SD25 vs SD22 Injection Pump Diaphragm

[gregsimms]

Hey folks,

Can someone please confirm if the SD22 and SD25 share the same injection pump diaphragm?

My injection pump diaphragm on my SD25 failed last year due to excessive wear on the pin end, I attached a photo. I could not find one for sale specifically for the SD25, so I compared the dimensions of the SD22 and they were very similar and I ordered one on ebay, part number 155020-2120 Bosch. I compared again in person and everything seemed to be the same. The same part number is listed on another diaphragm that says it will fit an SD25, but I dont see it cross referenced anywhere else so I dont fully trust it.

I have been running the diaphragm for about a year. Idles smooth, good power from 0-80km/hr, but from 80-110 or up hill at all it falls on its face. At first I did not really notice any difference, but I was always kind of paranoid that I did not confirm whether there was a difference between SD22 - SD25 diaphragms. I may be completely manufacturing the difference psychologically and there is no power difference, or it is related to something else.

So... Can someone please confirm if the SD22 and SD25 share the same injection pump diaphragm?

Thanks for all your help!

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[waynosworld]

I do not know the answer as I have never had to replace my diaphragm on either of my SD25 engines, I expect they are the same, the throttle body is bigger on the SD25 engines, the vacuum throttle works the same to control how much fuel it gets.

As for the engine falling on its face at freeway speeds and on hills, they all fall on their face, the SD25 is much better than the SD22, but they just don't do well on long uphill grades, and the steeper the grade the more gears you downshift into, that is a small diesel engine, my fix for this was a turbocharger, I went from 71hp to 120+hp, I got lucky and by pure luck the first turbocharger I found in a wrecking yard was a 1986 Subaru XT turbocharger, this was pure luck, the reason I say this is because I have never got the same result with any other turbocharger.

This said, putting a turbocharger on an SD25 creates other future issues, mainly EGTs(exhaust gas temperatures), it is easy to get above 1400 degrees if you are not careful, so one needs a EGT gauge, one should not run it over 1200 degrees, 1400 degrees is meltdown time, it's not if it will melt down, but when will it melt down, my probe sensor is at the entrance to the turbocharger, it's hard to say what temps are at the top of the pistons.

[gregsimms]

Thanks for the reply. Glad to hear your motor is still kicking. I am noticing some power loss compared to when I bought it six years and 100,000km ago. This may be related to injector fowling rather than the diaphragm. I spoke with a diesel shop in the UK and they said the SD25 diaphragms have unique part numbers compared to the SD22, and that they do not cross reference.

[waynosworld]

I have a question for you, did you put cod-liver oil in the cavity/injector pump side of the diaphragm?

[gregsimms]

I havent oiled it since installing it, but it came very well oiled. The old diaphragm was oil regularly, except for the last year of running it. Ran out of oil and procrastinated on buying more. No failure in the leather though, and it did not appear to be dry. No waxy build up on the low pressure side of the diaphragm.

[waynosworld]

OK, I do not know for sure, but I thought the Cod Liver oil did a couple things, it kept the diaphragm soft which we all know it needs this to move around properly, but the other thing I believe it does is dampen the diaphragms movement, it slows the movement of the diaphragm down as the spring/vacuum/oil work in harmony.

This might explain why your diaphragm post failed the way it did, I do not know this for fact, I am just always thinking.