It's A Mystery!!!

[ScouseJames]

So, at the end of October I put my '66 230SL into my mechanic to sort out some issues over the winter.  The two main problems were:
1. Smoky exhaust, and using a lot of oil (more than is usual) - There was discussion about having the exhaust valve stem seals done, but I had the engine rebuilt 10,000 miles ago so surely they should last longer than that? (I'm up to approx. 152000 now).
2. Cutting out when car is stopped - When I tried to reverse off the drive after first starting the engine or if I came to a roundabout or traffic lights not long after starting, the revs fell, and the engine cut out. This didn't happen once fully warmed up. Also, in Neutral or in Park, it's revs up around 1500 RPM.  This problem arose over a period of time.

The first issue has been resolved; I'm awaiting a detailed explanation of what was wrong but apparently there was an issue with the valve guides and not the valve stem seals. 

But the second issue hasn't been fixed, and in fact has gotten worse.  It was thought that it was a temperature-related issue but I had the car back for this weekend and whilst it ran fine at speed, when I pulled into a service station it would cut out as I came to stop in a parking bay or at traffic lights. The revs would just reduce to zero and the engine stop. This would be within minutes of pulling off the motorway so the coolant temperature would still be around 180F. The injection pump has been off, checked, and recalibrated, new electronic distribution been fitted, other things like the cold start function, and constant speed solenoids have been tweaked to no avail, and the issue has my mechanic scratching his head. 

He's going to get a second opinion, but if anyone has had any similar experience I'd be happy to hear from you.

[stickandrudderman]

Is the car auto or manual?

[mdsalemi]

Regarding the second issue, happened to me and there were two causes fighting each other; each was responsible for the stopping at one time or another.

1. I had an electronic ignition system installed when the car was restored in 1999-2001. That ignition was a Crane XR-700 that used an optical shutter wheel installed underneath the rotor inside the distributor, and replaced the points with an optical pickup. My problem was this worked fine for the first five years of installation, then was one of the causes of intermittent dying. When I probed, I discovered that the wires inside the distributor were making contact with the large shutter wheel, and as this wheel was not rigidly attached to the distributor shaft, as soon as they made contact, the shutter wheel stopped and thus the car died.

2. Second issue was the wiring to the fuel pump in the back of the car. As a bit of a [stupid] shortcut in the restoration, instead of carefully removing the wires AT THE PUMP, the mechanic cut them; then when being put back together, used inline crimp splices. Well, after a number of years of living underneath the car, these crimp connectors lost their electrical integrity. No power to the fuel pump means no fuel. I had blamed it on the fuel pump; when I went to replace the fuel pump the wires just gave way. The repair to this was new wires, and NO CRIMP SPLICES outside the car. Solder connections in the trunk/boot.

None of this may be your issue, but both in a sense, were electrical...

[ScouseJames]

I should have said it's an automatic.

[ScouseJames]

Thanks for your reply Michael,
I was thinking that the worsening of the issue may be electrical in nature but need to find time to have a good think about it.  My mechanic has replaced the electronic distributer so I will get confirmation of what type.

One thing I didn't mention is that the car is fitted with an immobiliser/alarm system.  Although I don't have to reset the immobiliser when the car suffers this problem, I will be having a chat with the installer to see if the unit could be failing.

[Pawel66]

We will see what the experts will say, but would bet my money on a simple linkage tour.

[Cees Klumper]

The fact that in neutral the engine revs up to 1500 rpm makes me suspect the constant speed solenoid function. The rpm should be the same whether the car is in gear or in neutral (or park). Also, 1500 sounds quite high, what is normally the rpm at idle in gear? (When it doesn't stall).

[ScouseJames]

Thanks for your reply Cees, but that has been looked at already and the CSS adjusted.  It now revs around 8-900 RPM.  The 1500+RPM reading was recorded before my mechanic got his hands on it.  It's the cutting out that's the issue now.

[Pawel66]

So it dies when you stop, regardless whether in gear or not?

Does she start easy then when warm/hot?

[ScouseJames]

Yes, it dies whether in gear or not when I come to stop, but not always just most of the time.  If it dies, it starts up straight away.

[Pawel66]

Then, sorry to march ahead of orchestra, I would say the idle is not set properly.

[UJJ]

Perhaps it has something to do with your brake booster vacuum?

[Pawel66]

Perhaps it has something to do with your brake booster vacuum?

I started typing that! But then I thought it increases idle rather than makes the engine stall...

Do you have Air Conditioner by any chance?

[ScouseJames]

No, no A/C fitted, and my mechanic says he's happy with the idling.

I'll have a read through the forum to understand how the brake booster vacuum could effect the idling.

But just to reiterate the problem, as an example I come off the motorway after a high-speed run so the engine is at optimal operating temperature, and having slowed-down for in-town roads/traffic, come to a stop at a set of traffic lights, then the revs quickly fall to zero and the engine stops.  I can restart the engine straightaway, and drive off from the when I get a green light.  This can happen each time I come to stop at traffic lights or a T-junction but not always.

We are arranging a "second opinion" at the end of the month, so the car will go back in storage for a couple of weeks.

[Pawel66]

Still, with all due respect - maybe the mechanic is happy with the idle, but the engine stalls, so there is no idle. I would click the idle adjuster one click to the right and see what happens. If you note number of clicks, you can return to where you were.

[glcg123]

I had a similar issue with my 1965 230SL. The problem only occurred during long highway runs on a hot day. We discovered that the electric transfer pump from the tank was only producing 1/4 of the needed flow, 250 ml per min versus 1 litre per min. Pressure was only 9 psi versus 14 to 15 psi. That flow is designed to cool the injection pump. If the injection pump gets too hot you could conceivably have vapor lock. We changed out the rear pump and everything works fine now. Checking the fuel flow is a simple process.

[J. Huber]

How are the points?

[Nevermind that...] just reread and saw "electrical distribution" which I take to be you no longer use points?

The CSS and/or linkage issue sounds reasonable.

[ScouseJames]

Thanks for your message James, yes it has electronic distribution, and that has been changed too.

I've had to put the car in storage for a couple of weeks but the posters here have given me a few things to think about.

Cheerrs,

Jim.

[ScouseJames]

So, at the end of October I put my '66 230SL into my mechanic to sort out some issues over the winter.  The two main problems were:
1. Smoky exhaust, and using a lot of oil (more than is usual) - There was discussion about having the exhaust valve stem seals done, but I had the engine rebuilt 10,000 miles ago so surely they should last longer than that? (I'm up to approx. 152000 now).
2. Cutting out when car is stopped - When I tried to reverse off the drive after first starting the engine or if I came to a roundabout or traffic lights not long after starting, the revs fell, and the engine cut out. This didn't happen once fully warmed up. Also, in Neutral or in Park, it's revs up around 1500 RPM.  This problem arose over a period of time.

The first issue has been resolved; I'm awaiting a detailed explanation of what was wrong but apparently there was an issue with the valve guides and not the valve stem seals. 

But the second issue hasn't been fixed, and in fact has gotten worse.  It was thought that it was a temperature-related issue but I had the car back for this weekend and whilst it ran fine at speed, when I pulled into a service station it would cut out as I came to stop in a parking bay or at traffic lights. The revs would just reduce to zero and the engine stop. This would be within minutes of pulling off the motorway so the coolant temperature would still be around 180F. The injection pump has been off, checked, and recalibrated, new electronic distribution been fitted, other things like the cold start function, and constant speed solenoids have been tweaked to no avail, and the issue has my mechanic scratching his head. 

He's going to get a second opinion, but if anyone has had any similar experience I'd be happy to hear from you.

Long story short, the "second opinion" found a defective injector.  Once this was replaced, and after a couple of distributor tweaks it's running fine