Motor won’t stay running

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moparhunter

moparhunter

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Hi All, bit of an odd question, but I’m gonna put it out there for thoughts. I recently freshened up a 400 that I have fired up on the floor. ( with a rad, of course.) the purpose of it starting on the floor was to make sure there’s no rear main seal leak before it goes in the car. It’s running on a points distributor. It’s a mild motor with camshaft / steel crank / ported 906s in it. Lots of oil pressure. It starts pretty quick. ( I haven’t timed it yet. ) but it only wants to run for a few seconds and then it shuts off. I’m thinking condenser has gone bad or possibly a ground. Anybody got any other ideas? I don’t believe it’s fuel related as I’m using known good carburetor. The most it’s probably run at this point is 30 seconds. Don’t worry it’s a used cam that’s not an issue.
 
Get a squirt bottle and dribble fuel into the carb venture while it's running. If it runs longer it's carb related. Or big vacuume leak.
 
What makes you think it's ignition related when you clearly have pretty much diagnosed it as a fuel problem?

"Soon as it dies, I give the carb a pump and it fires right back up"

Usually, a bad condenser won't run at all.
 
If the carb idle cir is not working properly exactly what you describe can happen.


moparhunter said:
So far, I can’t keep it running long enough to grab a squirt bottle
Click to expand...
Have some one else start it. While you stand ready with the squirt bottle.

Also just because it was tuned to run on another engine does not mean it's tuned to run on this engine.

I hope you find the issue.
 
It sounds like an idle circuit problem, open idle screw a 1/2 turn and set mixture screws a a 1 1/4 turns open. see what ya got.
 
How do you have it wired up? How do you start it? Jumping starter or is a key switch and ballast resistor wired in?

A stock points mopar will do this wil a bad ballast resistor, starts fine and dies when you release the key.
 
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Do you have the vacuum advance hooked up. If you do disconnect it. Try that.

Timing could be changing when it starts.

Could it be the points are not closing at rpm speed due to a weak spring.

Disconnect the condenser you don't need it for it to run. It is only there to stop the points from getting hot over time. I have seen bad condensers do this.

Are you using a Big Block points distributor.

Post a picture of your set ip to run the engine.
 
413 said:
A stock points mopar will do this wil a bad ballast resistor, starts fine and dies when you release the key
Click to expand...

Good thought. And good question.



OP says it will run for 30 seconds but maybe that's with the key in start?
 
Here is my run set up

image.jpg
 
So the motor is still on the run stand?

And will only run for 30 seconds

Do you have a ballast resistor?

I can't see the coil overheating in 30 seconds but who knows.
 
No ballast resistor . I just plug in a were directly from the positive battery to the coil. I have tried two different coils
 
Try with a ballast. The coil could be overheating. Most coils are not designed to run on straight 12 v at idle.

But I doubt it's the problem
 
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