190e won't start - odd

[stuarth]

190e 1989. I have not used it for about a month and it has been in the garage all the time and now won't start. The battery is fine and turns it well. There are sparks at the plugs and the tank is full. There are no blown fuses. The first time I tried to start it it did fire for about two seconds but now nothing happens. What is the logical sequence to fix this? It seems to me like it could be fuel supply or the injection system in some way. I don't hear the fuel pump ticking at ignition - should I? Flooding is pretty unlikely I guess.
Bit stumped!

thanks for any advice

 

[Dieselman]

It's probably the fuel distributor needle a bit stuck or gummed up. open the air filter and press down on the air flap when cranking, also check teh cold start injector is working.

If you definitely have a spark then try dribbling fuel down the intake as the engine turns over.

 

[stuarth]

Dumb question but where is the cold start injector?
I have not tried this yet but will do so today. Is there a way to check fuel flow to the injection system or is it a bit dangerous to switch on the ignition and then undo one of the inlet pipes? I guess so :-(

thanks

 

[jaymanek]

Yes just crack open one of the injector pipes.. should be some pressure there... can you hear the fuel pump running?

The cold start injector is at the front of the engine.. just looks like an extra injector plonked in the middle of nowhere.

 

[grober]

Fuel pump relay? Give it a tap of encouragement- sometimes gets it going. Its behind the flexible black plastic shield behind the battery and its usually marked kickdown 4zyl On first switching on you should hear the fuel pump running briefly to pressurise the system so is a possibility.

 

[Will]

Fuel pump relay? Give it a tap of encouragement- sometimes gets it going. Its behind the flexible black plastic shield behind the battery and its usually marked kickdown 4zyl On first switching on you should hear the fuel pump running briefly to pressurise the system so is a possibility.

I'm with Grober on this one. Sounds like classic fuel pump relay symptoms.

It ties in perfectly with the 'running for 2 seconds' as well - until the system depressurised. You should also hear the fuel pump run for a second or two to prime/pressurise the system when you first put the key in and turn it onto the ignition position.

You could try linking the relay out if you're stuck and need to move the car - it'll run the fuel pump continuously.

Will

 

[jaymanek]

You could try linking the relay out if you're stuck and need to move the car - it'll run the fuel pump continuously.

Will

To do this wrap some wire around pins 87 and 30 and put the relay back in.. the pump should then run..

 

[stuarth]

There are four pipes coming out of the top of the injection system that go to the cylinders and one coming in from the injection pump. On the injection pump there is a pipe at the rear and a pipe at the front, both of which disappear under the engine and go to the fuel tank I guess. I assume one brings the fuel and the other returns the excess.
When I open these two pipes. one has no petrol coming out (the rear) and the other has a bit. When I switch on the ignition, neither changes. Would it be correct to assume that when I switch on the ignition, the fuel pump should provide a lot pf pressure to each and so there should be quite a lot of fuel coming out? If so, the fuel pump is broken, jammed or has no electricity supply either because of a fuse (no) wiring.

What do you think?
thanks

 

[grober]

I don't think you are looking at the fuel pump we are talking about. Its located under the car just in front of the rear offside drive shaft. Its not in the engine compartment! You may be looking at the warm up regulator/primary pressure regulator.

 

[stuarth]

Sorry. I meant the fuel injection system.
I found the relay. I assume it plugs in? I can't get it out so is there some kind of hidden catch or is brute force OK?
I do NOT hear the pump running at all and there is no audible click from the relay when the ignition switches on.
So, how do I get it out without breaking it?


thanks

 

[grober]

It just plugs in to the socket. Support the mounting bracket/socket with one hand use the other hand to wiggle/pull the relay upwards. If this fails a bit of judicious levering under the relay base with a screwdriver-[careful not to short anything] should free it up

 

[stuarth]

You guys are geniuses (genii?) . Removed the relay (has a couple of plastic spiots to lever out of the way, shorted 87 and 30, plugged it back in - pump runs and engine starts.
Wish I could buy you a beer.
Thanks very much for your help and patience.
regards
stuart

 

[jaymanek]

So now you need a relay

 

[stuarth]

Just a thought. Is this relay electromechanical or solid state? In other words, would I hear it click or not?
There a couple of things that could be jamming the relay anyway - there is the cold start valve and hot start valve (retarder). Any experience with this?

 

[jaymanek]

Yes it clicks...

I had been having an issue with my SEC... it would randomly cut out at junctions... I changed the cold start valve and it hasnt happened after that.

 

[stuarth]

Looking at the circuit diagram, it looks like the cold start valve and the 'soupape de retard thermique' which I suppose is heating delay valve (?) are both directed by the electronic control box (line 24) and would, when working, be not earthed. I can then only suppose that if eithe failed then it would be because of an internal short circuit, earthing them and shutting the relay. So, it I disconnect them, the relay should work.
Is this logical and has anybody diagnosed beyond the relay to find out if something else is stopping it working? Alternatively, how can I test the relay before I buy a new one? I could go to Merceds and get them to connect their diagnostics I suppose but I doubt they would do just this and I would have to put the car in for repair.

 

[grober]

The relay is mechanical but can serve several units in addition to the fuel pump such as the cold start valve. What usually goes wrong with the relay is the small internal circuit board everything is mounted on develops dry joints in the soldered connections. Often a brief run over these connections with a soldering iron can repair it. the 'soupape de retard thermique' is a thermal delay switch which when cold provides an earth for the cold start solenoid valve circuit --- it has a bimetal strip and a built in heater coil. This causes the switch to go open circuit after a fixed period of time after being powered up or immediately if the engine block is already hot.

 

[Will]

It's almost certainly the relay that is at fault, they're a very common failure item on the 190Es.

You could try a repair - or just find one from a breaker, there's loads of 190Es out there in scrapyards etc and a relay will be peanuts.

Will

 

[stwat]

Just make sure you get the exact same relay as the one you have because they are all different from car to car. The relay controls the rev limiter among other things. Each model has a different rev limit and cars with auto gearboxes are different once again from manual cars. Make sure the part number is the same.

 

[stuarth]

What switches the relay on and off and hence the fuel pump on and off? I am assuming this happens during driving or does it just run continuously when the ignition is on? I am curious in case it turns out not to be the relay (I am hunting for a new one but might be forced to repair mine).
thanks