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1985 Audi 4000S, Cranks but will not

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Old 07-12-2017, 09:54 AM
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Default 1985 Audi 4000S, Cranks but will not

Just acquired a 1985 Audi 4000S, in pretty good shape, needs lots of TLC. Battery kept dying and I found that the radio was wired wrong and was draining the battery. Removed the radio. Then I installed a new Dist Cap and rotor, new coil, new Sparkplugs, changed the coolant and the Cooling Fan Thermostatic switch. After all was completed, sat in the seat, turned the Key and the engine will turnover but it will not fire, no power at the + side of the coil. Is there something in the radio circuit that must be connected before the car will start? The radio is still out and the wiring has been returned to factory. Does anyone have any thoughts? Thank you all
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Old 07-12-2017, 03:06 PM
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Does the fuel pump turn on while cranking (and or "prime" when you first turn the key)? Have you tested to see if there's spark during cranking?

-Rog
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Old 07-13-2017, 04:16 AM
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Originally Posted by Rogviler View Post
Does the fuel pump turn on while cranking (and or "prime" when you first turn the key)? Have you tested to see if there's spark during cranking?

-Rog
Hi Rog, thank you for your response. The fuel pump does prime when I turn the key and then I made sure the fuel was being delivered to the injector.
I did test for spark and have none at the plugs. So I used a meter and began tracing power backward and learned that I have now power coming to the coil on the positive (battery) side of the coil.
The car ran perfectly fine (just needed a tuneup) when I picked it up and drove it home. The only real issue was the Radio (not factory). The guy I bought it from told me that the radio never turns off and over a couple days it'll kill the battery. To me that is a pretty easy fix, so I removed the radio to look at how the radio was wired and found a huge mess of splices and jumpers and elect tape. At this point I decided to trace the wiring and return it to factory and soon purchase a replacement OEM radio. At this point the radio is out and disconnected.
After I return the wiring to close to factory, I did not try to start the car, I decided to do the tune up right away. As I mentioned the tune up was simply parts swap.
So I am curious if anyone might know if there is possibly an early type factory antitheft system or if there might be an issue with a main ground wire that requires the radio to be installed?
Soory Rog that this answer is soo long, but I thought that maybe more detail would be helpful for the Audi experts. Thanks for anything you can suggest......
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Old 07-13-2017, 04:43 AM
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Hello,

just install a wire from the battery to +15 on the coil and see what happens. If it runs, trace the wires back and find your problem.
As you mentioned you might have some crap installed that needs to go and get it back to the original wiring.
Good luck,

Ciao

Werner
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Old 07-13-2017, 05:08 AM
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Originally Posted by wego0002 View Post
Hello,

just install a wire from the battery to +15 on the coil and see what happens. If it runs, trace the wires back and find your problem.
As you mentioned you might have some crap installed that needs to go and get it back to the original wiring.
Good luck,

Ciao

Werner
Howdy Werner, a jumper wire great suggestion. Don't know why that thought didn't enter my mind. I'll certainly try it. As a matter of fact I'll give it a test over my lunch today.
Thank you for the idea....more to follow.....Karfreak
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Old 07-13-2017, 06:54 AM
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Interesting. I wouldn't be surprised then if whoever installed the radio completely didn't know what they were doing and got their power from places they shouldn't have. Hopefully you're on the right track.

-Rog
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Old 07-14-2017, 05:58 AM
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Hi guys, well I did run the jumper wire and that didn't work. So just to be sure of what I had for power in the system I metered at the Coil w/key on and got 12V on the 15(+) side and around 9 on the 1(-) side. Probed at the Distributor connector and have 10 Volts there. But no spark. I pulled a couple plugs and found them to be wet so gas is flowing.
My assessment, the Ignition Pickup has failed.\
What are your thoughts guys? Thanks again for all your assistance....Karfreak
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Old 07-14-2017, 10:36 PM
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The ignition pickup (usually referred to as the Hall sender/sensor on these) also controls the fuel pump relay, so if your fuel pump still works then the sender is fine, which is why I asked.

I'll have to look at the wiring diagrams for a bit and see if I can come up with another suggestion, although if the wiring's been altered that much it's going to be tough.

-Rog
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Old 07-16-2017, 03:00 AM
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Originally Posted by Rogviler View Post
The ignition pickup (usually referred to as the Hall sender/sensor on these) also controls the fuel pump relay, so if your fuel pump still works then the sender is fine, which is why I asked.

I'll have to look at the wiring diagrams for a bit and see if I can come up with another suggestion, although if the wiring's been altered that much it's going to be tough.

-Rog

Thank Rog for anything you can offer. Yesterday I purchased a Haynes manual because I think I need to see a wiring diagram also. I'm not that good with them and not familiar with Audi's so anything that the experts can offer I will gladly absorb and use. Thank you again for checking back on this issue....Karfreak
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Old 07-16-2017, 08:19 AM
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I would probably focus on this area:



Just make sure it all matches and nothing is cut. Without seeing it in person it's hard.

-Rog
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