Need advice, 70 Mustang 428SCJ
 

I never come on asking for advice but I am at a complete loss on this one. 70 Mustang 428 SCJ, all new all factory correct. Engine runs all day in shop. I go drive it and will die inside a mile. It will restart on prime but won't stay running. I have changed the fuel pump, have fuel pressure gauge on it and is not dropping fuel pressure, I have changed the coil as well, checked everything with the Holley carb. I have no restrictions I can find in the fuel system either. It acts like it running out of fuel. I have considered its either sucking air or vapor locking, only thing I have not done is rig up a temporary fuel pump. Any ideas.?:bang: :bang:

Mike
If you are running all factory stuff, the fords are famous for the ignition module dying, it will shut off park, then will reset itself and you cant find the problem. Hope this helps.

Mike

Gas cap vented?

Its a CA emissions car, non vented cap with the vent line running to canister up front. I have attempted to drive it with cap open, same results

Factory carb? Is there a stone filter on the inlet into the bowl?

yes, its clean

I know you said it doesn't lose fuel pressure, but how about the sock in the tank?

brand new tank, brand new sending unit, brand new lines. I have not pulled it yet, but I am considering pulling it next for good measure.

Is it safe to assume that you removed the filter and test drove it?

I'm out of ideas.

Yeah, me too. That's why I am here asking. I am not going to have any hair left if I don't figure it out soon.

Did you try venting the tank above the tank and filler level?

Eliminate the losing the ignition, see if you can rig up a timing light so you know if the spark stops at the same time while driving.
When it stops, if you remove the float level bungs and give he car a shake, does fuel come out?
When the car stops, have you tried removing the air cleaner and watching to see if the accelerator pump squirts fuel in?
When it stops, does it sputter or stop?
is the ignition feed hooked up to the main feed circuit breaker? The ignition uses a resistor wire, is the ignition compatible?

yep, did not fix it either.

Borrow a spark checker that taps a plug wire, not losing spark

I have checked bowl levels, sometimes its low, but never empty

Only driving it with no air cleaner, can't see or do anything with shaker installed, still squirting fuel when it shuts down.

when it stops, it acts likes its out of fuel, but I had a fuel pressure gauge tapped into it while driving never lost pressure.

all factory wiring, factory resistor wire, factory coil, which I have changed, even unhooked the factory rev limiter to see if it was shutting the car down.

Has factory carb spacer about 3/8" thick, which should eliminate boiling the fuel in the carb

It has to be losing fuel or spark unless the exhaust is clogged? I've seen it on modern cars where the cats will close up. Muffler batting? If that's not it, I'd swap the carb. It may have an internal clog in the primary circuit. Also, you may see a spark, but is it strong enough to jump the gap and still on every cylinder? Have you checked the coils resistance?

Describe the motor problem a little better......a quick die off would probably be electrical related.......stumbling before die off would be fuel. If there is any backfire.....could get into things like weak valve springs.

I starting to think its the floats hanging up or needle and seat issue. Its a brand new Holley, and I have adjusted everything to where its properly adjusted and purrs like a kitten in the shop, but the last couple times I have drove it now, it shuts down right after I stand on it like it running out of fuel. Whats driving me nuts is not the consistent failure, its the inconsistent way it shuts down.

Just swapped the coil, no change.

Already been into the heads. Had a vibration at idle I could not get out of it and found two cylinders that the valve were being held off the seat just enough to cause dead cylinder. Went through the heads and double checked everything there. I'm pretty certain its a fuel issue, just one I have yet to find.

Pull a plug to see if it's wet or dry when it dies.

I'm thinking about one other thing.....being a SCJ its a 4 speed car right? Is the factory rev limiter box still hooked up in the ignition circuit? My 1st car was a 70 Boss302 Eliminator and I went through some tribulations troubleshooting a miss that was finally diagnosed to the magic little box on the drivers fender. The box should be bypassed if its present.

o this problem happened after cylinder head replacement? What was holding the valve off the seat?

Can you clarify this from post 1.

"It will restart on prime but won't stay running"
Are you pouring fuel into the carb, where?

Does it just shut off?

where is the fuel pressure gauge installed?

Already bypassed it, no change

Didnt replace heads, they are original to car, only repaired the problem, the valve was being held off the seat. Problem was there before.

When it restarts it sometimes will stay running as long as no load on it. Other times it restarts like I just primed the carb and then dies.

pressure gauge was tapped into system just before carb.

Finally resolved my issue. Carb came with a micron style inlet screen, which was replaced twice thinking it was blocked. Once I finally nailed down the fuel was emptying every time, I removed the sock on the sender, changed all spring clamps to hose clamps thinking i might be sucking air, no change. So I finally poked a hole in the micron screen and finally got to drive it without it running out of fuel. Put a rock screen back in it and no issues. Who would have thought the micron screen supplied with the carb direct from holley, would be too restrictive to keep the carb fed? Its stupid crap like this I hate. Now I can finally finished this nightmare up and get it delivered. Thanks for everyones help. I appreciate it.

That's just crazy! As delivered and engineered by Holley... and I know you checked the sinistered bronze filter before finding this. Who woulda thought! I guess that's why a lot of the old school hot rodders always pulled those and the micron screens out of the inlets and put a filter in-line? Glad you figured it out Mike!

I was close, is there a prize?

Glad you got it fixed, it's frustrating beating your head off the wall with no logical explanation to the problem you are having.

It didn't have the bronze screen, I changed it too it.

its always the last place you look hu Donny?

good job Mike!

I had already looked there, the problem is the idiots at Holley.