1988 560 SL: Start After A Long Nap - PeachParts Mercedes-Benz Forum

Diseasel300 · #30 04-09-2021, 10:36 AM

Quote:

Originally Posted by Randy

I recallthat, on the ‘86 420, 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 don’t 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.