Injection Pump Issue while performing the Linkage Tour

[Tomnistuff]

While performing the Linkage Tour during the assembly of my linkage, I found an "issue" with the pump lever operation.  Item 1 under Adjusting the Pump Rod of the linkage tour says, "Check the arm on the injection pump to be sure it moves freely and seats fully against the idle stop."

My '66' 230SL PES6KL70/120R11 injection pump was rebuilt by Jerry Fairchild Industries, has just come out of the box and is freshly filled with oil so it should be good to go.  During the pump rod adjustment, I checked the pump lever.  It returns to the stop "if" I drop it from full open.  If I release it slowly, it drags a little at mid to low position and hangs up.  It's almost like the spiral spring in the "cup" on the lever is binding against the inside of the cup just enough to stop the lever at mid-range.

With the other "return" springs in the system, the throttle lever return spring on the throttle body and the accelerator pedal return spring on the firewall regulating shaft, I doubt that it is a problem.  However, all those springs are there for a reason.  If the pump rod pops off, then the pump lever can hang up at a substantial fuel flow.

Is there something simple I can check to try to fix the problem.  I know next to nothing about the pump.

While waiting for some jewels of wisdom to fly my way from this esteemed group, I'll try to find a view of the pump that is sufficiently "exploded" to help me investigate the lever spring (in the cup) without penetrating the sacred chambers on the inside of the pump.

HELP!

Tom Kizer

[DaveB]

I think you're right it will not be a problem once installed and running. In my (limited) experience, many pumps behave just like that, on cars that run fine.

[wwheeler]

I recall that the IP lever spring by itself is pretty weak and the IP lever does not respond as well as you might expect. The two other springs in the linkage system work in concert to make the whole throttle linkage system work as it should. When you work the lever on the IP, you are moving all of the internal mechanisms which create a lot of drag.

[Tomnistuff]

I'm not going to let this minor concern hold up the completion of my restoration.  I'll try to find a weak tension spring to add to the IP lever spring, just in case something causes the pump rod to disconnect.  I would rather the IP lever snap closed than hang up in a partly open position.  I know that closing the throttle would cause it to go really rich and pump a lot of fuel into the exhaust system if it happened and I would rather it not do that.

Maybe later I'll work on the original spring in the pump lever spring cup.

Thanks for your comments.  I never realized that the pump lever spring tends toward being insufficient.

Tom Kizer

[wwheeler]

I am curious why you are concerned with the pump rod coming off? Has that ever happened to you? If you replace the sockets on the rod and the ball studs are ok, I just can't imagine it coming off by itself. I have done the split linkage test probably close to a hundred times on the same rod that had new sockets. Each time it is securely on there. You can replace the ball studs as well. For the ones that are riveted on, you grind the rivet head, take the old one off and just use the threaded ball stud with a nut.

If you are really concerned, you might be able to fit the ball socket type that has the wire pin that absolutely prevents the rod from coming off. This type is used on the automatic trans cars. The rod with the wire pin socket is located between the solenoid and transmission on the right side.   

[Tomnistuff]

Hi, Wallace,

When I was installing the adjusted pump rod yesterday, just after noticing the weak lever spring, I noticed that one end of the rod was much easier to snap onto the ball than the other end.  On closer examination, I noticed that it had about a millimeter of movement relative to the ball, whereas the other end had none.  When I swapped the rod end for end, it followed the socket.  Earlier this morning, I replaced that socket with a new one.  It now takes much more force to install and remove and the movement relative to the ball is gone.

I'm 72 years old and have realized for many years now that a certain amount of paranoia is good for your health and longevity.

Philosophically, I don't like designing a system of parts (linkage system), where one subsystem (injection pump lever and spring) depends on a related part or subsystem (throttle body return spring) to help it do its job (return to its stop).  A failure in one subsystem can cause cascading failures.

If you are curious, here's a YouTube video that describes a fatal accident and NTSB investigation that, in my opinion, a little paranoia probably would have prevented.  I got interested in this one because of the similarity to an accident in which a close friend died a few years ago.  In my friend's case, he was too trusting of his airplane maintenance and repair.  If you want to read the text, you will probably have to pause the video regularly.

https://www.youtube.com/watch?v=8_4FS38z8pY

No, I've never had the experience of a rod popping off the ball and I don't plan to.

Thanks for your curiosity.  It shows your concern.

Tom

[450sl]

Tom,ease of lever operation also depends on the pumps axle orientation .

[Tomnistuff]

Wow, you completely lost me with that one.  What is the pump's axle orientation?

Tom

[dirkbalter]

Tom,
 
I can’t help you with the pump but I would like to thank you for the write up in the technical manual on “Soft top cover and Trunk hinge Torsion Rod”. I reassembled mine last night and followed your guide. Excellent. It would have been a lot more frustrating without it. I know it's off topic but I thought you might want to know.

[450sl]

Its depends how much the spacecam inside is activated . Try the effect on rotating the axle
(Where the timing marks are..)

[Benz Dr.]

I've had throttle linkage come apart while driving but it wasn't because the throttle linkage cap came off the ball; it was the throttle cap that came undone. Each throttle cap should have a nut beside it which locks the cap in place so it won't turn. Leave both ends loose and there's a good chance it will back off and fall apart. In every case the engine went to idle speed which isn't good in traffic at 60 - 70 MPH! It's something I pay close attention to as much as I do wheel screw torque.

 In more than 30 years working on customer cars I've had this happen 3 times.    Only once in what could have been a dangerous situation. All of them were cars that I hadn't started working on and that's what I was driving home after pick up.

I find at least one or two loose jam nuts on almost every car. Don't let this mistake be your mistake! 

[wwheeler]

Good point about the lock nut. The lock nuts are available for both left and right threads. The sockets for the linkage system have both left and right threads and make sure you get the right thread orientation. Factory The left hand thread lock nuts have a stamped slash on them and the left hand thread socket has a knurl at its base. Makes it easy to tell apart.

One lock nut per rod should be adequate to keep the rod from rotating during operation. But I would use one per socket and I believe that is the way the factory has it.

[450sl]

Tom in other words:  i think you are 100% ok .In a RUNNIING engine your   Ip lever will turn smoothly and returnspring-force is plenty.
Mark

[Tomnistuff]

OK.  Since a disaster does not appear to be just around the corner, I will reassess the situation after I have completed the other work and fired up the engine.  I'll probably be occupied trying to keep it or even get it running anyway.

I really appreciate all of your responses and reassurances.  I'll keep an eye on it. 

By the way, 450sl, I tried to turn over the engine manually but the fan gets in the way of my socket wrench, and I don't want to take it apart again at this point.  I'm only a few days from priming the engine with the starter, so I'll check the pump lever again after I've done that.  I suspect it will work smoother after the pump oil is stirred up and spread around a bit. 

Tom Kizer

[Shvegel]

Sounds like it is just a little draggy because the oil hasn't gotten thrown around yet.  The rack is connected to all 6 pistons (Elements)  by little gears and there isn't much spring pressure there.  If it is not lubed it will drag.

[Tomnistuff]

dirkbalter, thanks for the complement on the trunk torsion spring write-up.

Shvegel, I hope you're right.

By the way folks, the attached you tube video is really interesting, or would be if I spoke German.  It looks like a video version of our Joe's Linkage Tour combined with a bit of IP adjustment on a "very early 230SL.  If it's worth while, maybe someone should "dub it" in English.

https://www.youtube.com/watch?v=XmwXC7j1dqA

It's entitled, "Mechanische Einspritzpumpe 6-Zylinder - *Kurz* Funktion & Einstellung - Classic Akademie"

Here's another.   https://www.youtube.com/watch?v=4CtnBxqAmwc

I found them while looking for a few closeup photos of the pump lever spring area from different directions.  I'm not sure my spring is "hooked" correctly.  It looks cocked.

Tom Kizer

[450sl]

As said its all timing related do not worry.

[ja17]

Most likely all the new rubber seals in the newly reconditioned pump are a bit tight yet. As mentioned, with some oil circulation and running, things may improve.