Loud backfire and then won't start

Hey Guys,

New to the forum. Been looking for a good Bronco for a couple years. Finally picked up one that had been recently restored and having a good time. 302 w 3 speed stick, J shifter, Dana 44, Painless Wiring, new Edelbrock Carb, fresh rebuilds on tranny, engine, and transfer case. I'm working thru the kinks on the restoration as it wasn't quite finished. It's been running warm but getting it under control.

Just drove back into town from a trip 3 hours away, and exited highway to have it start sputtering and then a very loud backfire out the exhaust. Only blocks from the house. I couldn't get it to start. Acted like it was flooded. I let it cool down, would try to restart, then would try to halfway fire, then just nothing. It would only crank.

I plan to look at coil, points, condenser, cap/rotor tomorrow when it's light out. But wanted to get you guys input first on 1. What might have caused the backfire, 2. Where should I start first, 3. Nothing really damaged, right?

And yes, had to tow it with my other truck. But at least only a couple blocks.

Never actually got too worked up about it breaking down, so that was a big win.

Thanks for the help in advance,

Bill

Sounds like a timing problem, possibly timing chain.

Hi Bill.., welcome..!

Agree with Seabronc..,

As to your inspection.., there should be no points in your '76.  It should have the electronic "Duraspark" ignition.

The most common failures are the ignition module & maybe the coil.  The pick-up coil in the dizzy can fail.

However, a failed timing chain on a "fresh" engine would be highly suspicious.

(meaning no one should put an old timing gear set on a "fresh" engine)

Line up the timing marks & look/see if the rotor is pointing to #1 pin in the dizzy cap.

Check for consistant good spark at plug wire while cranking eng. over.

Have the Module tested.

Inspect coil.., is it new or an old beater.

No there isn't any damage due to an ignition failure.

Thanks for the direction and input. I'll give it a shot.

Hey myb, welcome.

Bully and Seabronc are some of the best minds on here, especially with the older Broncs. 

For my 2 cents I can only add that in some instances backfires can ruin the power valve in the carb. This is especially known to happen in Holleys. Since you have an Edelbrock and I think they are modeled after the Holleys there could be a problem there.  Sometimes a vacuum leak will make the engine backfire when de-accelerating from a high speed run.  

Let us all know what you find.

Good Luck

Latest update - Replaced Coil - no change, replaced ignition control module, no change, check Dizzy, getting spark, checked plugs getting spark, turned crank to check rotor and it turned, checked carb to ensure getting fuel, it was.  

I checked my paperwork on the carb. It's an Edelbrock 1406. Does not have a power valve that can be blown out. 

Thinking I'm going to have to go internal and I'm not liking that thought. Open to any other input before I go there. Thanks for some ideas so far.

Try this;

Rotate the crank again by hand (key off of course) & have someone (if you can't see both yourself) watch the rotor

as you rotate BACK-N-FORTH.   There should be no slop.., meaning both should move at the same time.

If there's an obvious delay.., the timing chain/gear set is bad.

Did you do a timing light test to see if it's still in time..!  If not.., it may have jumped a tooth on the gear.

If it turns out to be the chain/gear-set.., no biggie.., thats not a hard job to fix.

Is the dizzy actually locked down..? It could have rotated a bit if it's loose.

Thanks Bully. Checked to crank and rotor appears to be turning with no slop. I haven't checked with a timing light yet. Dizzy is locked down tight.

A friend of my Father-in-Laws stopped by and he works on race cars and he believes it's timing or the cam. He told me to pull the valve covers and see if all is moving correctly.  

I think I'm going to have it towed to his place and have him tear it down.

I appreciate all the advice and direction. I'm sure I'll be back for more over time.  I'l let you know what we find out as well. 

Sounds like a good plan.

Do let us know what you find.

Save those parts you took off that were NOT the problem. They may come in handy.

Sorry for the delay. Turns out it was a timing issue, but seems that the distributor went flaky. When I pulled it out, it was sticking slightly and not turning smoothly. Also the gear on the bottom seemed to be off just a bit like it had slipped. Bought a new distributor, plugged it in and it started right up. Had to adjust timing again, but running fine.

Thanks for all the direction. I'm sure I'll be back for more.

KEWL...!

Now you'll have time to fill in you signature with all you & your trucks info.

That way we don't have to ask a dozen questions upon your return......  >< <'>   /