Injection pump leak
02-04-2007, 07:24 PM
#46
Registered User
Join Date: Jan 2003
Location: Prince George, B.C.
Posts: 128
Likes: 0
Received 0 Likes
on
0 Posts
Absolutely. "Vent plug" or "return pressure regulator" are exactly same thing. Also, acts as one way valve until LP pump builds pressure ( starting and shutting down). Re-read reply #29 above. Compression of 17:1 in these engines can easily feed air back through "injector drain manifold" to return connection of pump even with no combustion - especially if injectors are older and leak by a bit more. That is one of the reasons Cummins suggested gently squeezing off the return rubber line with vise grips to test regulator in my case. You will be an expert on that VP44 pump when done but I hope you can get it assembled correctly without all the tools and test jigs a Bosch rebuilder has.
02-05-2007, 03:07 PM
#47
Adminstrator-ess
I've been distracted by work, family and weather, but I've got the IP mostly disassembled and am looking hard at every component and seal. No obvious seal breaks, but I'm not done yet. Quick question for anyone that knows anything about these things. There is a vent plug (item #336 on the Bosch parts list, handily posted https://www.dieseltruckresource.com/...ighlight=bosch by Jim Lane).
I notice that I can easily blow air through this fitting either way, i.e. both in and out. There is obviously a diaphragm of some kind inside the plug, but it seems to work easily both ways. Is this a likely source of the air that has been getting into the pump?
Thanks,
Darel
I notice that I can easily blow air through this fitting either way, i.e. both in and out. There is obviously a diaphragm of some kind inside the plug, but it seems to work easily both ways. Is this a likely source of the air that has been getting into the pump?
Thanks,
Darel
This is wrong. Dadburn overvalvers...
02-05-2007, 06:15 PM
#48
Registered User
Join Date: Jan 2003
Location: Prince George, B.C.
Posts: 128
Likes: 0
Received 0 Likes
on
0 Posts
Wannadiesel - thanks, I was wrong about the location of the pressure regulator. I do have 12 valves and a VP44 in my 91.5 but it was in 1997 when I had my big IP problems and have forgotten some of the details and advise I was given by Cummins.
Darrels -Sorry about mis-leading information. I went back and checked my correspondence with Josh Berman (Technical Rep) at Cummins factory in 1997 and he says that unlike the inline Bosch P7100, our rotary Bosch VP44 in 1st Gen only has an orifice <1mm and a fine screen at the return outlet of the pump to maintain fuel backpressure. That means it does not act as a "check valve" (unlike the P7100 which has a ball, seat and spring in return regulator).
Darrels -Sorry about mis-leading information. I went back and checked my correspondence with Josh Berman (Technical Rep) at Cummins factory in 1997 and he says that unlike the inline Bosch P7100, our rotary Bosch VP44 in 1st Gen only has an orifice <1mm and a fine screen at the return outlet of the pump to maintain fuel backpressure. That means it does not act as a "check valve" (unlike the P7100 which has a ball, seat and spring in return regulator).
02-07-2007, 01:33 PM
#49
Registered User
Thread Starter
Join Date: Jan 2007
Location: Memphis, TN
Posts: 27
Likes: 0
Received 0 Likes
on
0 Posts
Yeah, I talked to the guys at Mid-South Diesel service and they said the same thing - essentially there is only air at that vent. They're a little stumped at this point, agreeing that anything that lets that much air in should be letting fuel out also. They advised me to just go ahead with what I'm doing - replace all the seals, reassemble and see what happens. They've also been very helpful with advice and support during this, especially since the only thing I've bought has been the rebuild kit - if you need help in the mid-south, I can recommend them. I've got everything apart and cleaned, will begin reassembly tonight. Cross your fingers for me!
Darel
Darel
Thread
Thread Starter
Forum
Replies
Last Post
tommurray
12 Valve Engine and Drivetrain
5
02-23-2014 10:38 AM