IP Ball Pressure Valve Renewal

[DavidBrough]

I’ve finally decided to resolve my warm start issue which I am fairly sure is caused by a leaking IP ball pressure valve between the pump and the injection lines. The car always starts but when warm and left for more than about 1 hour it only runs on 5 cylinders for the first 15/20 seconds. I think this is due to one of the pressure valves leaking and wonder if it is permissible to change just one or must all six be changed as a set.

Whist changing all six would negate the need to track down the offender, at £75 each they are not cheap.

Does anyone have any thoughts on this and also the best way to isolate the leaking valve, can I just remove all the pipe connectors and fill the valve housings with fuel and see which one leaks?

Many thanks.


David Brough
1969 280SL Auto with A/C

[al_lieffring]

After hot starting your engine, quickly while the miss is still present, remove the spark cables one at a time and find the cylinder that doesn't change when disconnected. (pull them loose before starting so they will come off easily)

I had made up a pair of spark cable pliars with a wire that ran to the chassis ground so the spark voltage would ground through the wire instead of through me.



Al Lieffring
66 230Sl
a-cheesin with a new 85 l. tank

[Shvegel]

Also keep in mind the injector may be leaking down as well. either end of the line will cause a drop in pressure which will allow the fuel to boil(Vapor lock) in the line.

[DavidBrough]

Thanks guys,

I have recently replaced all six injectors and was rather hoping that there may be a better way of isolating a leaky ball valve than removing the HT leads, a good last resort but I always seem to get a jolt when I do things like that.

Does anyone have any thoughts on the advisability of just replacing a single pressure value?


David Brough
1969 280SL Auto with A/C

[waqas]

I don't see any reason why you absolutely need to replace all check-valves at the same time.

Another idea: have you inspected the the offending check-valve itself?  Is it scored/worn, or is there just some crud in the valve itself that can be cleaned out?  I suspect a Bosch service shop has the equipment to clean out any crud that may be preventing the valve from closing properly.

Waqas ('Wa-kaas') in Austin, Texas

[DavidBrough]

Thanks Waqas, I will remove all six and give them a good inspection and clean but sometimes it is quite difficult to see slight wear. I do remember reading somewhere on this forum that, when changing injectors, it is recommended they all be done together as the new ones are slightly different from the originals and I didn’t know if this may also be the case with the pressure valves.


David Brough
1969 280Sl Auto with A/C

[waqas]

Hello David,

I believe the later ball-check-valves have a plastic sealing washer underneath the check-valve seat. I don't know if these are user-replaceable, but if so, whilst you have the valves out for cleaning perhaps you can replace these washers first and see if there's still a leak.....

I can understand replacing all injectors at once, as these have a direct impact on combustion. But from my understanding, check-valves are there simply to keep the lines charged up whilst the engine is turned off. So, I think replacing just one should be ok.

Waqas ('Wa-kaas') in Austin, Texas

[DavidBrough]

Thanks Waqas, that all makes good sense.

David Brough
1969 280SL Auto with A/C

[Shvegel]

I read your comment about removing high tension leads. I always remove them from the distributor and not the plug and never get shocked.

[jeffc280sl]

David,

Any chance you can take some pictures of the ball valves?

Thanks

Jeff C.
1970 280SL 4-speed

[mbzse]

Originally posted by jeffc280sl
Any chance you can take some pictures of the ball valves?

Here's one
/Hans in Sweden

[ja17]

Hello,

Notice the groove around the ball check valve in Hans' picture. The groove indicates it is the later improved version.

Joe Alexander
Blacklick, Ohio

[jeffc280sl]

I have the same issue with my car.  How do you remove the check valves?  Is there an alternate method to using the MB or Bosch extractor tool?

Thank you

Jeff C.
1970 280SL 4-speed

[ja17]

Hell Jeff,
The side of the check valve is threaded. You can find a metric hose fitting to fit it. The Mercedes air suspension cars used the correct fitting find a used one or order a new one for a couple of bucks #112 997 1572. Screw the fittin on and grab the fitting with a vice grip and pull the valve out! I welded a used fitting on the end of a screw driver to make my own special tool.

Joe Alexander
Blacklick, Ohio

[jeffc280sl]

Thanks Joe.  I understand the check valve is held in place by the washer/seal.  I've been trying to figure out the thread size and think it must be 12mmx1.0.  The MB fitting will be a big help.

Jeff C.
1970 280SL 4-speed

[waqas]

Hey Joe,
The air fitting you graciously gave me at Blacklick for this purpose was labelled 112-997-1572.  I'm sure there's more than one air fitting with the same thread so these numbers will probably both work.

Waqas in Austin, Texas

[mbzse]

quote:Originally posted by jeffc280sl

../.. figure out the thread size and think it must be 12mmx1.0.

This is correct, M12x1 is the thread on the top part of this pressure valve

.

/Hans in Sweden

[ja17]

Hello Waqas,

Thanks, you are correct. I double checked my notes. #112 997 1572. I am not sure where I got the other number (possibly is the same fitting?). I am correcting the part number on the previous post.

Joe Alexander
Blacklick, Ohio

[jeffc280sl]

Thanks Hans and Joe!

Jeff C.
1970 280SL 4-speed