Hello all.


Year: 1991 Model: 190E 2.6L - Car won't start on warm/hot engine

So you've seen this hot-engine don't start issue posted probably a billionth time already but there's always something new. I've already scoured the forum and net and tried everything suggested swap/replaced parts to no avail.

The engine starts really nice, on one crank, when the engine is cold. After it's been running for awhile or engine reached operating temperature, I turn off the engine and won't start again...not until it had a chance to cool off.

Now, here is a twist...while the engine is still warm/hot, when I removed the cold start valve or injector(CSV), and after a few crank, the car starts fine and it does start again on one-crank on subsequent starts even when the engine still hot just as long the CSV is out.

So it looks like the engine was starving for air - it needed air but it wasn't getting it so it won't start. That doesn't mean the CSV is bad but removing it allowing air to pass through and helping the engine start seems like a clue.

So when engine is hot and won't start, it's either not getting enough air to lean the a/f ratio or too much gas going in.

I've read through numerous forums describing similar hard/no-start on hot/warm engine and replaced every part they mentioned that fixed their problems but my issue still exist.

Parts I've replaced so far:

- crank position sensor(new)
- coolant temperature sensor(the 4-pin, new)
- auxiliary temperature sensor(the 2-pin, new)
- cold start valve(new)
- fuel pressure regulator(fpr), fuel pump and filters and the fuel accumulator are about 5-6 years old - no leaks here
- fuel injectors are about 4-5 years old - no leaks
- EHA no leak (original) - idle control valve (3-4 yrs old) - tested with spare, no change

- OVP works - tried spare but no change

- Ignition coils, plugs, caps, rotors all new

Fuel pump works well even when the pins 1-2 bridge. Fuel pressure is good, no leaks as far as I know.

I also replaced my MAS and ECU with "used" units while the engine is having hot hard-start issue to no avail - I can't tell for sure whether the use parts are in good working order or not but I tried almost anything and I've ran out of ideas.

Again, when cold, engine starts very nicely with one crank and even idles nicely for awhile until it reaches operating temp. I've replaced most, if not all temp-related sensors on engine but no go. I'm probably one bad-part away from the fix but finding which one without throwing more money at it is the last big one.

Has anyone ran into this issue before? hot-start engine fail to start but with cold start valve out, engine starts fine.

Any help or suggestion is appreciated. Car been in garage for over a month now and I'm in the borderline of selling the car to our local JY for scraps.


Please help!


jav