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post #1 of (permalink) Old 08-12-2019, 11:09 PM Thread Starter
Stevew
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Join Date: Dec 2003
Location: Carson City, NV Class Champion Reno SCCA 2018
Posts: 1,028
Angry No power to fuel pumps.

On the way back from Autocross Sunday, I was on a freeway when the engine stumbled briefly, resumed normal operation for a few seconds but then began stumbling again like it was running out of gas.

Made it to the next exit and within 100 yards of a station, the engine was struggling and finally died in a turn lane. Helpful passers-by pushed me to 7/11.

Tank had just been topped off in the morning but immediately after that restart, the fuel gauge, which had been at about 1/4 did not move from its lowest, parked position. “Hmmm, another issue to debug”, I thought. (A clue?)

Back to the original issue, with the help of another innocent bystander I was able to determine there was no sound from the main fuel pump and $5 of “desperation gas” didn’t help. The engine just cranked.

AAA to son’s house and I went back this morning to investigate further. Used jumper cables to directly power up the main fuel pump (connections off) and the engine fired and idled. Had to return home shortly but plan to return soon for further testing.

Main fuse under parcel shelf will be first suspect, but research indicates if that’s OK, testing relays and connections is next.

I know Alfa eliminated the firewall mounted, inertia switch cut-off switch at some point in production but those switches are available for $15 and I’m sorely tempted to confirm the in-tank pump is working, then simply power the main pump and in-tank pump (since they are connected together) through an inertia switch via a switched power source. I know this will operate the pumps continuously during “key on” (vs shut off till signal from ignition coil) but I don’t see why that is an issue. Obviously I don’t plan to leave the key on with a non-running engine.

No doubt Alfa engineers spent a lot of time designing our two relay safety system to disable the fuel pump in a crash, and it does power other LJet systems, but since I’m clearly missing something, why did they make it so fiddly? Other power through the relays is obviously present, since the engine started. Am I missing unintended consequences? Should I have not posted till I checked the main pump fuse ?

Also, I have yet to consult a schematic, but I wonder if my failed fuel gauge was a “preview of coming attractions” and I have more to be concerned with than just main pump power (relay failure?).

Jump in anywhere, gang.

Steve Waclo Carson City, NV; '87 Spider QV, ES Champion, 2018 Reno SCCA (125k);'93 Honda Nighthawk 750 (105k);'03 GMC Sierra SLE 2500HD Turbo Diesel (155k);'08 Altima Coupe 3.5SE, 6sp (125k)
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