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Issues


crbnunit

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Here is a mystery for ya. 94 Ranger with a 4.0 and auto. Steep climb. Engine dies. No spit or sputter, just signs off. Fires right back up, goes about 10 more feet, dies again, starts and goes about another ½ mile. This time it dies and will not refire.

It starts to get odd now… When I try to refire the truck, the engine turns over like it should, it just doesn’t start. When I turn the key to start, the tack goes to about 6K RPM instead of the 1-2K the starter usually produces. So, I’m thinking something is wet or loose. I get under the hood and wiggle wires, check grounds and check sensors. There is pressure at the Schrader valve on the fuel rail. Don’t find anything wrong so I get back in and the truck fires up. Go another few feet and it dies again.

This time we notice the fuel pump does not run when the key is turned on. Ah HA! So we start checking fuses and relays. We swap relays and get the pump running again. Truck won’t fire though and we are baffled as to why. One of the relays seems to be bad so we swap it for a Rubicon front locker relay (fits!) and still get no fire. We hot wire the pump and the damn thing still won’t run.

I had poured in 5 gallons of gas from a can at the bottom of the hill and had no problems before that so we suspect foul play at work. We pour the little gas left in the can into a bottle and sure enough, water and silt. I bought this can from SARGE a while back and had never used it. Turns out he had used this one to collect water for an overheated Explorer! Suspecting the worst, we pull the fuel filter and find it full of fuel with no evidence of blockage. I had used this can a few weeks before as well so the tank could have gotten a double dose. We suspect the sock filter is clogged and the pump drawing too much current for the relay to support. Just guessing at this point…

I can tell you for a fact, coming off of Purchase dead stick is no fun without power steering or power brakes!!! We camped for the night and the damn thing fires back up the next morning. Head out and get a few miles out of it before it dies again, I have to coast out of Hatcher’s Pass and get towed back to town… By a Jeep. First time in 13 years my beast has left me stranded on the trail!

I dropped the tank expecting the worst. There is no silt or very little and only miniscule amounts of water. Nothing unexpected for a 13 year old truck. Everything looks good. Any ideas? I’m going to change the fuel pump while it is out but there seems to be nothing wrong with the old one. I’m stumped.
 


Wicked_Sludge

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start with the basics.

when its not starting, is there spark at the plugs? almost sounds like a control module.
 

crbnunit

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Ya, spark. No fuel.
 

smokey

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My 94 explorer did the same thing. tach flying up to around 6 grand and dying after a few miles.
It was getting spark also but the coil was Bad. replaced the coil pack and all was good again. find a coil pack to swap in to test it. a new one is about a 100 bucks.
 

MAKG

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Yeah, if the tach is obviously FOS, there just has to be a problem somewhere in the ignition primary circuits. And it does sound like an ignition module failure (though those happened when they were exposed to engine heat). You would get a no-spark condition only when the vehicle was warm; it would go away after cool-down. Though how such a thing could happen on a 4.0L with its remote mounted module is a headscratcher. I suppose a low resistance or short to ground might kick it in the head...

Note that the fuel pump circuit is also controlled by ignition, at least after the two-second prime.

With multiple electrical failures, one generally needs to go looking for commonalities, especially grounding and power issues.
 

crbnunit

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Now that makes sense.
 

crbnunit

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Well, havn't had much time to work on it lately but tried to pull codes from it yesterday. No codes... By that I mean I can't pull them. Comp. won't give. I'm guessing I have a ground that is not grounding or an hot that is grounding that shouldn't be. Let the fun begin!
 

MAKG

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Don't overlook a problem in the test connector harnesses. Especially, most of the EEC-IV wiring diagrams reverse STI and STO, and Ford oh-so-graciously used the same color code for both. STI is the single-wire connector, and it's what you ground.
 

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