Audi 100 no start

Hi there,
My C4 AAR 2.3E 1991 Audi 100 refuses to start after being totally OK the day (and many years) before. It cranks OK. Battery is fully loaded.
I've checked the ignition (coil cable sparks 15 mm against motor bloc, plugs spark). Seems thus OK but I do not know if the timing is OK though. I suspect the fuel pump relay (I hear the pump running for 2-3 secs every time I turn the ignition key, then it stops). I want to bridge this relay to prove the point. Where is it in this model ? It is not in the big fuse box in the bonnet (almost empty if you except the "retarded fan relay"). And, by the way, where is the pump ? Not under the back seat, in either case. Thanks for any help !
Flipflup
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Fuel Pump relay would have been my first guess but you say that you hear it running for a few seconds when the key is first turned. That is what it should do. It runs until it reaches the correct pressure then stops. I am quite sure that it would not run at all if the relay were bad. Still worth a check.
You can use a jumper to connect the large holes if the relay socket to eliminate the relay as the problem.
Relay is in the main fuse box by the drivers side hood hinge. Some of the years do not have the fuse position in the top of the relay.
Check your fuses too as there should be one for the fuel pump in addition to the relay. Still if it cycles when you turn the key they should be fine.
Other than the relay there can be a number of things to cause a no-start: - Bad ignition switch - sticking air plate in the fuel distributor - vacuum problems - non-functioning cold start injector or its temperature sensor - compression problems
Check to see if you can see fuel one spark plugs after trying to start.
Tony '91 100q 5spd '98.5 A4 1.8TQ 5spd
Flipflup wrote:

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Hi Tony,
Thanks for the hints !
Your suggestion #2 was the right one (sticky air inlet platter) !
By the way and for future documentation: when you say that the fuel pump relay is in the main fuse box, do you mean behind the fuses cluster at the driver's side (continental Europe)of the dashboard or somewhere between the pedals and the door hinge ?
All the best !
Philippe

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I have owned four T44s (84 - 91). The 87 and 91 have both a relay and fuse for the fuel pump in the main relay box that is located under the hood by the hood hinge and just in front of the windshield.
IIRC the 84s seemed to only have the relay.
Hope you got it running.
Tony
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On 17 Mar 2005 00:26:15 -0800, snipped-for-privacy@hotmail.com (Flipflup) wrote:

Oil vapour gets to it through the various hoses and eventually it gets sticky - the symptoms are an uneven idle.

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wrote:

Where do I find it and how do I get to it. It seems I should check mine before it fails completely.
Christoph
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If you remove your air filter you can reach up into the fuel distributor and you will feel the plate. It should lift quite easily and return when you drop it.
If it doesn't move easily it could be binding ad affect mixture, idle and possible no-start condition.
Don't force it.
If you are having a similar problem this could be something to look at but other things can also be involved.
Tony
Christoph Bollig wrote:

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Thanks will try it.

I haven't got a no-start problem, but idle is sometimes iregular (not always) and I recently checked the current into the idle stabilisor valve. In addition, it seems to be slightly down on power, but I am not too sure. Will see how the fuel consumption is when I fill it up next time.
Christoph
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