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-   -   No power to fuel pumps. (https://www.alfabb.com/bb/forums/spider-105-115-series-1966-1994/684780-no-power-fuel-pumps.html)

Stevew 08-12-2019 11:09 PM

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 :smile2:?

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.

IRONBLOCK 08-13-2019 02:47 AM

Steve,

I am not familiar with L-Jetronic fuel systems but you should check all your fuses. My 1974 (Spica) Spider had a clogged rear fuel filter that showed similar symptoms. With the fuel line to the Spica off, the fuel pump would fill a peanut 'catch can' in a few seconds but the car would stall after running a while and not restart until the next day. I finally got a gallon jug to use as a catch pan. After pumping about a quart of fuel the flow just stopped -due to a clogged fuel filter.

Here are some L-Jet links to get you started:

https://www.google.com/search?q=Trou...hrome&ie=UTF-8

Mark

alfaparticle 08-13-2019 07:45 AM

I am no L-Jet expert either but I know that there is a relay that is held in by pulses from the ignition system which enables the fuel pump.

Stevew 08-13-2019 08:55 AM

Thanks guys, but remember, my engine did not cut off abruptly, as would be evidenced by a blown fuse. It sputtered and drove for about a mile before giving up the ghost. I don’t believe residual pressure in the fuel rail would permit such a scenario, but maybe I’m wrong.

At this point, I’d appreciate advice on a quick fix (jumper?) to get the pumps running so I may return to the comfort of my own garage.

Realizing of course, that a crash en route could result in fuel continuing to pump all over.

For now, I’ll look under the rear shelf and ID a source of switched power that I may drop through the floor to the pumps.

A half hour home, and diagnosis will continue.

alfaparticle 08-13-2019 09:51 PM

I am on vacation, away from electrical schematics. I know that on a V6 you can jumper a pair of contacts on the dual relay to make the fuel pump run whenever the ignition is on and I expect that you can do the same thing with your spider, even though the V6 uses a microswitch in the AFM to hold in the pump relay.

Philip Shanks 08-14-2019 04:15 AM

I had similar issues which took ages to diagnose. I suspected the relay, I even bought another one. The pump would work every time I looked at it, I even pulled it out to test and also hot wired the relay. In the end I notice the pump not making a sound at one point, so I hit it and it worked... Turned out to be a faulty pump. Nothing wrong with the relay. As with anything electronic, things fail and often they fail periodically. Try testing the pump, ill bet thats what the issue is. I put a new pump and filter in mine and have never had another problem. Now I have a spare relay and in 30 years when this one fails im all set!

Mario Romagnoli 08-14-2019 05:35 AM

Quote:

Originally Posted by Philip Shanks (Post 8453368)
In the end I notice the pump not making a sound at one point, so I hit it and it worked... Turned out to be a faulty pump.

Reminds me of a joke, referring to the old Spica fuel pumps mounted near the gas tank beneath the right rear fender on the early 105 Spiders.

Q.: Why are Alfa lug wrenches shaped like a hockey stick?

A.: So you can hit the Spica fuel pump without getting your clothes dirty!

65Sprint 08-14-2019 06:21 AM

Quote:

Originally Posted by alfaparticle (Post 8453314)
I am on vacation, away from electrical schematics. I know that on a V6 you can jumper a pair of contacts on the dual relay to make the fuel pump run whenever the ignition is on and I expect that you can do the same thing with your spider, even though the V6 uses a microswitch in the AFM to hold in the pump relay.

It has been awhile and I don't have a diagram handy but I think you can jump terminals 30 and 87 on the fuel pump relay (0280 230 001) to run the pumps whenever the key is on.

Stevew 08-14-2019 09:27 AM

Correctamundo on the two points to jumper, however my pumps don’t shut off with the key :(.

Gotta ID a source of switched power back there...

Working on it now.

Stevew 08-14-2019 10:35 AM

All better
 
1 Attachment(s)
Several years ago, I did some work on the fuel pump wiring (at the pump) and a connection I “repaired” then turned out to be the source of my current (no pun intended) problem. The ground side connection came off in my hand as I was making some checks.

I shall permit others to fill in the lessons learned here.

Ya know, at 75, I’m discovering I need to relearn lessons I should have learned years ago...

65Sprint 08-14-2019 10:51 AM

Good news.

6alfas 08-14-2019 06:39 PM

Quote:

Originally Posted by Stevew (Post 8453602)
Several years ago, I did some work on the fuel pump wiring (at the pump) and a connection I “repaired” then turned out to be the source of my current (no pun intended) problem. The ground side connection came off in my hand as I was making some checks.

I shall permit others to fill in the lessons learned here.

Ya know, at 75, I’m discovering I need to relearn lessons I should have learned years ago...

Glad to hear it. I hope I'm still fixing stuff at 75.


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