Hi All, This is a long and complex story so excuse me if I miss anything relevant. Originally came in complete non-runner but with immobiliser code (001176, signal too low, IIRC)and found no chip in the key. I was unable to get the PIN code out of the immobiliser so I took it to my auto locksmith where we found the EEPROM data was completey scrambled. One new immobiliser later, new chip in key and engine started....on 4. Traced this to crossed ignition leads. Don't you love it when customers try and mend their own cars? Customer claims he did not dismantle the key either. Vehicle stood over night and started perfectly the next day when collected. Car returned the next day, will not start on key. Diagnosis returned 00514 ignition point sensor and 00515 camshaft position sensor. Not certain with this engine code but most VAG cars return these codes when the engine is not running anyway. Codes still present but flagged as intermittent when the engine is running. When cranked from cold no rpm is shown on tacho or VCDS but vehicle will start quite happily from a push start. When warm it will usually start ok, the clue is the tacho indicates rpm and the engine will go. In between the tacho will sometimes flicker and the engine can be heard to fire, stick with it and the engine will eventually start. When it is running it goes really well. A new crank sensor has been fitted (genuine) and the camsensor gives a good pulse when checked on the scope. The ECU went to ATP for testing with no fault found. I am pretty sure I checked the sensor wiring but can't see it in my notes so I will recheck that. The crank sensor is adjustable and I have fitted the bracket back on the original witness marks as far as I can see (access is awful) but I would like to know the setting method for that. The other possibility I can think of is perhaps the starter motor is electrically noisy, it certainly seems to be quick enough. Typically as I have had the battery on charge and it is warm today the damn thing starts! Running out of ideas now. Shaun
Just a few thoughts. I would have thought you have got the Crank Sensor in the right place because it runs Ok. The clue is in the starter motor. When under high load ie: when cold the vehicle fails to start but on a push start the vehicle goes ok and also when under low load when engine hot. Is it possible to measure LT feed voltage to the coil when the vehicle fails to start in case of excessive starter draw? Also, I remember many years ago on little Fords that the main lead to the starter motor would interfere with the crank sensor wiring due to its close proximity on cranking causing non-start. I got round that by insulating the crank sensor wiring using silver foil and tape which solved the problem. Probably not the answer but something to consider.
Hi All and thanks for replying, Will check starter draw and waveform. Will also check coil voltages on cranking. Pete, yes I was also concerned about interference from the starter motor. I replace loads of VW ignition switches but very few Audi,also it will go if you persevere on many occasions, the tacho starts to flick and the engine can be heard to fire, then if you keep going the tacho comes up and the engine starts. It certainly feels like cam/crank sensor problems as given by the codes but is it slow cranking speed, interference or the signal getting lost. I had one of these many years ago and it turned out the ECU had gone low sensitivity on one of the inputs, unfortunately ATP could find nothing wrong with this one. Just got a gallon of unleaded for it as it ran out of fuel yesterday..... now where to put it, in the tank or on the back seat? Shaun
Hi Shaun, What about scoping cam and crank signals at the ECU under both non start and starting conditions. compare the perk voltages and the quality of the reference mark on the crank signal/corralation with cam signal. Also look at the base voltage of the system under cranking. HTH
Regards Mark Modern cars, Its all wizardry and witchcraft
Fixed #
Posted by Shaun Dale on June 24, 2010, 8:16 am, in reply to "Re: Audi 80 will only start from a push" Message modified by board administrator June 24, 2010, 3:00 pm
Hi All and thanks for the replies, Went back round the houses yesterday while I had it in the workshop in a non-start condition only to find I had no cam sensor signal. Frustrating thing is it was one of the first things I tested and I had it in my head that it was good. The trouble with this one was it was sitting on the edge of working all the time, so you have to keep checking to see whether the engine was startable, seems I must have slipped up and tested it in the startable condition. I still can't understand why it should be speed sensitive as a Hall sensor should work statically, perhaps it was supply Voltage sensitive. Always difficult when the customer is whinging about cost all the time, when the crank sensor did not fix it I should have put a cam sensor on regardless, but at £108+vat it gets hard to explain to the customer that you have spent another hundred quid and it still doesn't go. Spent much more than that in wasted time that I can't charge. Thanks again Shaun.
on June 21, 2010, 6:50 pm, in reply to "