Karfreak905

Thanks for the schematic pic and the advice Rog.
Tomorrow (Wed 19 Jul) I will be back to the Audi to work this issue. I agree with you that the problem rests somewhere in the area of the Ign Control Unit. I have pretty well convinced myself that there is something about the mess of wires that came out attached to the radio. Because the Ign Ctrl Unit is behind the Glovebox I feel that when the previous owner added his own "home made" radio harness that he may have some how tapped into the wiring for the Ign Ctrl Unit. And when I began my attempt to undo and return to factory the wiring that I may have disconnected a wire that services the Ign Crtl Unit. So it appears that you and I are thinking alike. I'll have an update for everyone by Thursday the 20th. Thanks for the help....karfreak

Rogviler

Hmm, in fact now that I think about it, it would be very tempting to run a stereo off of fuse #24 (the one off to the side by itself in the fuse box), which powers the ECU. It's been awhile, but I think it's a blue and black wire. Anyway, that may or may not be the one, but it's along the lines of what probably happened.

At any rate, good luck!

-Rog

Karfreak905

Hello guys, I know it has been a while since I last wrote a progress report but sometimes daily life stuff takes priority. So here is the point I am at with the car.
I replaced the Distributor because the original had a broken connector and the internal components were hugely corroded. Unfortunately the new Dist did not solve the no start problem. Next I spent several hours metering all the wires under the counsel / instrument panel and rewiring things back to original configuration. The radio now works as it was designed. But, this did not solve the no start problem, so using the schematic that Rog provided and a Haynes manual metered all the ignition wiring. I removed the glove compartment to get to the ICU and Hall Generator connectors and I found that the car does not have a Hall Generator. Apparently that unit was removed and by-passed sometime over the cars lifetime. But I did order a new ICU, since that seemed to be the only item left in the ignition system that hadn't been replaced. At this time the ICU has not been delivered. In summary guys at this point all wiring under the dash ( that was modified in the past) has been returned to factory. The Radio now functions without draining the battery. There is a new Dist, Cap/rotor, Spark plugs, Coil and today the new ICU should be delivered. I am worried that the ICU will not solve the problem but I cannot see anything more that could be causing a problem. Later today (I'm EST) I will provide another update once the ICU is installed. Again thanks to all for your help. More to follow....Karfreak

Karfreak905

Just returned from my house. I installed the new ICU, turned the KEY and still nothing. Now I'm running out of ideas. I'm getting fuel, I checked the mainline coming to the fuel regulator and at the injectors. I pulled number one plug and it was wet. Looks like gas is flowing. Next I decided to temp install the old Ign Coil just to see if maybe the new one isn't working but that little test didn't work. As a reminder guys before I removed the old radio (which was hot wired and killing the battery) the car was running fine. I had ordered the tuneup parts and while I was waiting for them to be delivered I decided to do a very simple (so I thought) radio exchange. So I pulled the old radio out and found the huge wire mess that the previous owner had created. As a side note, after I pulled the radio I did not attempt to start the car. I didn't really see a reason to run it. Well while the radio was out, the tune up parts arrived so the next day I installed the plugs, cap/rotor, and coil. I then tried to start the car and this is when the car began the "Crank, but no start" issue. But changing the basic parts should not have created this situation. Yesterday I installed the new distributor (electronic pickup) that I ordered because the old one had a broken connector and it might be causing the problem. NOPE! Today I installed the new ICU and still no spark. If this were a breaker point ignition I'd be checking the points for short to ground. So just now I went back to the schematic that Rog provided and I think that I might try to run jumper from the coil (dist side) down to the Dist connector. What do you guys think? One final thing...today while I was attempting to start it...I noticed that the TACH is not working and it was working before. If the TACH is connected like any other (electronic) TACH, then I have to assume that of the 3 leads in the Dist connector one is TACH and one is input from the coil. What do you guys think, is the plug that connects to the distributor possibly bad? Also I did pull every fuse just to be sure that I didn't have any bad/blown fuses.
Thanks again for all your help guys....Karfreak

Karfreak905

Hello everyone,


Well over the past few days I have continued to trouble shoot the Audi's no start problem. I thought I'd provide a summary of everything that I have done with this car. I will start from the beginning and bring you all up to the point that I am at. About three weeks ago I brought home a 1985 Audi 4000S. The car was running and I drove it home. The only issue that the person I bought it from told me about was that the radio was draining the battery. Once I had it home I gave the car a thorough look over and decided that I will purchase the basic tune-up parts and do the servicing of all the lubs and fluids. I changed the oil and water, couldn't get the Tuneup parts at the local parts stores so I ordered the Dist Cap, Rotor, Plugs and Coil. At this point the car was still running. While I was waiting for the parts to arrive I decided to solve the battery drain problem. As you guys read in my original posts I pulled the radio out and discovered a mess of wires cut , spliced taped and no specific color coding. In this mess I found that the person who installed it did not use the connector to power his radio (not a factory radio), instead he tapped the radio into an arbitrary power source that kept the radio hot all the time but to ensure that the radio maintained memory he wired the memory wire to the radio power wire. The only way to turn the radio off was to remove the faceplate. I decided to pull the makeshift wiring and return that part of the electrical to factory. Simple task done this many times in other vehicles. Well as I was working this the tune-up parts arrived. So I switched from playing around with the radio to installing the new parts. Guys, this was a very simple, basic part swap, take out the old install the new. Now I never attempted to start the car before I began changing parts because in my mind that car was running fine. I installed all the tune parts sat in the seat, turn the key and....it would crank but not fire off. At first I thought I connected something improperly so I did a one for one check and everything was installed properly. Because I had no "fire" and I could hear the fuel pump working I thought that maybe I had a bad coil. So I disconnected the new coil and placed the old one back in line. Nothing, no spark. Then I metered the new coil and it passed. Added it back in, thinking just maybe the act of pulling it out of line and back in might bring the engine to life, Nope. Up to this point the only real maintenance that I had been doing was removing the poor wiring of the radio. Because the car wouldn't start I began to think that , just maybe this car had one of the original anti-theft systems installed. This was the type that was wired through the radio connector so if someone tried to steal the radio it would shut down the engine. Very early systems. Bought a Haynes and traced the wiring and also came to this forum to ask some guys and gals who have more Audi experience to ask if anyone could come up with what the issue could be. Next, I decided the replace the distributor. Although the engine was running fine with the old one, the connector at the Dist was broken and hanging down, so I thought that this connector might be what is causing the no-start. Ordered and installed the new Dist. Now I'm thinking, this has got to solve it. NOPE. Now I'm down to serious, indepth trouble shooting. I used the diagrams Rog provided and my new manual and began Ohms checking and power checking every Ignition system wiring and connectors all the wires passed their tests. Just as a hunch, I decided to replace the Ign Cont Unit (ICU) that is located behind the glove box. Replaced the older ICU with the new. NOTHING, just cranking, no fire. According to the Manual and the diagram that Rog provided there should be a device called the Hall generator. I searched everywhere in this car, in the engine compartment, inside the car along the fire wall, under the seats, I removed the console, nothing, so I have to assume this version of Audi doesn't have one. At first I thought maybe it was by passed, but I can't even find where the connectors for this unit would be. Back to troubleshooting, tested the connector at the dist and it has all its power needed to start and run the engine. My next thought was that if there is power at the dist connector then just maybe the cap and rotor are not the correct type. To test this theory, I compared the old with the new and the new cap appeared to be a bit wider at the top than the original cap and the rotor was longer that the original. Just to put my mind to ease I reinstalled the old parts. Again Nothing! Folks I am at a loss. I don't know where to turn I just can't seem to narrow this issue down, at this point the Ignition system is like new. To me my gut feel is that the Ign system has lost its ground. Now if this were a points type ignition system I could find this easily enough. But in this electronic system part swap was so easy that a person would have to TRY to mess the system up. I just can't seem to run this problem to ground and I am coming to the experts for anything you can offer. I'm Stumped. Thank you all for reading this.---Karfreak

Rogviler

Okay, so the Hall system is inside the ignition distributor itself, under the rotor. If you replaced the entire distributor then you should be good there. If the Hall sensor goes bad it can basically interrupt either the spark or the signal to tell the fuel pump to stay on. But also since your whole problem seems to be wiring I would only concentrate on that.

Obvious question, but it sometimes comes up... There IS a fuse in slot #24, right?

The ECU grounds at the intake manifold, BTW, which is totally weird but you might check those wires there. They'll be brown and I think one has a red stripe. Also check continuity from there to the connector that plugs into the ECU if you can.

-Rog

Karfreak905

Hi Rog, thanks for lowing up on this issue. Sorry for my slow response , I was out of town for the past three days and did not have access to the internet.


Thanks for the education on the Hall Generator. Yes the Dist is new so I agree with you that it eliminates that problem.


The question about fuse in slot 24 , good question and yes there is a fuse in the slot and its good. I actually checked this fuse several times because I wanted to be absolutely sure it did not get fried. it's good.


Rog, does it help you at all if I mention that the Tach is not functioning either. Does this tell you anything at all?


I really have to agree with you about the wiring. Deep in my mind I an convinced that the jerry rigged radio wiring was actually keeping the car running and when I began my work to eliminate the mess and potential fire hazard (lots' of exposed, twisted wires and nocaps or Tape) that I undid something without knowing it that was keeping the car running. I just have to find what it was that I undid.


Question Rog, if the
cold start valve/plug were bad would the engine still start? If its the same as VW then engine will start but it will run poorly until its warmed, is this correct Rog.


Thanks for the "tid-bit" about the ECU ground. I will run this down, it just might be this.
Thank you again for you working this with me. More to follow tomorrow. Karfreak

Rogviler

Yes, the tach gets its signal from the coil. Seems like the wire is like red/black/yellow. So that could be a clue or it could just be a symptom of the coil not firing for some other reason.

Good question on the cold start valve. I've never had one go bad, nor have I heard of one going bad. But I'm sure you could still get the engine started.

-Rog

Karfreak905

Hello Rog and everyone else I wanted to post the latest info about my Audi 4000S and its no start issue.


Today, I took a long lunch went to the Audi and began end to end wire continuity and power delivery checks. I could not find any shorts to ground or any wires that might be open/broken. I had just enough time to do power checks at the Dist, the ICU and the ignition switch. I am getting power to all. I did not have time to check/test the ECU. I will do this tomorrow. But from what I am seeing and from what I have read in the manual it appears that the ignition control portion of the ECU might be bad.


I can't really see what may have caused the ECU to fail, because the engine was running fine when I brought the car home. It might be that the ECU was on the verge of failure and I just became the unlucky recepient or it might be that the changing of the parts could have caused an already worn and weakening unit to finally fail (not very likely, but I've seen this happen before). At this time I am only speculating about a bad ECU but to this point I can't really see anything else to check.


Rog, question for you, do you know a quick check method check the ECU to tell if its functioning or shall I expect that I will be doing power tests at the coil and Dist during my lunch break tomorrow?


Again my friend in summary, electronically the car seems fine. The only thing that is not fine is that it will not start when I "crank" it. It does not even attempt to start , it is just flat/no life. The only other issue that I mentioned earlier is Tach does not respond or move. To me this is an indication of the coil not sending a signal.


Rog, do you know a quick test that I can try?


Has anyone else had this issue if you did may I ask what you did to solve it.


Thanks for any help you guys can offer. --- Karfreak

psparky

Any luck with getting this car running?