I have a 1990 300e mercedes that will start but will only run for a few seconds then die? Does anyone have any suggestions on what it might be?

To disarm the alarm, you press the unlock button on the remote.

Perhaps you could click Edit and make the second part make sense. Why is your car 'having lunch', and 'you don't die I'll codes are clear'??

..

There are a few things effected by heat that could be causing this. Crankshaft position sensor (if your car is equipped since Mercedes started using them sometime around 1991-1992), Fuel pump relay, fuel pump itself, ignition coil (s) and ignition control module (EZL). The only way to narrow down which one it is, is to diagnose the problem WHILE its not starting, so test for fuel and spark during those times and narrow it back from there.

If you need further help, reach me via phone at https://www.6ya.com/expert/daniel_4061c3d97c12c4c7

if I'm reading this right...
... the engine starts and dies within a few seconds.
... you jumpered the fuel pump test connector and it will keep running.
... you smell fuel after trying to re-start when it dies.

Disconnect the plug to the cold start injector. Even if you have an issue with the engine running then dying after a few seconds after doing this, if you don't smell fuel after disconnecting the cold start injector and try to restart it, the cold start time injector time switch may be failing.

Buy a can of starting fluid and have someone start the engine then spray short bursts of the fluid around all the intake fittings. If spraying the fluid in any particular area keeps the engine running, I'd start looking for leaks around that area.


It does sound like an AFM or COR issue considering it dies after a few seconds, but the fuel smell when trying to restart the engine may be a separate issue that needs corrected / isolated first.it will keep running.

... you smell fuel after trying to re-start when it dies.


Disconnect the plug to the cold start injector. Even if you have an issue with the engine running then dying after a few seconds after doing this, if you don't smell fuel after disconnecting the cold start injector and try to restart it, the cold start time injector time switch may be failing.


Buy a can of starting fluid and have someone start the engine then spray short bursts of the fluid around all the intake fittings. If spraying the fluid in any particular area keeps the engine running, I'd start looking for leaks around that area.


It does sound like an AFM or COR issue considering it dies after a few seconds, but the fuel smell when trying to restart the engine may be a separate issue that needs corrected / isolated first.

If it starts and runs for about a half second or appears to run for that long then you probably just lost your key sync. Also happens when the remote battery dies on you. Look in your owners manual near the back or in the index for resyncing your key. It is easy to do and takes a few minutes or a few tries. Or you can spend about oh $200 for the Benz stealership to do it for you ;-]

typically, this describes a dirty fuel filter.

If the car has a carb (not fuel injected) try removing the air filter cover and pouring a small amount of gas down the carb . Now try and start it aND see if it will start. If it starts and runs for a 10-30 seconds and then dies, it is a fuel delivery problem. Car should start if you add gas unless the car is being flooded out. I can't really help you with a fuel injection system except to suggest to replace the fuel filter and see what happens. Just remember you need spark, fuel and air to make combustion. YOu say the car fires so you have spark. I would focus on the fuel delivery.

does it have old fuel how long has it sat and does it have good fuel pressure check filter

If the crank sensor (reaR at bellhousing) is dirty, will not start, clean up and visually inspect

First run a code check, see what you find. Second, you can do individual component testing with a decent volt/ohmeter to pinpoint problem. (instructions for tests in any decent manual)
Just off-hand, most common failure with similar symptoms to yours is crank position sensor.

The crankshaft position sensor was seriously problematic in those old jeeps. It's located towards the top of the bell housing slightly to the driver's side I think.