M939 IP to primer pics

[ke5eua]

I am trying to sift through the tm's for the 939 and see where the primer pump connects to the ip and that is better said than done. Can anyone post a couple pics of the nhc 250 model of the primer pump to the ip and where it hooks up.

Thanks in advance.

 

[Floridianson]

Do believe in the start they had it hooked to the correct bottom port on the PT on the 250 cummins. Then they switched to the elbow that is screwed in the PT with the incomming fuel line. You just have to get the correct bottom port if you go the old way as one is under pressure. I like the way they taped threads in the elbow incomming fuel fitting. I need to strip some of the taped elbows from parts trucks that I have and replace the primer pump pick up from the bottom port pick up to the elbow.

If I rember there are two ports on the bottom of the PT and we use the one on the inside close to the motor not the outside one. If you get it wrong when the truck is running and you open the primer it would show up pressure on the cab gage on the M809 series. If the truck was running high rpm it would peg the gage and you could not get the primer back in and locked till the PT stoped makeing pressure.

 

[M35A2-AZ]

Here is a pic, it goes into the fitting that the fuel line hooks to on the end of the pump.
I just replaced the one one this truck.

 

[ke5eua]

Thanks to both.

Now to brainstorm, the 818 pulls off the bottom of the ip and feeds to the intake. I like the idea and design on the 939 better so I think I'm going to switch it around.

 

[Floridianson]

PT! Yea here is another pic off the elbow and a pic of the pressure switch on the PT. Believe the pressure switch on the bottom port of the PT is used troubleshooting. Now I learned something too the New PT's do not have two ports on the bottom of the PT just the one.
I do have some USMC 817's that have the elbow mod. Are the Marines smarter than the Army. They order the primer pick up in a better place and order Lockers in the rears. The USMC has my vote for more working Gray matter.

 

[Floridianson]

Was just checking and you have a M818 and where is the primer pickup on your PT? Is there two ports on the bottom of your PT.

Not put down the feed line you used M35A2-AZ but I would have used the synflex DOT plastic line not that soft line.

 

[ke5eua]

It is on the bottom of the pump on the port closest to the engine.

Mainly troubleshooting at this point since I pulled the manual pump and put electric priming pumps on it.

The 818 design has it dump the prime into the intake and I'm a little hesitant about that so I was looking at a separate place to dump it.

Right now I have one pump acting as the prime dumping into the intake and another dumping into the return off the injectors but I think the pressure is too much on that line so I'm looking at other alternatives.

Since I'm designing a ecm module to control the truck I want to tie in priming function as an automatic function and since I now know the other port comes off the main pressure feed I can place a pressure sensor there to control the prime function and monitor the injector pressure.

 

[TruAg]

Curiously following your primer project. I have a M936A2 that is giving me fits having to prime it after it sits overnight. Replaced fuel filter and lines around selector (left vs right tank), but still having issues. I have to inject air into the fuel tank and hand prime it to get going.

What type of electric fuel pump did you install? Is there a thread on that project?

 

[ke5eua]

Curiously following your primer project. I have a M936A2 that is giving me fits having to prime it after it sits overnight. Replaced fuel filter and lines around selector (left vs right tank), but still having issues. I have to inject air into the fuel tank and hand prime it to get going.

What type of electric fuel pump did you install? Is there a thread on that project?

My build thread shows the ones used but those will be changed to a cummins pump off a dodge when I get all the electronics done.