Merc 190e Won't Start - Bosch KE-Jetronic - FIXED

[Tepper]

Probably best to go from the beginning...

I've had the car for about 2 months now and it's been great. It has always had a slightly rough idle (low compression on cyl. 2, mechanic said it might be a hydraulic tappet but runs fine when revved and I can live with a shaky idle). Sometimes it hunts between 500-1,500 rpm at idle, not very often but it's probably the idle air control device, which I cleaned today.

Anyway, a few days ago I ran out of petrol, we put some more fuel in and the car was fine after that. But yesterday, after an evening of driving, the car refused to start. Letting it cool down didn't change things. The RAC man turned up and checked the fuel flow through the pump/filter, which he said was fine. He also checked the ignition with an inline test light and didnt find any problems there. He eventually managed to get it started with some easy start straight into the air metering plate (if that's what it's called ) and giving it some throttle. It ran, but you needed to keep the revs up otherwise it would die, but after a while it settled down and would just about idle, and I drove it home like that.

So I went out this morning and it fired, but wouldn't run. It did that a few times, then wouldn't fire at all. I eventually managed to start it with the throttle open and it ran, but backfired a few times and wouldn't idle.

Thus far I have removed and cleaned the contacts of both the OVP (over voltage protection relay, a common problem on these) and the ECU, which I also tried to check for dry joints, although the OVP didn't want to come apart so I left that (the fuse was fine). No joy. So I bridged the terminals on the socket for the OVP as suggested in a workshop manual. No difference. I then put the OVP back. I don't think there's anything wrong with the fuel pump relay because you can hear the fuel pump running.

Any light you guys can shed on the matter would be hugely appreciated. Have a picture for reading all this...



Thanks in advance,
Will

[MrSpeedy]

First off, the RAC man should be shot! FFS, what sort of mechanic uses easy start?!

Anyways, I had a similar problem with my old 2.0 KE Merc 190.
It wouldn't start at all until it had gotten a bit warmer. Or it would start with no pedal but would die if you touched the throttle until it had warmed up. Turned out to be the thermostatic switch for the 5th cold start injector. Located in the cylinder head near the thermostat outlet.
Might be worth having a look at that.

If it were the hydraulic tappets causing issues, believe me you would hear them rattling Quite an easy job to change them if you need to tho

[Tepper]

Thanks for your advice MrSpeedy, much appreciated.
To be fair to the RAC man if it had started on easy start that might've pointed to fuel supply problems? Either way once it was running he offered to tow me home anyway, I said I'd give driving a go to save him the bother of towing it and he followed me home. No complaints there
I checked a temperature sensor by the thermostat outlet that had 4 pins, tested with a multimeter and the values I got for it are within spec, so no problems there. Is that the sensor you were referring to?
Regarding the tappets, the engine is very tappety before oil pressure builds up when you start it and to my ear it still sounds a bit rattly from the top end once it's warmed up, but I'll deal with that once it'll start
Today's progress:
I took off the fuel lines, fuel metering head, air metering assembly and the idle air control valve, i.e. most of the injection system. The rubber housing that joins the air metering assy. to the throttle body is seriously deteriorated, and the hose that joins the IACV and this rubber thing has been heavily bodged in the past. Hopefully that's our problem! Any ideas as to where to get replacement hoses & the rubber housing anyone?

Thanks for all your help.

[wooffy]

Check for splits etc in the ducting from the inlet to the airbox/metering unit. It needs to be in good condition otherwise the vacumn from the engine won't lift the plate enough when cranking over to start. Had the same thing with one of my mk1 golf gtis so till I got a new hose I used to squirt a bit of fuel into the inlet before trying to start it.

[Tepper]

Wooffy, cheers for that. The lower half of the air filter housing fits straight over the air metering unit with a rubber seal, which I'll check over. There's also a pipe from the grille of the car up to the air filter housing, which looks to be a fairly loose fit from factory. Is it worth sealing that up?

[bortaf]

Mar 23, 2012 18:19:15 GMT MrSpeedy said:

First off, the RAC man should be shot! FFS, what sort of mechanic uses easy start?!

Anyways, I had a similar problem with my old 2.0 KE Merc 190.
It wouldn't start at all until it had gotten a bit warmer. Or it would start with no pedal but would die if you touched the throttle until it had warmed up. Turned out to be the thermostatic switch for the 5th cold start injector. Located in the cylinder head near the thermostat outlet.
Might be worth having a look at that.

If it were the hydraulic tappets causing issues, believe me you would hear them rattling Quite an easy job to change them if you need to tho

I often use a squirt of sniff up the inlet to diagnose non starters, that is what it's for after all ? perfectly fine on the odd occasion but deadly to use it all the time
TBH 90% of the time on these it's a cold start issue or at least it seems to be with the ones I get see if not then usually a split pipe, hidden in amongst the ribs

[MrSpeedy]

Mar 25, 2012 19:15:11 GMT Tepper said:

Wooffy, cheers for that. The lower half of the air filter housing fits straight over the air metering unit with a rubber seal, which I'll check over. There's also a pipe from the grille of the car up to the air filter housing, which looks to be a fairly loose fit from factory. Is it worth sealing that up?

I'd forgotten about that.

The rubber diapraghm that seperates the two halves of the metering housing had also split on mine!

[Tepper]

Sorted! After I stripped everything down, I cleaned everything, adjusted the air metering plate zero position (it was miles off) and sorted out the vacuum leaks. And hey presto, she's running better than before with a much nicer induction noise.
Thanks all who helped out with this

[Onne]

Well done, solved the problem on mine too.
Now running on a CO of 1.5% , 157 HC PPM.
Not bad for an old boat CO is even better on LPG (0.07%)