I need a 1990 V8 Quattro expert, I have a perplexing situation. For the past month, every time I drive the car long enough to warm it up, if I let the car sit for 45 min to 3 hrs. After running, the car will just crank and crank without starting. I thought it was the fuel pump the first time it happened. I sprayed some ether (starting fluid) into the air filter area and the car starts right up and runs great. This happens time and time again. If the car sits a short time after running, it will start right up. If the car sits overnight in the garage, it will start right up in the morning. I thought it was the fuel pump relay, but that is working fine. I am sure the fuel pump is running, but the car will not start after sitting until I spray some ether into the air filter. It seems to be a temperature situation as it always starts after the engine is cold. I am baffled. Any advice as to where to begin to troubleshoot? Has anyone had this similar situation? Any advice is welcome. Thanks a lot for your help.
I agree with Ruedi; crank position sensor. There are two sensors that are culprit. I have cut and pasted some info you might find usefull:
"If the speed sensor should fail while the engine is running then the engine will stop. If you crank the engine you will also notice the the tach will not bounce while the engine is cranking (Dead speed sensor).
For peace of mind change both sensors together. Both sensors are held in place with a bracket and offset. The one more toward the engine is the crank position sensor and the one closer toward the transmission is the speed sensor." - Bob Moy
"timing reference sensor. Next time, take a funnel and pour some cool water up against the block between the headers of the 3rd/4th driver's side cylinders. If it starts right up, there's yer problem." - Dave Head
"The black one is 077 905 381, ignition timing sender. The gray one is 077 905 381A, engine speed sensor. They are identical except for the color of the plastic on the connector and at the sensor head. Reportedly, the black one is NLA. I couldn't find one a year or so ago when I replaced mine. So I installed two of the gray ones and put black electrical tape on the one that went to the black connector in the wiring harness. They're such a PITA to get to, I figured I should change both if I was going to change one.
No idea whether either fits the symptoms you describe. One causes the engine to be hard to restart when hot (the one I wanted to change first) and the other causes the tach to drop to zero, which I guess would indicate a dying engine, eh?" - Kneale Brownson
Good luck Mark!
Regards,
- Jeremy
1990 V8Q Zyclam
Portland, Oregon (USA)
http://www.MyV8Q.com/
Fun, Fun, Fun auf der Autobahn
Jeremy, Thank you so very much for your help with my starting problem. I was not sure which sensor Ruedi was talking about with his referencing it as the "OT sensor". Is that the same as the crank position sensor that you mentioned in that you agreed with Ruedi? I will definitely try the cold water trick against the engine block, it seems to definitely be temperature related. I do not understand what the timing reference sensor has to do with temperature? Also, why when I start the car using the ether starting fluid, does the car start and stay running just fine, I do not see the relationship, can you explain the connection? I would not expect the engine to start and run just fine with the starting fluid trick, but I have done it time and time again. It seems like it is getting a signal not to start when the engine is warm. Is there a temperature reference in addition to the crank position reference sensor? Thanks again for all your help and insight. I will let you know what solves my problem. Yours truly, Mark, Salt Lake City area
I had the exact same problem with mine, I just replaced both sensors. Problem is now cured. Parts are available from the dealer but they are not cheap. 077-905-381 $167.38 077-905-381-A $166.58
Thank you all for responding to my problem. I am still working on it. I will most likely have to replace both sensors to be sure to solve the warm starting problem. Funny thing, it is getting a bit colder here in Utah now and I have not had the problem for a little while. How hard is it to access the 2 sensors? Any suggestions as to best route to access and replace the sensors? Thanks again for your help.
