Power at the Coil but no spark

[bartgillam]

I have a completely stock 1986 bronco 2 2.9l 4x4 that will run fine but once it heats up it dies. I have replaced the distributor completely including cap rotor distrib and the tfi. I have replaced the coil. I placed a new shorter ground on the coil that has almost 0 resistance on it compared to the crappy ground ford had. The coil has 12v at the input plug but no spark comes out. This obviously points to it being a bad coil but the thing is this coil is essentially brand new. I bought it about a year ago and it did not seem to fix the problem. Does the coil need 12 volts? Maybe it is being over volted? I have to believe its the coil simply because it has power going in but not out. I also checked the coil wire going to the cap for continuity and it had a great connection. I was thinking maybe if its over heating for some reason i could buy perhaps a high performance coil? I would like to stop dropping money in this thing but i love it and don't want to scrap it. When it runs it runs great including the 4x4 but keeping it running for longer then thirty minutes seems to be an issue. I also checked the SPOUT wire for exposed connection that could lead it to be grounding out (another thing i read on a post on here as ive basically tried everything) I believe it is most definitely the coil but i want others opinions simply because it is essentially brand new. Also a side thought im not opposed to rigging things up and was thinking maybe i could wire a switch from my battery to a the cab and back to the coil with a simple on off so when i want to start it i shoot 12v directly to the coil instead of relying on something else? Idk..this was just something that crossed my mind im tired of it not running ha. Thanks in advance

 

[WNYBroncoBill]

I'm having close to the same problem with my 89 BII. See my post nearby. I get spark to the distributor, but no spark to the spark plugs. Yesterday I replaced the coil ($22 at NAPA), the rotor and the cap.

Last week I replaced the TFI module, swapped an ECM from another BII and still no spark to the plugs. It is definitely getting fuel to the cylinders, almost new pump (38 PSI) new filter, new fuel pressure regulator.

I have examined the wiring from the TFI module at the connector, no bare wires or chafing there.

It seems like the spark from the coil is going nowhere when it gets to the cap and rotor, like the rotor is between posts when the coil fires - so the spark never gets to the plug wires through the cap. The vehicle does occasionally fire on one or two cylinders when I try to start it, but I believe this is just an errant spark that finds its way to one of the posts in the cap.

This is frustrating, I can't find anyone who knows anything about these vehicles, they have been long extinct in our part of the country. My BII recently came up here from South Carolina.

Someone must know what your and my problem is, perhaps a Ford technician who is a board member.

Bill

 

[bartgillam]

I wish someone would chime in im very frustrated i really dont want to buy another coil before someone gives me some input since this one is practically new..i get no spark though so you got me beat by one step ha...

 

[WNYBroncoBill]

TFI - ECM - Coil

I have been reading more about the ignition system in the Bronco II from 1986 thru 1990.

The TFI module on the distributor has three spade connectors and six output connectors that go to a connector that snaps onto the TFI module. The TFI module gets it pulse signal through the case of the distributor, That signal is then sent to the ECM which is located under the right side kick panel in the passenger compartment. That signal tells the ECM where the position of the crankshaft is. It is called the PIP input.

The output from the ECM is called SPOUT (Spark output signal) it goes back to the TFI module where it is then compared to the PIP signal through the electronics in the TFI module.

This combined signal is then sent to the spark coil at exactly the precise time and the spark is then sent to the distributor through the distributor lead wire.

The rotor then selects the proper cylinder to fire in sequence, and the engine should run if it has fuel.

I believe in both of our cases, the TFI is at fault (or the wire from the ECM to the TFI module (SPOUT signal - wire #2 on the connector.) Check yours by removing it from the TFI module at the connector and examine it for any chaffing or bare wires.

I believe mine is a failed TFI module as I have checked the SPOUT wire. I may have a defective "new" TFI module that I purchased last week. Looks like another $42 gamble on the Bronco II!

Good Luck,

Bill

 

[WNYBroncoBill]

I spoke with a factory trained Ford technician today regarding my problem with spark occurring at the wrong time. He believes I should try to diagnose the distributor as that might be the problem.

He offered the following:
Get the engine on top dead center on #1 plug. (Passenger side, front plug.
Check the position of the rotor to see if it points to #1.
Remove the distributor to determine if the gear has slipped due to a roll pin failure.
Replace the distributor with a rebuilt one as the hall effect mechanism might also be bad.

If that doesn't work - "Drop it off at my shop"!!!

 

[bartgillam]

All that is brand new on mine and none of the wires look bad or exposed..i actually might try an ecu from another bronco 2 at the junkyard to see if that might do something cause i imagine the coil wont spark till the ecu tells it to so that could be it..i can replace the wires the harness is like 700 dollars for all those wires...i could almost buy a used bronco 2 for that lol