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1985 Audi 4000S, Cranks but will not


Old 10-11-2017, 10:55 AM
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1985 Audi 4000S, Cranks but will not start -- UPDATE

Well Psparky and Rog and to anyone else who might be following this thread. Here is my situation as of today, 11 Oct. I did receive the replacement Fuel Pump Relay. I installed it and with some anxiety I tried to start the engine, but as I expected I got the same result as I have been getting since I began this adventure. I will admit guys, I am totally "STUMPED", There are no components remaining to replace, the Dist, the Ignition Control Unit (ICU), the ECU, the Coil, the plugs and wires are all new. I have pin to pin checked all wiring and find no opens or shorts or breaks. I am getting all required power at all units except on the HT side of the coil at the Dist connector. This was where I tried a jumper wire but that didn't work either. So I wanted to tell you guys what my next step will be, and if this plan doesn't work then my only other step will be to sell the car as is.
Here is what I am planning to do next. I plan to reinstall all the original components. Basically return the car to its original configuration like it was when I bought it. I will reinstall the original ICU, Distributor and Coil. Then try to start it. It ran when I got it so just maybe by returning it to how it was I can get an idea of what isn't working by replacing each of the original components one at a time (each time cranking it over to ensure it starts) with the newer parts until I find what part it is the engine doesn't like. Now if it still doesn't start even after I put in the old parts and try it, then I am back to that initial wiring mess that I mentioned I found in one of my original posts. So guys, what do you think. Any other suggestions? I plan to swap the parts tonight so I should have something to tell you guys by tomorrow.
Thanks for sticking this out with me and I really appreciate all the help you guys have provided up to now.....Karfreak
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Old 10-12-2017, 10:35 AM
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Success, Success SUCCESS!!!! Rog and Psparky and anyone else who has been following this thread. Well guys I did what I said, I began reinstalling the old parts beginning with the distributor then the cap and rotor, next was the coil and with each swap of a part, I would try the engine. But it wasn’t until I changed the new ICU with the old one that I began to get a positive response from the engine. Well it seems that the ground wire that goes to the ICU connector plug (on this Audi it is pin #4) is losing connection when the connector is seated on to the plug. You guys might remember in one of my earlier posts that I mentioned that I had seen this symptom before on a Triumph TR7. But that problem was a bit easier to locate because I could duplicate the problem by moving the distributor. In the Audi I found the weak connection when I decide to use a self-tapping sheet metal screw as a temporary fastener to hold the ICU to the car body. When I did this I accidently twisted the connector wires and this tightening of the wires forced the ground wire to reconnect to its pin. So what I did was remove the ground wire from the connector, install a new female connector end and the engine has been firing off with each attempt since.

Rog you may remember back when I asked about a miscellaneous wire that I found when I was trying to repair the radio harness. That wire was connected to a screw under the shift lever in the counsel. Apparently that wire was somehow completing the circuit and providing the ground for the ignition system. I am sure that whoever added that wire didn’t know what they were doing, it just happen to work. SUCCESS, thanks guys for all you support. This is one for the record books. I’ll post pic’s of the car as soon as I get her road worthy.----karfreak
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Old 10-12-2017, 05:35 PM
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Very interesting. I'm glad you got it figured out! I've been busy and sick so I haven't been doing much car stuff.

Reminds me a bit of when my mom first got the '84 that I have now and the stereo would cut out randomly. Took forever to figure out that the antenna was loose and for some reason that was part of the ground for the radio. Sometimes it's those stupid little things that get you.

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