[W126 Coupe] Stalling issue

[rltimmerma at cox.net]

More background on the stalling issue.

Car has 136,000 miles.  I've owned it for 6 years and put an average of 3000 miles per year.  Mostly Sunday after noon drives with an occasional run up Palomar mountain and back.

The problem first showed up in June after a long period of the car sitting idle.  My first thought was condensation of moisture in the gas tank. (sloshing of water in the bottom of the tank by rapid acceleration got into the fuel lines  making the car stumble).  I  put a container of STP gas treatment in a half tank of fuel and drove it around town for a week to no avail.

Spark plugs and wires were replaced last summer,  Rotor and  cap appear to be in good shape.

Other than stumbling when I put my foot down the car runs fine. (although it's not nearly as much fun to drive as it used to be)

I've traced all the vacuum lines I can see without taking the intake apart.
The air flow /fuel metering plate moves freely. (slight resistance when pushing down and returns smoothly)

If it had a carburetor I'd be rebuilding the accelerator pump.

Thanks for the suggestions, I'll be studying the service manual CD to try to get an understanding of how the injection system handles off idle acceleration enrichment.

Ray Timmerman

---- Axel Wulff <axelwulff at hotmail.com> wrote: 

=============

Well, it could be a number of things, such as the EZL (ignition control module), the ECU, the fuel distributor or the fuel metering plate, among other things.

 

The fact that it only hesitate/stumble when hot may indicate that the EHA is malfunctioning.


How many miles on the engine? What is the age/condition of spark plugs, caps, cables, distributor, coils?


Axel Wulff
610-731-5453 Cellular
610-572-4611 Home



 

> Date: Sun, 27 Sep 2009 15:18:34 -0700

> From: rltimmerma at cox.net

> To: mbcoupes at mbcoupes.com

> Subject: [W126 Coupe] Stalling issue

> 

> I need some help with a stalling problem. My 1990 560 SEC has taken to dying on rapid acceleration.

> 

> If I try to accelerate sharply from idle the engine quits. It always starts right back with no problem and idles perfectly. If I accelerate gently it also has no problem including WOT acceleration from moderate speeds. I found while checking this morning that the problem doesn't happen until the engine warms up. (accelerates as it should when engine temp is cold.)

> 

> I checked the fuel pump pressure by disconnecting the supply line to the fuel distributor, installed a 0-100 psi gage and jumped fuel pump relay terminals 7 and 8. fuel pressure is over 100psi (it pegged the gage) I don't have the metric fittings to check the lower chamber pressure or test while the engine is running.

> 

> Am I correct in thinking this is a fuel supply problem? Is there some electronic enrichment on rapid acceleration?

> 

> Any help is much appreciated.

> 

> Ray Timmerman

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