Timing off....bad Inj Pump?

[befland]

Recently (within the last two days) I replaced the DB2 4911 Injection pump on my 1983 6.2. The reason for replacement was due to the "hot start" problem that I have experienced with the 4911. I bought the pump from a rebuilder but it was not a 4911....it was a rebuilt 5209. My understanding is that this is the military version of the 4911 with hardened internals and 24V. The rebuilt 5209 was converted to 12V during the rebuild.

After installing the pump using the method in the DP R&R manual (removing the timing gear bolts through the oil filler tube hole) everything seemed to go flawlesly. When I tried to start it the timing was WAY off. I tried adjusting it by rotating the pump but I couldn't even get it close.

Now at this point I should mention that I have the dual idler setup. Since I never removed the gears in any way and I put the pump back in exactly the same orientation (the pump gear will only bolt on in one orientation) then I should be golden....but as you already know, that's not the case.

So...this morning...I removed the water pump and the pump cover so I could see the gear setup. Everything seemed to be lined up exactly as it should. The only thing that I have changed is the pump...and with everything else seeming to line up...I'm leaning towards it as the guilty culprit. I really hate to cry wolf though if there is something I'm overlooking. Plus I don't want my truck to be out of commission while I remove and wait for a new pump!

Any ideas or suggestions!?!?!?!

Truck details: 1983 6.2, Banks turbo, Bully Dog marine injectors, 1993 Serpentine conversion, HO water pump, Dual Crossover, DSG Dual Idler Gears, 270K miles on original engine....and like I always tell the parts guy...it has AC and white letter tires. :-)

[gmctd]

See if the HPCA solenoid and the Fuel Shut Off solenoid click when you apply and remove +12v power - +24v solenoids will be very quiet.

[befland]

Have not looked at this....but I will! :-)

Thanks, Bill

[More Power]

Does the light-load advance piston move freely side to side (lever on pass side of the pump moves on the piston)? Is the cam plate on the side of the pump appear more or less oriented correctly? The cam plate acts on the lever, which moves the advance piston.

I'm not familiar with the pump number you're using. Otherwise, timing can't be off unless the advance piston is pushed one way or the other, or the drive collet on the front of the pump's rotor shaft has sheared the pin.

The alignment pin on the pump shaft collet can only work in the oblong hole in the gear. It won't line up and allow the three bolts to fit if you try to use the other round hole in the gear. So, you must have the gear correctly bolted onto the pump.

Does the timing appear to be too advanced? If so, my experience has been that you need to retard the pump about 1/8" at the scribe lines to get it timed right after installing a gear drive.

Jim

[john8662]

The rebuilder should have updated the internals inside the pump to reflect the 4911.

I've done a few of the odd 831 pumps, converting them over, well, I take to a local diesel shop that does it.

The advance pistons and some calibrations are the only difference so far.

Sounds as though it's the pump that's the culprit if the gears are still aligned.

J

[befland]

It was the pump. I received another pump from the rebuild shop and it works. He sent the other pump out as soon as I told him I suspected it was the problem. Pretty good deal when you don't even know the guy your dealing with.

The 1st pump may have been damaged during shipping as it looked like the box had been dropped from a helicopter. There was a hole in the side of the box and one of the injector ports was hanging out...and missing the cap plug.

Bill