its broken again
Thread Starter
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Senior User
Joined: Apr 2003
Posts: 159
Likes: 1
From: nowhere town nj
ok so it goes liek this, since i straightened out teh plug wires adn set teh timing to 10* with the spout removed the truck wont start when cold unless i prime it with some throttlebody cleaner first. i dont have a fuel pressure tester but i think it has something more to do with teh timing or something. Does this make anyone think of somethign new?
Cargo Master
Joined: Apr 2003
Posts: 2,408
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From: Parkesburg PA
You may want to check that the ring on the harmonic balancer hasn't shifted. Pull the plugs, turn the engine over by hand until you feel air coming out of the spark plug hole. Just stick your finger over it. Keep turning till the air stops, this will be top dead center, and should line up with the 0* mark. Also the rotor in the distributer should be pointing to right around the #1 (should be a hair past it).
As for the fuel pressure, it should be about 36-38 psi at idle.
As for the fuel pressure, it should be about 36-38 psi at idle.
Thread Starter
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Senior User
Joined: Apr 2003
Posts: 159
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From: nowhere town nj
okay, so i got a fuel pressure tester, and with the engine running at idle i have about 38psi which is normal. when i have the key on and the engine off i should have fuel pressure shouldnt i? the gauge reads zero. what might cause this, bad pump or pump relay?
Cargo Master
Joined: Apr 2003
Posts: 2,408
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From: Parkesburg PA
When you turn on the truck, the fuel pump should energize and pressureise the system then turn off. If the pump works fine when the truck is running, but doesn't energize when you first turn on the key, it's not the relay or the pump, it's what controls the relay which should be the computer. Not positive though... Can anyone else out there confim this?
Cargo Master
Joined: Apr 2003
Posts: 2,408
Likes: 5
From: Parkesburg PA
I was looking at my service manual for the 87-91 trucks and I found out a few things.
The way the circuit works is that there is an fuel pump cutoff relay that is controlled by an oil pressure switch. With no oil pressure, it cuts power to the fuelpump.
To bypass this and allow the truck to start a feed is taken from the starter side of the starter seloniod. This is a dark brown wire that connects to the brown wire that passes through the firewall in the large round connector. The brown wire goes to the intertia switch under the dash then to tank selector, then to the pumps.
There should also be something that runs the pump momenteraly when the key is switched on. Use a test light on the brown wire at the inertia switch and start with the key off. There should be no power. Trun the key to the on possition and note the results. Then turn the key to the start possition and note the results.
The way the circuit works is that there is an fuel pump cutoff relay that is controlled by an oil pressure switch. With no oil pressure, it cuts power to the fuelpump.
To bypass this and allow the truck to start a feed is taken from the starter side of the starter seloniod. This is a dark brown wire that connects to the brown wire that passes through the firewall in the large round connector. The brown wire goes to the intertia switch under the dash then to tank selector, then to the pumps.
There should also be something that runs the pump momenteraly when the key is switched on. Use a test light on the brown wire at the inertia switch and start with the key off. There should be no power. Trun the key to the on possition and note the results. Then turn the key to the start possition and note the results.
New User
Joined: Nov 2003
Posts: 16
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From: Rhode Island
The pump should come on for a second when you turn the key on then when you try to start the engine it should turn on and stay on. have you done any other changes to the truck exaust system air intake anything like that check the conection on the injectors and plug wires.
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Senior User
Joined: Apr 2003
Posts: 159
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From: nowhere town nj
the number one reason i like fords is- THEY FIX THEMSELVES. my truck is fixed for the most part and i didnt do a thing. went to drive it tonight and it worked fine. actually better than ever befor.
all i did was move the wires arounf on the selinoid looking for the one that is brown and goes to the fuel pump shutoff. i didnt see a brown one but they're 18 years old i expected them all to be the same color. there are molded fuseable links in those wires i think one of them just might be bad.
all i did was move the wires arounf on the selinoid looking for the one that is brown and goes to the fuel pump shutoff. i didnt see a brown one but they're 18 years old i expected them all to be the same color. there are molded fuseable links in those wires i think one of them just might be bad.
