Trouble with 78 Bronco.

[RustyRai78]

I am having difficulty with my 1978 Ford Bronco.

I just bought the bronco, and it supposedly has a newly rebuilt engine (10k miles on it)

But when I accelerate, it starts sluggishly. Sometimes starts to stall when I get to around 30 mph. Then when it starts to stall, if I floor it a little, it will (backfire?) then go forward fine. It also seems to have trouble going past 60mph at all. I could have the pedal down to the floor but that is as far as it will go. I was thinking maybe dirty piston rings, but if the engine is newish, then it shouldn't be that?

I am just hoping for some suggestions before I take it all apart. Seems to lack some power.

Thanks.

 

[Bully Bob]

Hi Rusty., welcome..!

"...suggestions before I take it all apart."

Naw..., you just need to do the basics...

Insp. fuel (& air) delivery to be correct.

Do all the ignition/timing/electrical tests.

Do fill in your info. pages so folks will know what we're dealing with here.

It's not uncommon for a PO to put the timing chain on wrong..., or use the OLD one during re-build.

Didn't you get (rebuild/repair) receipts with the purchase..?

 

[RustyRai78]

Sadly, I did not get the receipts on it. Bad move on my part, I know.

I was also thinking maybe the accelerator pump just needs some "tuning".

AND I'm new to the carburetor world, so, I'm going to have to learn. :blink:

 

[Bully Bob]

Ya., it sounds like fuel or timing/ignition issue..., or both.

Fuel pump (leak out the "weep-hole" when going bad) ., fuel filter clogged., Dirt in carb./needle & seat., float sticking.

As I recall., that accel. pump is accessible W/O disassembling carb.

However, that doesn't sound like the prob.

The "power valve" inside the carb. may have issues.

OOPS..., just noticed you have a Holley carb.

Great carbs but can be troublesome. backfires usually ruin their power valves.

BTW., there's inexpensive kits for the Holley that prevent power valve blow out fr. backfire.

 

[RustyRai78]

Well I definitely need a new fuel filter pretty soon. But I didn't think that was the problem. I would be overjoyed if that was it.

As for the Holley kits, I'll have to check it out. Thanks!

I'll have to check everything out. I hope I can figure it out. :/

 

[Bully Bob]

I use/suggest using clear plastic filters..or even what I now use is the glass tube style cleanable one..., comes with spare cartridges.

Point being, it's unknown whats in the fuel these days... corn, beans, rat-tails, etc. ...? Not to mention melting rubber fuel lines.

I think Summit Racing has the Holley power-valve protector kits.

Holleys are actually pretty easy to disassemble/assemble ... just setting them up gets a bit tricky.

 

[Rons beast]

As Bully suggested the carb could be a big issue. You may also have a vacuum leak.

An old school test is to get the truck on the highway at about 40 to 50 mph. Jump on the gas ( be sure the road is clear, be safe.)If the truck accelerates well the secondary ignition system is ok. Your problem is most likely the carb/ vac leak. If you get a stumble the ignition is breaking down. Check the timing. Not going over 60 make me think timing is off.

Inspect all wires. look for vacuum leaks.

If all that doesn't help, replace the fuel filter and tune the carb. holley has a great info page on their website.

Good Luck