Start / stall issue with '93 v8 quattro
07-25-2010, 07:00 AM
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Start / stall issue with '93 v8 quattro
I haven't pulled any codes yet but was wondering if anyone knows what could be causing this problem. The car sometimes wont start when warm only,it just cranks. If I wait a 5 minutes and try again it starts right up. When at a light and it turns green and I push on the gas it dies. Happened several times already. The starting issue is only when the engine has been driven and the engine temp. is normal. The intake gaskets are new, there are no vac leaks, the starter is 2 years old and the fuel pump was replaced about 4 years ago. Any ideas? Is there a fuel pump relay? Can it be bench checked? Can the fuel pressure reg. be bench checked? Thanks.
07-25-2010, 11:35 AM
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Classic problems with the V8, either crank positon sensor or rpm sensor is going bad. When you can't start the engine; crank it and watch the tach to see if it bounce. If it doesn't bounce then the rpm sensor is bad. If it does bounce and the engine still doesn't start then it is most likely the crank position sensor. Do a search for crank sensor and also rpm sensor, this topic is pretty well documented. You can also pull the DTC codes; it will tell you which of the two or both signals are missing.
Last edited by audiqv8; 07-25-2010 at 11:56 AM.
07-25-2010, 07:23 PM
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There is a test you can do with an ohm meter described in any Type 44 Bentley to check the condition of these sensors.
However, on a V8, the connectors you need to access to do the tests are so buried, you might as well pull the sensor completely to do the test.
However, on a V8, the connectors you need to access to do the tests are so buried, you might as well pull the sensor completely to do the test.
07-26-2010, 09:35 AM
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OK It would not start again today when engine was hot and the tach. only bounced one time. Is it supposed to bounce alot while cranking or just once? When I turn the key to start it the tach shows one bounce and the engine just cranks with no start. do you have part numbers for the RPM and crank sensors?
07-26-2010, 01:05 PM
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Actually the tach only bounced one time when I turn the key to on position. It does not bounce while cranking the engine. Is that a sign its a bad rpm sensor? Also where do I find these sensors on the engine?
07-26-2010, 01:27 PM
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The tach should bounce while cranking. Since both these sensors are magnetic, it might be wise to replace both of them.
https://www.audiworld.com/forums/sho...5&postcount=16
Last edited by audiqv8; 07-26-2010 at 01:36 PM.
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07-27-2010, 05:37 AM
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One guy's version:
http://www.audifans.com/kb/V8_No_Sta...ailing_Sensors
The sensors themselves are the same from the 5KTQ models through the 200s and V8s. Only the wiring differs (in color and length). So you can use a much cheaper 5000/200 sensor with the longer wires as long as you direct the wires to their connectors so that they cannot contact the exhaust system. I see those advertised on Fleabay occasionally.
For me, with short/fat arms and a bit too much stomach in front, the best access to the sensors was from below. First time I did these on a V8 I used a 10 mm open end wrench with a longer 10 mm box end taped to it to break the shield bolts loose and then a 1/4 inch drive ratchet to get them out. Now I've got some gearwrench-type tools.
Not a lot of fun with all that exhaust spaghetti in the way. The mention in the Audifans piece about bruised knuckles applies.
http://www.audifans.com/kb/V8_No_Sta...ailing_Sensors
The sensors themselves are the same from the 5KTQ models through the 200s and V8s. Only the wiring differs (in color and length). So you can use a much cheaper 5000/200 sensor with the longer wires as long as you direct the wires to their connectors so that they cannot contact the exhaust system. I see those advertised on Fleabay occasionally.
For me, with short/fat arms and a bit too much stomach in front, the best access to the sensors was from below. First time I did these on a V8 I used a 10 mm open end wrench with a longer 10 mm box end taped to it to break the shield bolts loose and then a 1/4 inch drive ratchet to get them out. Now I've got some gearwrench-type tools.
Not a lot of fun with all that exhaust spaghetti in the way. The mention in the Audifans piece about bruised knuckles applies.
07-27-2010, 01:06 PM
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OK it says I need a LED test light to pull codes. Where do I get one of these? Or can I make one? what wattage bulb do I need to make one up myself? Radio Shack carry these LED test lights?