So my truck went into runaway last saturday. It broke the woodruff on the fuel pump gear and the cam gear had walked half way off the cam. So I took the pump to progressive diesel injection in new castle. Very great people with years of experience and know how with fuel pumps. On friday I picked up the pump. They rebuilt and resealed it and maxed the pump out on their machine until the governer would put the pump into runaway then he backed it off some. He said be prepared for runaway when you put the pump back on the truck because our machine can not exactly mimic how it will be on your truck. So I installed pump and it wanted to run away as I expected. Did all the fun stuff till I got it to just hang then backed it off some.

Heres my dilemma. Before all this I could pound out 48 psi of boost with a slight haze of smoke and I dont think my pump was near run away then because I never had it hang or anything. Now I can only push about 36psi with a really light haze at wot with the pump a 1/4 turn before hanging high rpms.

Im positive the timing is exactly where it was at before and that the gears are lined up. I tried moving the pump both ways. 1/4 in advance would pop under load and dropped boost to 30psi. Retarding it just smoked a lot all the time.

The mods done to my pump are : afc milled off of pump top and tapped and plugged. 3200 spring and 15psi constant wot. Timing 1/4 in from head.

What would internaly cause this after a pump rebuild? After all I assumed picking up a fresh pump vs a 200k mile pump that id be pushing more fuel. Im stumped. Is there possibly something that could have went wrong on the rebuild or something that would cause less fuel am I just stuck getting bigger injectors. Definatly can feel an in seat power loss.

 

Just went for another drive. 3rd gear is 38 psi. I shift to fourth and fifth its like it falls on its face and drops to 30 psi. Kinda slow building boost also

 

Well problem is solved. The throttle return spring that sits on top of the indexing (not sure of exact name) was causing the issue. When they rebuilt the pump they replaced it and the new spring is either not as long or has too much tension so it was limiting me to 3/4 throttle at most.

The spring was a new bosch replacement. Pump shop tried numerous other new springs and all did the same thing. Must make thrm differently now?? Hopefully no one else ever has the same problem

Luckily for me they tossed my old spring in a box full of other good but used parts and when they put it back on it runs like it should. finaly days of frustration are over.