Thomasgarrett

Hi, this is my first post, just bought a 1990 200 Turbo with a no spark issue, hoping it wouldn't be too hard to chase down, tested and am getting nearly 12v out of the feed for the ignition module next to the coil with the key turned on, checked resistance across the coil and can get a reading of 7500 ohms between the main HT lead connection and either of the + or - terminals of the coil but no resistance reading between the + and - terminals of the coil with it disconnected. Is this an indicator I have a bad coil and if so can I connect a regular 12v coil between the + and - terminals to test if that gives me a spark before shelling out for the $150 replacement coil for this particular model?

Hopefully my description and question make sense, any more troubleshooting help would be great, I do not have a fault code reader so cannot go that route, is it worth getting one, and will I be able to diagnose this quicker with it, I have always had wild goose chase experiences with fault code readers on older vehicles in the past...

Any help much appreciated, thanks

toml99

You can blink out the codes with a radio shack LED....if not familiar with ,SMJ Autotechnik's site has info on blinking out codes/tons of other info you might want to check out. My first thought would be reference/speed sensors, as they are almost always the problem. ECU needs signal to go forward(spark/fuel). Only time I've been stranded (twice) in the v8's was because of bad speed/reference sender. I looked in the book, and secondary resistance on coil is between 5-9K, so your good on that. Ebay search for audi 90/100/200/5000 reference sensor.....$26 just have to zip tie up extra wire....get 2...if you want to keep the car, you'll feel better having replaced both regardless if it's something else, but it's always the sensors...Ha. Good luck, Tom

toml99

For clarity, the speed/reference senders are identical in function, but came from the factory as 2 different part numbers(way different prices...Ha), one had a grey connector(speed?)/one black so you didn't confuse which plugged into which. Still need to keep the connectors in their right place, but sensors are identical so can use 2 of the cheapo's in both.....To go even more dirtbag, someone used generic ABS wheel sensors(identical) and had to cut the connector off, but got them even cheaper bulk. Car won't do anything without talking to these sensors.....Tom

Thomasgarrett

Thanks for the quick response, sounds like a have a good reading on he secondary on he could do you know if there should be a reading for the primary and if so what it should be?

Is there a way to test the output from the sensors you mentioned before replacing? I see crankshaft position sensors on eBay, is this the reference sensor?

Also I was looking up some troubleshooting pages and can see there was MAC11,12 and 14 ECU's on this car, mine is a 1990 is there a way to confirm which system I have? Again thanks for your help, I didn't realize this car was going to have so much electrical on it...
Thanks

Thomasgarrett

Ok, so I read a little on testing the crankshaft position sensor and engine speed sensor, pulled them from the car, and tested them with the meter. The info I was reading said that they should test "APPROXIMATELY" 1000OHMs across pins 1 and 2 (looking at plug with center bump on top) On the one I got a static reading of about 950 Ohms, seems good, on the other (crank shaft position sensor) I go a fluctuating reading of between 850 and about 1600 Ohms, which did not stabilize... so I would say that is a Bad sensor but without jumping to conclusions, can anyone tell me of that is close enough to the "APPROXIMATE" reading I was supposed to be getting of 1K Ohms?

although I think I know the answer ;-) hopefully my problem.....

audi_marv

I would say both are bad. Had one around 970 that turned out to be bad. Try swapping the two (and the connections) and see if anything changes. Clean off any metal bits attached to the magnets also. Make sure the ground at the back of the throttle body is secure (if you have this) as it goes directly to the ECU also.

Thomasgarrett

Ok, so I was messing with these sensors a little more and magnetized them to something just to see if it made a difference, now I get a consistent reading of around 1100 Ohms on both sensors..... back to perplexed...

@Audi_mary, my next test was going to be switching the two sensors to see if I got a change in symptoms, I will check for a ground on the throttle body when I get back to the car.

Thomasgarrett

Anybody have a link to timing instructions on this car?
Thanks

toml99

Since these sensors tend to fail when they get warm(car starts fine, but won't restart when warm), you need to put a heat gun to them when testing. On the V8 they are such a pain to get to, I just replace both at same time....When I got my first V8, dealer wanted $225 for one of them and $170 for the other....if that was still the case, I'd probably test them, but for $24 each....cheap insurance since yours might be 25 yrs old and you know one's flakey.....Good luck, Tom

Thomasgarrett

These are the timing marks and distributor when at top dead centre, does this look ok? Seems as though from what I look at online the rotor arm seems way off with he distributor cranked around to where the no.1 mark is towards the front of the motor...