What are your thoughts/advice - injection pump rebuild

[BobQ]

I'm getting ready to get a rebuilt injection pump for my stock '83 K2500. I have a spare 4581 pump from an '89 LD K2500 and I was wondering if that would be a better rebuild candidate than the 4153 pump that originally came in my '83. Were there many updates/upgrades over the years that would make the 4581 a better pump to use? Could the 4581 be build to stock HD '89 specs? Both pumps are from manual transmission trucks.


Also, when having a pump rebuilt, what would be good to look/ask for? I had a list going, but wanted to run it by you guys to get your thoughts.


- steel sleeve for advance bore to prevent wear?
- all new Stanadyne parts
- new solenoids such as the HPCA and engine shut off?



Thanks!

[Robyn]

The later pump would be my choice.

Talk to the rebuilder (YESS TO THE ITEMS LISTED)

Be sure the shop doing the work has a test bench to run the pump and test it completely

In many cases the difference between the pumps is just the fuel settings...

There are several upgrades that were done over the years...ask the shop what they recommend....


Some pumps had ceramic rollers and other hardened parts, but mostly these were Military stuff.

The big deal is to wind up with a pump that has good internal tolerances in the plungers and won't have issues with hard or no start when hot.

Some shops just clean and reseal pumps and do not test under load on a test bench.


If the rebuilder does not have a powered test bench....pass and find one who does.

[Yukon6.2]

Or watch eBay
I bought 3 new military pumps over the years and never paid more than $150.00 each for them.
The military pumps have ceramic plungers and head in them

[Robyn]

I am careful about pumps from ebay.

I bought a few over the years to try.....

I got a MIL pump that was sold as NEW IN BOX

when it got here it looked like new, but after installing it the issues started.

It had been contaminated with some nasty fine dirt....likely dust from some rig used in sand box with a filthy tank.


Be careful of ebay pumps.

I always use a local outfit that is a certified Stanadyne service shop and does pumps by the book.


If I am not mistaken the fuel shutoff coil in the mill pumps are 24 Volt and must be swapped out ????? been a long time since I dealt with one of these....

[DmaxMaverick]

......If I am not mistaken the fuel shutoff coil in the mill pumps are 24 Volt and must be swapped out ????? been a long time since I dealt with one of these....

Correct. The HPCA, as well. New or recently fresh pumps will work fine in a healthy electrical environment, but usually see issues after some duty at 12V, primarily the ESS, but the HPCA does less often or goes unnoticed (rough starts, usually blamed on something else). The actual Mil-Spec rated duty voltage is 15-28V, but they will cycle as low as 10V, albeit weakly. It's best to install the correct voltage solenoids (not too involved or complicated) to prevent issues, but many 24V pumps are installed, never to offer so much as a hiccup.

[BobQ]

Thanks a lot for the tips. I’ll be sure to keep those things in mind when shopping for the pump. Appreciate it!

[Robyn]

You betcha :):)