Starting/Running W124 300ce

[livcraig]

Hi Guys,

I am new to the forum, but have always been a huge Merc fan. I bought myself a lovely 1989 300ce coupe from a Merc enthusiast last year. The car has 55000 miles,is in lovely condition and never missed a beat. I put it in the garage in September 09 and returned a couple of week ago - it would not start - obvious it was the battery.

I put the battery on charge, which when re fitted was full of juice and turned the engine over no problem at all, but it just would not fire several frustrated attempts later it fired, ran very lumpy for 5-10 seconds and cut out. After re trying it fired first time but the second I put my foot on the throttle it instantly cut out.

Of course all the attampts to start it has flattened the batery again - its a viscious circle but I am really at a loss as to what could be the problem - has anybody had this issue with the W124 straight six engine?? The only small giveaway may be that in the boot when I bought it there was a distributor cap cover and a couple of cartridge fuses. The previous owner never mentioned anything (funny that) but he may have had issues with the ignition system

Any help/expertise on this matter that you are willing to share would be extremely appreciated.

Many Thanks

Craig

 

[grober]

Almost certainly damp ignition on the high tension side. Take off the distributor cap and dry it out. Try to give the distributor body a dry out as best you can with a hair drier also. Water tends to condense in there. Remove the spark plugs and dry/clean them up- better still treat the old girl to a new set. If the petrol dates back to Sept 09 drain it and put some fresh in. Chances are it will start on the button.

 

[RBYCC]

In addition to Grober's suggestions, also check the fuse(s) on top of the OVP ( Over Voltage Protection ) relay located in the battery area...
It acts as sort of a main control point along with the fuel pump relay.
If the fuse(s) are fine, then tap the relay or unplug it and plug it back in again.

What makes me suggest this is that the engine cut out in 5-10 seconds.
The circuit is such that if a speed ( tach/engine run ) signal is not proven in about 10 seconds, the relay will drop out the fuel pumps.

Always start with the least expensive fix attempt....

Ed A.

 

[isobars]

Hi All,

This looks like it may help me diagnose a puzzling and frustrating problem with my 300/24.

The car starts fine and dandy when the battery has been re-connected, and will run smoothly all day. Turn it of for five minutes, it will oblige once more, however, leave it a couple of hours and nothing. Not remotely interested in playing the game.

Is this a FPR problem?

Would anyone know the part number?

Is there way of wiring it to work to test the theory?

Thanks in Advance,

Paul

 

[nabbott]

Just had a similar problem on my 4 cylinder. Turned out to be the fuel relay (which is located under a cover behind the battery on my car.

 

[isobars]

Thanks for that, much appreciated.

Looking for a relay right away.

Cheers,

Paul

 

[Ian B Walker]

Is there way of wiring it to work to test the theory?



Paul

I seem to remember reading somewhere on here that by bridging 2 contacts you could bypass the relay. Pin 37 comes to mind but the other one I cannot remember. Try a search though the threads for the info.

 

[219]

Pull out the fuel pump relay ( the one with 'Kickdown' printed on top , about the size and shape of a 20 pack of cigarettes ) , pry off the plastic cover and inspect the solder joints on the circuit board - chances are some of the joints will be 'dry' or will have actually broken and be making intermittent contact . Re-solder for a cost free repair .

 

[isobars]

Hi,
Thanks for the extra info.
Two forum references for jumping are 15/87 and 30/87. I hope it will be obvious when I pull it.
From Ian's part ref, these 24v relays don't have kickdown on them, just KPR, which I guess is Kraftstoffpumpe Relay?
Cheers,
Paul

 

[bolide]

I would say the OPs problem is a bad battery - leave any W124 for 6 months and I wouldn't expect the battery to survive

Nick Froome
the independent Mercedes Estate specialists