1987 560SL Stalls Turning Right

I can only imagine how much fun Ray and Tom would have with this one. Yes, my car can’t be driven above ~20mph if a right turn is involved. I would love some non-political solutions. :wink:

The issue started when a friend helped me put in a new starter. I got the car started just to test the starter, but did not take it for a spin. My wife took it out the next week and found it was stalling whenever she took a right turn/bend in the road. I took it out and confirmed this really was happening.

I can only assume that the starter repair contributed to this issue. We do not have to be driving very fast for the problem to occur. Below 10mph, I can get through a turn without stalling. As speeds approach or exceed 20mph the car will stall every time we turn to the right.

Could this be electrical? I don’t notice any sputtering before the car stalls. It stalls very early in the turn.

Any suggestions on where I should be looking or testing would be appreciated.



I would guess that there’s something wrong with the pick-up filter in the gas tank.



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Think my 1980 Grand Prix did that. Would stall out on turns. Something about the module inside the distributor? I know your motor has distributor.

I think this model uses CIS injection so a weak fuel pump is always a suspect. The starter motor may be a coincidence.The CIS system runs at about twice the pressure of “normal” fuel injection systems and the pumps do take a beating. The commutators on the pump armatures have a tendency to wear badly and I think (?) this car has 2 pumps and one or both may be mounted externally. See my last sentences.
Unfortunately. to test the fuel pressures (plural as there are more than one figure) requires a special test gauge.

I can’t speak with authority on Benzes as I have done omparatively little service work on them but some other makes that use CIS have a fuel pump relay input from the starter motor. Sure the starter wiring is correct?
Sure there is not a vacuum source dislodged and iffy? CIS systems do not tolerate ANY vacuum leaks no matter how small.

db4690 is a Benz guy and maybe he will weigh in on this. I know CIS pretty well (it’s an abomination to the Lord IMO) but maybe he knows something about the Benz I don’t; which is nearly everything.

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Forgot to hook up a wire, and when you make a right turn it swings and grounds itself.


It could be there is a problem with the wiring to the engine. I would check the wiring in the engine compartment and look for any signs of damage to the wiring due to heat from the exhaust manifold. You could also try moving and tapping on suspected wire harnesses while the engine is running to see if you can locate the trouble. Also check for a loose connection.

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Sounds like there are a few options.

Let me know if you all agree with degree of difficulty and cost – that’s how I’d typically prioritize the possible solutions.

(1) Fuel pick up… I can go fill the tank and see if the problem goes away
(2) Fuel pump(s)… these are very easy to change on this car
(3) Electrical issue… time to take it to a mechanic? :-/

I have already changed out the fuel filters. When I was typing out #2 above, I had the realization that maybe I didn’t put everything back together well enough. I’ll look the filters over to be sure as well.

My friend was the one on the ground actually hooking up the new starter. I’m pretty sure he did it all correctly, but there is always a chance something wasn’t done. Since the screws/bolts are different sizes, it isn’t easy to attach something wrong, but he could have missed something, for sure.

I’ll report back as I tackle this. I’m in central FL this summer, which means I’m not prioritizing this too high. I’ll try to remember to fill up the tank this weekend and see what happens.

If you’re sure about that assumption of the starter repair being a contributing factor - and that’s a big if - then re-trace the steps you took to replace the starter. While almost certainly not directly related, it could be that you moved a wiring harness or re-connected a battery lead or something improperly.

Otherwise, one of the suggestions above is the direction to go. Generally speaking, unless the issue started immediately after replacing the starter, and not “the following week”, then the timing is probably coincidental.

If you were driving it frequently before the repair, and it stated with the repair, then something happened. I’d go over every wire that might have been touched. Did the car get jacked up? Maybe junk in the gas tank was moved near the fuel pickup. If wiring isn’t the problem I’d rig up a fuel pressure gauge to see what happens when you turn right.

Since I did have to disconnect the battery to do the starter that might hold merit. I’ll have a look at the battery. Also, I replaced a relay (the fuel pump relay, I think?). I wonder about the wires behind the glove box now too.

Thanks, that gives me some more relatively easy things to look at.

My first pick for the trouble would be an electrical problem. Like a loose connection, fuel pump relay problem, or something within the main power distribution panel under the hood. Tugging on the wiring of suspected areas of trouble while the engine is running may show where the problem is at.

A car that old could have corroded battery cables, with internal breaks that might contribute to this problem.

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Bosch KE-Jetronic, so one of the later versions of CIS


It has 2 pumps, and both are mounted externally, right next to the filter and the other device . . . accumulator?

The fuel pump relay is right behind the glove box, and they’re also known to fail. Pop out four push-pin clips and you’re looking at the relay. You can even use banana plug leads to energize the pump in a pinch . . .

As a matter of fact, I remember at least 1 560SL which had a failing fuel pump which would for some reason only fail when making turns.

Considering the fuel pump relay is easy to get to, it should at least be easy to confirm power to the fuel pump without actually raising the car. I’m talking backprobing. If the car isn’t starting, but you’ve got proper power and ground at the pump, then you can eliminate an electrical problem, I would think

Considering the age of any CIS vehicle, I would expect a few leaks. But what specific vacuum leak would cause such a profound problem only when making a turn . . . ?

Did you replace all the copper sealing washers?

After it was running, did you lie underneath and make sure there were no fuel leaks

What brand . . . ?!

I’m speaking from experience here. It’s imperative you use only the highest quality parts. I’ve even seen German aftermarket parts fail after a short time, especially anything related to drivability in any way. Sometimes only factory parts will work, and most importantly, continue to work

My reasoning behind the vacuum leak theory is that maybe there’s an iffy engine mount and the engine stance could be changing enough to open up a split or the end of a vacuum hose. Right or half-baked; that’s the thin reasoning behind it.

Over the years and just for hoots, I’ve cut open half a dozen of those Bosch pumps just to find the specific reason they failed. In all 6 of those pumps the commutators on the armatures were worn and not just worn but badly worn. A few would still work but were erratic. Those pumps really spin when operating and considering the 4 to 5 Bar of pressure they take a real beating.

Another possibility is that maybe there is not as much fuel in the tank as the gauge shows and the slosh effect while cornering starves the pump.

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ok4450, there are definitely engine munt issues. Some fluids have been leaking on the mounts for years degrading the rubber.

It’s sounding like it’s time to find a good old MB mechanic and give your SL a thorough inspection.

I do not know whether or not this would apply to your Benz or not but something happened with my previous Lincoln once that caused me a bit of grief before I finally found the problem.

One day the car suddenly started bucking for a bit. It would ONLY do this while accelerating out of a turn.
There’s a 35 MPH curve near me and people who tried it at 60 often ended up in the ditch or field. That includes me one night on a motorcycle…

It got to where every time I exited that curve (and right around 35 to 50 MPH) the car would start bucking. The CEL would come on briefly but there were never any diagnostic codes set. Other than that the pedal could be nailed anywhere and at any speed with never a problem. This thing was starting to chew on me pretty good.

I finally discovered the problem was a razor blade like slit in the PCV hose. At certain engine loads (which affected manifold vacuum) the vacuum would open the slit up and that would affect the fuel/air ratio along with the MAF sensor. An analogy I guess would be a non-visible slit in a soda straw that only becomes visible if you bend the straw a bit.
Anyway, replaced that 6" piece of hose and all was well.