Truck Wont Start?
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New User
Joined: Oct 2004
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Truck Wont Start?
I've got an 87' F150 302 EFI which was running fine until yesterday. I drove the truck for a while then parked it for about 4 hours. When I came back it would crank over but it had no spark or fuel. I came back to it about 10 hours later and the same thing happened. A few hours after that I tried it again and it started right up, no problem at all. I assume this is the main computer itself stating to go, any ideas?
Elder User
Joined: Sep 2004
Posts: 941
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If you have no spark, most of the time you will have no fuel. The reason is that "main computer" looks for pulses from the TFI module on the distributor to know when to fire the injectors. If the TFI or Hall effect pickup is dead, you will have no spark and no pulses to the computer.
Conversely, the TFI arrangement is capable of generating spark even when the computer is completely dead. So the computer is actually low on the list of potential problems here.
I had similar symptoms to you most of last summer. The problem turned out to be bad ground connections -- the battery post, ground wire to same, and the chassis grounds on the radiator support right in front of the battery were the main culprits.
If you are sure these are good, your TFI module may be going bad. Intermittant hot start failures is a known TFI failure symptom. Finally, make sure you have 12 volts DC going to the hot side of the coil and to the computer. The power supply relays and/or fusible links may have some issue.
Conversely, the TFI arrangement is capable of generating spark even when the computer is completely dead. So the computer is actually low on the list of potential problems here.
I had similar symptoms to you most of last summer. The problem turned out to be bad ground connections -- the battery post, ground wire to same, and the chassis grounds on the radiator support right in front of the battery were the main culprits.
If you are sure these are good, your TFI module may be going bad. Intermittant hot start failures is a known TFI failure symptom. Finally, make sure you have 12 volts DC going to the hot side of the coil and to the computer. The power supply relays and/or fusible links may have some issue.
