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Cummins Pump Timing Bulletin #

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1st gen newbie question

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Hey First Gener's!

I'm getting closer to rebuilding my injector pump and thought I had things all worked out with my local shop regarding pump timing. I stopped in to buy some oil filters and the conversation turned to pump rebuilds & "Spill Port Timing" once again.

I've lost some of my confidence in this shop when I began to ask detailed questions about "Spill Port Timing" on VE pumps.

Old School (or others) would it be possible to obtain copies of Cummins Bulletin # 3810348-01 & 3810486 regarding the the proper procedure via email or fax?

If these guys don't regain my confidence for accurate pump timing I'm in search on another shop! Anyone know of a great shop in the Southeast?

In search of accurately obtaining that magical 1. 35mm timing spec!

Thanks Keeno!

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1992 W250 5spd. 3. 54 gears, LSD, Banks "Stinger Plus" consisting of a 14cm2 wastegated housing, 3 1/2" exhaust/muffler, pyro/boost gage, K&N, Skyjacker 2 1/2" front suspension lift to clear 305/70R/16 Goodyear MT's, Mag-Hytec, Amsoil
 
KEENO: I have at hand here Cummins Bulletin (manual) #3666017-01, B Series Shop Manual '91-'94, and #3666037-04, Injection Pumps and Injectors, Midrange Engines.
Both thoroughly illustrate the dial indicator spill port timing method.
The bulletins were sent to me OVERNIGHT by my Cummins distributor.
I'd suggest two things... no. . three
1 Call your Cummins dist. about the bulletins
2 Consider another injection shop
3 email me for the option of faxed/mailed pages (although you will want the books for yourself)
Go for it

noserider@snet.net

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'92 CUMMINS/DODGE 5SPD, 4WD 16cm2 turbo, mod. /maxed pump and injectors, max. flow exhaust, K&N... .

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[This message has been edited by old school (edited 05-10-2000). ]

[This message has been edited by old school (edited 05-10-2000). ]
 
Cummins doesn't know squat about internally timing the pump. In order for that 1. 35 MM timing setting to mean anything, the pump itself must have it's lift-to-port-closure set correctly. Any good Bosch authorized repair facility knows how to do this, and can verify that it's set dead-on. Setting the lift to port closure is part of an extensive rebuild, although it's entirely possible that it might be skipped, if major components of the pump are not replaced.

Here's how it works: The plunger in the pump rotates, and it's base is riding on a cam plate that has six lobes. These lobes ride up and over rollers as it spins. What has to be set at rebuild (or service on the pump) time, is just exactly how far from the valley of the lobe the plunger travels before the ports in the head/on the plunger reach the "closed" position and fuel is pumped.

When we time the pump to the engine, we check the plunger lift, and set it to a specific dimension at TDC. If the pump itself begins pumping at a higher-than-spec lift to port closure, then your true injection timing will be retarded, even though you've set lift @TDC. Inversely, if it's set too low - your timing will be farther ahead.

This info also applies to the P7100 on the 2nd generation trucks as well. However, a Bosch shop will set the pointer on the pump via port closure - rather than by lift, as Cummins does. This means that the Bosch method is actually more accurate.

Also, you MUST verify your TDC pin. Finding them off by 1 to 4 degrees is common. I've posted a suggested procedure for doing so elsewhere in this forum.

I guess this whole thing boils down to one point: There are a LOT of variables that come into play when it comes to making your engine run good, and the quality of workmanship you get with a new pump/rebuild of your pump can make a very big difference, even if both are set precisely to the same fuel and installed at the same TDC point.

I've probably now confused the heck out of everyone, but if you need clarification, let me know, I'll try #ad




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