I'm having cold starting problems with a 1989 740GL. I have checked as many electrical and vacuum connections as I can find; no blown fuses; and the cold start sensor checked out for resistance, but I'm not getting any voltage to the cold start sensor or valve.

Also, the ECU does not display any codes at all. Not even a 111 (no codes detected).

It does seem to start somewhat easier with the air mass meter disconnected.

Runs great when it's warm, but it's getting it there that's the problem.

I'm thinking that the problem is in the ECU. Is there any way to check to be sure? Are boneyard parts reliable? And, if so, how close do I need to be for this year, make and model?

Please keep in mind I'm just a retired firefighter with only self taught mechanical experience doing a favor for a friend.

Thanks in advance for any help and advice you are able to give.

I'm guessing it's like the 240 (same LH 2.4 FI), where the cold start injector should get voltage* from the Main Relay with Key ON, but needs a ground from the ECU (when The Engine Coolant Temp sensor says it's 5° or colder). Maybe try cleaning the ground connections on the intake manifold?

* This is a common 12V feed to the injectors. Idle Air Control, and CS Injector.
--
Bruce Young,
'93 940-NA (current)
'80 GLE V8 (Sold 5/03)
'83 Turbo 245
'76 244 (lasted only 255,000 miles)
73 142 (98K)
'71 144 (track modified--crusher bound)
New 144 from '67 to '78
Used '62 122 from '63 to '67

89's were known for bad CPU's. I'm don't know what other dash numbers, if any, would be compatible. How about at least checking the harness plug-in at the CPU for dirt/corrosion, and also any associated ground points that you might find in that neighborhood.