Mercedes-Benz Forum banner

1 - 11 of 11 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter #1
Project car purchased on ebay. Starts up fine but struggles off the line with the pedal all the way down. Zero power...can't get up a hill. Running it for a while doesn't make a difference. Top speed about 50mph...then engine temp starts to spike until overheat. First indy swapped the fuel distributor from another SL in the shop and that didn't fix it, so he gave up. Then MB of Manhattan said compression on the engine is good but the cat was clogged and engine should come to life with a new exhaust system. They said one of the spark plugs was laying on its side so one cylinder wasn't firing. They re-threaded that so now it sits properly. They suggested I take it to an indy for an exhaust install, which I did. Indy swaps the exhaust and there is no improvement whatsoever. That indy checks the timing which is perfect, swaps in a new fuel filter which makes no difference in performance. I’ve scoured posts and found similar but not quite exact symptoms. Indy is confounded and is about to test the fuel pressure. Any ideas? Accumulator, fuel pump relay, maybe some sensor causing this?
 

·
Registered
Joined
·
10 Posts
it might be the O2 sensor.

once the engine was brought up to temp (after about 30 mins) the engine would starve for fuel stutter and not be happy. this is what i figured the issue to be and my local mechanic agreed with this. so i had the 02 sensor replaced and things really improved. it then led to having to replace both fuel pumps, filter and a fuel line because the engine wasn't starting on first try initial pressure was not ideal. since these fixes, i have had no issues.

now before all of this, i did replace my fuel injectors, seals and hoses myself. they were bad. fuel distributor wasn't the problem for me.

so when you had the exhaust replaced did you replace the O2 sensor?
my situation is not exacting the same as yours but it's worth a try.
 

·
Registered
Joined
·
26 Posts
Top speed about 50mph...then engine temp starts to spike until overheat... indy checks the timing which is perfect
I'd suspect that something is still not timed correctly. Low power+overheating can be due to retarded ignition timing, which leads to slow fuel burning without putting much force on the pistons, but delivering excessive heat to the exhaust ports and valves. Perhaps have the cam timing checked too, although your mechanic said compression was fine.
 

·
Registered
Joined
·
2,210 Posts
beast, what do you mean?
Hehe, I should have said instead:

"Air leaks are what do the previous owners in."

These issues crop up and the skills needed to troubleshoot have faded from most shops' memories.

And the ones that do have it charge for it and the cost to repair scares them away which leads to new enthusiasts having to sort through them.
 

·
Registered
Joined
·
26 Posts
Hi @theflow

Your 560SL has electronic timing. There's nothing to check or modify so that rules out that one.

Most likely, there are some severe air leaks in the intake which the KE Jet system can't over come. These air leaks are typically what do these engines in and most owners don't want to commit to rebuilding it.
Thanks for the explanation, I am just getting acquainted with this car, but I should have known as an '86 Audi we had years ago used a Hall-effect trigger in the distributor. But a question; if the distributor had been removed, can it be installed a tooth off? Also, seems to me that a bad enough air leak downstream of the airflow plate would not only tend to lean the mixture, but max the O2 sensor, which should be easy to determine with a Voltmeter.
 

·
Registered
Joined
·
2,210 Posts
Hi @theflow

Your 560SL has electronic timing. There's nothing to check or modify so that rules out that one.

Most likely, there are some severe air leaks in the intake which the KE Jet system can't over come. These air leaks are typically what do these engines in and most owners don't want to commit to rebuilding it.
Thanks for the explanation, I am just getting acquainted with this car, but I should have known as an '86 Audi we had years ago used a Hall-effect trigger in the distributor. But a question; if the distributor had been removed, can it be installed a tooth off? Also, seems to me that a bad enough air leak downstream of the airflow plate would not only tend to lean the mixture, but max the O2 sensor, which should be easy to determine with a Voltmeter.
Yes, an easy test you can do right now is to put a dutycycle meter on pins 2 and 3 of the x11 connector. If it pegs at 1 or 99% that would indicator either a fuel pressure issue and/or an air leak.
 

·
Registered
Joined
·
3 Posts
Discussion Starter #8
Thanks for all of your input

My independent (who is a genius) figured it out. Take any benz to Willy's Auto Service in Great Neck, NY with your problems, btw. Willy was confounded by the issue, ran tests on everything, then pulled the transmission. Sure enough there was a problem with the flywheel which prevented the gears from engaging and shifting correctly. It seemed to have been re-installed incorrectly, perhaps during a previous repair as they noticed new bolts in the wrong places. The car came to life instantly and runs at the perfect temp. Sounds great. Now time to attack the interior. Thank you again for your help on this.
 

·
Registered
Joined
·
2,210 Posts
Yeah, that's very odd. Was the car driven that long after the repair? I'm surprised the previous owner didn't make the shop fix this issue on their dime with such a muck up.

Regardless, welcome to the group and enjoy the 560sl!
 

·
Registered
Joined
·
3 Posts
Discussion Starter #11
Previous owner was not very helpful as he was selling on behalf of a friend who passed away. I learned that the transmission was worked on two months before I bought the car, with the reverse gear being replaced, and basically not driven after. So it looks like that shop messed up the transmission for me. Did I mention this was a blind ebay purchase after several bottles of champagne on new years eve? Regardless I'm thrilled to be in this club, as this car now moves gracefully down the highway. It really is a tremendous machine.
 
1 - 11 of 11 Posts
Top