O.K., here we go. 1986 Bronco, 351 HO, Edel Carb. Had problems running and starting the last two weeks. THe engine seemed to fire while starting but would die as soon as the key was in run. Took to a shop and the said it was either the module, ignition switch, or pickup coil. Replaced the module with a new one. Everything ran fine. 4 days later the bronco has trouble starting at gas station and sounds like weak batery or bad start relay. Make it home and that was it, one start again. clicking sound, sometimes buzzing sound came from starter relay. Replaced starter relay with a new one. Same thing. Bye the way, battery cables are new 2 gauge, alt is 130 Amp running on 8 gauge and 100 amp fuse, all good.

Figure, it mudt be the starter since it has 12+v at the battery and jumping doesn't seem to help. Enter new starter, same problem. Just buzzing from the starter relay. Checked battery at parts store and they said it was bad. Still under warranty but NAPA was closed today so I went and nabbed the battery from my dad's dodge van. I know it was goo. still no start. Same sound same problem. Tried a few experiements. The starter will turn if the ignition is at start and I have jumper cables from battery POS to the starter wire. So the starter is working. Battery is good, low now but still good enough for a starter I would think. To make sure, I jumper over the relay and let it run for 30 min. Charging at 14.2-14.5. Double checked and still nothing. Noticed that when the key is at run, the pos terminal and wire get s very hot at the battery within 20 sec. Also noticed that the battery reads 12.5 volts terminal to terminal. Read 12.1-12.3 from pos side of relay and ground. With the key in run, that voltage drops to 9.4-9.1 volts. So it appears I have a short somewhere. I have removed every fuse under the dash to narrow it down. Removed all alternator connections to rule out my 130 amp mod. Still no start, still hot wire will sitting in run.

I need some help. I have worked on this 20 hours +. I'm thinking of replacing the iginiton switch to rule it out. any ideas?

Thanks

Mike

 

mike when you put in the new the new relay in are you sure you didnt cross the switch wire with the field wire to the alt? second are you sure you didnt chafe the wires to the alt? just a long shot, thought i would ask. also try removing the electronic ignition. use the dist., cap, rotor, wires, points, condencer and coil (if you dont have one) from a 78 351. you might get a check engine light but it will run. thats what i did.

sean
81 bronc
new 302 removed all smog related crap

 

Can you exlain a little more about crossing the switch wire with the field wire to the alt? How could I have done that? The switch wire is the red booted wire that turns the starter relay on and off, right? I've unplugged everything from the back of the alt to make sure something it wasn't caugint the short. I really don't want to regress back to points just from all the problems I've seen others have with points. The engine module is new so it should be fine. I'm really at a loss. Tomorrow, I'll probably bye a ignition switch and try that. Then if that fails, take it to a shop. Is it normal for the pos bat. terminal to heat up significantly in just run? I've never noticed it before but it seems like it could be part of the problem. And I'm pretty sure that the starter won't turn over becuase the voltage drop is soooo geat. ( volts is probably not enough to turn 351 ci.

Thanks sean.

 

normaly if the bat. post is warming up its a good sign that you have a short some where

 

No way the battery post or cable to the starter shoud get hot. Perhaps a little warm after repeated cranking but not hot. My guess is that one of the rectifier diodes is shorted. This would provide a direct path to ground from the battery. (Be glad it's not your outboard motor, rectifier for my 200 was almost $400 CDN)

 

you might need to run even larger cables for both neg/pos and running to the starter itself.

good luck

 

isn't the rectifier diodes in the alternator? If so then thst's not it, I've disconnected every wire from the alternator. If this helps at all the resistance between pos and neg wire(battery removed) while in run or acc. is only 89 ohms. To me that seems wrong. I know there should be a little current running through for any lights that I've not already removed but not that much. In the mean time I've replaced the ignition switch, same thing. I've removed the wires from the rear defrogger switch, and from the wiper motor. Disconnected the new module and a few other plugs around it and it still seems to be shorting out on something. New battery only gives 9.1 volts to starter.

Thanks again

 

here's something else. I did some more testing and what ever it is seems to be flashing, when I put the car in acc or run, the voltage at the starter relay flucuates between 10.6 and 12.6 with a new battery. So that means the short is on something with a circuit braker, shorting, then clearing, then shorting, over and over again? It's a clue, come on guys, somebosy has had to have this happen before!

Thanks
Mike

 

hot wiring it would elinate the iggy switch
have you checked all the fuse links can be a pain atleast con't know if it would cause your prob

 

This is getting really strange. It's common to start replacing everything when the obvious doesn't work - try to resist.

I'd start at the beginning and check your relay, wire connections, (I know they might be new - clean them anyway).

Get that new battery.

Pull the ignition switch wire off the starter relay and check for 12Vdc with the key turned on - long test leads and alligator clips help. On the 86 Broncos, I believe the ignition switch is wired through the neutral safety switch which, in turn, is controlled by a wire to the ECM.
It could be as simple as checking to make sure the connectors on the ECM got pushed in all the way when they replaced it.

 

I've given up. I'll take it to a shop today if I can get it there. I know this is strange but I asure you that my battery connections are probably the cleanest in this forum. I can't stand corrosion, old cables, or messy wiring. I replaced the old battery cables a while back with 2 gauge high quality wiring. The 130 amp alternator (4th one I've installed in my fords) has new high qulaity 8 gauge wiring through a 100 amp fuse. I've test the resistance of all cables=good. I've tested the ground connection=good.

There is such a stinking load on the battery when it is in run or acc, the radio shuts off and resets the clock when I roll down a window. I've tried so many things, it's like the whole damn truck melted into one blob. I can't believe that a short of this magnitude has not cought the whole thing on fire by now. I've listened for circuit brakers, nothing. I pulled each fuse one by one and nothing. Well, the weird one of the bunch was the fuse to the interior lights that feeds the light switch. When I pulled it the volts at relay went up by two. THe odd thing is that none of my interior lights were working. I guess I could unplug the light switch and give that a try.

My reasoning has been that since it only does it at run or acc, then it must be someing coming off the igntion switch that is in the run and acc wiring. I've traced almost all of those to dead ends.

It's not in the windshield wiper motor, not in the trailer lights, not in the engine module, cole, distrib, rear window, side windows, door locks, alternator, radio, battey, starter relay, or battery cables.

 

soelenoid could be the problem check the wires with fuseable links I had one burn off today from ( I think) alternator voltage regulator going bad

 

I know this is a really old posting, but I am curious as to what the problem turned out to be?