Still looking for the root cause of my intermittent startup on my 240 DL 1989.

I read somewhere that the ECU (BOSCH Jettronic) can be faulty causing such problems....

I have been unsuccessfull in finding a poor contact anywhere which is causing my fuel pump relay to intermittently click when engine is cranking. The relay is new with one from Groton.

So does the ECU actually control the fuel pump relay? If so, can it be faulty, or can I have a connection issue at the connector to the ECU? I am asking this question because noone here ever pointed me to the ECU, so I am wondering if anyone has ever heard of this problem.

The car never died after starting up. It runs perfectly, no problem codes either. It still appears to have the problem in the humid mornings... I must fix this before the winter hits.

Thanks,
Greg
greg_mustang@hotmail.com

Does your '89 240 have a rpm sensor that attaches to the flywheel.
If you do check the plastic band by the electrical connection.

If it's yellow, it's the original and needs to be replaced. The new rpm sensors are more reliable and have a white band.

RPM sensor failure is common with intermittent start up

Thanks,

Where is the sensor located and can I get to it easily?

Greg

rpm sensor is back of engine by firewall, attaches to flywheel housing of transmission with single 10mm bolt, the other attaches to electrical connector on firewall by drivers side.

I have not studied the wiring for that year (and you should get a Bentley manual) but usually the ECU reads an rpm signal from the ignition (coil or ignition unit) and then turns on the relay. This is to turn of the pump if the engine stalls.
I would use a meter to check the voltage to the relay while starting. Also as this is just a starting problem, not running, then it is most likely something unique to starting. Studying the wiring diagram could narrow it down.
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744-16v,745-16v,242Turbo.245DLT

Thanks for the recommendation.

You have 16v cars, B234Fs?

I too have a 940 GLE '92 with the B234F. I recently had to dish out 2000$ for a head rebuild because the oil pump pulley bolt broke, hence... (you can guess)... Make sure you have your pulley bolt replaced every timing belt change (at least!). If you are aware of this weakness, any recommendation on what I can to help ensure I don't get stuck with it breaking again between now and the next timing belt change?

Greg