec 2013
Location: United States
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1991 f150 truck will not start

I changed relay, I checked inertia switch, how do I check PCM? Is there a ground for PCM?
Old 12-23-13, 09:50 AM
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I have this same problem on my grandpa's F250. Let me know what you figure out! I assumed that both fuel pumps have a bad ground, but I'm not about to drop the fuel tanks myself without some help.
Old 12-23-13, 10:37 AM
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Assuming two fuel tanks.
Have you located the three wires and plug from each tank ?

I'm looking at a service manual that is incomplete.

When you turn the key on does the relay under the hood activate ?
The Lt blue/orange is the control signal from the PCM and it supplies ground to the fuel pump relay for, I think, 10 seconds. The red wire on that relay is "key on" 12v.
Old 01-08-14, 12:44 AM
Join Date: Jan 2014
Posts: 2
Try turning the key forward (but don't roll it over) to see if you can hear the fuel pump in the tank. check for spark ,pull one of the spark plugs out roll it over to see if you got spark. And another thing spray some starting fluid in the throttle body and if it starts you have a fuel problem.

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