W124 - cutting out when warm

[howzat1976]

Hi All

Need some help with my W124 1992 E300-24V, it starts from cold when warmed up it begins to stall at low revs until it cuts out. It then only starts from cold. Now it cuts out almost straight away (after 3/4 miles), I've been told it could be the Over Voltage Protection Relay, then the AA said its the Crank shaft sensor.

The car is in mint condition with only 78k on the clock.

Any ideas?

Vass

 

[westcliff]

You could try changing the OVP relay, it's cheaper than a crank sensor I think and it's easy to fit. The part number is 000 540 6745 (that's the later one; your car will have 000 540 5245 - they both work). I got one for £20.00 from a breaker and it sorted the starting problem my W124 had.

 

[westcliff]

I forgot to add that I recently did a search here on OVP and found a post which stated that the OVP relay can cause a crank sensor error to be reported. I had my crank sensor changed, with no joy, before I changed the OVP relay.

 

[supercharger]

i concur with the above. also the symptoms you describe also indicate a fuel pump relay again common fault on mercedes its located to the left rear of the battery as you look at the car.


supercharger

 

[howzat1976]

Thanks to all, I was told that if it was the OVPR then the ABS light would come on, no light on.

Vass

 

[howzat1976]

Thanks westcliff, is located behind the battery? what does it look like?

Vass

 

[howzat1976]

Supercharger, thanks...AA said it wasn't the fuel pump relay. He carried out some sort of test..

I guess I may have to change one at a time before I locate the problem.

Vass

 

[westcliff]

Behind the battery is a curved plastic panel, which pulls out (a bit of a fiddle to get it out and back). The OVP relay is on the right, with plastic cover over it. The cover just lifts off. The relay is silver and about 4 inches high x 1.5 inches by 1.5 inches. It has a clear top with a fuse visible. On my car, the relay is secured to the bulkhead by 2 small bolts and is quite a tight fit in its 9-pin base, so take your time pulling it out.

 

[howzat1976]

Thanks again, I know it. Right behind the battery as you described sliver rectangle box.

I take it you just plug it in?

Vass

 

[television]

Fuel pump relays do get dry jointed inside and are easy to fix.

An easy test is to pull the relay out and put a jumper from pin 30 to 87 and the fuel pump will run all of the time, and the engine will run if this is the problem.

The crankshaft sensors do pack up and go Open circuit, the can be tested in situ and should read 1k ohms when good and over 100k ohms when bad.

If you have 12 volts on the engine ECU then it will not be the OVP relay

 

[howzat1976]

thanks televison, AA done the test for the Fuel Pump Relay, its not that. So I guess it's either Crank Shaft Sensor or the OVPR. I'll get those test carried out and see what happends.

Regards
Vass

 

[howzat1976]

problem fixed it was the dizzy cap, lesson to be learned always get a second opinion. After the AA and a Merc specialised mechanic looked at the car both said it was crank sensor. ****** W*****S!!!