I have a 91 f-150 4x4 302 that is having trouble starting. Problem happened over a short period of time were the truck would have trouble with cold starts as if the battery did not have enough juice to turn it over. So I replaced the old battery with a nice optima yellow top and was good for a little while. Than one morning came out to a dead truck so I tried jumping it with my CJ7 that stalled. Being in a hurry I started it with the cables still on and burned up the fusible link between the syleniod and the alternater. After replacing all above parts (fusible link, syleniod) with a fresh battery and all when I turn the key there is now now fuel pump noise when you cycle the ignition. Replaced fuel pump reley still nothing. Ever since the bad jump the dreeded check engine light has been constantly, and by that I mean even when no key in ignition. It will go to turn over but is not getting fuel(obviously with no fuel pump working). I even checked that dumb fuel reset swith on the firewall. Is the electrical issue with the alternator? What is going on with the fuel pump(forgot to mention duel tanks)? Thanks for any help I want to get it running good again before I start resto/moding it.

 

You must have a couple melted wires that are stuck together for the ECM relay, causing it to stay powered up....hince the engine light that stays on all the time ? Could also be a defect in the ign. switch ? It is strange that you burned wires just by a simple jump start ? There was a reason the battery was weak in the first place. Hope you didn,t accidentally hook up the jump cables wrong ?
Phillip

 

On the CEL see if the EEC Power relay has its contacts welded closed.

I would also check the small black wire with a white stripe going to the Negative post of the battery or radiator support.
If this wire does not have a good ground the fuel pump and no solenoid will work including the fuel injectors.

 

sounds to me like you hooked jumper cable up wrong

 

If you hooked up jumper cables incorrectly, I'm sorry to say almost anything electrical may have been damaged. Did you try pulling codes? Engine does not need to run for that. Is the battery reading 12v before you do anything? Make sure the voltage is not low to begin with otherwise you need to charge it first. Alternator is only into play once the engine is running. It only charges battery while engine is running. If the altenator is bad, it would run your battery down while driving. I suppose if it was damaged, it might bring the battery down while trying to start. Try disconnecting it electrically while trying to start, that would answer that. Quick check (once engine runs again) is volt meter across the battery while engine runs, should read around 13.5 volts. Engine not running , 12v.