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Calling all HO Gurus! Stuck with no start on '91


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I've been having issues with my '91 HO 4.0L as far as fuel delivery. Started with the balast resistor: changed the electrical ends and it ran great for a while. Then it started acting up again... did a pressure and leak down test and signs pointed to the pump. Sure enough, the pump was failing. New pump in it and now it left me stranded 70 miles from home. I do not have power going to the pump with the key on. When I jump the wiring for the pump, it engages and puts pressure to the system but will not start the engine. I have jumped the fuel pump relay as well. Swapped around the relay with the starter and auto-shutdown relays and everything remains the same.

 

So, how do I go about checking whats next? Is there something else I'm not checking for the injectors? Maybe CPS?

 

Thanks everyone! :bowdown:

 

edit... tried checking codes too. I've done it in the past, but won't even give me a "55" now. Won't give anything.

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Went through all of the fuses under the hood. Big green 30 amp fuse for the engine control... why would that have blown? Well, it did. I'll change it out, but what can I look for as to why it went bad? There doesn't look like there was anything too dirty or wet in the fuse block... :hmm:

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Old fuse that just had enough after 20 years of service is a possiblity. Also the pump putting to much draw on it could have popped it too. If it does it again then you have bigger problems.

 

Thanks. :thumbsup: I put a new fuse in there and it started right up. If it should happen again... being that I still have a 70 mile drive home... anything that I should look for if it happens again?

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One of my '88s gave me intermittent problems with the fuel pump and it was driving me nuts trying to troubleshoot and fix it. I eventually figured out that the pump wasn't getting a good ground at the connector. Apparently the common ground for the fuel pump is located behind the driver's tail light. Once I popped it off, I saw a bunch of ground wires tapped into the same crimp terminal screwed down to the sheet metal of the bed. It was very rusty, so I popped it off, cleaned it up with some emery cloth and reinstalled. No problems since.

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One of my '88s gave me intermittent problems with the fuel pump and it was driving me nuts trying to troubleshoot and fix it. I eventually figured out that the pump wasn't getting a good ground at the connector. Apparently the common ground for the fuel pump is located behind the driver's tail light. Once I popped it off, I saw a bunch of ground wires tapped into the same crimp terminal screwed down to the sheet metal of the bed. It was very rusty, so I popped it off, cleaned it up with some emery cloth and reinstalled. No problems since.

 

Doubt a bad ground at the tail lamp ground would pop that 30A fuse. That "Big green 30 amp fuse" in the PDC is the gateway to many subcircuits besides the fuel pump. The easiest way to troubleshoot this, if it blows again, and hopefully it will not, is to start tracing out the subcircuits serviced by this fuse one by one based on the FSM schematic. Sounds like an intermittent short in the harness or a bad/rotten connector. It's easy to fix it it it's a constant fuse blow, but the intermittent stuff is hard to find. The PDC harness passes closely to the fender well; unbolt the PDC, lift it up a bit, and eyeball for obvious skinned wires under there. But only if it blows again down the road.

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