Latest update is that the Motronic ecu has been sent for testing and repair if found faulty.
Can't start my car!!
- Thread starter brian williams
- Start date
peanut
Active member
sorry I didn't see this thread earlier.
From what you've said it sounds like the ECU is either not getting the power or the sensory imputs it is expecting to see.
It is very unlikely that your ECU is at fault. They very rarely expire suddenly unless there has been a voltage spike fromwelding or battery reversal etc or water ingress.
I strongly suggest you do not buy a replacement ECU without carrying out the following checks first
The ECU provides both the pulsing for your ignition spark and the pulsing to the fuel injectors .
Power to the ECU and injectors and various sensors mostly come via your DME relay which contains 2x seperate independant relay switches.
The easiest way to test the ECU and DME relay is functioning correctly is to remove the DME relay and plug a 3x wire bypass into the DME relay socket ,linking together terminals
30 ,87 & 87b
(This will bypass the function of your DME relay completely eliminating that as the cause and should provide power to your fuel pump , fuel injectors, sensors and ECU )
First remove the DME relay and check that you have 12v+ on terminal 30 of the relay base with the ignition off.( Use a paperclip or file a spade connector until it fits in the relay base slot. )
If you have 12v+ at terminal 30 then fit the 3x wire bypass you have made . [Take care to fit the wire into terminasl 30 last because it is a constant live connection.]
If you now do not hear the fuel pump pumping continuously then you'l need to check the fuel pump fuse F34 for 12v+ .
If you have 12v+ at the fuse then check your earth point for the fuel pump just under the rear hatch lock behind the carpet.
If the pump is still not working then it may be jammed so give it a sharp tap.
lastly you'll need to check the wire from the fuel pump fuse to the fuel pump . The easiest way is to run a length of wire from the fuse to the fuel pump power terminal.
Assuming the pump is running you need to check that you also have 12v+ at the fuel injectors and terminals 37 and 3 on the ECU connector.
Terminal 37 of the ECU is fed from terminal 87 of the DME relay and Terminal 3 of the ECU is fed from terminal 85b from the DME relay
If you have power at both ECU terminals and the injectors and fuel pump is running and it still doesn't start I'll let you have the next things you need to check.
From what you've said it sounds like the ECU is either not getting the power or the sensory imputs it is expecting to see.
It is very unlikely that your ECU is at fault. They very rarely expire suddenly unless there has been a voltage spike fromwelding or battery reversal etc or water ingress.
I strongly suggest you do not buy a replacement ECU without carrying out the following checks first
The ECU provides both the pulsing for your ignition spark and the pulsing to the fuel injectors .
Power to the ECU and injectors and various sensors mostly come via your DME relay which contains 2x seperate independant relay switches.
The easiest way to test the ECU and DME relay is functioning correctly is to remove the DME relay and plug a 3x wire bypass into the DME relay socket ,linking together terminals
30 ,87 & 87b
(This will bypass the function of your DME relay completely eliminating that as the cause and should provide power to your fuel pump , fuel injectors, sensors and ECU )
First remove the DME relay and check that you have 12v+ on terminal 30 of the relay base with the ignition off.( Use a paperclip or file a spade connector until it fits in the relay base slot. )
If you have 12v+ at terminal 30 then fit the 3x wire bypass you have made . [Take care to fit the wire into terminasl 30 last because it is a constant live connection.]
If you now do not hear the fuel pump pumping continuously then you'l need to check the fuel pump fuse F34 for 12v+ .
If you have 12v+ at the fuse then check your earth point for the fuel pump just under the rear hatch lock behind the carpet.
If the pump is still not working then it may be jammed so give it a sharp tap.
lastly you'll need to check the wire from the fuel pump fuse to the fuel pump . The easiest way is to run a length of wire from the fuse to the fuel pump power terminal.
Assuming the pump is running you need to check that you also have 12v+ at the fuel injectors and terminals 37 and 3 on the ECU connector.
Terminal 37 of the ECU is fed from terminal 87 of the DME relay and Terminal 3 of the ECU is fed from terminal 85b from the DME relay
If you have power at both ECU terminals and the injectors and fuel pump is running and it still doesn't start I'll let you have the next things you need to check.
Latest update is that the ECU is fine, so must be a wire somewhere. Just a question of tracking it down. The car isn't being worked on continuously, just when other jobs allow.
peanut
Active member
Brian you really need to give the car to a Bosch trained technician to sort out
I mean no disrespect but the average garage mechanic won't have a clue where to start troubleshooting a Motronic fuel injection and ignition system .The fact that they sent your ECU off without first checking the system shows this .
All they are likely to do is bolt on one new part after another until hopefully the car runs. Its going to cost you a bomb .[
]
I mean no disrespect but the average garage mechanic won't have a clue where to start troubleshooting a Motronic fuel injection and ignition system .The fact that they sent your ECU off without first checking the system shows this .
All they are likely to do is bolt on one new part after another until hopefully the car runs. Its going to cost you a bomb .[
]
Phoned up today and my car has started. Apparently it was the crankshaft/flywheel sensor that was the problem. At first they said it wasn't this but when queried it was told that it wasn't putting through enough current to allow the ignition to fire up the car. When the new part was fitted........VAROOOOOOOOM! I did read somewhere on Rennlist that there was a minimum amount of current required!! There is some excellent advice on Rennlist just waiting to be discovered.
I love happy endings, and great to see good info again from another forum members experiences.
Yes it's great having my car back, but now the central locking won't work with the remote or the key! I can lock it manually from inside with the round knob on each door, but the remote won't open it. I've looked at the relay box in the passenger footwell and the known fault that can be found there (where a contact becomes loose etc) is still soldered, I think I did it some time ago. Fuse 12 is fine, so I'm not sure what is next to check, unless there is something else wrong with the relay box, although it does make a clicking sound when he remote is pressed. Any help gratefully accepted!!!
vitesse
Active member
How stiff are the round knobs(oops!) to turn-it may be that without regular use of late ,things have "dried up " somewhat-this symptom appeared on our 964 ,mainly the passenger door-I used to remove the round knob& rear trim,apply liberal amounts of WD 40 /GT85-manipulate everything until all felt free-he -ho it worked again-this was just using the key in the driver's door--just too much friction for the solenoid to overcome.
They don't seem to be too stiff, but I'll still try and lubricate them both and just maybe it might work? Thanks.
Steve Brookes
Moderator
Does it work from the central locking button in the centre console? If not it might be the relay itself. I had to change the relay on mine albeit that it was only the passenger door that wouldn't remote lock/unlock.
Steve Brookes
Moderator
It's on the wall of the passenger footwell and is about the size of a pack of playing cards. Not easy to see without getting your head and a torch right in there! Sometimes it can be a bit iffy and works sometimes and not others because of a bad connection. so just unplugging it and cleaning the pins can fix an iffy one.
I think the relay was either moved or done away with on later cars.
I think the relay was either moved or done away with on later cars.
Steve, the central locking switch on the centre console will unlock both doors when I've manually locked them from inside, but won't lock them at all. This suggests that the knobs aren't too tight from not being used as suggested earlier? Think I might have to get a different control box to see if this works?
Steve Brookes
Moderator
Ensure both knobs are in the unlocked position (maybe lock them and then unlock them to be sure), start the car, try locking with the console button and then unlocking. What happens?
Strange things happen with the central locking when the car has not been used for a while or the battery is low. Hence the questions.
Strange things happen with the central locking when the car has not been used for a while or the battery is low. Hence the questions.
Tried what you suggested and it wouldn't lock either door but it would unlock both doors, after I had manually locked them with the knobs. Also tried locking both manually and then unlocking from front passenger door knob and they both opened. Think I will get a new (old) control box from you know where as there is a 944 one on at the moment and it's only a tenner plus postage. You never know might just be what's needed and hopefully cheap to fix too?
Steve Brookes
Moderator
Yes, sounds similar to the symptoms I had albeit only with one door. I too fixed it with a used relay from a 944. The box that covers the relay is different to the 964 box. I transferred the relay from the 944 box into my 964 box so that it would fit back on the car as it should.
BTW when you get round to unplugging the relay....you'll find it is very difficult to unplug...just keep working away at it...it will come undone eventually.
I've managed to get it all apart once so far so should be ok doing it. Just hope it fixes it! Thanks Steve
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