924Board.org

exd · Joined: 04 May 2008 Posts: 26 Location: Prague

hi,
i bought 924 few months ago and now I'm having a fuel pump problem. the pump stopped working, so I bought a new one. but when i put it in a car, it was pumping fuel just for few seconds and now nothing. i can hear it running but no fuel goes out of it... it is possible that it doesn't work even if a can hear that it is running?

p.s. sorry for my english - i hope you understand..

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

Where are you watching for the fuel to come out? At the injectors? If so, it is highly likely that the fuel system is blocked or clogged somewhere between the pump and the fuel distributor. Best bet is start with the fuel filter.

Trouble shooting 101: start in the middle and eliminate one half of the system; take what's left, and start in the middle of that, and keep doing this until you find the fault.

e.g.
fuel tank -> in-tank pump -> external pump -> accumulator -> filter -> fuel distributor -> injector

If you get flow TO the filter but not THROUGH the filter, the filter is your problem.
If you don't get fuel TO the filter, it would have to be the accumulator, or one of the lines connecting pump-to-accumulator, or accumulator-to-filter.
If you get fuel THROUGH the filter, but not to the injectors, then it would have to be the fuel distributor, or one of the lines connecting filter-to-distributor, or distributor-to-injectors.

If there is a clog in the system, it's conceivable that it could have caused your pump to fail in the first place.

The other thing to verify is that you have proper eletrical to the pump itself, which is easy to verify using a multi-meter. If the electrical connections are in bad shape, too much resistance can result in not enough current to operate the pump at sufficient system pressure.
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erstwhile owner of just about every 924 variant ever made

exd · Joined: 04 May 2008 Posts: 26 Location: Prague

thank you for a quick answer..

sadly i tried almost all this. first of all i was watching fuel coming out of the fuel filter, but it was working just few seconds.. i took off the line connecting pump - accumulator and almost no fuel is coming out of fuel pump. i tried to connect the pump directly to the battery, so the wiring isn't bad. i can hear it running, but that's it. the fuel is coming through the pump, but at no pressure.
i still can't find out how the fuel pump actually works. i would like to know if hearing it rotating means that it is working or not.

Smoothie · Posted: Sat Aug 23, 2008 3:30 am Post subject:

Depending on year (put your model and year in the signature area of your profile), you will or won't also have an in-tank pump. In-tank pump working and external pump not working might account for low pressure fuel coming out. Hearing the pump is generally a good sign, but you don't know if it's just an in-tank pump you're hearing, or the external pump. A clog in the tank might cause the same symptom. Check for current at the external pump or/and touch it when it's supposedly running to determine if it actually is. If there's a clog in the tank, best get it cleaned out or you'll burn up the new pump.
_________________
"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

Smoothie · Posted: Sat Aug 23, 2008 3:32 am Post subject:

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

Yep. Works every time. It forces you to be systematic and methodical, and not take anything for granted. It helps to write stuff down as you go, particularly for large sets of variables, as there can sometimes be multiple minute problems throughout the system that aggregate into a larger set of symptoms. But I digress

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erstwhile owner of just about every 924 variant ever made

exd · Joined: 04 May 2008 Posts: 26 Location: Prague

i'm not sure if i have in-tank pump, but i certainly know that the external pump is doing something (?working?). if i touch it i can feel it running a i hear it as well. but the fuel is just going out of it at no pressure at all! it is just going through. nothing else.
the biggest mystery is that it was working for a minute or so... the engine started once.
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924, 1984, Europe version

Smoothie · Posted: Sat Aug 23, 2008 4:04 am Post subject:

I'd suspect a clog in the tank and start there. It's not as clever as a binary search, but better to prevent possibly burning up the pump. Presence of an in-tank pump is easy to determine - just look at the line where it exits the tank - there'll be 2 wires attached at either side of the fuel line if you have an in-tank pump. -And you should have one based on the model year = '84.
_________________
"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

exd · Joined: 04 May 2008 Posts: 26 Location: Prague

i tried to put fuel directly to the fuel pump, but it is not helping. it just go through.. i just don't believe that it it was new and working just for a minute.

is it possible to run the car with not-working in-tank pump?
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924, 1984, Europe version

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

Actually, the boolean approach still works here, because if the pump is barely dribbling and is new, then it must be upstream of the pump, which would indicate the tank, the internal pump (if there is one), or the line from tank-to-external pump

Re: the internal pump...just cuz there's electrical connections, doesn't mean the pump is intact...on one of the chassis I inherited, the previous owner had removed all of the internal components of the pump itself and just screwed the cap portion back onto the tank. Looked like it had a pump, but nothing there when I unscrewed it!

Anyway, it does sound like a occlusion upstream of the exterior pump.

(that's our vocabulary lesson for the day

)
_________________
erstwhile owner of just about every 924 variant ever made

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

exd · Joined: 04 May 2008 Posts: 26 Location: Prague

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

It might not be completely clogged...enough of an opening to allow some fuel to get through (hence the vocabulary lesson above...the occlusion connotes a partial blockage), but not enough flow to produce system pressure required by CIS. As far as I know, the only way to be certain is to drain the tank and inspect the in-tank pump. It's a messy job, but at this point, it seems like one of the few paths left to investigate (back to that binary method).

On that note, have you checked voltage to both pumps yet?

If your car is not a turbo car, you should be able to operate without the in-tank pump, provided you have a good working external pump that can produce 6.5 bar.
_________________
erstwhile owner of just about every 924 variant ever made

exd · Joined: 04 May 2008 Posts: 26 Location: Prague

yes. i checked the voltage and it's ok.

tomorrow i will inspect the in-tank pump and i will see..

last question from me.. can the pump not work when i hear it "working"? i would like to know how it looks inside to understand it..
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924, 1984, Europe version

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

Some helpful reading. I seem to recall a photo or diagram floating around either here on one of the other forums, but I can't locate it at the moment...
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erstwhile owner of just about every 924 variant ever made