The injector shields are single use items that you swap when you remove the injectors for any reason. If you did a compression test through the glow plugs, then no problem.

If you did remove the injectors and don't renew them, then you stand a chance of leaking fuel around the injectors or risk damaging the nozzle tips. But at this point those would be the least of your concerns.

Yeah, but I won't be able to get them until this weekend, and I can get the mystery oil tomorrow. Just wondering if they will cause the engine to not run (which I'm assuming they won't).

Reusing the ones you have are better than none at all. But I wouldn't get worked up over them while you're troubleshooting. Just realize that you might risk long term damage to the nozzles.

There's plenty of threads floating around about how to remove them and which side faces up/down when you put them back in place.

BTW, did you adjust the valves before you did the compression check? It might not help the compression numbers *that* much, but then it might bump them up a bit. There's plenty of how tos on that, as well.

Ok, I didn't do the valve adjustment yet. I'm assuming it wouldn't bring cyl 4 anywhere close to 250, so I will have to pray that it's a stuck piston ring that will come loose.

Should I maybe try pouring the mystery oil right into the cylinder while the injector is off?

A cold compression test is pretty useless. There can be 140 psi difference between cold and warm compression test.

In my experience the risk of not renewing the heat shield is soot build up in the injector thread, so that you cannot remove the injector after a while (or you remove the entire prechamber too). The fuel is burnt before it can "escape" past the heat shield.

Here is what I usually do about heat shields, although I haven't attempted to reuse any 15 times:

Heat shields, Reuse or No reuse; that is the Question!

Ok, the injector shields are actually only $1.50 each on this site, so I don't mind buying new ones once I figure out the problem. I'm going to pour some of the mystery oil into the cylinder and see if it loosens up a piston ring.

Update: I've poured some MMO into each of the cylinders, and will let it sit until tomorrow. Fingers crossed.

A little more patience would serve you well. Let the rings soak for at least 48 hours. A week would be better. That will give you lots of time to adjust the valves, or at least check clearances, which will give you a much better sense of what improvement you can reasonably expect. Make sure that you crank the engine a few times with the injectors still out, to expel any fluid that remains in the cylinders. If this were my car, I'd then try to get it warmed up using the old injector seals- and then do another compression test.

I like your plan. I think I'll do that. This weekend I'll remove the MMO and try another compression test with the engine warm.

I've just got to pick up one of those feeler gauges.

I have another question... What are the small rubber fuel hoses that go between the injectors for? Are they necessary if I just want to try running the engine a little to heat it up for a compression test? Most of them broke when I tried removing them.

The hoses route the excess fuel not used in each injection back to the tank. The injectors actually only use a fraction of the fuel delivered to them, so without the hoses there will be quite a mess created if the engine is started.

Ok, thanks for the info. That's what I figured, just wanted to make sure.


I checked on the MMO that I put into the cylinders, and after about 48 hours, it had mostly seeped down. I checked the compression on cyl 4, and it's still 150psi. I refilled the cylinders and I will check again in a few days.

Your 220D is the same colour as my uncle's '69 was if I remember correctly. Looks sharp! Looks like by '72 they had switched to the newer gearshift & steering wheel styles.

While it's useful to know the compression, I can't imagine it would have anything to do with the stalling symptom - that would be either a fuel (most likely) or air restriction, or something bogging down the engine when you put it into gear. Since you have to replace the injector return lines now anyway, might as well go through the entire fuel system and see if there are any cracked/leaky lines or ill-fitting parts (like the fuel filter canister and any metal lines).

The other thing I noticed was the noise. It does not sound healthy! Exhaust leaks obviously magnify sounds, but it sounded to me like you have some dirty/sticky injectors and possibly (hopefully not!) a rod knock. If you were up to cleaning/testing/rebuilding the injectors while they are out, you wouldn't regret it as you could use them for another engine or sell them if needed.

The cheaper/easier approach would be to attach a temporary fuel can filled with Lubro-Moly Diesel Purge or a substitute (search the forums) and run the engine from that. Even if it doesn't "fix" the injectors it probably will clean & improve them a little bit, and while the engine is running on the Purge, the injector nailing should be almost unnoticeable. That way, when you rev the engine, you can hear other knocking sounds (the bad ones) more easily.

The oil pressure gauge: Is the gauge glass pressing against the needle, pinning it at "30"? I had problems like that with my old cluster. Often the plastic bits that hold the gauge glass get broken. The instrument cluster just pulls out with no tools - you'll need to unscrew the speedometer cable & the oil pressure line and the electrical plugs and then you can take out the cluster. With the cluster out, you can check/fix the gauges, bulbs, dimmer, and start/stop knob.

I would think that if a cylinder has low compression, it won't be enough to ignite the fuel and therefore would cause low power. Which could explain the stalling and rough idle.

I'll look into cleaning the injectors. As far as the gauge, the needle is not pinned, it goes right to 30 when the ignition is turned on, so I would assume it's an electrical problem. Thanks for the help.


Unfortunately, the Marvel's Mystery Oil doesn't seem to have worked. I let it sit for a few more days, but the compression remains at 150ish. Is it pretty much a loss at this point? I guess I will try and do a warm compression test.