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I took my 88 Alfa out for a spin this evening and as I was coming home the engine cut off as I was coasting up to a stop light. I rolled into the gas station nearby and tried to diagnose the problem. My first guess is the fuel pump but I could hear it cycle when I turned the key on/off. After sitting a bit I tried to start again and she started but cut off immediately. I got out of the car and opened the fuel tank and there was a substantial vacuum. Got back in the car and she started up without any problem. I put some more gas in just in case and she only took about 6 gallons. I drove home (about 2 miles) without any more issue and I could hear the in-tank pump running as well as the one under the car.

(Also of note, I had just driven on the interstate for several miles at 70+ mph and then the road where I stalled was around 50+)

Could too much vacuum be the culprit? I checked the one way valve when I got home but there wasn't any vacuum in the tank at this point.

Another also of note: I'm running a Megasquirt fuel injection system and I mistakenly had the logging turned off... so nothing to see there.

Thanks!
Adam
 

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Could too much vacuum be the culprit? I checked the one way valve when I got home but there wasn't any vacuum in the tank at this point.
That would be my first guess. There is a one-way valve and an air inlet valve inthe vapor recovery/tank venting system. They can get gummed up and act as no-way valves. Squirt some carb cleaning spray in them and blow them out until clear.

Another guess would be a failed in-tank pump or faulty stepped hose. When the fuel level is below ~ 1/2 full the main pump will struggle if the in tank pump is not supplying fuel. A faulty stepped hose will cause the main pump to suck in air when the fuel level drops.
1626119


1626120


1626121
 

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to test the intank pump
Lift the carpet and that rubber protection thing to get at pump spade connectors.

put a wire straight from the battery plus to the middle spade (that is the pink/white wire)
and from the battery negative to the separate ground spade (black wire)

you should hear it hum along nicely
 
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