Ignition problem
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Ignition problem
I have a 1986 F-150 with the fuel injected 302. It has an intermittent problem of, at startup when the key is turned on, the fuel pump will not shut off and the engine will not crank. (This is caused by the computer not grounding the injectors if I'm not mistaken?) I was told it was the computer, and I have replaced it several times, then the problem would go away for a few months each time and come back. I noticed the last couple times that if I hooked up a battery charger and set it to 200 amp engine start, and turned the key on and off a couple times the problem would resolve. Only to return the next morning. What could be causing this problem?
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I've tested and even replaced the fuel pump relay, sorry, I should have stated that originally. And the engine will turn over fine, it just won't start.
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From: Virginia
You can try and ground the terminal in the test plug above on your truck. The test plug should be under the hood.
If the relay clicks and the fuel pump runs, then all that is good. I would then pull the codes from the computer from this plug. You can use a testlight or old voltmeter to read the codes. You might have a problem with the TFI module, and if the computer doesn't see signals from the dist, it will not turn the fuel pump relay on.
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From: Virginia
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From: Virginia
Did the fuel pump run when you grounded the terminal?
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The truck runs great when it will start. And after you get the pump to shut off the first time, it works correctly when you try it afterwards. If it sits for a few hours or overnight, the problem returns. You can turn the key on and the fuel pump will start running but it will not shut off. You can turn the engine over but it will not start, and the fuel pump will not shut off. The fuel pump does go off when the key is turned off.
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From: Virginia
The fuel pump does go off when the key is turned off.
This is a interesting problem. Why don't you try taking the battery cable off, go in and take the computer out(plug and all) and then put it back. You said each time you replaced the computer it worked for awhile. If it starts working ok again for awhile after you take the computer out and put it back in, I would suspect a connection problem at the computer plug or something related like that.
I would also find the main computer ground out at the battery(should be a smaller wire on the fat negative wire) and follow it down, there will be a disconnect that needs to be checked, it likes to corrode.
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From: Saskatchewan Canada
Curious if there is pressure at the fuel rail when the pump runs. If it is low, might be the regulator? Still should be shutting down if the engine is not running.
Strange symptoms.
Strange symptoms.
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That's because the fuel pump relay is fed from the EECIV relay, which is controlled by the key.
This is a interesting problem. Why don't you try taking the battery cable off, go in and take the computer out(plug and all) and then put it back. You said each time you replaced the computer it worked for awhile. If it starts working ok again for awhile after you take the computer out and put it back in, I would suspect a connection problem at the computer plug or something related like that.
I would also find the main computer ground out at the battery(should be a smaller wire on the fat negative wire) and follow it down, there will be a disconnect that needs to be checked, it likes to corrode.
This is a interesting problem. Why don't you try taking the battery cable off, go in and take the computer out(plug and all) and then put it back. You said each time you replaced the computer it worked for awhile. If it starts working ok again for awhile after you take the computer out and put it back in, I would suspect a connection problem at the computer plug or something related like that.
I would also find the main computer ground out at the battery(should be a smaller wire on the fat negative wire) and follow it down, there will be a disconnect that needs to be checked, it likes to corrode.
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I checked to make sure the computer was getting power and ground. I also cleaned the ground connection at the battery. I also replaced the computer with another reman one, and the problem still persists.
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From: Virginia
Ok, this is a wild guess. It's cheap, and not too hard, but like I said it's a total guess(throwing parts at it). Replace the ignition switch. They have been known to give intermittent problems. It's located on top of the steering column, underneath the dash.
I followed the instructions in the book, and it said to take loose the cable that goes to the PRND321 indicator, take the u-bracket loose that holds the column to the dash, let the column drop and then you can see and get to the switch. Make sure to follow the instructions that come with the switch(you can get these switches at most parts stores), they have a little alignment pin that you stick in the switch to hold it in position when you are installing it. Then pull the pin when you are done.
I followed the instructions in the book, and it said to take loose the cable that goes to the PRND321 indicator, take the u-bracket loose that holds the column to the dash, let the column drop and then you can see and get to the switch. Make sure to follow the instructions that come with the switch(you can get these switches at most parts stores), they have a little alignment pin that you stick in the switch to hold it in position when you are installing it. Then pull the pin when you are done.