What are the symptoms of a bad IP Governor Diaphragm - PeachParts Mercedes-Benz Forum

Diesel911 · #1 05-28-2008, 04:53 PM

74 240D with a pneumatic govenor. If the IP Govenor Diaphragm was no good what type of problems would I expect it create?
Compression on all cylinders around 350 psi is good but engine putting our a lot of dark to blueish smoke.

HighDesert Benz · #2 06-08-2008, 12:10 AM

when the one in my '75 240 went bad it smoked like you describe and also had a noticeable surge under light throttle around 25 to 30 mph. The idle was smoother after repalcement too.

nhdoc · #3 06-08-2008, 10:13 AM

I have heard that this diaphragm costs a lot of money but when I ran the PN from the EPC it looks to list for only $50 from M-B. I heard rumors that it cost several hundred...anyone bought one recently?

Diesel911 · #4 06-08-2008, 10:43 AM

I started this thread due to a question from another member. When I looked in some of the internet Parts dealers that I do business with they were all close to $200 each.
Back I the late 70s I worked in a fuel injection shop where we used SPACO gasket kits for the fuel injection pumps. They are made in Italy and I though it might be a cheaper source but when the member contacted the seller I do not know if he ever recieved an answer. Here is his thread:
Fuel adjustment - '74 240D

nhdoc · #5 06-08-2008, 11:23 AM

I'd suggest trying to price the OE part from an M-B dealer. I ran the PN from one of the online dealers and it was only $50. It would not be the first time an M-B part is cheaper than aftermarket, especially on an unusual one.

HighDesert Benz · #6 06-08-2008, 01:42 PM

Last year I paid nearly $200 for the diaphram at a Bosch shop to do my car. Found another source later for around $150 of course. They're proud of that little piece of goat hide. $50 would be a great price, buy two.

Diesel911 · #7 06-09-2008, 02:34 AM

Quote:

Originally Posted by HighDesert Benz

Last year I paid nearly $200 for the diaphram at a Bosch shop to do my car. Found another source later for around $150 of course. They're proud of that little piece of goat hide. $50 would be a great price, buy two.

I seems expensive but the fuel cost you save and decreased engine wear due to excess fuel that you save by replacing the diaphragem might pay for itself in a year or so.

nhdoc · #8 06-09-2008, 06:46 AM

Can someone explain the function of the governor/diaphragm and what happens when the diaphragm leaks?

dabenz · #9 06-09-2008, 12:42 PM

OK, I'll bite. This has been covered several times in the past....

The governor adjusts the air/fuel mixture when the engine is running faster than low idle. You asked about the vacuum controlled governor (somebody else can explain the other variants).

Trace the vacuum line from the governor and it ends at the "throttle body" or "mixture controller" contraption just upstream of the intake manifold. Now think of a gasoline engine with a carburator - stepping on the gas pedal opens the carburator's air-throttle valve and increases the air velocity in the venturi. Gasoline is sucked from the float bowl to the neck of the venturi. Don't worry about the carburator's jet pumps at this point.

Going back to the diesel with a vacuum governor you see you have the same idea, except that the venturi neck vacuum doesn't suck fuel. The vacuum moves the governor's diaphragm. The diaphram is connected to the injector pump's rack. There's also a spring to balance the diaphragm force, adjustment shims, and movement stops in the governor housing, but the end result is the same as with a gasoline carburator - air/fuel mixture modulation. A leaky diaphragm (or vaccum line or connections) means more spring force and an air/fuel mixture that's too rich.

A bad diaphragm is rare, in my opinion, but easy to diagnose and the last thing I would look at. You pull the vacuum line at the throttle body and apply a small vacuum with a hand pump - just enough to move the needle. Engine off. No leak is good, usually the problem is a leak in an old vacuum line or at the vacuum line connections. Make sure you know your hand vacuum pump. Some, like mine, have a built-in (very small) leak.

My drill: most of my time is spent making sure ALL the mechanical linkages are working as they should. Usually the biggest culprit is worn bushings on the firewall rotating rod, and fixing that fixes a lot of "problems." Then it's a misadjustment of the tickler and/or the start/stop cable. Then a butterfly pin that is binding in the throttle body housing (dirty). Check for oil in the vacuum pump outlet hose.

Then and only then do I start the engine and make adjustments. Set the idle speed and tickler then check the high rpm limit. Make sure the tickler "doesn't work" when rpm is faster than idle - the governor should be in charge. You do this by moving the throttle open and watching the tickler rod - it should move, stop, then not move again until the throttle is released. Stop the engine and adjust the high idle cable if needed. Double check that start/stop pin. Then start the engine and use your hand to play with the throttle at the throttle body. If the engine doesn't quickly react to changes (small and large) then I would start to suspect the governor vacuum line or it's connections, and then maybe the diaphragm itself.

Kind of make sense? To me, that governor diaphragm is the last in a line of things to look at. But if I made a living selling parts....

nhdoc · #10 06-09-2008, 12:51 PM

Thanks for the education. I never realized the operation of the "tickler" was so important. Actually I am not quite sure what the "tickler" is?

I'll print out your tips and have a look at mine later this week when it cools down to below 90 here.

Diesel911 · #11 06-09-2008, 06:55 PM

Here is some places to look for info
Main page
http://www.pauldrayton.com/uploadfiles/merc/Service/W123/Index/616index.html
fuel injection; has operation of the pneumatic and mechanicl governors.
http://www.pauldrayton.com/uploadfiles/merc/Service/W123/Index/616/07MechElec.html
the section where the tickler is mentioned
http://www.pauldrayton.com/uploadfiles/merc/Service/W123/w123CD2/Program/Engine/615/07-100.pdf page 3 of 8 mentions the tickler shaft but I cannot tell which one it is.

dabenz · #12 06-09-2008, 11:04 PM

Tickler is the rod that goes over the valve cover then down to the engine side of the injection pump. Same function as the governor (air/fuel mixture) but at idle speed. Too light of a tickler and the engine is going to "lope" or make rpm oscillations. Too heavy of a tickler and the governor will seem slow to react. You want the tickler in control at idle and the governor in control at rpms faster than idle.

Another way to think of it is that the governor is always working, but it overcompensates at idle. The tickler compensates for the governor overcompensation....

nhdoc · #13 06-10-2008, 07:54 AM

Great, thanks again for the tips.

I have an odd smoking problem with my '74 240D. I have noticed that I can climb a moderately steep hill under WOT and get nearly no smoke out the tailpipe (watching the rear view mirror), but, if I climb the same hill after turning onto the street I get lots more black smoke. Any idea why the turning before the hill would cause more smoke? It's a left turn BTW.

dabenz · #14 06-10-2008, 11:44 AM

nhdoc: you probably have a grill gremlin next to the left headlight. An ice cream stand on that corner? If so then the grill gremlin is mad because it saw the ice cream stand and you didn't stop.

There really isn't enough information to have a good idea about the corner smoking. Driving habits have a lot to do with these engines, as does the simple things like keeping the engine oil level below "half." My first guess is that you're coasting to the turn and you're seeing the crankcase breather do it's thing. A long time ago I made a few graphs that showed the relationship between hp, torque, and road speed for my (220D) engine. Try a search as I'm not a computer genie and have no idea how you guys insert the underlined links in your posts.