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Discussion Starter #1
I've tried searching around the forums some but not sure what to do now.

1988 Bronco 5.8L automatic transmission.

Truck just got tuned up only put on about 50-100 miles since then
(New plugs, wires, cap, rotor)

Also has new ignition switch (That thing you put the key into on the column :toothless)

It all started one day when I started it up. When I touched the gas it stumbled off idle. It was like it wanted to shut off but it would either A. get past the rough spot and then drive smooth/normal or B. let off gas and it would idle ok. I got it on the road and like I said it would drive fine with partial throttle and WOT. But driving down the road if I let completely off the gas then touched it a little I could feel/hear that stumble.

After that I waited a couple days and went to start the truck and it sounded like it was going to start for just a split second and died. Tried to start it a few more times after that and now it turns over but wont start.

Next day I went to start it and again it had that split second like it wanted to start but died. I don't know how to explain it just barely did something. After that again just cranks and doesn't do that little thing like it was trying to start.

So after sitting a long time the first time trying to crank it acts almost like it wants to start up for a split second. But after that it just cranks and cranks.

This is what I've tried.

#1 Used screwdriver to press shrader valve on fuel rail and gas came out. I just hit it really quick and I would say it shot up about as tall as a bic lighter or a little less.

#2 Pulled wire off spark plug and used OLD spark plug to check for spark. I did try to use a little sand paper between the tip of the old plug but I didn't get it all that clean. The spark was yellow so I'm not sure if it didn't have a weak spark? Would this be weak spark from coil or just cause I had an old crappy plug?

#3 CEL light is working and codes didn't read anything except 96 which I was getting that code before when it ran good.

#4 I can hear the fuel pump noise so it's coming on and running then goes off

I'm not sure what to do now. I heard someone say on one post that you could get a weak spark from the coil and my ignition coil does look old as hell so I was tempted to just buy a coil for it.

Also my ignition relay/solenoid(thingymabobber :toothless) on the passenger fender looks old but I'm assuming that it wouldn't crank if that was bad or am I wrong?

What should I do? Thank you very much :thumbup
 

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I wonder if it's a timing issue? Are there a lot of miles? Not long ago I had a car that did the same thing and it turned out to be the timing tensioner had broken and it jumped it's timing. I know these vehicles don't have the tensioner, but I remember in the 80s, Ford had a problem with timing chains.
 

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I'm putting my money on a weak coil. Check the resistance like they tell you to in the Haynes manual.
 

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Will it start if you hold the gas pedal down half-way? I've seen a bad IAC cause a problem like that.

I don't really have any other advice, sorry.
 

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I'm with the guys in thinking it's coil related. I had almost the same problem. It would stall out after 20 feet or so, then finally quit starting all together. Had to call Ye Ol Roadside Assistance to drag it home ONE mile :doh0715:

I used this thread on the FSB and it came down to a bad coil:


http://www.fullsizebronco.com/forum/showthread.php?p=2730897

Worked like a charm. I'm convinced if you can't find out how to fix it on this board, it simply can't be fixed.
 

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#4 I can hear the fuel pump noise so it's coming on and running
With the key in the run position (not start) is the fuel pump coming on for the ~2sec prime and shutting off or does it come on and stay on? If it comes on and stays on the truck will not start as there is something that has the fuel pump relay ground switch from the ECU 'stuck' grounded. Also when this happens you will not be able to retrieve codes from the ECU. The ECU is stuck in the 'prime' mode and will not let the injectors turn on which is why is will not start.
If this is happening there are several things that can cause this:
Make sure the fuel pump test circuit is not grounded.
Check all the engine wiring grounds make sure they are clean
Check all the three wire sensors in the engine, like the TB sensor, O2 sensor...the easiest way it to unplug them one at a time, turning on the key to see if the fuel pump only runs for ~2 seconds.
Check the ECU itself, remove is and open it up and most leaky there will be some leaky capacitors and or a bad circuit board, this is a common problem with our trucks. Sometimes it will still be the ECU with no visible damage to the capacitors.
 

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Discussion Starter #8
jjandascog thanks but the pump comes on for a few seconds and goes off. The way I said that was confusing so I edited it to say it does go off.

I'll be sure to update this thread when I figure it out though. Going to try and get a coil because I don't have a manual for the truck to test coil. We will see.
 

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Check your fuel pressure. You need 39.5, some say 40, but who cares. you need around those numbers to run.

Second, check spark. These things are known for Eating TFI's and well they don't run, or will run intermittently.
 

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@crw87 - I hope you are troubleshooting and not throwing parts at it. But if you are insistent on throwing parts at the problem without testing you might find it interesting as to what the above suggestions would cost so far:
(Prices from RockAuto)
Timing set and water pump (because if you are going to change the timing set, you might as well change the water pump) - $110
Coil - $30
Idle Air Controller - $60
Ignition control module - $60

That's $260 (plus coolant) so far. It's your money.
 
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