KE-Jetronic M110 - White Flag Time

[Citroënbender]

First post here, and I’ve jumped in with grease up to the elbows…

• Car: ‘82 Australian delivery 280SE (W126), SLS, AIR pump (disabled) and EGR. Close to 300K (~180K miles). Later 15” wheels but otherwise as when sold.
  
• Summary: Sorting the worst parts for a friend who bought in with eyes shut, looking for help with items that either received “expert attention” or have been badly neglected.
  
• Immediate Problem: Throttle plate (butterfly) found misadjusted.

Note: I have not touched the mixture screw, I promise!

Chasing a number of poor performance issues, identified a sticky throttle. After dismantling, cleaning, re-greasing every point in the linkage from the pedal base to the butterfly, I removed the injection unit as a a whole to clean and inspect the throttle plate.

The plate was shutting so hard on its spring, it was starting to chafe a groove into the throttle bore. The stop locknut was loose and stop setscrew about 30 thou clear of the lever! Also, the vacuum line from vapour canister to throttle was open where it’s rubber end-piece was 70% torn apart. This detail might go towards explaining some of the issues.

I removed the throttle body, gave it a light clean and checked all vacuum passages were fully clear. Refitted the TPS by carefully aligning the witness marks its large flatwasher had made, applied a super-light film of Permatex No.3 to the gasket and bolted it back down. Throttle stop is currently set close as possible without binding - kerosene would drain slowly through but it’s near enough airtight to a running motor.

Is this set right? I have literally spent hours over several days, trawling the internet for throttle stop specs. One forum for another marque mentioned a notional gap of 15 thou (at widest point) from throttle plate to bore.

My confusion is made worse by not knowing the idle air valve’s direction of airflow - whether it goes into the injector assembly’s chamber or starts from there.

Advice on both the stop setting and idle airflow direction would be really appreciated, and I thank anyone who offers advice.

[Frank Reiner]

Before continuing, please tell us how an M110 happens to be equipped with KE-jet.

[Citroënbender]

I concede; it may well be K-Jet, and I’ve attempted to amend the subject title accordingly. What threw me was a thermostatically controlled idle air supply - not an electronically modulated shutter as described on a lot of online overviews of K-Jet - and the first result from Googling the part number on the fuel distributor head, ascribed it to KE-Jetronic.

Either way, I’d like to set the butterfly right, reassemble the whole fuelling/intake side and see how it runs with one less vacuum leak. The whole motor was bathed in grease and oil when I started; the SLS pump supply hose and power steering pressure hose had both failed prior and only perfunctory cleaning done in repair. Hoping the cam box is still sealed!

I’ve attached an image that encapsulates the general state I received this car in. How it could happen - I have no idea. Removed, cleaned, straightened, checked, lubricated and re-fitted.

[Frank Reiner]

Cb:

Re: Throttle plate.
The MB manuals do not provide any setting data for the plate clearance. It is usually accepted that a stop position that prevents binding of the plate in the bore is sufficient.

The presence of the throttle switch (not a potentiometer) indicates that there is a Lambda feedback system (K-Lambda). The switch senses closed throttle & WOT.

[Citroënbender]

Thank you for looking that detail up and advising; I’d not wanted to get this wrong as it’s so well “buried” in the manifold that to adjust later could be a pain, but was aware from burring to the throttle spindle screw heads (and that backed-out stop), somebody’s been here before.

I’ll leave it at the current stopped position, which is probably <2 thou clear at the widest. It’s so far been “soggy” IMO on the pedal and I’m hoping the vacuum leaks have been a part of this, plus the misaligned kickdown.

With respect to the throttle switch, can’t find a lambda sensor- I have attached pictures of the exhaust manifolds - I also felt underneath in case a port had been plugged. There’s no cat, Australia began transitioning to unleaded in 1985 or so and it took until the late nineties for all forms of leaded fuel to be phased out for road vehicles. Is it possible the microswitch just informs the ignition driver?

Besides the site which referenced a small clearance (https://bigcoupe.com/phpBB3/viewtopic.php?t=15721 - first few posts) the other reference found to setting the butterfly was on Ferrari Chat, which has generally seemed a well-filtered (informed) site with tech details: https://www.ferrarichat.com/forum/threads/adjustment-of-k-jetronic-on-f328.343572/ (Post 5 posits, and is affirmed by others, that their engines will just, barely idle with the idle air screw wound right in.) This was why I’d been so determined to mine for accurate data.

[Citroënbender]

A further note, there’s seemingly either a generous vacuum leak I’m yet to find, or a fault in the thermostatic idle air control (does this happen to the coolant heated type?) as it’s not particularly fussed by screwing the idle adjustment screw into the stop. Fixing the two vacuum leaks spotted on the throttle body takeoffs, has improved the vacuum signal to the economy gauge, but not perceptibly changed pedal response.

I returned the idle air screw to the “as received” position of 1.5 turns out, but won’t be surprised if this needs a tickle once the idle air is otherwise under control.

[Frank Reiner]

Originally Posted by Citroënbender

I’ll leave it at the current stopped position, which is probably <2 thou clear at the widest. It’s so far been “soggy” IMO on the pedal and I’m hoping the vacuum leaks have been a part of this, plus the misaligned kickdown.

Originally Posted by Citroënbender

A further note, there’s seemingly either a generous vacuum leak I’m yet to find, or a fault in the thermostatic idle air control (does this happen to the coolant heated type?)

The "soggy" throttle response may be due, in part, to retarded ignition timing.

1) Disconnect any/all vacuum lines at the distributor.
2) Set idle timing (as low an RPM as you can manage) at 10* BTDC.
3) At 3500 RPM check that timing is ~35* BTDC.

The water-heated aux air valve (AAV) is an ongoing source of trouble. They either stick closed, or more often, take 10-15 minutes at 80C water temp to close, if at all.

[Citroënbender]

Great information again, thank you. I had the car up on a hoist last night to change the ruptured rear accumulator spheres (apparently DOT4 was once added in place of hydraulic oil) and took a peek at the WUR, (tried) also to eyeball the AAV. In the way of seeing the AAV were the cruise actuator and what’s left of the smog-to-throttle linkage.

The WUR doesn’t look tampered with - encouraging - and the crust of grime blockside of power steering pump suggests nobody’s delved deep for a long while, if at all. So the AAV is probably in a more-or-less original state. I’ve skim read the BenzWorld and Jag Lovers’ threads on AAV dismantling/tweaking, and will be re-visiting them.

Coolant flush number 5 this weekend - have switched to a truck grade product due to amount of fine iron oxides in system - following that will check vacuum lines, and thence timing.

[Frank Reiner]

Cb:

If you have not already done so, a check of valve clearances is in order. The M110 tends to lose clearance; a bit on the loose side is much to be preferred to too tight.

[Citroënbender]

I took your advice on the valves, and nudged up the priority of this job. A couple were nil/negative lash while around eight presented one or two thou shy of target. Adjustment was tight but possible with a Blue-Point combination open end / ratchet in 17mm, could see it taxed the mouth but didn’t spread it.

Apart from the detritus of mileage and underchanged oil, everything looked more or less as you would want to find. Cam lobes normal, no shrapnel or missing rocker clips.

Have yet to reassemble and test, will be re-using the gasket out of short term necessity (they are a breathtaking $125 here for a Febi part, and I’ve got one sitting in a Pelican order yet to be processed) - will be cleaning the cover inside and all mating surfaces to use just a smear of sealant with the old gasket.