A100 No start / Timing oddity

Sorry for posting here, but I seem to have exhausted the Audi forums for help on this one. The primary question is of a general nature though...

What problem can be overcome by advancing the timing?

Background: Patient is a 1988 UK Audi 100 (with 2.0 5-cyl RT engine, K-Jetronic) which broke down 2 months ago. It is extremely difficult to start. If I can start it, then it will run for about 10-15 mins then cut out. Difficult to restart if turned off. Not driveable as stalls too easily. I can't find anything wrong aside from the symptoms. I have swapped the warm-up valve, fuel distributor & ISV for known good ones but no change. Cold start valve ok, idle switch ok, no vacuum leaks found. Plenty of fuel getting to the fuel distributor. Hall sensor ok - anyway I always get a spark.

Recently I checked the ignition timing and made an interesting discovery.

18° BTDC is the standard figure but I'm using regular unleaded for which I believe the timing should be 8° BTDC. However, I found that by advancing the timing to about 30° BTDC it will start on the 2nd crank instead of about the 30th! Initial testing suggests it's much less likely to cut out. Cam timing seems in order and all my TDC marks line up together.

Can anyone explain what's happening?

Thanks, Gary

Reply to
Ovalking
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compression fuel ign

Are you sure the cold start valve is functioning properly? I just had to repair wiring at the starter for an 85 Audi 5000S. Cold start valve was not getting energized by the starter.

I have also seen timing belts on an Audi 5000 go bad in such a way that the teeth were somehow crushed. The engine would start sometimes and sometimes not. When it didn't the engine sounded like it had no compression for a few revolutions and then the compression would return. New timing belt solved that problem.

I have had to repair the crank sprocket on one Audi 100 that lost it's key due to it's bolt loosening up.

On the Audi 4000s some people remove the FI fuse and have problems starting or keeping the engine running. Not sure on your model though.

just throwing out ideas. good luck and let us know what you find!.

later, dave Reminder........ Before you criticize someone, you should walk a mile in their shoes. That way, when you criticize them, you are a mile away from them, and you have their shoes. Frieda Norris

Reply to
dave

You say that "plenty of fuel is getting to the fuel distributor". What do you mean by this? Have you put a pressure gauge on it? Your symptoms sure sound like low fuel pressure to me. I'm sure you have replaced the fuel filter (right?)

Just throwing out suggestions. Used to drive an 81 Audi 5000T. Used to wrench at a VW dealership, but don't hold that against me :)

Reply to
noone

I used to have one of these, an '87 with the 2.0 five cylinder engine, and I too started using standard unleaded, but I found that I didn't have to do anything much to the ignition timing to prevent pinking. It was always a 5 to 10 second crank time to start, so thats normal. If you need to set a static 30 deg BTDC timing to get good starts, that suggests the distributer advance / retard is not working/ jammed or that the cam timing is out. Check that belt out first, anything else can be repaired, but a wrecked engine is bad. With a basically correct setup, I found that tweaking the idle mixture helped a little with cold starts. Have to tweak it back for the MOT though! Not a great system, especially on older cars. Great car, lousy fuel injection system!

Reply to
Laurence D'Auvin

Yes, have monitored the voltage and fuel comes out at the right time.

Visual inspection suggests no problems.

No evidence of this - all TDC marks line-up. (Mine did come loose though

- accidently left a spanner on it when cranking :-)

Fuse present and correct!

no>You say that "plenty of fuel is getting to the fuel distributor". What do

I did a fuel volume check (about 1.5 litres in 40 secs) so ruled out pump (70000 miles) and filter (7000 miles). Don't have a pressure gauge but after replacing fuel distributor and warm-up valve didn't think it necessary. Injectors could be leaking but this doesn't match the symptoms.

snipped-for-privacy@landrover.com.>suggests the distributer

Some other people have suggested the distributor but I haven't understood why this could be. Is 30° normally required for cranking and then the distributor retards it to 8° as it gets up to idle speed? Timings were measured with strobe focused on flywheel. Belt looks fine. I don't think mixture is an issue - my 'replacement' fuel distributor is known good with unleaded.

I have wondered whether the fuel is dodgy, not sure how it could be tested though.

Thanks, Gary

Reply to
Ovalking

After cranking it and it doesn't start, remove a spark plug to see if there is fuel present on the tip. If No Fuel......... We have already discussed good NEW ign parts like a Bosch cap and rotor and it runs well when it does start? Is the spark at the plugs very strong while cranking it? Spark plugs are what brand and type? IIRC they should be Bosch either W7DC or W7DTC?

Has this problem always been there since you owned this vehicle? Did you just buy it?

Hmmm I thought your Fuel Injection system did not have a "Warm-Up Valve"??? It should have a Fuel Pressure Regulator, Idle Valve, and Coolant Temperature Sensor to name a few components. Did you check/measure the Fuel Distributor Flap's resting position?

Pressure gauges are nice to have. ;-)

later, dave Reminder........ Before you criticize someone, you should walk a mile in their shoes. That way, when you criticize them, you are a mile away from them, and you have their shoes. Frieda Norris

Reply to
dave

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