Posted September 3, 201410 yr I thought there was a procedure on here but I can't find it. Can someone point me in the right direction?
September 3, 201410 yr Just found a pic of overflow valve.. I always figured when pressure was below 14 psi, there was NO return to tank... Not true! there is a second unregulated port (free flow) that always allows at least a little flow Probably there for 2 reasons... to help allow air out... and to ensure some cooling no matter how pathetic the lift pump is.. are you wanted to test it for 'amount of return' ?? Or to see if it's stuck open ? Edited September 3, 201410 yr by rancherman
September 3, 201410 yr Owner I thought there was a procedure on here but I can't find it. Can someone point me in the right direction? All right here... http://articles.mopar1973man.com/2nd-generation-24v-dodge-cummins/25-fuel-system/88-bosch-vp44-injection-pump-overflow-valve The bottom hole is only for air bleed it too small for cooling. Even Bosch states 70% of the fuel should be return for proper cooling and there is no way you can get proper cooling in that tiny hole.
September 3, 201410 yr Author Just found a pic of overflow valve.. I always figured when pressure was below 14 psi, there was NO return to tank... Not true! there is a second unregulated port (free flow) that always allows at least a little flow Probably there for 2 reasons... to help allow air out... and to ensure some cooling no matter how pathetic the lift pump is.. pressure-valve.jpg are you wanted to test it for 'amount of return' ?? Or to see if it's stuck open ? See if it's stuck open. My hard start cold condition is back and so bad that I need to bleed fuel system every morning if I want to use it. Someone else changed O.F. valve and fixed problem.
September 3, 201410 yr Author All right here... http://articles.mopar1973man.com/2nd-generation-24v-dodge-cummins/25-fuel-system/88-bosch-vp44-injection-pump-overflow-valve The bottom hole is only for air bleed it too small for cooling. Even Bosch states 70% of the fuel should be return for proper cooling and there is no way you can get proper cooling in that tiny hole. THANK YOU!!
September 3, 201410 yr Author Oh, And what are the sizes of the sealing washers and the easiest place to buy them?
September 3, 201410 yr Bring the washers into any hydraulic shop & they can match them up. I want to say 12MM or 14 MM Ed
September 3, 201410 yr yah, I figured too the hole was too small for cooling... I just pasted the pic and some text from another forum... heres a post that caught my eye, this was posted in 2002, in a reply to the exact same question as OP here ^^^^^ KYLE--- Your electric lift pump has little or nothing to do with fuel return,except to bleed air out of the system after filter change etc. The lift pump can then force fuel and air thru the small orifce under the overflow valve and back to the tank. The VP pump has a 5 blade vane type positive displacement pump that pressurizes the high press. plungers,provides pressure to operate the hydraulic advance system,and provides a internal housing pressure in the VP assembly. The over flow valve maintains the housing pressure at 14 psig. This return aids the cooling and lubrication of the internal components and also vents out any air bubbles that get in the pump. The vane pump pressure is a function of pump/engine speed,and the pressure is regulated by the internal pressure control valve. It is a spring loaded slide/piston valve that is adjustable during calibration. It simply returns excess pressure to the inlet side of the vane pump. The vane pump pressure is approx. 150 psig . Estimate, as I am not priveledged to test specifications. ^^^^ if this is correct, then this answers my question on fuel flow through the body.. 1. vane pump supplies high pressure to head and the advance system. 2. internal pressure regulator maintains this pressure 3. overflow from THAT goes back into pump body.... then back to tank via overflow edit: I can agree with everything said except for the opening sentence....'nothing to do with overflow".... ummmm, pretty sure 'volume' must be there (at the inlet side).... and of course one way of measuring volume is psi (which most are monitoring these days) so a weak pump that can't supply enough fuel, will have poor psi, and may or may not 'fill' the vane pump efficiently. (starve). which then limits severly the amount available for downstream cooling Edited September 3, 201410 yr by rancherman
September 3, 201410 yr So, in reality, a stuck open overflow shouldn't effect how well the vane pump operates??? as long as it's being fed plenty of fuel, it'll supply the head and advance system ..???
September 3, 201410 yr Author Yeah, but if it is stuck open and there is a slight air leak in the fuel can it will create a siphon effect and suck air in the feed line or at least that's what I am hoping. Disabling my LP at startup helped for a little while. Now after sitting overnight I pretty much need to do a total priming to get it to start. I'm going over the system looking for leaks and have found none but white smoke and foaming fuel mean air is in there. The other day I took off both my FP gauges and plugged the ports on the fuel can to rule that out. So the fuel can was open ( just the 2 test ports) for a max of 5 min. The truck started and ran for a sec w/ the fuel in the VP and then shut off w/ a white puff of smoke. I see no way for air to siphon down in to the feed line so quickly unless overflow is open . And the air was not up at the injectors cause the truck ran briefly. I'm pulling my hair out with this thing so I'll take any suggestions.
September 3, 201410 yr Have you checked the return line going to the back of the head? It is a pain to get to but there are a couple of sealing washers on a banjo fitting back there that are very common to fail. Even on the return system, if there is a leak it will cause problems starting. Also, I have seen the drain valve on the stock filter canister not sealing all the way and causing a small leak down over time. Geno's garage has a replacement drain valve that works very nicely.
September 3, 201410 yr all I can suggest right now is to look for ANY signs of dampness at the fittings and lines.. might as well start at the tank! Although a bleed back won't be too easy if the leak is near the tank. Your problem almost has to be after the lift pump I know after bleeding, everything is soaked and wet.. and it's hard to see any 'new' dampness.. wash it up as good as you can, and check again. I swear, sometimes I find the dangest things... a fitting that may seal up fine on pressure, but as soon as a vacuum hits... poof. ilikeoldfords has a good idea with the drain valve. BTW, when you get this fixed, could you snap some pics of how you got your flat bed attached? Edited September 3, 201410 yr by rancherman
September 3, 201410 yr Author Have you checked the return line going to the back of the head? It is a pain to get to but there are a couple of sealing washers on a banjo fitting back there that are very common to fail. Even on the return system, if there is a leak it will cause problems starting. Also, I have seen the drain valve on the stock filter canister not sealing all the way and causing a small leak down over time. Geno's garage has a replacement drain valve that works very nicely. I have checked and tightened them a little. None where even damp but I'm gonna order new washers and grommets and a new Overflow and start there. Anyone have any shortcuts to rebuilding that T in the return line? Looks like it would be easier to pull the dang motor to get to it.
September 3, 201410 yr Author all I can suggest right now is to look for ANY signs of dampness at the fittings and lines.. might as well start at the tank! Although a bleed back won't be too easy if the leak is near the tank. Your problem almost has to be after the lift pump I know after bleeding, everything is soaked and wet.. and it's hard to see any 'new' dampness.. wash it up as good as you can, and check again. I swear, sometimes I find the dangest things... a fitting that may seal up fine on pressure, but as soon as a vacuum hits... poof. ilikeoldfords has a good idea with the drain valve. BTW, when you get this fixed, could you snap some pics of how you got your flat bed attached? No problem, I'll get you some pics of the bed mounts. Hopefully I'll get this fixed soon. Hunting season's coming and I need this truck to start in the morning.
September 3, 201410 yr Get the new grommets from Cummins, do the lower first, then do the horizontal, then pull the upper & back of head banjo & lay across the valve cover. Stick the tube in the T, with the nut & grommet on it, then tighten the banjo. Then, tighten the T fitting. Hold the T in place when tightening any of the grommet nuts. To make it easier & less bloody, remove the bracket with the 2 electrical connectors on the cowl, pull the bolt that holds the dipstick & swing it out of the way. Pull the stock fuel pump if it is still there. Be sure the kids aren't around, because you will be swearing like a drunk sailor that got mugged by a transvestitie prostitute. Ed
September 3, 201410 yr Jeese...I had no troubles with the banjo fittings and grommets on mine. Was just in there putting on a new IP and injectors. Smartest thing I did was building a platform like a big set of steps right in front of the truck. Lots of room for tools and parts. It helps that I am not a very big lad and can just about lay down on the valve cover LOL. Regards Chris
September 4, 201410 yr Owner All the internals of the VP44... If you need better pictures of anything let me know I'll put it apart and shot more pictures. http://articles.mopar1973man.com/2nd-generation-24v-dodge-cummins/25-fuel-system/437-bosch-vp44-injection-pump-exploded-view
September 4, 201410 yr Author . Be sure the kids aren't around, because you will be swearing like a drunk sailor that got mugged by a transvestitie prostitute. Ed They're already used to that. Remember I probably bled the thing 5 times in the last week Seriously though, thanks for the tip. I'll try it.
September 4, 201410 yr Author Have you noticed your oil level creeping up... getting thinner... I have not, but crossover tubes I know are suspect also. Could I tell otherwise if they are leaking ?
September 4, 201410 yr oil level going up is the only way I know to tell. I was originally thinking about the fuel return circuit.. the circuit that comes out the back of the head, like Yankneck is talking about, but INSIDE the head... is there any possible way that could leak internally?
I thought there was a procedure on here but I can't find it. Can someone point me in the right direction?