No voltage at in tank pump?

1466 Views 11 Replies 6 Participants Last post by zahniser, Apr 19, 2011

zahniser

Discussion Starter · Mar 27, 2011

Hello,

New to the list and alfa's in general. I have been lurking on the list for a little while. I picked up a '87 Quad last fall and with the weather getting nicer, I am beginning to sort it out.

I am currently troubleshooting a starting problem that I think is being caused by a lack of fuel to the engine (cranks but doesn't fire) and the spark plugs are completely dry.

I had just replaced the fuel hose on the low pressure side of the high pressure pump to address a problem of poor gas mileage... (drip, drip, drip). It started right up after that and I drove it two miles before it died and hasn't started since. The replaced fuel line looks ok (not pinched on the bends)

When I turn the ignition on, I can here the relays click, but I don't hear the fuel pumps spinning. I have the great Papajam wiring diagram, and have replaced the fuse next to the ECU. It looked fine, but just to be safe. There is power through that in-line fuse. Battery voltage looks OK (12.6V and 10.9V when cranking).

There doesn't appear to be any power at the in tank pump (no voltage on the pink/white wire). I assume that there should be power there when the ignition is on to run the pump. When I apply power directly to the wire in tank pump (in the tank), it seems spins just fine so I think the pump is ok.

Is it safe (only as a test) to jumper around the drive relay (fuel pump). Is there another way to test the relays or is there something else I am missing? Thanks for any guidance.

Jim.

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racer1958

· #2 · Mar 27, 2011

If I remember correctly, the pumps will only quick on when the AFM opens up due to the engine turning over.
Disconnect the air hose from your AFM, with ignition on, and prop open the the AFM gate. You should hear both pumps turning on.

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Tifosi

· #3 · Mar 27, 2011 (Edited)

AFM doesn't deal with fuel in the spider L-jet. (it can be completely unhooked and the pumps will still function)
Startup/cranking bypass circut and pulse signals from the coil to the tachymetric drive relay when the engine is running is what activates them in the spider version.

I seem to recall that papajam found if the ground wires on the AAV mounting studs were disconnected, the pumps would run continuously when the key is on regardless of the start circut or coil pulses. Don't quote me on that, but I'm fairly certain that he accomplished it on his monopod S3 while fiddling about with stuff one day.

In any event, if all is proper, ya, they aren't going to run more than a half second or so each time the key is turned from off to on.
One could disconnect a feed line at the injector rail and flip the switch a few times to see if fuel comes up, or, just crank it with a line undone. (all provided you have a safe means of catching and containing any fuel that does flow of course)

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papajam

· #4 · Mar 27, 2011

The fuelpumps receive power only when;

A) the starter is engaged or
B) the engine is running

The easiest way to check if the main pump is running is to listen/feel the pump while someone cranks the engine. If no go, test for voltage at the pumps while cranking the engine.

Have you checked for spark and/or cranking voltage?

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ghnl

· #5 · Mar 27, 2011

10.9V during cranking should be OK but it is on the low side. Our Spider shows 11.6-11.8V during cranking. First thing I'd suggest is to clean all electrical connections between the battery & the starter. While you are doing that put the battery on a charger.

It is imperative that you check for spark. (remove one of the spark plug wires, connect it to a spare spark plug, ground the threaded section and have your trusted assistant crank the engine while you look for a snappy blue spark) Obviously no spark = no start but the drive relay is also expecting a tachymetric signal via the coil sense wire to know it should send power to the fuel pumps. Thus no spark also = no fuel. (That is considered a Good Thing in the event of an accident where the engine stalls.)

Don't forget to post some photos. We likes photos. Of your Spdier is good. If there a pretty woman in the picture that'd be even better.

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zahniser

Discussion Starter · #6 · Mar 27, 2011

Thanks. That makes sense why there was no power with just the ignition on. The cranking voltage at the battery is ~10.9V but only ~9V at the in-tank pump (and is fluctuating pretty wildly). As you said, there is power at the pump when the starter motor is engaged.

I will recharge the battery just to be safe. It looks to only be 2 (or 12 years) old. It looks new so I suspect 2 years.

Spark looks good. I did replace them with fresh plugs to error on the side of caution. The engine runs very rich and quickly fouls the plugs (with black carbon soot). I was getting ready to work on that problem when the new one surfaced.

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ghnl

· #7 · Mar 27, 2011

Peruse the Spider L-jet diagnosis page. I suggest you go through all the steps. L-jet is a system - all the bits have to be 100% for it to work well (or at all). The most common issues confounding L-jet Spiders are iffy electrical connections (including & especially grounds) and intake air &/or vacuum leaks. The 'L' in L-jetronic refers to the German word 'Luft' (air). L-jet has to measure all incoming air (via the Air Flow Meter) to properly meter fuel injection. 'False Air' (intake air or vacuum leaks) mess with the AFM's measurments leading to erroneous computer outputs (GIGO).

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zahniser

Discussion Starter · #8 · Apr 8, 2011

Starting for a few seconds... then not

Hello Alfa Intelligentsia,

Continuing to follow through this thread. I have gone through most of the Spider L-jet diagnosis page with no clear cut issues. The air and various sensors seem to be all testing out fine; but, I suspected the cranking battery voltage was too low. I still need to to do fuel pressure test this weekend after picking up a test guage for it.

We have an new development after some part replacements (and copious grounds scrubbing). Now, the car starts and runs for few seconds before conking out. It will not start again until the next day (or so...day job, only an hour or so a night to play). It still seems like the engine is not getting fuel after the initial start. It is my understanding that the fuel pumps are triggered from the negative side of the coil (is tachometric really a word!?!) The tank and main fuel pumps seem to spin fine but I won't know the effectiveness until I have a fuel pressure guage....

At this point, we have replaced the various fuses, battery, plugs, rotor, and distributor as these were of unknown origin/quality. The coil _seems_ to test out fine from a voltage perspective. I am waiting on new wires to complete the ignition side inside the engine bay. I also have a fuel relay on order but I fear I am grasping...is the ECU next... Suggestions?

Thanks.

Jim.

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Tifosi

· #9 · Apr 8, 2011 (Edited)

Tachy: swift/rapid/consistant/cyclic pulses/ticks/noises/etc (woodpeckers make a tachy noise when tapping a tree)
Metric: monitor/meter/measure/count

Tachymetric: device with ability to measure/monitor/count or react to consistant pulses/ticks/noises/etc, such as the rythmic feild collapse of an ignition coil.

Simular device operates the electric tachometer gauge in the dash, but that translates it into a needle movement over a scale rather than converting it into an electrical relay switching function.
Same premise though: meter for the presence of pulses, and then make something happen because of them.

Oh, and while cleaning connections and such, have you pulled apart that one on the single white wire on the firewall between the wiper resevoir and the hood latch and cleaned hell out of it?
(might be a white into white or a white into a black, I don't recall right off, but it'll look really out of place for its location regardless)

If present, that's where the inertia switch would have been on older models, and where they jumpered past it due to the upgrade the L-jet offered.
(no need for it anymore as the tachymetric relay delt with shutting down fuel flow in the event of an accident)

If its grody or poorly connected you 'could' get symptoms of start no run as you describe.

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ghnl

· #10 · Apr 8, 2011

zahniser said:
I have gone through most of the Spider L-jet diagnosis page with no clear cut issues.

As mentioned, L-jet is a system and all the parts have to be working for it to work.

...the car starts and runs for few seconds before conking out.

The good news is that would seem to indicate that the ignition system is working and it is likely the fuel pumps are working OK.

My next guess is that the fuel pumps are getting power during cranking but not after the engine starts (when the key is released from 'start' to 'on'). There is a start signal via the ignition switch that bypasses the drive relay. Once the engine starts & the key is released to the 'on' position that tachymetric signal from the coil is supposed to trigger the drive relay to keep the fuel pump powered on. So, either the sense wire could be faulty or the drive relay could be faulty (or both).

Alternatively, the engine might be starting on fuel from the Cold Start Injector (CSI) - which would normally squirt for only a few seconds then not squirt again until the Thermo Time Switch (TTS) has cooled off enough to again allow power to flow to the CSI. Since the cold start system (CSI & TTS) is a stand-alone system (no computer interaction/control) those symptoms do not rule out a faulty computer...

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sloboy89

· #11 · Apr 8, 2011

zahniser said:
We have an new development after some part replacements (and copious grounds scrubbing). Now, the car starts and runs for few seconds before conking out. It will not start again until the next day (or so...day job, only an hour or so a night to play). It still seems like the engine is not getting fuel after the initial start. It is my understanding that the fuel pumps are triggered from the negative side of the coil (is tachometric really a word!?!) The tank and main fuel pumps seem to spin fine but I won't know the effectiveness until I have a fuel pressure guage....

This sounds a lot like a problem I had several weeks ago. I thought that both pumps were working, but in fact, only the in-tank pump was working. I got a pressure guage and found out that the pressure at the fuel rail was virtually nil. Presumably, the in-tank pump was able to get enough fuel into the line to cause the engine to turn over, but obviously could not provide the fuel necessary to run the engine. After doing everything that you've done, I replaced the main pump, and it has not had a (fuel-related) problem since.

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zahniser

Discussion Starter · #12 · Apr 19, 2011

Just too close out this topic. Rich was right. The core issue was the main fuel pump. The fuel pressure at the rail was 0... I didn't believe the gauge, so I left the hose open expecting fuel to squirt when I cranked, but nothing.

The pump made a click sound when power was first applied to it, but no continuous sound even when power was applied directly to the pump.

Starts right up with the new fuel pump. Thanks to all for the assistance in diagnosing.

Jim.

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