SL500 W107 chassis stalling problem

[Diamond Girl]

Help! I have a problem with my 1985 SL500 cutting out randomly and being difficult to re-start. My garage has replaced the fuel pump and ignition amplifier but it's still happening. It happens both when idling and when my foot is on the accelerator. Any ideas would be welcome.

 

[Myros]

it might be the OVP

put th first six figures of the VIN number up, and I'm sure Malcolm will be able to tell you if you have one, and between us, work out where it is.
It could also be a lot of other things. Did your garage check the distributor cap for cracks, did they read the fault codes on the diagnostic?

A bit more description of the symptoms would be good. Is it only when cold, only when warm, only when at normal temp, only in drive or only in N or P. that kind of thing.

 

[star]

a 1985 would make it a 500SL not a SL500. If all the obvious check have been done, check the fuel pump relay.

 

[Diamond Girl]

put th first six figures of the VIN number up, and I'm sure Malcolm will be able to tell you if you have one, and between us, work out where it is.
It could also be a lot of other things. Did your garage check the distributor cap for cracks, did they read the fault codes on the diagnostic?

A bit more description of the symptoms would be good. Is it only when cold, only when warm, only when at normal temp, only in drive or only in N or P. that kind of thing.

Hi, thanks for responding. I'm sure that the basic checks were carried out by the garage but I will ask those specifics when I go back this week. My VIN is 107046.

As for the detail, it has happened both when warm and cold, I've only noticed the problem occuring in drive, as it's generally when I'm driving along when it happens. It does sometimes cut out when I'm stopped at a junction in drive with my foot on the brake. I have also noticed that the performance suffers when I put my foot down - it's like a buffeting sensation and the power is noticeably less. I am aware that my nearside manifold is going, the garage has told me that this could be affecting the performance although I'm not convinced. I would expect a bit of noise but not hampered performance. Looking at some of the other posts on here I winder if the MAF senser could possibly be something to look at?

 

[BlackC55]

Has not got a MAF.

Is it fuel related?

Get the fuel pressure checked.

 

[Myros]

I'm on all fours with the last post

it sounds like a fuel/air mix problem. If the exhaust manifold is leaking, that could be a factor in it, but it sounds more like an over/under fuel issue.
Do you have any associated petrol fume smells when driving along, or backfiring. What are your spark plugs and leads and distributor cap like? They could also cause the symptoms, by messing up the spark, but if it runs half okay, it's probably not them, as the dizzy stays pretty dry on a v8 107.
Sorry if I'm not helping much, but I'm trying to scope it out from first principles.

 

[Diamond Girl]

Hi, plugs and leads are all OK, the garage have also checked the distributor cap. It's back with them now and they are sure it's electrical because you can keep the engine running by keeping the ignition key forced as far as it will turn. This is what led them to change the ignition amplifier which has not turned out to solve it. I don't get apetrol smell or backfiring, it just feels like it stops breathing!!

Thanks for all your suggestions, if you have any more anything's worth a go, as the garage seem pretty stumped.

 

[stats007]

Whereabouts are you based? There are a lot of specialists I could recommend.

 

[MIW615]

I'm not too familiar with the 500SL, but owned a 350SL for many years, It sounds like a fuel problem to me. The system is K-jetronic and is a very basic FI system, as mentioned you need a FULL pressure check of the system including testing the pressures of the warm up regulator (in hot and cold conditions) also when checking the main system pressure they must check to see that the fuel pressure is maintained to certain pressures even when the ignition is turned off.

The most common faults with your system is the pressure leaking back, there is a one-way valve in the system to control this (most are fitted to the fuel pump) and the fuel accumilator is another weak link.

Be sure that the repair shop that does the test fully understands the system and has the correct Bosch tooling

 

[Diamond Girl]

I'm in poole, dorset

 

[stats007]

A chap had similar symptoms with his SEC that shared the same engine. Check the fuel pump relay as it could be intermittent, as well as the OVP relay which feeds the ECU for the ignition. Fatigued solder joints are a possibility in both.

It could also be the ECU of course.

 

[Diamond Girl]

Thanks for the advice, I will suggest these checks.

 

[stats007]

I'm in poole, dorset

You have Jacksons the main dealer there. Mervyn Wright the head of classic parts knows more about 107s than anyone I know.

 

[star]

Hi, plugs and leads are all OK, the garage have also checked the distributor cap. It's back with them now and they are sure it's electrical because you can keep the engine running by keeping the ignition key forced as far as it will turn. This is what led them to change the ignition amplifier which has not turned out to solve it. I don't get apetrol smell or backfiring, it just feels like it stops breathing!!

Thanks for all your suggestions, if you have any more anything's worth a go, as the garage seem pretty stumped.

if you have to keep the key turned to start position, (which powers the fuel pump directly and by passes the fuel pump relay whilst in start pos) check your fuel pump relay out.

 

[Diamond Girl]

Thanks, I know of Mervyn, am just reluctant to pay jacksons prices, but armed with this knowledge looks like it may be money well spent!

 

[Diamond Girl]

Interesting - they've not mentioned that. I've just come back from the garage and they've ordered a TV lead for it - does this sound way off the mark?

 

[star]

TV lead?? are they gonna watch Eastenders? HT lead maybe, i dont think its that. sorry. another thought, its loosing its TD signal to the fuel pump relay, or it has an alarm fault(after market alarm fitted??)

 

[MIW615]

Interesting - they've not mentioned that. I've just come back from the garage and they've ordered a TV lead for it - does this sound way off the mark?

Did they check the fuel pressures? I wonder what it is they have ordered - TV lead, sounds strange???

 

[Myros]

Transmission Vacuum?

there is a vacuum pipe and a cable link to the box on a 107. Can't see a vacuum problem causing stalling though. Messy changes yes, stalling no.