Duel fuel line mod M818 855 cummins

[Scar59]

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.

Thanks, I plan on modifing two trucks,maybe three.
JC

 

[Floridianson]

[QUOTE=AMGeneral
As far as rail pressure,I will check that this weekend and post the results here.
Report finished yet Soldier.

 

[AMGeneral]

I didn't work on it this evening, we had 2 cats attacked by a dog from the trailer park about 1:30 pm this afternoon,both had to go to the vet,1 got shots and antibiotic medication.

The other had to have his right rear leg amputated below the hip,as well as a cast on his right front,plus a stay overnight in the vet's care.

 

[IsaLandr]

I used 3/8 inverted flare steel lines for the fuel lines. One was 40" the other 30". The tee is a 1/4" NPT. I used 1/4" to 3/8" Inverted flare adapters out from there to the lines. The adapters at the heads are 1/8" npt to 3/8" flare. (Plus remember you'll need to space out the front head fitting.) I used a 1/4" npt to a JIC adapter to plumb the tee into the adapter that comes out of the emergency stop valve. (It has a O ring and a straight thread)

Parts list:
JIC flared fitting to 1/4" NPT adapter
1/4" NPT tee
1/4" NPT to 3/8" inverted flare adapter (two)
one 20" 3/8" inverted flare steel line
one 30" 3/8" inverted flare steel line
two 3/8" inverted flare to 1/8" npt adapters
one 1/8" npt male to male nipple
one 1/8" npt 90 or straight female to female coupler

This is kind of an old thread, but I'm looking at doing this modification relatively soon, and I would like some clarification. I've read the whole thread all the way through several times and I don't see a correction, nor do I see anyone else asking this question. In the quote above, it says we need two new steel lines, 40" and 30". But in the parts list, it says 30" and 20". Which is correct?

Also, for my own understanding, what was the reason why the front fuel feed had to be modified? I didn't see a clear explanation of why that was done, either. If I'm going to do this, I want to do it right, start to finish. It helps my working process to understand each part so I know what I'm doing. I read the bit about spacing out the front head fitting, but I don't understand well enough what that means. Would you mind explaining?

Last questions (for this post): is there a brand name or something specific I should ask for to get lapping compound for getting that fuel rail cap out? And could/should I use a penetrating oil in conjunction with the lapping compound? Thanks in advance, this thread has been most instructive.

 

[elkhtr]

IsaLandr, on mine a 40" was perfect for the rear.
20" is too short for the front, I used a 30" cut down to about 26" and re-did the double flare.
As far as why replace the front, my guess would be to match line and fitting sizes, I believe the stock line was 5/16.
Clover compound is a brand of lapping compound commonly found at good auto stores, usually a double can with 2 grits.
As far as spacing out the front, that is simply to clear the casting boss for the front head bolt.
Just use a nipple and a 90 degree instead of just a 90 deg by itself, gets it out just far enough to clear the head.
In my opinion the mod is worth it, faster start, smoother idle, maybe a litlle better botom and mid, just seems to run out smoother.
Hope this helps.

 

[IsaLandr]

Thank you for the clarification, Elkhtr.

Okay, trying to follow along here. JIC to NPT from the emergency shutoff valve into the 1/4" NPT T-fitting. 1/4" NPT to 3/8" inverted flare on each outlet of the T-fitting into the two 3/8" steel lines, 30" for the front, 40" for the rear. 3/8" Inverted flare to 1/8" NPT adaptors at the ends of the two steel lines. I can get that far, and it makes sense.

Now the question is, what do we do with the 1/8" male to male nipple? Are we moving the current 90 degree fitting from the front to the back, and using the male to male nipple and the female to female 90 degree coupler as a spaced fitting on the front?

 

[elkhtr]

1/8" male-male nipple into the head, 90 deg 1/8 pipe female-female onto the nipple, female inverse flare x 1/8 male into that.
Same setup front and rear.
Bend the 40" tube carefully, needs to hug the block pretty close, it's just long enough if bent correctly.
Have fun!

 

[IsaLandr]

1/8" male-male nipple into the head, 90 deg 1/8 pipe female-female onto the nipple, female inverse flare x 1/8 male into that.
Same setup front and rear.
Bend the 40" tube carefully, needs to hug the block pretty close, it's just long enough if bent correctly.
Have fun!

Thank you, I think I have it now. So on the parts list, where it says we need one male to male nipple and one female to female 90 degree coupler, what we actually need is *two* of each? And then discard the original 90 degree fitting from the front head entirely?

I'm hoping to have the time to pick up the parts and get this done tomorrow, but... so much other stuff going on right now, it may just have to wait till next week.

 

[elkhtr]

Thank you, I think I have it now. So on the parts list, where it says we need one male to male nipple and one female to female 90 degree coupler, what we actually need is *two* of each? And then discard the original 90 degree fitting from the front head entirely?

I'm hoping to have the time to pick up the parts and get this done tomorrow, but... so much other stuff going on right now, it may just have to wait till next week.

Two of each is correct.
On mine it took longer to remove the shifter tower and doghouse than it did to do the mod.
The insulated plastic cover on mine was glued to the doghouse and covered the bolt heads.

 

[IsaLandr]

Two of each is correct.
On mine it took longer to remove the shifter tower and doghouse than it did to do the mod.
The insulated plastic cover on mine was glued to the doghouse and covered the bolt heads.

I haven't looked under the floor covering yet to see how bad it is. Somebody else posted they were able to do it from the top in the engine compartment. If my flooring is like yours, I may explore that route. I do not fancy the idea of tearing up my floor covering to do this.

 

[ke5eua]

Honestly no, I don't have any part numbers. I simply walked in and knew what I was looking for.

From the emergency cut off valve I used the following parts.

JIC flared fitting to 1/4" NPT adapter
1/4" NPT tee
1/4" NPT to 3/8" inverted flare adapter (two)
one 20" 3/8" inverted flare steel line
one 30" 3/8" inverted flare steel line
two 3/8" inverted flare to 1/8" npt adapters
one 1/8" npt male to male nipple
one 1/8" npt 90 or straight female to female coupler

Everything except for the JIC flared fitting was purchased at the local auto parts store. The JIC flare to NPT I got at the local hyd. hose place. But if you're buying from a NAPA, I'm sure they'd have that. (Or a parts store that does hyd. hoses)

Ok so I'm off to napa either tomorrow or friday to secure parts for this and my filter to ip priming pump idea.

If I bring this list that is all I need, and can I use fuel hose instead of pipe?

My filter to pump idea:


|----pump----|
--in--| |--out--
|--------------|

This allows me to prime the ip and it still have the 1/2 line for main flow.

 

[IsaLandr]

Ok so I'm off to napa either tomorrow or friday to secure parts for this and my filter to ip priming pump idea.

If I bring this list that is all I need

Change the last two lines in the parts list to

TWO 1/8" npt male to male nipple
TWO 1/8" npt 90 or straight female to female coupler

Because as we were discussing earlier, you need two of those assemblies to do it correctly without re-using the original 90 degree fitting from the front head.

I don't know about using the hose instead of steel line, somebody else will have to chime in on that one. I'm going with the steel lines, for simplicity and durability.

 

[elkhtr]

Ok so I'm off to napa either tomorrow or friday to secure parts for this and my filter to ip priming pump idea.

If I bring this list that is all I need, and can I use fuel hose instead of pipe?


My filter to pump idea:


|----pump----|
--in--| |--out--
|--------------|

This allows me to prime the ip and it still have the 1/2 line for main flow.

Hi ke5, are you talking about custom made hydraulic type hoses with swaged ends, or just fuel hose and clamps?
You could do hydraulic hoses I would guess, but I would think the cost would be prohibitive compared to the steel line.
Being on the high pressure side of the pump, I would not recomend regular fuel line.

 

[162tcat]

Between the IP and the engine, it needs to be solid tubing. Anything else will cause strange issues with throttle response and won't last.

 

[ke5eua]

Ok, will do solid tubing. Just figured I'd ask.

 

[juanprado]

Two of each is correct.
On mine it took longer to remove the shifter tower and doghouse than it did to do the mod.
The insulated plastic cover on mine was glued to the doghouse and covered the bolt heads.

Just a quick side note as I am adding a winch to my m923 and would like to use the doghouse off a winch truck. Does it bolt from the inside of the cab or from the engine compartment? How does the cover come off? I take it the transmission shifter is removed and the cover slips off giving access to the dog house?

 

[elkhtr]

Juanprado, it bolts on from the inside.
The way it looks, the factory bolts in the doghouse, then glues the insulated plastic cover to that.
Then they put the floormats on top of that.
I took a razor knife and carefully slit my floormat so it could be pulled out of the way.
The bolts on the top are the tough ones.
I could hardly see them, it took a long extension and a universal joint to find them by feel.
Lots of stuff in the way.
Good luck!

 

[juanprado]

Thanks for "painting the picture"
Helps a lot.

 

[IsaLandr]

Patracy and others who have compleated this modification:

I went and picked up most of the parts I need today, finally. Got almost everything required to begin the work. However, I hit a snag. When looking for the JIC fitting, we could not determine which one to get, and it's not directly listed in the parts list, unless one is to assume that the !/4" applies equally to both sides, NPT and JIC. I hate to make an assumptiona nd jump to the wrong conclusion. Apparently there are multiple JIC sizes that convert to 1/4" NPT. So, the question is, what size JIC do we need here? Is it 1/4" NPT to 1/4" JIC?

 

[patracy]

I will have to dig around or take mine apart to figure out the - (dash) size. JIC or AN fittings have their own sizing.