Runaway on startup 3,750 rpm

[moparguy]

Update. Today was a rainy cold day so headed to the shop, fired up the heater and started removing/moving stuff to facilitate pulling the injection pump. Only hic-up was I managed to shear off about half the little tit on the end of tdc locating pin (above the pump). Also forgot to disconnect the fuel return line where it goes to rubber near the fuel filter until the pump was inhand and about 50% clear.

Job wasn't as bad as I'd imagined but that's usually case. Since tomorrow's a holiday guess it'll be Monday before the shop gets to figure out and fix my little issue.

Happy New Year!!!

RonR

 

[moparguy]

Installed the P7100 pump over the past couple days after a local Bosch certified shop went through it. They replaced a worn throttle shaft, along with other normal wear items on a 300k mile 25 year old pump to include a full breakdown, balancing the barrels on the high end of capacity (175 pump), disassembled and checked governor, new overflow and delivery valves, end stop, lever shaft, taper pin, membrane, all seals and I'm sure other items I'm forgetting. Oh, they did pin it at 16 degrees as requested.

The tech that did the work said he only found normal wear, the rack wasn't stuck when they checked which verified what I'd found.

The good news is I left all 6 injector lines loose and after several minutes of purging the system (installed a new Bosch lift pump that I pumped a couple hundred times while rotating the engine) and three series of cranking for several seconds had fuel at all injectors. Snugged the injector nuts down and it cranked right up. No miss, no drama. I was standing at the turbo with my 2x8 air knife on the ready when the wife cranked it though just in case.

The test drive showed no problems other than a noticeable power gain (and a little more smoke than I like). I'll back the star wheel back a bit since the tech thought he was helping me out. The idle was smooth but a bit high (1,000rpm) I'll lower back to 750-800 or so.

While I'm really happy with how the truck does with the freshened up/slightly turned up and balanced pump, I'm disappointed the shop didn't find a smoking gun on the high idle issue. They did say a pump going to high idle and sticking wasn't unheard of in their world when it had age and miles on it.

Cost wasn't bad, $1,200 after a $150 credit for a handful of excess inventory, a stock fuel plate, new in the Cummins package '98 overflow valve, low mileage 215 delivery valves and a set of stock governor springs.

Given a choice, I'd sure like to've avoided this exercise but I now have a fresh pump, plus a new Cummins lift pump and newly sealed tappet cover. Not to mention the good looking bead blasted P7100 pump that I cleared to protect the nice natural finish.

Thanks all for the helpful comments and support.

RonR

 

[Cummins12V98]

Happy ending........hopefully!!!

 

[Joe Mc]

P7100 pump that I cleared to protect the nice natural finish.

Glad you have your truck back! Good call on clear coat.

Can't wait to get mine to Tim (TRE Diesel Performance) so he can address things I've not been able to, due to buying/selling home + cold, can't get to tools since garage had to look ready for sale and mostly no inside place to work on and all the other "life" things that get in the way. Pulling the Prius down to Tim's tomorrow and leaving the truck with him, looking forward to his call telling me "you can have 'your truck back', it's all set". Hopefully end of this week. Don't care what it'll cost, within reason, just want her to run right again.