Engine stumbling when accelerating

[Nomad]

Stock Tornado. Took the 715 to town, or attempted to. Engine started stumbling and sputtering when I was climbing a hill and had very little power. It seems to occur when accelerating past half pedal or climbing a hill. It would climb hills, just very slowly in first gear. I was able to limp it back home. On level ground if I back off the pedal it smooths out and seems to at least idle
and run smoother, but when the you try to accelerate the engine starts to stumble and it still lacks power. Any ideas as to whats going on? I'm guessing fuel filters/carb. I'm running two filters between the tank and carb, one before pump, one after. Running stock carb that I rebuilt a couple years ago.

-Damon

[brute4c]

It is possible...and has happened before...that the "sock" on the end of the pickup tube in the tank...a kind of plastic prefilter...may have "melted" and is restricting flow to the motor.

It has been fixed by blowing high pressure air back down that line from the engine side to blow that "sock" off the pickup tube.

Unfortunately, this is not uncommon...

[Nomad]

Thanks for the reply brute. My tank was in bad shape when I found my truck. I had a radiator shop boil it out twice, remove that sock, patch up all the pin holes, and put in a new pick up tube.

[brute4c]

Hmmm...actually now that you say it, I remember that...well...its probably not that then!

Have you checked that the points are installed correctly and are in good shape?

[Nomad]

Running pertronix. Ordered two filters. Gonna replace those and rebuild the carb. I'll post back with results.

[brute4c]

well....if not in the fuel delivery, then a vacuum leak maybe but you would think that would show across the power band...I think you are on the right track...let us know if that fixes or not...

[Nomad]

A friend at work mentioned the Diaphragm in the fuel pump going bad. Will check and follow up. - Damon

[brute4c]

If you didnt know...the diaphragms in the stock pump dont hold up to modern gas well at all...there is a kit you can buy that has the right ones for modern gas OR if you send them the pump, they do the rebuild...

Here is a link to the M715 kit...though I think you need 2 to do both the fuel and vacuum pump diaphragms...

https://www.then-now-auto.com/produc...fuel-pump-kit/

[AlanS]

Take a look at your distributor advance weights to make sure the springs haven’t broken. Mine was running similar to what you described. Advance springs were broken.

[Simon J]

I’ve had the same thing with my truck. Thought to be ignition so checked it all over. Plugs, leads, points, rotor and cap were all good. Timing set up and it ran perfectly in the workshop.

But, when out on the open road it would run well on the flat and not being pushed too hard. The moment heavier acceleration or climbing up a hill the engine would cough and splutter, which pointed to fuel starvation. We knew this wouldn’t be the carb as that had already been rebuilt with an ethanol resistant pump diaphrgm.

Back in the workshop we checked the fuel line and found the rubber flexi pipes were really quite soft. The one that links across from the chassis to the engine block was bery soft. So much so it could be seen to collapse when plenty of throttle was applied when in the workshop. All flexi pipes were replaced and hey presto problem solved.

Hope this helps.