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starts and dies


vonzipper27

Member
Joined
Jun 11, 2010
Messages
5
Transmission
Automatic
a friends 85 bronco died on his way to my house. We towed it here, and this is what i have found.

When to turn the key to start, the truck fires right up, but as soon as you let go of the key, it dies. It appears everything under the hood is plugged in as it should be, but its not mine so i cannot be 100% sure. As a "test" i had him turn the key to the start position and hold it there, and I disconnected the wire to the solenoid so the started would not keep running. The truck ran fine, and when he let the key go back to run, it kept running fine. As soon as i plugged the starter wire back into the solenoid ( the trigger wire) it stumbles and dies off. Now dont laugh at me here, but, I figured ok, well, if it runs fine with the trigger wire off, what the hell, i will hot wire it so he can drive home. Long and short of it, I used his horn wire to plug in as a trigger. So, now he turns the key to start and hits the horn, the rig starts and runs fine. Well, so i thought. As soon as you put it in gear to go home, it died. Will start right back up, but when you put it in anything other than park or nuetral, it dies. Obviously there is some sensor, wire, or something out there in the system telling the computer to shut her down. Do you guys have any clue?
 
could be the ignition switch get a cheap one from the bone yard and see if that works and if it does he can dill out the bucks for a new one if he wants but start there and check all the wires and connectors for melting breaks or shorts and maybe it threw a code to point you in the direction.
 
According to the haynes book, there are 4 things that could lead to it:

1) Loose or damaged wire harness connections at distributor, coil or alternator

2) Intake manifold vacuum leaks. Make sure all mounting bolts/nuts are tight and all vacuum hoses connected to the manifold are attached properly and in good contition.

3) Insufficient fuel pressure

4) Fuel injection or engine control systems malfuntion.

I'm sure there are a billion more things that it could be, but that should be a good start. Keep in mind that this came from the Explorer book...but i'm sure that problem isn't explorer specific. lol.

Anyway, good luck with it.
 
ten to one it's the ignition switch. They're cheap, just buy a new one.
 
number 2 and 3 of the four are not it, it runs fine. I will look at the ignition today. Thank you everyone so far.
 
ok, so how do I know if it is the switch? I pulled the cover off, checked out the wires and the plug, all looks good. I did start it though, and wiggled the actual key switch part around and was able to put it in gear without it dying. But, i could not replicate it enough to really get a good feeling that the reason it kept running was from what i was doing. I am about 10 minutes away from ordering a 79 distributor and module for it and throw the computer out the window....
 
when we checked the codes, it threw one saying the tps was out of whack, and then a ton of the 80 codes about the egr. the egr is not on it, so i can see whay that is.
 
If you go duraspark you might have the same problem if it is the switch. get a switch at the bone yard for cheap and see if the problem persists. It sounds like a loose or bad connector or the ignition switch it dont sound like the normal symptoms of the dizzy maybe the computer going goofy with the egr and who knows what else is not working. If you dont have to pass emissions do the duraspark and a carb and be done with the computer crap If you disconnect the battery for at least 15 minutes it will reset the computer and see if that helps if yes you need to get all the sensors working or it will go goofy again. With the duraspark you can get rid of all the sensors and 95% of the wires and most of the vacuum lines and the engine will regain life I am still amazed at the difference every time I start it and stop at a light. Use the tech Library and ask questions the ignition system cost me about $130 plus whatever carb you decide.
 
do i really need to replace the carb? It has one on it, i just "assumed" the tps would be disconnected and everything would be happy. We have no emissions tests here :)
 
If it has the computer and TFI it will never be happy believe me I was having to pop the hood daily to make it back and fourth to work. the biggest problem is the feedback solenoid on the carb and the dizzy not advancing proper. With the duraspark you have the vacuum and mechanical advance. And I have a 2150 motorcraft 1.08 venturi carb with #46 jets one of these days I might put in the #50 jets but these came with the carb and are working just fine I get arount 17-18 mpg cold starts first crank and it idles by itself at lights if it is puffing smoke when you start it I highly recommend valve guide seals also.
 

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