Dangerous electrical issue w 1988 300ce
 

Hello,
I'm wondering if anyone can help steer me in the right direction. My 1988 300 CE runs just fine and then boom, engine dies suddenly, windows wont work, no power , but all the lights on the dash light up.
If i try and start the car right away it wont start. It turns over but wont start. All the electrical is back on now. Then wait 30 secs, car starts and drives great until it happens again. Suddenly car dies, no power. It has happened on the highway which was dangerous.
is it the ignition module?
the ignition switch?
Any help is appreciated

Fuel pump relay caused the sudden shut-off problem on my car. One way to test the relay is to bring the car up to temperature, open the hood and whack the relay with a screwdriver. If the engine shuts off, there's your problem.

Another possibility is the OVP relay. They can cause strange electrical problems like that, especially when you lose power windows as well as engine.

If the engine runs it's pretty much not the ignition module. They either work or don't

not the ovp...

i had this happen and initially thought it was the fuel pump relay....but I always carry a spare..... and the car kept dying...


crank position sensor solved everything.... i got one off ebay for 75 dollars.

coincidentally it was on the CE, too.... never lost one of those on any of our other 124s

i am working on johnea's car. i have a shop and we specialize in aircooled VW's but i own two 124 MB's so we work on those some also.

he has symptoms of the so-called SSS. john bought the car last summer and i have done lots of work to it including complete ignition tune up with OE parts, new exhaust system, tidy up in engine bay, new fuel filter and check valves. last thing we replaced the CPS. OVP is new from the PO and it's a dealer unit.

i've read about SSS in this forum, dozens of threads. benzworld has a few threads. i've read the worldpac internal forum, threads there. we've done everything that's pointed to except replace the hall sender.

car has only stalled on me once, when it was idling in park, so that points away from the hall sender. last time it happened to john he is pretty sure that as the car was rolling along in the stalled state, he had no power, as noted that the windows did not work, so this seems to point to the ignition circuit (terminal 15) being interrupted. my next thought is that the ignition switch electrical portion may be intermittent bad. i am having trouble understanding exactly how the issue arises on the road because i have never been driving the car as it's happened.

in johnea's post above he says "windows wont work, no power, but all the lights on the dash light up." these two things don't make sense to me in terms of ignition switch bad. if ignition switch is bad and #15 is interrupted, there should be no lights on the dash, i believe the dash lights are powered by #15?

we have not tried fuel pump relay, we may have a spare to use as a tester. the fact that the car cannot start until 30 seconds after it stalls points away from ignition switch bad and points towards something else such as FP relay.

Scott, pull the voltage regulator from the back of the alternator and check the length of the brushes. If they are worn down to stubs replace with a new Bosch voltage regulator.

ferdman,

nice idea. will do today.

1988 300CE lost power on way to work today
 

exactly the same symptoms as others described: completely lost power while in slow down freeway traffic (~20mph), all dash lights on, didnt try the windows so not sure, radio was still on and glided to shoulder, put in park and started her right up again....so weird and just a bit scary
...so the posts suggest either fuel pump relay or crank position sensor?? i should note that i just bought her 3 months ago with only 53K miles on her....seems only to have been driven 3,500 miles since 1996 (last noted oil change).....ideas???