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Discussion Starter · #1 ·
I just took my first test drive with my newly rebuilt p pump 4bt. It ran fine for a while then seemed like the idle was creeping up. The rpm started going up like crazy and there was a cloud of steam. I got out of traffic, checked for stuck throttle and restarted. Immediately went to high rpm. I limped home by starting and coasting. One of the frost plugs has blown out and the coolant is gone. The oil is full and clear. The whole experience was a bit too frenzied to check gauges. I had the pump adjusted while it was apart and set the timing to 16 degrees. The turbo is a brand new hx30w. I ground the fuel plate to a 10 profile and slid it forward but haven't adjusted the star wheel. Any advice?
Thanks
Ian
 

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Discussion Starter · #2 ·
An update. This was not an overspeed event. Shutting off the fuel stopped the motor. It restarts then quickly goes to wot. I found a loose screw on one side of the fuel plate and when I move the throttle lever the pawl that contacts the fuel plate doesn't move back to the same position every time. Before this started the engine was idling and running fine. Getting the pump out would probably involve removing the front clip of my 46 Dodge pickup so I'd really like to explore any other options. Any help would be appreciated.
 

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When you worked on the injection pump did you change the governor springs? If so, that could be one possible problem. The #10 torque plate is usually left in the stock position, not slid forward. A blown freeze plug is not that common. Would take a lot more pressure than the radiator cap would normally allow. Were the plugs replaced and are they Cummins parts? Some aftermarket plugs may not be the correct fit. Blown head gasket could be another cause but again the radiator cap should have vented that.
 

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Discussion Starter · #4 ·
Thanks Char. I've had a further look at the pump and the rack is moving freely. The problem appears to be with the governor springs. Looking down from the afc housing one of the large governor springs is out of alignment with the bore in the governor. I'm going to say all the bad words I know then pull the pump and the head. I checked the diameter of the frost plug and it's hole and it is correct so I'm pretty sure I blew a head gasket. ARP studs this tme!
 

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Hope it's just one of the governor springs out of alignment. We had another member whose P pump had problems and it turned out there was a broken part in the governor housing. Luckily, he found a good used part to replace that piece. You don't want to be buying lots of parts from Bosch. People think Cummins is expensive until they buy some from Bosch for an injection pump. One thing positive is the governor assembly on a 4bt P pump is the same as the one on a 6bt Dodge from 1994-1998.
 

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Discussion Starter · #6 ·
I got the head off and the pump out without removing the front clip. Thats the good news! The head gasket is blown at the back of number 4 cylinder. Im going to go with a genuine Cummins gasket and hopefully re-use the stock bolts. I dont want to machine the rockers for arp studs. Something has failed in the pump governor. The case is chewed up inside and the plug for the springs was bent and hard to remove. The springs posts are bent. Off to the injection shop tomorrow.
 

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Bad words, Bad words. New governor housing and parts are not cheap. If you could find a scrap pump off a '94-98 Dodge the governor should be the same. Also, many medium duty trucks with the 6bt and 6ct had P7100 pumps. If you look on the end of the governor assembly it should have the model number there. If you wanted to do studs the machining of the rocker arms is not a major ordeal. Biggest chore is taking all the parts off the stand to put them in the milling machine. There is a gauge to measure the head bolts to see if they are reusable. Here's a guy who had problems with his P7100. Land Rover Disco2: Out with the old, in with the 4BT!
 

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Discussion Starter · #9 ·
And the bad news...$5500 to rebuild the pump. It is badly worn as well as the governor damage. Now my question is repair or replace. I see Dieseltuff.com has new pumps for $1700. Obviously Chinese pumps, but that country has millions of 4bts in use. Anyone dealt with these guys or have some knowledge of Chinese p7100 pumps?
 

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Yep, that got real ugly. Don't know if any other rebuilder would be cheaper. Like I said, Cummins is expensive until you start looking at Bosch. One big reason for the cost on that pump is rarity. Although that pump shares parts with the one used on a 6bt or 6ct, the 4 cylinder parts are just rare. Don't know about Canada but here in the US there are tons of companies who rebuild pumps. One that caught my eye is Area Diesel Service Diesel Specialists for Powerful Diesel Solutions | Area Diesel Service . They have 3 locations here and from what I saw of their facilities, they would rank near the top. No idea of cost but here's a video you might watch. Won't solve your problem but gives an idea of why these pumps are so expensive to repair. The one they did in this video was a cheaper pump. They have different technicians who work on the P pump.
Guys with this kind of expertise don't work for $10 per hour. You can contact Mark at Diesel Tuff and I believe he'll give you an honest opinion about his pump. Certain ones of those copies are licensed by Bosch and carry Cummins part number.
 
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