230SL Injection Pump Stuck Rack

[mistertj]

The rack on a 230SL used injection pump I just purchased is stuck...won't move. I have done a search but did not come up with anything that points me on where to start fixing the issue. I read that it's a slow process and takes time but did not find any insight into what's involved. Perhaps I missed it but sure would appreciate any help. Many thanks

[ja17]

The rack becomes stuck when the IP pistons get stuck in their bores, usually from rust or varnish. Remove the six 19mm fittings at the top of the IP. Be careful of the loose spring inside each fitting. These early pumps have a cone shaped check valve. Remove each check valve by lifting out of each bore. Keep all the parts in order. Once the check valve are removed, you will be able to look in bore and see the top of the tiny pistons (plungers). Soak all the bores and pistons with penetrant. Turn the injection pump by the large nut in front. Observe each piston as you turn the IP. You will find some pistons that are not moving. These are stuck in the "up" position. Gently tap these pistons down with hard wood dowel  or a soft metal punch.  If the piston does not move down when tapped, turn the pump and try it in another position. Repeat as needed. Eventually when all the pistons are moving up and down, the rack will become free. During re-assembly it is critical to torque the 19mm fittings 19 ft./lbs.

[Shvegel]

I will only add that when you are installing your fuel injection lines you need to hold the outlet fittings(19mm fittings) with a wrench so you don’t overtighten the fittings and strip the threads out of your pump body.

[mistertj]

Thank you for the insight. I have attached a couple of photos that show a mess...I know...lots of rust. Are those rusty round things the "cone valves" that should just lift out? Mine are stuck in there but I'll work them with penetrating oil to see if they can be freed. Should I be unloosening any of the screw heads on the side of the unit? Thanks again.

[Pawel66]

These plungers look bad! I am not sure if making them move will be ok and enough. It may be a pump to re-build... What did the seller say about the condition of the pump?

[mistertj]

The seller has been good and will give me my money back if the pump is not rebuildable. My main interest was just getting the pistons out to use for parts. From the dismantling I have done so far...the pump is full of rust in the fuel chamber.
You said the "plungers" look bad. Are the circular things I've shown in the photo, the plungers? In a healthy pump, should they be able to be moved downward?

[Pawel66]

Ok, sorry, no, indeed. I wrote too fast a stupid thing, thinking somone just tricked you.

This is R11, early one, a bit different than what I have been messing with (R25).

What you see is, I think, the check valves in the terminal state. This may be, I suppose, after removing the unions. I would expect what is underneath may look similar.

Let see what someone more experienced will say.

Maybe the attached will help, where:

1. Plunger
2. Cylinder
3. Check valve
4. Union
5. Seal

The described slot is what you see after removing the check valve (drawing 1).

In essence, looking at drawing 2, you would see the element under the cylinder (without number, just with description "dzwigienka" - lever) - it is attached to the rack and makes the plunger rotate back and forth while the IP shaft makes it move up and down via cams. These two movements make the pumping action. That is also why when plunger is stuck, so is the rack. There is a hole on the side of the cylinder and a dent in the plunger. It is sort of: through this hole the plunger takes fuel, turns and moves it up. If the cylinder turns with the plunger (there is a pin there to prevent that), there is no pumping as the hole is always in front of the dent.

So the plunger has to rotate back and forth and move up and down. Cylinder cannot rotate with the plunger.

Normally you remove the check valves with a simple tool (I do not know it for R11), but in your case - I am not sure how to deal with it to look at the plungers, as the check valves look fairly rusty.

[ja17]

Looks like your check valves might be missing all together.  When you removed the 19mm fittings, on this early pump, you should have found a spring and a cone shaped check valve. I do not see these in your pictures. Those rusty cylinders you see are the bores and the small pistons are inside. The cone shaped check valve also inserted in the top of the bores and the spring kept the check valve closed when the 19mm fitting was installed. There are some good factory illustrations in the early BBB.

[rgafitanu@gmail.com]

Having done this to my pump several times, I can tell you that the rusted cylinders that you see are actually the bottom part of the check valves, see first picture part on the right. The top internal lip is also conical mating with the conical part of the plunger on the right. With that much rust, the mating surface is gone, also as Joe mentioned, you should have found springs and plungers on top of those.
Under the rust they are threaded M12x1. You can make a tool to try to extract them (see other pictures). With these out you will be able to see the top of the actual injection pistons (Pawel's first picture, cavities 1,2 5 and 6).
You should be able to find check valves but that heavy rust means that the pump had no fuel for many years and the exposed steel rusted. If the pistons are in the same condition you might as well look for another pump.

[ja17]

Thanks for the good photos Radu!

[Pawel66]

Indeed great pictures!

I saw before both on the picture and "in nature" the later check valves with a ball inside (like on pictures from Joe I provided above), but I have not seen the earlier check valve yet - its bottom, top and, as I read, there should also be a spring.

In case you want to make a check valve puller - you have one example above, there is more if you search the forum and in the Tech manual in FIP Timing section, link in Diagnostics Steps.

[mistertj]

Thank you all for the excellent input. I ordered a 12mm x 1.0 brake line num that I will make a puller from and then go from there. A question I have remaining is the purpose of the 6 screw heads in the attached photo. I assume that they have to be removed but curious as to what they hold in?

[Jonny B]

There are a few other photos and some background on the early pumps - an article by Richard Simonds in Pagoda Notes Vol 8 no 1

[Pawel66]

Jonny, yes, indeed - the check valves are there, thank you!

mistertj, I do not know in this type of pump what these screws are holding. In the newer pump, more or less in this place there are pins preventing cylinders from rotating together with the plunger (on the picture of the pump with removed cover you see them in the midddle of the triangle-like tags on top edge of the opening - they are in the little round holes).

But in your pump - someone more experienced would have to tell.

[ja17]

The screws pin the cylinders in place.

[mistertj]

Want to thank everyone for their input. Think I have all the info needed.

[mistertj]

Made a check valve removal tool. Used an inverted flare nut 12mm x 1.0 purchased on eBay for $1.00 (shipping was $1.95 additional). No grinding necessary, it fit snugly in cylinder. Worked like a charm.

[450sl]

Very clever setup mistertj !