'87 W124 PreChambers (advice requested)

[BrianCostello]

Hello All!

I have started this new thread because Search did not turn up what I'm looking for exactly.

I have a 1987 300D. 603.960 motor. #14 head And the prechambers are leaking.

The leaks are causing very hard starts. This car is not a daily driver, so after sitting all week, air gets into the system, and you have to crank all day long.

On top of the prechambers leaking, 2 of the injectors are also leaking.

To verify that the prechambers are in fact leaking, I did a "brake clean" test. I sprayed brake clean around the injectors & prechambers with the motor running. When I sprayed the back 3, brake cleaner got into the prechamber and cause some really loud knocking!! a little scary.

So, thanks to this site I figured out what tools I need. It appears that the "early" 603's use a prechamber similar to the 617. Later 603/602's require a spline shaft style socket.

So special tools are on order. The question is "How far do I go?"

Do I simply remove the injectors (fix the ones that are leaking), and torque down the Prechambers (using the proper prechamber collar tool)?

Or do I go all out, remove injectors, glow plugs, and pull the prechambers? Give the precambers a full cleaning, de-carboning, and re-install?

Am I just asking for trouble if I pull the chambers?? Can I/ should I replace the prechamber sealing rings? (I know I have to do the injector heat shields)

I want to do what's best for the car. I am big on the "while your in there" method of repairs. I also fully realize that it's sometimes best to leave well enough alone. . .

So I am looking for a collective opinion, how far should I go?? just torgue and run, or go for the full prechamber R&R?

Thanks.

I will take lots of pics, and post them up. I think the leaking prechambers are common, and there is not a ton of info or how to's for the 602/603 crowd.

Brian

[NJ300sdl]

Leaking pre chambers will not let air in the fuel system and I doubt if they are the cause of your hard starts. Try to leave the pre chambers in place. Loosen and tighten the collars, repair the injectors. If further tests reveal the pre chambers leaking a little (bubbles in light oil sprayed around collar) it would be good enough for my use.

[vstech]

soooo... you spray brake cleaner at the injectors, and you get knocking from the motor?
I'm thinking more likely the intake manifold is sucking in the brake spray...

the hard starts are likely caused by the fuel heater under the IP leaking, and possibly the delivery valve seals on the IP letting air in.

for the hard starts you could park with the nose of the car facing downhill, you'll drip a little fuel, but it likely won't get air in the lines.

for the PC's, how bad are the leaks? is it a slight bubbling through motor oil dribbled on them, or is it SPRAYING out the oil?

[BrianCostello]

soooo... you spray brake cleaner at the injectors, and you get knocking from the motor?
I'm thinking more likely the intake manifold is sucking in the brake spray...

I was able to spray directly onto the injector/pre chamber area . .So very little if any should have gotten into the intake. I won't rule it out however


the hard starts are likely caused by the fuel heater under the IP leaking, and possibly the delivery valve seals on the IP letting air in.

Which is what I also assumed. So I installed a fully rebuilt IP I had on the shelf. I purchased it from GSXR, so I know it's good. It's not leaking one bit.

for the hard starts you could park with the nose of the car facing downhill, you'll drip a little fuel, but it likely won't get air in the lines.

for the PC's, how bad are the leaks? is it a slight bubbling through motor oil dribbled on them, or is it SPRAYING out the oil?

I have not tried oil, good idea. I would assume a bubbling. . .but I will test.



Thanks for the input so far. Keep it coming!

[funola]

With a cold engine, squirt shaving cream around the pre chambers/ injectors. Start the car and look for bubbles through the cream.

Shaving cream = neat stuff. I use it on the injector halves to detect leaks when I rebuild them.

[Jeremy5848]

Originally Posted by BrianCostello

the hard starts are likely caused by the fuel heater under the IP leaking, and possibly the delivery valve seals on the IP letting air in.

Which is what I also assumed. So I installed a fully rebuilt IP I had on the shelf. I purchased it from GSXR, so I know it's good. It's not leaking one bit.

The fuel pre-heater is not part of the IP. Replacing the IP with a known good one is always nice but the fuel pre-heater is a separate item.

Jeremy

[BrianCostello]

Originally Posted by Jeremy5848

The fuel pre-heater is not part of the IP. Replacing the IP with a known good one is always nice but the fuel pre-heater is a separate item.

Jeremy

Correct. I'll check it out.

But as far as I know I have no known leaks.

are the pre-heaters known for tricky pin holes?? Something that leaks but you can't see it?? just asking

[Diesel911]

If you end up pulling out the Prechambers (of course remember to pull the Glow Plugs out first) do not pull the Chamber unitl the Piston is up close to Top Dead Center.
Pulling the Prechamber out peels a lot of deposits off of the nose of the Prechamber.

Having the Piston at Top Dead Center allows the crud to fall on the top of the Piston where you can get at it.
I found that sticking the Vacuum Cleaner Pipe down the hole easily sucked out the particles (that in my case were dry).

(Also a good time to ream out the Glow Plug holes.)

[ROLLGUY]

I believe the pre-chambers have seals that seal against the aluminum head. You should have them on hand before starting the job. I would also advise pulling them with the engine hot (operating temp). My head guy has an oven that he uses to preheat the head before removing the chambers. Since your head is still mounted on the engine, heating it first (driving the car) should make the chamber removal easier.

[Bio300TDTdriver]

Originally Posted by BrianCostello

Correct. I'll check it out.

But as far as I know I have no known leaks.

are the pre-heaters known for tricky pin holes?? Something that leaks but you can't see it?? just asking

It is not a pre-heater it is a fuel thermostat. Yes they have an o-ring that can fail. Mine would only show a problem at highway speed. I was able to find the drip and replace the o-ring.

You ruled out the big ticket item, you might want to try the .99 item as well. The o-ring is behind the white plastic 90 on the fuel thermostat.

[BrianCostello]

Originally Posted by Bio300TDTdriver

It is not a pre-heater it is a fuel thermostat. Yes they have an o-ring that can fail. Mine would only show a problem at highway speed. I was able to find the drip and replace the o-ring.

You ruled out the big ticket item, you might want to try the .99 item as well. The o-ring is behind the white plastic 90 on the fuel thermostat.

Thank you! I give it look soon. I am keeping a sharp eye on that area for leaks. For good measure, I may replace all the fuel hose, I believe its original.

I am aiming towards NOT removing the pre-chambers.

I will be, Removing the injectors, pop-testing and rebuilding the ones that leak (I got the lapping materials)

Then just releasing the the pre-chamber collar nuts. cleaning the threads, and the gunk that gets stuck in there, and re-installing at the proper torque.

followed by the re-built injectors, also at proper torque.

And see what happens.

The tools should be here wednesday!

Brian

[vstech]

take pics please.

[BrianCostello]

Small update:

I got the proper prechamber tool. it's the same one used on the OM617 motors. Later W124's use the splined socket.

So the prechamber collar removal/cleaning/re-torquing went well. While I had the injectors out I pop tested them. All six were around 1400 psi. too low

So I ordered up some shims, and a lapping kit.

Got everybody shimed up to 2100 psi, lapped the bodies, torqued to spec and re-installed this Saturday.

Took a test drive, and at every red light light the car was shaking like I had bad engine mounts. . . .

2 of the injectors were leaking SO BAD diesel was basically pouring out. I was very careful on cleaning/rebuilding etc. . .I was quite dissapointed at my work.

So today, I take a bad leaker out. Clean it up again, being extra super careful. Went to torque it back together, and something BROKE

injector back apart, I somehow broke the top small piece that slides inside the nozzle. I have no idea how I managed this debacle.

So these are decent 50k or less Bosio nozzles. My friend is a Bosio dealer, so I drive over to him to see what he can do.

We are waiting on a answer from Italy. . . If I can get a nozzle fairly quickly I will just replace the one nozzle. But If I have to wait like 6 weeks. . . .I getting a whole set of injectors.

Man! I just want to cruise in this car. I got a new hose for the AC. . so my plan was motor running sweet. Ac blowing cold. Summer weekend cruising here I come!

Best laid plans. . . . .

[Diesel911]

Originally Posted by BrianCostello

Small update:

I got the proper prechamber tool. it's the same one used on the OM617 motors. Later W124's use the splined socket.

So the prechamber collar removal/cleaning/re-torquing went well. While I had the injectors out I pop tested them. All six were around 1400 psi. too low

So I ordered up some shims, and a lapping kit.

Got everybody shimed up to 2100 psi, lapped the bodies, torqued to spec and re-installed this Saturday.

Took a test drive, and at every red light light the car was shaking like I had bad engine mounts. . . .

2 of the injectors were leaking SO BAD diesel was basically pouring out. I was very careful on cleaning/rebuilding etc. . .I was quite dissapointed at my work.

So today, I take a bad leaker out. Clean it up again, being extra super careful. Went to torque it back together, and something BROKE

injector back apart, I somehow broke the top small piece that slides inside the nozzle. I have no idea how I managed this debacle.

So these are decent 50k or less Bosio nozzles. My friend is a Bosio dealer, so I drive over to him to see what he can do.

We are waiting on a answer from Italy. . . If I can get a nozzle fairly quickly I will just replace the one nozzle. But If I have to wait like 6 weeks. . . .I getting a whole set of injectors.

Man! I just want to cruise in this car. I got a new hose for the AC. . so my plan was motor running sweet. Ac blowing cold. Summer weekend cruising here I come!

Best laid plans. . . . .

What is borken is the top part of the Pintel of the Injector Nozzle. You will need a new Injector Nozzle.
Why it broke; the part with the Red Arrow in the picture was assembled upside down.

The other way is if you mix some of the parts between the 2 different Injector Body types; the pic of Injectors.

I have managed to do both back when I worked in a Fuel Injection Shop. Was in too much of a rush to pay proper attention to what I was doing.

There may be other ways to do it but those are the ones I discovered.

How to prevent it.
Look at a properly assembled Injector and note the spacing of the Nut to the upper Body.
Always turn the Injector Nut all the way down by Hand before torqueing.

If the parts I have mentioned are assembled wrong the Nut will not turn down as far.
And, you can see and feel that if you are looking for it. On the Injector assembled wrong you will also feel more spring tension on the Nut as you turn the Nut down.

Another thing that helps if is before torquing you lay all of the Injectors on the Counter and look and see if any of the Injector Nuts are not all the way down.

In the last pic the Green #4 Arrow points to the part that can end up installed upside down.

[retmil46]

Just did the full monty this weekend and pulled all my prechambers. Not that big a deal with the right tools - took on average less than a minute of upper body workout with the slide hammer per prechamber to pop them out. I had leakage on 1 thru 5, and given what I'd seen of the PO's other maintenance efforts on the vehicle, I wasn't going to roll the dice on this one. Needed to change out the GP's anyway.

On the 603, THERE ARE NO SEALING RINGS BETWEEN THE PRECHAMBER AND THE HEAD. Direct metal-to-metal fit between the prechamber flange and the head.

The only rings that might be used with 603 prechambers are "spacer" rings - if the seating area in the head is gomered up, such that you have to use the special MB tool to shave off metal and smooth out the sealing area, depending on the amount of metal removed, there are four different thickness spacer rings that can be added to maintain the prechamber at the proper height to keep it from being struck by the piston.

From what I found, I have to believe that the entire head was removed sometime in the recent past - for an engine with nearly 215K miles on it, everything was just too bloody clean - compared to what I found on my first 87 with only 133K miles - hardly any black gunk in the intake manifold or on the intake valves and their passages - only a thin coating of soot on the prechambers, washed right off with hardly any effort in a quick bath of gasoline.

On 1 thru 5, both the injectors and the collars were way loose - as in practically no torque at all. Only one that seemed anywhere close to being torqued properly was 6 - the only one that wasn't leaking.