Car stalling AGAIN, Updates- none of them good. Options

[rjames]

Drove around for 30 minutes in 80+ degree weather. All arterial roads, so several stop lights, etc. No problems until I was almost home. Car stalled when I stopped at a light. RPMs just dropped to zero. Was able to start it again with a little difficulty and had to keep my foot on the gas to keep it from stalling out again. Power seemed ok though the rest of the way home (I think). It stalled once again at a stop light a couple of blocks from home and then again when I pulled in the driveway. I let it sit for 30 seconds, started it again and it idled just fine. Rock solid at 1000 RPMs. Pulled it into the garage where it sits now.

Prior to today the car has been running and idling perfectly since I went through the FI parts last year, which included installing a 123 distributor, new CHT sensor, a newly rebuilt mps (calibrated for correct afr on my engine), new vacuum hoses, NOS throttle body, rebuilt injectors, new fuel pump, valve adjustment and timing.

I haven’t checked the AFR since last year, not sure why it would change though.
It’s a ‘75 so the fuel pump is in the front, so I can rule out vapor lock I think.

Anyone have ideas as to why it would be stalling?

[rjames]

Ok, tried adjusting the MPS, but can’t keep the car running after it warms up unless I’m on the gas. Revs easily though.

Pulled vacuum on the MPS and it does leak. About 1 inch per 2 minutes. So that’s no good.
To make sure that’s the issue, if I disconnect the vac hose from the MPS the car will also stall.
Should it idle with the hose to the MPS disconnected? (Albeit maybe badly)
Actually, I just realized that if the hose was disconnected from the MPS it would think the car was WOT and flood it with gas which would cause it to stall, right?

I guess I’m rebuilding the MPS to see if that fixes the issue.

[BeatNavy]

Actually, I just realized that if the hose was disconnected from the MPS it would think the car was WOT and flood it with gas which would cause it to stall, right?

Yes. Do you have access to a spare MPS for testing? I've got a spare 043 I could loan if you need it. May take me a day or two to send. The alternative is to go ahead and drill this one out and verify a bad diaphragm and get the repair kit from Chris.

[rjames]

Actually, I just realized that if the hose was disconnected from the MPS it would think the car was WOT and flood it with gas which would cause it to stall, right?

Yes. Do you have access to a spare MPS for testing? I've got a spare 043 I could loan if you need it. May take me a day or two to send. The alternative is to go ahead and drill this one out and verify a bad diaphragm and get the repair kit from Chris.

That’s a very generous offer, thank you.
The MPS I have was already opened up and I have a spare rebuild kit for it. I bought it as a recalibrated unit from Jeff Bowlsby last year, but it still had the original diaphragm I think. If I can’t get it to seal after rebuilding it I may take you up on your offer.