Duel fuel line mod M818 855 cummins

[swbradley1]

I are confused.

Thanks for clearing it up.

 

[Floridianson]

Just looking through older threads about duel fuel and RKrug post #59 you used a compression fitting. I would think you should have used an inverted flair brake line. Sorry just my .02

 

[wrenchturner6238]

I have done this mod to my M931 and it seemed to make the engine idle smoother and gave me 3MPH on a hill compared to before doing the mod. Just for info on the fitting coming out of the emergency shut off valve; I used a #5 o-ring boss plug and drilled and taped to a pipe thread to convert to inverted flare.

 

[Scar59]

Gents.
I contacted Pittsburg Power and they have the kits, however their concern was the size if the line on the M939 NHC250. Their question was the end fittings; 1/8' or 1/4 inch ? I have not gotten back to the truck to take measurements. Can anyone answer this. Also will the M813 have the same fitting dimension?
Thanks
JC

 

[patracy]

Complete parts list here:

http://www.steelsoldiers.com/showthread.php?93233-Duel-fuel-line-mod-M818-855-cummins

Can be made for less than $40 at any parts store.

 

[MartinB]

On the Pittsburgh Power website, this modification is discussed in detail. They use all Cummins parts for this mod.

 

[jarhead1086]

Pittsburgh Power (Pete) said that they also sell a complete fuel pressure kit that measures to 300 psi. It was out of stock but he thought it was about $250. He said you need to use a heavy duty transducer to survive here. I have other higher priorities with my truck budget money. I like their dual fuel kit because it has cleaner bends than I would get on my first try and it comes with the tubing clamps and thread locker on the 90 elbows. Factory look with less effort and time. I bought my pyro from them too. I am supporting a company that supports us too. Now I need to order some PT buttons thanks to Patracy getting me the PN's. I will borrow a mechanical gage from work to check the pressure deltas if it helps. I think we should have a gage with the right thread and pressure range.

 

[Scar59]

Jarhead,
What series truck (M939 or M809) engine did you get the kit for? 1/4 or 1/8 npt fittings? I haven't had time to make it under the hood of my unit. The factory kit is a lot cleaner install.
Thanks
JC

 

[patracy]

Jarhead,
What series truck (M939 or M809) engine did you get the kit for? 1/4 or 1/8 npt fittings? I haven't had time to make it under the hood of my unit. The factory kit is a lot cleaner install.
Thanks
JC

M809 and M939/M939A1 configs would have the same NHC-250 engine. Only a M939A2 config would have the Cummins 8.3.

 

[Scar59]

patracy,
I understand that the same engine is installed in both series trucks. The question is; Are the fuel line end fitting the same? (1/4 or 1/8 npt) respective to the newer M939 trucks. I ask because Pittsburg Power asked the same question. This led me to believe that the newer NHC 250s in the M939 trucks may have larger fuel line/fittings compared to the older M809 trucks. Your mod was to a M939 (nice fab by the way) do you remember the end fitting size that threads into the block?
Thanks
JC

 

[patracy]

patracy,
I understand that the same engine is installed in both series trucks. The question is; Are the fuel line end fitting the same? (1/4 or 1/8 npt) respective to the newer M939 trucks. I ask because Pittsburg Power asked the same question. This led me to believe that the newer NHC 250s in the M939 trucks may have larger fuel line/fittings compared to the older M809 trucks. You mod was to a M939 (nice fab by the way) do you remember the end fitting size that threads into the block?
Thanks
JC

Parts I used are listed in this thread:

Complete parts list here:

http://www.steelsoldiers.com/showthread.php?93233-Duel-fuel-line-mod-M818-855-cummins

Can be made for less than $40 at any parts store.

 

[Kawgomoo]

On those pump bolts that are impossible to get out, have you ever tried using a stubby allen socket with an impact screwdriver to popem loose?

 

[patracy]

On those pump bolts that are impossible to get out, have you ever tried using a stubby allen socket with an impact screwdriver to popem loose?

View attachment 475569 View attachment 475571 View attachment 475570

Pump bolts? You mean the fuel rail ports on the head? I tried that. Shattered a bit. Problem is, they're so small.

 

[Vintage iron]

It is locktite that is holding it in. Just add some heat, let it cool and it comes out easy cheeasy.

 

[patracy]

It is locktite that is holding it in. Just add some heat, let it cool and it comes out easy cheeasy.

I tried heat, but didn't have much luck. Of all things, the trick of the valve lapping compound worked wonders for me. I'll keep that one in my bag of tricks now always!

 

[Kawgomoo]

yeah sorry about that...terminology fail on my part.

i know their tiny. Not all allen keys are not equal. As I'm sure you found out.

I find the impact driver to be highly effective...the smaller the screw the more likely i am to use it. I try to size the weight of the hammer to the job im doing. and press the tool into the work before you wack it. I found it can be used very to break loose very delicate fasteners you would otherwise wring off. 4x35mm stator screws on my kids dirt bike for example.

Everything in my world is held together with a 5/32 or 3/16 allen, then red loctite. We battle these things daily.

Another good tip i was taught early on, if you strip an allen bolt {socket head} you can repair with a slightly oversized punch and a good wack. it folds the corners right back in where they need to be and gives you another shot before drilling that sucker out!

Anyways, just spitballing. getting ready to do this mod myself this weekend. {children permitting} I haven't taken a hard look to see how much room ive got, but if people are cutting holes in the firewall to get these buggers out. Dang.

Torch + Fuel Rail seems so high risk.

 

[AMGeneral]

I started working on the dual fuel line modification for the 813A1 this evening, I'll post here how everything turns out.

 

[AMGeneral]

Well,the modification is finished!

The 250 didn't change much from 550 to 1300 rpm,but after 1300 it definetly revs to governed speed much more quickly.

It seems to have more mid range pulling power as well as upper rpm power out on the interstate,I was able to maintain 48 mph up the same hill it dropped off to 40 ish before.

I did not change the idle plunger(button) from the stock 27 button to a 22 or 20,and probably will not.

As far as rail pressure,I will check that this weekend and post the results here.

 

[Scar59]

AMG,
Did you piece the kit together or use a Cummins kit? Did you remove the toe board in the cab?

 

[AMGeneral]

AMG,
Did you piece the kit together or use a Cummins kit? Did you remove the toe board in the cab?

I used patracys list of parts earlier in this thread.

I didn't even have to remove the transmission tunnel,I removed the rear fuel rail plug with a allen wrench from the top.