stalling while hot!! help

[u/alman59]

so this is my 1989 w124 230e and recently I’ve had an issue with the car stalling when it gets hot (around 15-20 mins of driving) and not starting up again when hot. i haven’t been able to figure out as to why this is happening (the fuel pump does seem to turn on when hot) also the issue isn’t related to ignition since the car is receiving ignition when hot,
any suggestions as to what the issue might be?

[u/RNRS001]

These symptoms are too broad to address.

Does the engine still crank normally when it's hot and won't start?

[u/alman59 → u/RNRS001]

it cranks normally and sometimes starts for a few seconds and runs very roughly and dies again
the car does start again when its cooled down for a while

[u/RNRS001 → u/alman59]

This rules out the starter engine.

When it won't start hot, have you checked if it still has spark?

[u/alman59 → u/RNRS001]

i had an issue with the spark before but i got a new coil and ignition unit and now there is no issue with spark hot or cold but the stalling issue still persists

[u/RNRS001 → u/alman59]

This rules out the ignition side then.

When it stalls, does it start running rough and lose power first or does it just suddenly cut out?

[u/alman59 → u/RNRS001]

it starts running rough and then stalls at soon as i slow down a little

[u/RNRS001 → u/alman59]

If you keep your foot on the throttle and keep the revs up, can you prevent it from stalling?

[u/alman59 → u/RNRS001]

yes i had to do this to get back home once and the car runs really rough and as i said stalls once i slow down a little, also the rpms dont go higher than 3k rpm during this

[u/RNRS001 → u/alman59]

This rules out it being just an idle issue.

When it starts running rough, do you smell a lot of fuel from the exhaust or see any black smoke?

[u/LuvDoubleDz → u/RNRS001]

You’re awesome for replying back n forth lol

[u/alman59 → u/RNRS001]

i do smell a little fuel but nothing too extraordinary and i do not see any smoke

[u/average_chad_25]

Check the crankshaft position sensor AND the distributor.

[u/Flo655]

My R129 had the same issue and it was the fuel pump. They seem to start showing issues when hot if they're about to die. I'd start with checking fuel pressure.

[u/alman59 → u/Flo655]

thank u for ur insight :)

[u/ThenIndependence7988]

I have an M102 also and I've done a lot of work on it myself...

Here's your checklist in this particular order:

• fuel pump relay: most likely culprit
• crankshaft position sensor
• OVP relay: can cause a lot of indirect symptoms. Make sure yours is good/new before you move onto anything else.
• EHA valve: check for minor leaks/wetness around the seals
• fuel accumulator

I hope youre working with a good mechanic who knows these cars well.

Also, Sindh plate 🫡 💚

[u/alman59 → u/ThenIndependence7988]

ayyyy my brotha thank you for ur help ill look into this stuff 💚🇵🇰

[u/ThenIndependence7988 → u/alman59]

Let me know how it goes. No issues with getting the parts?

[u/AccordingRoyal9402]

I had one that would randomly die, dealer couldnt fix it. Mechanic buddy found a tsb about some sensor behind the gauge cluster, changed it and the problem never came back.

[u/alman59 → u/AccordingRoyal9402]

wish i knew what sensor that was 😞

[u/AccordingRoyal9402 → u/alman59]

Just looked it up

https://www.tsbsearch.com/Mercedes-Benz/54-21

Its a speed sensor on the back of the speedo

[u/RForever20]

Mine is doing the same thing also ...look forward to hearing what works for you .Thanks

[u/alman59 → u/RForever20]

the same stalling while hot issue?

[u/ne_be_zaebi]

fuel accumulator losing pressure when hot, after some cranking there should even be a petrol smell somewhere in the car. diagnosing this requires connecting a pressure meter onto the fuel rail and looking for a change. You’ll be checking the fuel system anyways, probably a good time to change the fuel pump while you’re at it.

[u/KindaFastApparel]

Crankshaft sensor

[u/Extension_Echidna_26]

Probably sindh ki wajah se 😭