Fuel delivery issues (Solved)
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Mountain Pass
Joined: Apr 2019
Posts: 128
Likes: 18
Fuel delivery issues (Solved)
1990 f150 4.9 efi:
Need some help,
Truck wouldn't start, no noise from fuel pump. Replaced fuel pump still won't start... sometimes pump is loud (when priming) sometimes quieter. I'm thinking fuel pump relays? I've read the tank selector switch can cause trouble? Any insight would be appreciated thanks.
Need some help,
Truck wouldn't start, no noise from fuel pump. Replaced fuel pump still won't start... sometimes pump is loud (when priming) sometimes quieter. I'm thinking fuel pump relays? I've read the tank selector switch can cause trouble? Any insight would be appreciated thanks.
Logistics Pro
Joined: Nov 2013
Posts: 3,928
Likes: 1,199
From: Mojave, Ca
Could be bad ECU, bad ECU relay, fuel pump relay, bad power distribution block terminals, bad inertia switch, bad fuel pump selector switch, or bad fuel delivery modules in the tank.
You're gunna need a fuel pressure gauge, a test light, and a multimeter to find out what's going on.
Don't randomly start replacing parts, hoping to stumble on the problem. Use the tools above to diagnose it properly.
You're gunna need a fuel pressure gauge, a test light, and a multimeter to find out what's going on.
Don't randomly start replacing parts, hoping to stumble on the problem. Use the tools above to diagnose it properly.
Thread Starter
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Mountain Pass
Joined: Apr 2019
Posts: 128
Likes: 18
I'm looking at the tank selector switch, with the switch disconnected I'm getting a reading of 6.8 at the red/yellow wire. With switch connected I'm seeing nothing at any wire except yellow / white which reads 4 with front tank and 1 with rear. Wondering if this means bad switch?
Thread Starter
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Mountain Pass
Joined: Apr 2019
Posts: 128
Likes: 18
Bypassed pump relay, bypassed inertia switch, bypassed fuel selector switch, 12v to pump, still no start. No fuel on spark plugs after 3 cycles of prime/crank.
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Logistics Pro
Joined: Nov 2013
Posts: 3,928
Likes: 1,199
From: Mojave, Ca
I'm looking at the tank selector switch, with the switch disconnected I'm getting a reading of 6.8 at the red/yellow wire. With switch connected I'm seeing nothing at any wire except yellow / white which reads 4 with front tank and 1 with rear. Wondering if this means bad switch?
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