Need Help, 73 911E will not run when warm

[Jackflash]

She starts great when cold. Once the engine warms up the engine dies and will not restart until the engine cools down. I am at my wits end! Does anyone have a clue?
Need Help

[Early_S_Man]

Jack,

Check your points.

[David E. Clark]

Jack,

This chart has helped me in the past:


© Up-fixin der Porsche, Volume IV, page 270 Posted here for educational purposes only.

[Grady Clay]

Jack,
Welcome to the Forum
You will find a lot of help here.

Does the 911 ‘progressively’ quit while driving a longer distance as opposed to just not re-start when hot? Is it more prevalent when warmer ambient? Is it more prevalent with less fuel in the tank?

If so, a not-too-unusual problem to investigate is your fuel pressure. That is easily done with a “T” fitting, a long length (10') of inexpensive hose from NAPA, some clamps and a 15-20 psi gauge. The T-fitting goes in the hose from the rear-most line from the fuel filter console. The long hose allows you to monitor the pressure while driving.

Make sure there isn't the slightest gasoline leak from your test set-up. Gasoline is probably the most dangerous substance you normally ever come in contact with. A burn injury is one of the most devastating.

What you are investigating is the common problem of fuel tank rust particles getting on the filter screen at the fuel tank outlet fitting. When driving (and getting the engine up to temperature) the particles accumulate on the screen. When stopped (and engine cooling off) they fall off.

If this is the issue, the fuel pressure will be normal when cold and drop to near zero when after driving and up to temperature.

If confirmed, the next test is to inspect inside the fuel tank through the fuel level sender port. Tale a long (2’) swab and see what is on the bottom of the tank.

If this is the problem , the cure is to remove the fuel tank for a through cleaning and possibly replace the screen filter.

There are other possible cause of this symptom but this one is common and easy to eliminate.

Best,
Grady

[Jackflash]

Thanks,

If the points are a problem, will the dwell change as the car warms up?

[Jackflash]

This diagnosis chart is a great reference. Thanks,

[Jackflash]

Thanks Grady,

I recoated the tank once but the car has sat for awhile. Because I let it sit to long is why I am having this trouble. I had to have the MFI rebuilt again and once I reinstalled the pump I started having this problem.

What should the pressure gauge read on the fuel line if the fuel pump is working properly.

I will also check the tank screen.

Is there a chance the fuel mixture on the rebuilt pump is too lean?

[Eagledriver]

The fuel pressure should be about 14PSI but the main thing is to look for a change as the engine warms up.

-Andy

[RSBob]

If your plug wires are old you may consider replacing them (old wires when hot increase resistance - and really old ones will make your car virtually undriveable). The cheap and easy way is to swap with some one and see if that's it.

[mobius911]

And another possible cause- I had a faulty CDI that only quit when hot.

Jeff

[69911e]

If it runs good then stops suddenly, check the ignition for spark when it stops hot. The coil or CDI could be at fault.
If you have spark, look at the fuel delivery system.
Ed