First concerning issue

[Rawkkrawler]

I say concerning only because it's intermittent and the motor quit thus forcing me to pull over to troubleshoot. No real warning, slightly under load, just a sputter than tach to zero.

Basic info:

Carb'd 5.0 with Quickfuel 650
Mallory Max-Fire distributer (1 year, 1600 miles old)
Mallory coil
Electric fuel pump

First thing I did was turn the ignition on and read the fuel pressure gauge under the hood, it was at 6.5-7lbs. Nothing alarming there. Then I moved the throttle linkage, gas squirt in as usual. I pulled the coil wire and cranked the engine, spark popping like normal. I pulled the distributer cap and cranked it, rotor spun normal. The only thing I did was clean (scrape) the cap contact points a little and put everything back together. It fired right up and drove the 5 miles back home.

I took it out later that night and it sputtered once at a light but didn't stall. About a half mile later it had a loss of power under a slight load. Had it at about 1/2 throttle and it barely maintained 1000 rpm then quit again. I had an overwhelming fuel smell almost bad smelling. This time I was able to restart it by just holding the gas pedal to the floor as it appeared to be flooded. This may not be a symptom as I had the pedal 1/2 throttle right before it stalled.

So, it appears to be either an ignition problem or a bad fuel problem.

All of the wires are connected firmly. I'll double check the ground this morning.

I'm a little worried about the Mallory dist. It's an all in one unit and there is no real way to troubleshoot it I don't think. Is it possible that a worn out dist cap could give me these issues? Seems a little sudden to just shut the car down. I'd understand a lack in performance.

Sorry for the long winded post but I'm puzzled on this one.

Thanks!

[Rawkkrawler]

57 views and no thoughts

Ok, here's some more info...

I drained the entire tank and added 10 gallons of super unleaded. I also added a can of Seafoam to the tank. I then drove it around for about 20 miles in varying conditions.

The only noticeable issue after 15 miles was a little stumble off 2000 rpms. Sounds a little like vapor lock to me. It's about 80-85 here in Tampa in the shade. I did have an issue last year but added a 1/2 inch phenolic spacer that seemed to clear things up.

Nothing has been changed leaded to this issue.

Dirt in carb? Vapor lock? Mallory dist failing?

[PeteF]

Sounds like bad fuel (you mentioned a bad smell), or contamination in the fuel bowls. I assume you have a good filter installed. The only things I could recommend now is to spray some Seafoam through the air bleeds of the carb, and/or pull the front bowl and look for debris. Good luck.

[keezling]

By your description sounds like fuel boiling in float bowls. Mine did that sometimes on hot days. Fixed mine by accident when I added a turkey pan. Carb stays nice and cool on hot days now. Next time it happens put your ear near carb, if quiet enough outside you'll be able to hear it if that's what is happening.

[Rawkkrawler]

Both thoughts crossed my mind. I appreciate the ideas.

The fuel boiling issue was bad last year and it seamed as though the 1/2" spacer fixed it. Maybe a combination of some bad fuel and boiling.

I'll keep searching.

[Gaz64]

I'd be checking the needle and seats for fuel line debris, then pull the float bowls to see if any rubber debris has made it's way into the metering blocks.

How much rubber line after the fuel filter?

How old is the rubber and when did you last "service" the rubber? ie: change fuel filter or replace a hose?

[strictlypersonl]

I say concerning only because it's intermittent and the motor quit thus forcing me to pull over to troubleshoot. No real warning, slightly under load, just a sputter than tach to zero.

Are you saying that the tach goes to zero with the car in gear? If that's the case, you are having an intermittent ignition failure.

[Rawkkrawler]

Thanks to everyone for the responses!

The car was completed in June of last year. The entire fuel system is brand new. Fuel pump, fuel filter, steel line up to the firewall then back to a 3/8" fuel line to the new regulator then a small piece to the carb, which is also brand new.

The car has 1600 miles on it already. In Florida I try to take it out once a week. The 1/2" spacer helped last year but this just seemed to have just come out of nowhere. I did look at the sight glass on the front and rear of the carb and the floats seem high. I never adjusted them when I pulled it from the box but maybe I can drop them a little to see if that helps.

I'll also get in there after that and clean the needle and seat.

I mentioned the tach going to zero but I may have had the clutch in pumping the gas, I can't remember for sure. I haven't ruled out the ignition problem yet.

[vref120]

I was going to say dirt in the needle and seat also. Will flood the front primary and kill the car. Had this issue with a QF 750. Had the same symptoms as you.