* Pneumatic Governor Diaphragm *

#16

checked at my local pump shop..(50yrs experience) and they say clean engine oil as lub on diaphram..they say have done hundreds if not thousands..always used oil..no probs...

#17

zen wrote:checked at my local pump shop..(50yrs experience) and they say clean engine oil as lub on diaphram..they say have done hundreds if not thousands..always used oil..no probs...

The diaphragm is leather. Ever study leather shoes worn by oil change techs? Does "no probs" mean the vehicle is never seen again or if it is, the life span was acceptable to the customer? There is a reason Nissan has a preservative oil specified which ... has nothing to do with lubrication.

#18

zen wrote:checked at my local pump shop..(50yrs experience) and they say clean engine oil as lub on diaphram..they say have done hundreds if not thousands..always used oil..no probs...

Likely will work and last till after that owner of the truck has sold it.

Petroleum products tend to soften leather.

I have not ever checked the diaphram on my MZ, but I planning on it.

Carey

#19

only reporting what they said...i trust them..their previous info has always been spot on and free of charge..oh they ain't 18yrs old either so have plenty of experience...

since i am doing replacement of dia and cleaning up rack,i will be giving it a go..if it goes wrong then i can blame them and get a free replaxement!!

but i really do expect their advice to be ok..time will tell..

just hope it cures the surging..

#20

asavage wrote:Cracked diaphragm = overfuelling at all but full throttle, and lots of black smoke.

I'm sorry I just caught this, and wouldn't say anything otherwise, but it's a bit unclear and it's worth elaborating.

If there is a leak at the diaphragm or any of the hoses that might diminish vacuum at the diaphragm, the result will be overfueling and WHITE smoke, the severity depending on the size of the leak. It may begin to darken as the motor is loaded, and at some point be black, but the majority of the experience will be white smoke which is unburned raw fuel.

This tear appears significant, and was assuredly affecting mileage, but it was not causing smoke anywhere near the fog created when a vacuum line broke at the thermoswitch at the back of the oil cooler.

#21

Knucklehead wrote: If there is a leak at the diaphragm or any of the hoses that might diminish vacuum at the diaphragm, the result will be overfueling and WHITE smoke, the severity depending on the size of the leak.

In an experiment long ago with a adjustable leak in the vacuum line to the governor diaphragm, the larger leak resulted in more BLACK smoke so long as combustion was not being flooded out by GROSSLY excessive fuel delivery. At this gross delivery stage is when exhaust changed from heavy black smoke to white vapor ... obviously fuel is passing through that escaped combustion. Easy to do at idle ... fairly hard to do with engine loaded. Keep in mind at the time, I had no outright faulty injectors.

Knucklehead wrote:This tear appears significant, and was assuredly affecting mileage, but it was not causing smoke anywhere near the fog created when a vacuum line broke at the thermoswitch at the back of the oil cooler.

The Coolant Temperature Switch that screws into the side of the oil heat exchanger? One line leaving the CTS tees into the Venturi Vacuum line that also feeds the pneumatic governor. With considerable amount of that venturi vacuum now vented to atmosphere, most certainly the engine would start racing against a closed throttle.

#22

That's the line. And you didn't give it a yank to see what happened? Well, I can only speak from experiencing the leaks I had. Maybe my timing was more retarded than yours is now 'cause that will contribute to the white smoke problem.

#23

Al: Tomorrow comes ... I survived another night.

Ok. It is given ...

A) A four cylinder engine has half as many intake strokes per crankshaft revolution as an eight cylinder engine. So at low RPM, intake manifold is going to be violently pulsed by comparison.
B) The more air volume between the vacuum gauge and the intake manifold when the air volume is pulsing, the lower the reading will be.
C) The vacuum signal generated for the pneumatic governor is venturi vacuum ... not actual manifold vacuum. (Both kinds of vacuum exist in this diesel because there is an air throttle that also has a small parallel venturi to generate a butterfly valve angle sensitive vacuum signal).

That said, and wishing to get some kind of useful cranking vacuum reading at or near the pneumatic governor, I used the Tee fitting on the metal line feeding the governor diaphragm located alongside #4 cylinder.

Closed throttle cranking was a highly pulsed 0-3" vac.
Idle speed vacuum at this location was a steady 4" vac.

Skipping the "How I dun it" part, the governor diaphragm starts moving the fuel rack away from max delivery at 1.5" vac and is at its full travel stop (minum fuel delivery) at 8" vac.

Galen: Just for you ... I pulled the little hose off the Coolant Temperature Switch that connects to the metal vacuum supply line that feeds the governor diaphragm's "pull side" . Idle sped up to (guessing) 2,000-2,500 rpm and NO smoke of any color. Repeat but this time pulling the big vacuum supply hose off at the governor diaphragm housing. Engine RACED much higher and there was considerable black smoke. Scary as the air throttle was closed in both experiments.

It takes very little vacuum to pull the fuel rack back away from full throttle delivery.

#24

Well, my apologies to Al. That gives me hope that maybe my timing was retarded all that time and there is potential for improved performance.

#25

well ..looked at my govn diaphram last night(at midnight in the dark )it was fine..covered in oil(engine )and super flexible..(its the original one)..so i left it alone..bought a new one too($80us)...

pushed the rack in and out a couple of times,and put it back together...

now the surging is much better!!maybe i ought to strip it down again (in the daylight) and give the rack and bitys a clean??wonder if that would totally remove the surging??fit the new diaphram?(seems awaste to me)

your thoughts please..

#26

which i now have done...

no change in throttle response..definate decrease in smoke on acceleration..maybe increase in fuel economy..time will tell,but so far looks good..no decrease in preformance

POINT TO NOTE!!!THE DIAPHRAM HAS A SPRUNG LOADED RETAINER IN THE END THAT SLIDES ON THE RACK ROD..WATCH IT DON'T DROP OUT INTO PUMP..(OR INDEED THE NEW ONE SHOOT OUT ACROSS THE ROAD!!..DOOH

)

#27

zen wrote:POINT TO NOTE!!!THE DIAPHRAM HAS A SPRUNG LOADED RETAINER IN THE END THAT SLIDES ON THE RACK ROD..WATCH IT DON'T DROP OUT INTO PUMP..(OR INDEED THE NEW ONE SHOOT OUT ACROSS THE ROAD!!..DOOH )

Ah ... you have met the Ungleich spring. The little spring does not have sufficient strength to propel the plunger out of the bore. Scroll up a few entries to see a pneumatic diaphragm out on the bench.

#28

philip wrote:Ah ... you have met the Ungleich spring. The little spring does not have sufficient strength to propel the plunger out of the bore. Scroll up a few entries to see a pneumatic diaphragm out on the bench.

Bounces well though!! And you try and find those shims!!

#29

Are there any special warnings I need to hear before I attempt to inspect my diaphram? My manual describes removing it with the pump on a bench so that doesn't help much. I plan on replacing the vacuum lines asap and I would like to inspect the diaphram before I order a new one if that is feasible. I am trying to find the solution to my cold-start miss/surge with lots of smoke and slightly disappointing MPG numbers. Thanks for any tips.

#30

Do a vacuum bleed down test just for baseline first, then have a very small pair of magnetized needle nose to pull out the clip. You're good to go!

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* Pneumatic Governor Diaphragm *

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