500se just cut out

[Stedan 126]

good afternoon all,

A bit of help if you can. Just fired up the old S Class after not moving for weeks. The battery had been connected to the Optimate and after a few cranks, she stuttered and fired up.
Went to the fuel startion to top up and put air in the tyres so only a couple of miles of a run, no heater, lights etc on keep the battery good to crank up when leaving the fuel station.
Anyway, cranked her up, a bit slow, but fired. Left her ticking over for 2-3 mins and then it just stopped. Turned her over again, cranked over at normal speed and fired up, revved her a bit and then she stopped again. No coughs or judders, just like turning off the key.
3rd time, she fired up, ticked over for a few mins and then risked the trip back home with no problems. Started and stopped her a few times back at home and all seems OK.

What do you think, Damp? just strange there was no judder or cough and splutter, all the guages just went down which makes me think electrical

Thanks for reading.

 

[Stedan 126]

Update:

Just been out to move the old girl back on the drive and she fired up first time, starter went over at normal speed, ticked over at around 600 (ish) and never stalled.
System is charging at around 13.8v and the engine tone changes when I turn on the rear heated screen so I'm convinced both battery and alternator are good.

Maybe a good blast out may help.

 

[television]

A lazy fuel pump relay is well known on this car, bridging pins 7 and 8 would make the fuel pump run all the time for testing purposes

 

[Stedan 126]

Thanks Malcolm, I will try it again tomoro and if she stalls, listen if the pump primes on ignition and if not bridge out the socket?

I'll let you know. Thanks.

BTW, the last time this happened, it was a few years back on a cold snowy night and again, the car hadnt moved for a while and by pure coincidence, cut out a a different petrol station after another short run!

 

[Stedan 126]

Another Update:

Went to start her this morning, and she fired up fine but the revs were high, around 1300rpm and the ABS was on. Turned her off and then re started, same thing. After around 40 secs, revs dropped to under a 1000 like usual on start up and the ABS light went out, shortly after, the revs dropped to around 600 as usual.

Is that a clue to my stalling issue yesterday?

Thanks again all for reading.

 

[television]

Yes that points to the OVP relay as being defective and will give both faults when bad

 

[Stedan 126]

Heard so much about these things........

Many thanks Malcolm for a quick response. I gave the OVP a tap today when running to see if anything happened, but no.
I'll pull it out tomoro and have a look inside. Failing that, just purchase a new one.

Thanks again for your help.

 

[rpe2]

Check for damp in the dizzy cap..

 

[Stedan 126]

Thanks Richard, will check that out too but from memory, the damn screws are old, rusty and tight so never managed to take it off before!

Give me something to do on Saturday morning though.

Thanks again guys for your help.

 

[television]

The OVP relay is the only one that could put the ABS lamp on along with rough idle. they get bad soldered joints and best to re flow all joints adding new solder as you go, it would only take 4 mins to do the lot

 

[Stedan 126]

Thanks Malcolm.

Stripped down the old OVP this evening and condition wise was ok, just a bit of green on a couple of pins and the socket, so the cracked it open and it was like new with no green anywhere!

I removed all the old solder and reflowed with new and then cleaned the PCB. Will clean the socket tomorrow and try it out.

Will let you know how it works out

 

[television]

That was the best way it takes a magnifying glass to spot some bad joints, even then you cannot see them all.

I hope it is OK

 

[Stedan 126]

Well, cleaned the socket up but it was only surface and only on ign 15, and all were clean inside too.
She fired up straight away and the revs were around 600 which is unusual on start up as its normally around 900. Turned off and on again, revs were around 900 this time and then after 20 secs or so, dropped to around the 600.

Did a short run, engine off and minutes later, fired up straight away - good!

Went for a quick 15 min blast, some lanes and motorway and she never missed a beat, kickdown and everything. I forget how quick and fun this car is when its warm. Tried a couple of start ups when back home and all good.

Fingers crossed, that may be it but there isn't much to the OVP in mine, 1 diode, 1 resistor, a 10 amp fuse, a large chassis mounted Zener and a relay.

 

[television]

So pleased that has worked for you,,, It should be OK now