W124 230CE - will not start!

[Will]

Hi,

Posted on behalf of a friend of mine who has just bought a 1992/3 (K) 230CE Auto.

Basically the car hasn't been used in about a year, and before that it 'cut out' on the previous owner (apparantly due to lack of fuel?)

Anyway, he's got it sitting at home and has started to look at it.

He's checked some basics so far - there's fuel getting to every injector nozzle under pressure, ie - fuel supply seems ok, there's a spark at every plug and has good compression on all four cylinders - but will not fire?

I've not had an opportunity to look at it yet but he's covered what I'd have checked so far? He's put a new set of leads on it and new plugs, as well as a spare fuel distributor.

Can anyone shed any light on what could be causing this? I'm thinking compression/fuel/spark should produce some sort of attempt to fire, even if the timing was out etc? What's involved with the throttle part of this engine? Blocked cat?

Any help much appreciated and I'm sure it'll relieve my friend to see it back to life

Many Thanks,

Will

 

[Dieselman]

Is the fuel old or new petrol. Old petrol degrades so won't ignite.
Try pouring a small amount of petrol down the inlet manifold to get things going, if you're sure you have a spark.

 

[Will]

Thanks Dieselman - that's one of the things I suggested but when I mentioned it earlier he was pretty convinced that it wasn't to blame. He's been trying some 'eezi-start' too so I'm not sure if that helps the diagnosis?

I'll suggest an amount of fresh petrol for starters and then see how it gets on.

12 month old petrol can't be a good 'start' can it!

Cheers,

Will

 

[Ian B Walker]

Will, has anyone been playing with the distributor? Is the cap on correctly, sometimes they go on 180 degrees out. Failing that and if you have a spark and new fuel I can only think that the timing is out. Not sure about this but what about the OVP relay?

 

[Will]

Thanks Ian,

I've already got him to check the OVP (fuse on top is ok) and fuel pump relay (primes ok and pump runs when turning over). Fuel pressure appears to be fine as it is spraying nicely from the nozzles he says. Spark is present at all four plugs - I also asked about the timing/distributor and he reckons they've not been touched. Cap 180 degrees out was similar thought - I considered misplaced leads too.

New fuel and checking cap isn't on 180 out are the two strongest suggestions so far Thanks guys I'll keep you posted

Will

 

[Howard]

OVP relay can 'go' without blowing the fuse .....

 

[grober]

Has he renewed the fuel filter? could check that the fuel supply pressure is within spec. Might be an idea to take off the cam cover and check that the correct valves are opening and shutting at the right time in relation to the distributer rotor arm position. (mark the position of the various cap leads on the side of the distributer body before taking it off to see the rotor arm).Is he getting a nice fat healthy spark at each plug and not just a weak little spark in the open air? just a few suggestions.

 

[Will]

Hi Guys,

Bit of an update on this - popped round and he's drained the fuel out and put some fresh petrol in, in doing so encountered on closer where the problem lies.

With the fuel pump relay fitted, the car will not start. With it removed (but system primed of fuel) it will.

If you prime/pressurise the fuel side, it will run for 5 or 10 seconds (until the pressure drops and the fuel supply is exhausted). If you are to bridge the terminals 30 and 87 to enable the pump to run without using the relay (ie, pump powered and running continuously) it will cut out immediately.

Have firstly tried a different fuel pump relay and OVP relay without any difference. Quick look in an old haynes manual for a 190E shows that linking 30 and 87 will also apply power to an auxilliary air heater?

I'm thinking to try and disconnect the fuel pump at it's +ve terminal and run power straight to the pump for the purpose of fault finding? Apparantly the car had an old 'Laserline' alarm system removed some years ago (previous owner reckons 4 or 5 years back...)

Anyone know where the auxilliary air heater is located/connected? I'm guessing somewhere on the throttle body but not sure exactly where.

What is slightly confusing in all this is that there is definately a spark present when the engine is cranking over on the starter motor with the fuel pump relay fitted?

Anyone come accross this before?

Cheers

Will

 

[Dieselman]

What fuel pressure is generated when the fuel pump primes? It doesn't make sense that the pump stops when the relay is bridged, are you sure there is 12v feeding the relay.
How are you priming the fuel system without the pump?

At the end of the day you just need to check there is 12v and a good Gnd at the pump for it to run.

 

[Will]

Hi Dieselman,

Fuel pump seems to be running ok - it pressurises up fine with the relay fitted (and the relay has been tested in another vehicle). With either the relay powering the fuel pump as it would do normally, or by bridging terminals 30 and 87 out (so that there is power directly to the pump constantly) it will not run. With the power to the pump removed, it will.

Obviously this doesn't make much sense - I can't see why powering the pump would prevent the car from running - hence I suspect some sort of fault with the wiring from the relay to the pump or whatever else it's connected to (eg this aux air heater)?!?

I'm planning to leave the relay out, but allow the pump to run (by powering it directly - by-passing the normal wiring to it) to be certain that the pump is not to blame?

Will

 

[grober]

Quick look in an old haynes manual for a 190E shows that linking 30 and 87 will also apply power to an auxilliary air heater?

dont know if your 230 would have this (you may have the fully motorised idle speed control item 113 in 2nd diagram referenced below) but the auxiliary-air device is a fast idle device which bridges across both sides of the throttle plate. Its normally connected via a maze of rubber pipes. In the electrically heated one(item 74) when the engine is cold its open and idle speed is increased (its like the throttle has been opened slightly) a shutoff plate is connected to a bimetal strip heated electrically. As the bimetal strip heats up it "shuts" the bypass. Might be worth disconnecting it electrically temporarily for test purposes as if its faulty it might be shorting to earth . the only result of disconnection would be you will have a permanent fast idle. you will have to remove the aircleaner to see clearly. its item 74 in the first diagram here http://www.detali.ru/cat/oem_mb2.as...GM=717.412&CT=M&cat=504&SID=09&SGR=060&SGN=02