1989 240GL B230F with Jetronic 2.4

Having issues with the engine dying 3-4 minutes after startup. From cold, the engine starts and runs fine for a short period before it stalls. After that, each subsequent start gets shorter and shorter until I can't get it to start at all. If I let the car sit for a while, I can start it again and it runs nicely for 3-4 new minutes before stalling again. The stalls are instantaneous and happen without much stumbling/coughing, with one exception: When we tried starting without the AMM/MAF, then reconnected it while the car was idling, it ran okay at first but with fluctuating RPMs. When we plugged the MAF back in, the car ran smoothly and steadily for about 30 seconds before losing RPMs, then revved up just before dying, lost RPMs again, revved up again just before dying, and finally died (it behaved as if someone was sitting in the car trying to prevent it from stalling).

Have already:

• Replaced the fuel pump relay
• Replaced the crankshaft impulse sensor
• Tested the throttle position sensor
• Replaced the external fuel pump and fuel filter
• Replaced the air filter
• Tested the airflow meter (with an ohmmeter, but unable to measure burn-off)
• Checked that fuse clips aren't losing contact
• Replaced the lambda/O2 sensor

Curious if anyone has experienced something similar — tips are very welcome!

 

Goldenblock Senior Member here,
Based upon your symptoms it seems like a classic case of a bad or ruptured diaphragm in your rail fuel pressure regulator!

Pull the vacuum hose off it and smell small opening for gas smell, if so the regulator is not holding pressure!!

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Thanks for the tip! Tried, but no sign of moisture or gas smell. Hose is totally dry. Here's a clip of the engine stalling after running for about 4 mins from cold start:

 

After you have run the car a few times and it won't start, do the fuel pumps run? Run the following diagnosis on the pumps:

https://cleanflametrap.com/transferPump.htm

If the car starts with the fuses jumpered then I suspect you have a failing ECU. '89 versions of the LH 2.4 Jet fuel injection systems had issues with the fuel pump circuit causing them to fail over time.