Hi team,
just back on deck after touring our mighty Snowy Mountains Hydro/electric Scheme, and Ski Fields in the surrounding areas--- it is summer here and the snow is all but completely gone, just a few patches left in sheltered areas.
We stayed at Jindabyne on the side of one of the schemes lakes, we encountered a week of 30-33degC temps.--a heat wave for the locals--average summer max temps are in the 20-23degC range--global warming ??? we drove home in temps of 40-42degC temps through Gippsland yesterday!!!!!

The "Vee" grouve cut outs on the side of the pump plunger working area is to give a steadier (non hunting) low idle. These pumps cannot be mixed with others without the Vee as it requires a greater position of the rack to give an idle volume of fuel. Leakage of injection fuel occurs across the Vee and affords a larger movement of the rack to change the volume of fuel injected and this in turn steadies out the Low Idle hunting.
IF the two types of pumps are mixed the Vee grouved units will tend to display a miss at low idle due to the lower volume of fuel delivered per unit of rack setting as compared to a non Vee grouved plungered pump.
This subject was covered recently either here or on the ACME BB.
The pump plunger and barrels are selective fitted at the factory for best fit, so it is possible to mix and match parts if they are in the tolerance range of each of the plungers and barells. In a production run there will always be a plus and minus variation of the target dimension for the particular component and these parts are often identified in say car pistons and bores as A or B,C,D etc size for mixing and matching for best fit IE they can use std oversized pistons to best match an oversized bored cylinder---here we are talking in the upto plus or minus one thou range not 10 or 20 thou. Although during WW2 I believe many makers used std over/under size components in their engines so as to cut wastage.

OM, sorry do not have 7J P/B, have D6 4R1-up P/B and it also shows the 2A3895 Pump Ass only (form 8885 / March 1945) as does my TM5-3100 War Dept D6 maint&parts catalogue for D6--4R680-up and 5R903-up. Also 9K grader.
Hope this helps,
Cheers,
Eddie B.

Hi edb,
Thanks for the info.
Can you verify that the 2.6575 - 2.6577 in. is the correct new length for the pump plungers for the 2A3895 pumps? Thanks

Hi OM,
sorry can not verify a length for the above tall pump plunger. My before mentioned 4 1/4" bore books do not give this test or dimension. Also can not recall ever reco-ing one of those tall pump units to that depth, usually the pumps were shot from dirt by the time we saw them.
Looking through my short body forged body pump books from 3 3/4" to 4 1/2" bore they all have the same dimension you enquire about.
Hope this sheds some light on the subject, I believe the early tall pump units usually were worn out due to fuel contamination before the plunger length became an issue. Once the cotton wound filters came in then I believe the situation changed and the plunger length became a factor and subsequent fuel systems then had the dimension given. I stand to be corrected as this is my theory on the lack of dimension for early pumps.
Cheers,
Eddie B.

PS in my "saved junk" I have just found an un Part/No'd pump of 8 mm bore and it is in the range of 2.657" long, believe it is from a D4400 engine, numbers are scuffed off from fretting against the neighbouring pumps. Body cast No 6B5791.

PSS have included a scan from S/M Dec 31 1953 of the revised test stand Instruction Plate.

Hi edb,
Well I've done my homework best I can and I'm about to make a broad statement:rolleyes: It seems that all the forged body pumps have the same length plungers, just the diameter changes. I verified the length for the D8800 and the D13000 with tall pumps and the new plungers are the same 2.6575 - 2.6577 length with a 0.005 shot wear length. Can't find it in print for the D4400 & 4600 but I'm certain they are the same.

Need to amend that a little to a cut off year of 1959 on the pumps.

Attached is the complete test procedure for injection pumps.
Basically comes down to how well they can pee in the jar:D

Hi OM,
I agree with your assumptions, your amendment date now ties it up nicely for early tall type pumps only--that was the only area of concern I had but overnight you have amended and tied it up nicely.
Did test many pumps by the "peeing in the jar" method when an apprentice, but I do not recall measuring the plunger lengths on those plungers. Certainly with forged body and compact pumps etc with a spec. dimension given we checked them all, but again usually dirt had done its job on the helix and ports before the dimension became a factor.
I feel for hobby machines that a little more plunger wear is acceptable and can be adjusted out by subtracting the wear dimension of the plunger from the lifter setting to compensate---this will bring the start of injection timing back to the spec. dimension.
My preference for timing is to spill time each pump after varifying the TDC positions and marking the spill timing points on the front pulley. I used to work out the circumference for the pulley, divide the circ. dimension by 360Deg to get the circumferential distance for each degree, and with a home made pointer to line the marks up to proceed to spill time the unit.
Usually for hobby units just resetting the lifter settings will make a world of difference. I have known of engines to have been rebuilt and then not start and run any better than before. A lifter setting check and adjustment cured the problems.
Well done OM,
Cheers,
Eddie B.

Hi edb,
I seem to have missed something here:confused:
Would you not add the plunger wear to the lifter setting to restore to original injection spec. start......then be a little short by that amount on the plunger stroke??

Hi again OM,
I can see where the confusion is, my statement is to "Shorten the Lifter Dimension"---not the screw--- indeed you will need to lengthen the screw by the amount the plunger is worn below std. dimension.
A plunger which is worn say 0.005" short will need its' lifter screw screwed out by 0.005"---thus shortening (reducing) the lifter setting dimension by 0.005". The wear of the plunger length retards the timing, and raising the lifter yoke screw counteracts this to keep the top of the plunger at it's designed height above the pump housing face and it's relationship to the pump barrel inlet port for the start of injection. If we made the lifter setting 0.005" deeper we would then have the effect of a plunger worn 0.010".

Reducing the lifter setting--shallower--advances the timing as the plunger does not travel as far below the inlet port and so covers the port sooner on the upstroke.
Increasing the lifter setting--deeper--retards the timing as the plunger travels further below the inlet port and so covers the port later on the upstroke.
Hope this helps to sort it out.
Cheers,
Eddie B.

Hi edb,
OK, got it. I was thinking of the yoke screw and lifter being an assembly. Makes sense when separated. Thanks again.

Hi OM,
pleased to be able to help understand. Sometimes I have to take a step back and think through doing lifter settings to refresh my mind as to what we are trying to achieve.
Cheers,
Eddie B.

Just sitting here reading and admiring the 'team work' and comminication going on between you two...for the benifit of others!! Great work! I don't even own a Cat.
Just to think.... and from different sides of the world too!!!!