Replacing 7.3 Injection Pump Drive Shaft Seals  7-10-2012

My 89 F250 started leaking fuel out of the IP drive shaft weep hole on the bottom of the pump.  Leaking really don’t describe it,  it had almost a steady stream running out of it. The old truck ran really well,  and I hated the thought of putting a rebuilt pump on it which had all the adjustments set back to the stock settings. The way she smokes and runs,  I’m pretty sure that this IP had at least had the fuel screw turned up some when the ole truck followed me home.

I am a DIY kind of guy,  and with a cheapo (and suspect) rebuilt IP starting at $350 or so,  I really wanted to find out if there was a way that I could replace the drive shaft seals myself.  I figured it’s my pump and with a good manual I have been into some pretty detailed stuff before so why not.  I figured if I mess this one up too bad,  I do have another dead pump off my parts engine that I could use for a core if I had to go the rebuilt route.

So I started reading about everything I could find on the forums,  and what I found wasn’t very encouraging.  Everybody says you just don’t mess around with an IP,  that there are to many adjustments and settings to get out of whack.  Well, I’m just not a guy who can take no for an answer,  so I kept digging the web for info,  primarily for some kind of service manual on these pumps.

Somewhere in all this I came across a post on a 7.3 IDI forum where a guy had done what I wanted to do and more.  He literally rebuilt his own pump and when he took it to a pump shop to have it‘s calibrations checked,  he had done such an outstanding job on his rebuild that the shop tried to hire him!  What he found and used was a Navistar service manual on the 7.3 IDI,  and he stated that the last section in this manual was in depth directions on rebuilding the Stanadyne DB2. The manual part number he used was Navistar CTS 4245G, Volume 2

I found a copy of this manual and have included on this site the parts of it which pertain to the Stanadyne DB2. There are 26 pages on disassembly,  6 pages on inspection of parts,  29 pages on reassembly,  plus a section on test bench calibrations.

Next step was to find seals,  and I found an ebay seller who had the kit.  For $31.00 including shipping I got everything I needed here:  Ebay pump parts supplier

So with this CD manual on my trusty laptop,  I went to the shop and built a rotating holding fixture which mounts on my workbench,  and after mounting the IP,  I went to work on it.  I will be the first to tell you that there are in fact numerous settings that have to be calibrated for it to perform correctly,  but my thought was that if I could mark/measure these accurately,  I should be able to reinstall them in the same position.

What I found was that to take it apart to the point that you can get to the driveshaft snap ring and pull the shaft out, there are really only 2 calibrations you have to concern yourself with.  One is the position of the face cam (advance cam) on the throttle shaft.  Click Here and look at page 2.   It is just simply clamped on the shaft and wherever you lock it down is where it is. There is no key, no spline,  etc.   So I just marked it lightly with a chisel to line up with the roll pin that is driven through the end of the shaft ,  and was able to put it back on exactly like it came off.

The other calibration is the allen head guide stud which inserts into the mini-max governor rod assembly.  It screws into the front of the upper box shaped part of the pump housing on the hard lines end,  right above the little lock plate and screw that locks the transfer pump end cap in place.  Click Here and look at page 3.  I just measured how far out of the housing the stud protruded with my caliper,  and lightly chisel marked the top of it so that I could re-install it back in the exact same spot it was before. The most important thing is to go slow and think/measure/mark anything that has some sort of calibration before you start messing with it.

I finished my reassembly and I got the pump installed back on the truck.  After cranking for a while, (these IDIs take some time to bleed the injectors),  she finally coughed,  and I bled it some more,  hit the manual glow plug button for a few seconds and she fired up.  I went for a short drive and it is running great,  and NOT LEAKING ANYMORE!!!

The outlook I have on all this is that if you are a person who can follow directions,  take your time,  and be fanatically clean and careful with precision parts,  then you can take this manual and satisfactorily disassemble,  inspect and reassemble a Stanadyne DB2 pump.

The manual does call for a few special tools,  like a seal expander to install the new drive shaft seals over the shaft, but I made it fine without them.  I just took my time and was able to work the seals in place by hand without much trouble. The only “special” tool I used was a little wire hook I made to hold the fuel shutoff solenoid plunger back while installing the top cover.  And, the manual showed me how it needed to be shaped.  Other than that it was just an inch lb torque wrench,  snap ring pliers and ordinary hand tools and allen wrenches.

happy wrenchin ~ diezelcrazee