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  #31  
Old 03-16-2021, 09:54 AM
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The engine started from cold but was hesitant: it started to try to fire but required continued starter engagement to get going. It idled very slowly for 5-10 seconds then accelerated to its fast idle (I have ordered an idle control box). It idled very smoothly until
it warmed up and I turned the key off. After a couple hours I trued it again and the performance was the same: hesitant start then up to fast idle circa 1000 rpm.

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  #32  
Old 03-21-2021, 06:39 PM
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Cold start function and repeated dying and dtarting, but it runs great until it starts dying suddenly
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Providing a home for these cars:
1951 Buick Special De Luxe
1977 Rolls-Royce Silver Wraith II
1970 Rolls-Royce Silver Shadow
1986 Mercedes-Benz 420 SEL
2005 Mercedes-Benz E 320 CDI
2012 GMC Sierra 1500 4X4
1927 Pierce-Arrow Series 80
1931 Pierce-Arrow Series 43
1926 Ford Model T coupe
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  #33  
Old 03-21-2021, 07:06 PM
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Quote:
Originally Posted by Randy View Post
Cold start function and repeated dying and starting, but it runs great until it starts dying suddenly
The common element in difficult cold starting and sudden shut-off is the fuel pump relay.
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  #34  
Old 03-29-2021, 01:24 PM
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Quote:
Originally Posted by Randy View Post
Cold start function and repeated dying and dtarting, but it runs great until it starts dying suddenly
Did you ever run the simple on-the-car fuel accumulator test I referred you to in post #11? It's in a thread started by me...easy search.

Duke
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  #35  
Old 03-30-2021, 12:20 PM
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I have a new fuel accumulator to install when I have time to do it.
One interesting thing about the run-die episodes: it involves temperature. Engine runs perfectly until it suddemly dies. Restarts get more difficult as it continues to heat up. 5 minutes engine off with the hood up restores engines ability to run for a few miles, and the more it cools down, the longer it will run before dying. Seems a typical electronics failure. My ‘86 420 SEL did this when the crank position sensor on the flywheel failed; this engine seems to have only a front sensor for tdc.
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Providing a home for these cars:
1951 Buick Special De Luxe
1977 Rolls-Royce Silver Wraith II
1970 Rolls-Royce Silver Shadow
1986 Mercedes-Benz 420 SEL
2005 Mercedes-Benz E 320 CDI
2012 GMC Sierra 1500 4X4
1927 Pierce-Arrow Series 80
1931 Pierce-Arrow Series 43
1926 Ford Model T coupe
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  #36  
Old 04-08-2021, 09:37 PM
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I recallthat, on the Ď86 420, the ignition module was mounted on the steel fender liner which served as a heat sink. There was heat transfer paste between them and it was said to dry out and lose effectiveness so I removed the module, cleaned out the dried-up paste, and replaced it.
Is this true for the module on the 560 SL?
After replacing the fuel pump relay, it still hard-starts, like it needs a choke, but runs perfectly for 2-3 miles then dies suddenly. It will restart immediately but die within 20 feet, but the longer I wait ( and let it cool), the longer it will run after restarting, so the fault is obviously temperate-related.
Hard starting cold, like it needs a choke. I replaced the idle control module and cleaned the idle control valve but no change. The struggle continues...
If it seems like I donít know what I am doing, well...
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Providing a home for these cars:
1951 Buick Special De Luxe
1977 Rolls-Royce Silver Wraith II
1970 Rolls-Royce Silver Shadow
1986 Mercedes-Benz 420 SEL
2005 Mercedes-Benz E 320 CDI
2012 GMC Sierra 1500 4X4
1927 Pierce-Arrow Series 80
1931 Pierce-Arrow Series 43
1926 Ford Model T coupe
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  #37  
Old 04-09-2021, 08:34 AM
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Randy, you should apply heat transfer paste to the back of the ignition control module. It's important that it be there. An electronics store should sell the paste. Those ignition control modules cost thousands of dollars. Don't want to fry one.
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  #38  
Old 04-09-2021, 10:36 AM
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Quote:
Originally Posted by Randy View Post
I recallthat, on the Ď86 420, the ignition module was mounted on the steel fender liner which served as a heat sink. There was heat transfer paste between them and it was said to dry out and lose effectiveness so I removed the module, cleaned out the dried-up paste, and replaced it.
Is this true for the module on the 560 SL?
After replacing the fuel pump relay, it still hard-starts, like it needs a choke, but runs perfectly for 2-3 miles then dies suddenly. It will restart immediately but die within 20 feet, but the longer I wait ( and let it cool), the longer it will run after restarting, so the fault is obviously temperate-related.
Hard starting cold, like it needs a choke. I replaced the idle control module and cleaned the idle control valve but no change. The struggle continues...
If it seems like I donít know what I am doing, well...
The 1986-1991 W126 and 1986-1989 R107 share a common engine management system. The EZL is more or less the same design, and yes heatsink goop is required. Lack of it will not cause the EZL to overheat and die as quickly as you're experiencing though.

When you have a stall condition, you need to determine if you have spark. If you fail to do so, you're farting into the wind for any other troubleshooting.

If you do have spark, you have a fuel problem. Pumps, fuel pump relay, ignition switch, fuse box, wiring, etc.

If you do not have spark, you have a problem with the OVP relay, EZL, crank sensor, ignition coil, or distributor. For what it's worth, a failed crank sensor will also cause the fuel pumps not to run after the initial prime.

One step at a time. Inspect items and deem them good or bad then move on. Firing the parts cannon at the car isn't going to fix the problem. If it does, it's sheer luck and will cost a LOT more than following good troubleshooting procedure.

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