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"Lapping" fuel lines to rail to fix leaks.
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=89179		 Page 1 of 1
Author:  Sir Sam [ Sun Aug 26, 2018 11:17 pm ]
Post subject:  "Lapping" fuel lines to rail to fix leaks.
Ok so red project CRD I just picked up, codename: "Ruby" was having some issues getting the fuel injector hardlines to seal against the fuel rail, no matter what I did, careful torque, keep straight, etc.

I tried some very fine sandpaper to cleanup some scoring marks from being removed and reinstalled several times(some from before I owned it), to no avail.

Finally out of desperation I took some old rubbing/buffing compound from a dremel kit and used it as a lapping agent. I coated the metal hardline with a little bit and then tried to work it against the rail seat by hand keeping it plum as possible.

With about 1-2 minutes of work and refreshing the compound, and a good cleanup to remove the compound, I reinstalled it. To much surprise and pleasure it was sealed! I have never had so much trouble getting the hardlines to seal, and just this small bit of "lapping" managed to solve the leak.

Maybe this will help someone in the future, I was expecting to have to find a used rail and new hardlines! Very pleased with the fact it worked!
Author:  rancherman [ Mon Aug 27, 2018 1:47 pm ]
Post subject:  Re: "Lapping" fuel lines to rail to fix leaks.
Sir Sam wrote:
Ok so red project CRD I just picked up, codename: "Ruby" was having some issues getting the fuel injector hardlines to seal against the fuel rail, no matter what I did, careful torque, keep straight, etc.

I tried some very fine sandpaper to cleanup some scoring marks from being removed and reinstalled several times(some from before I owned it), to no avail.

Finally out of desperation I took some old rubbing/buffing compound from a dremel kit and used it as a lapping agent. I coated the metal hardline with a little bit and then tried to work it against the rail seat by hand keeping it plum as possible.

With about 1-2 minutes of work and refreshing the compound, and a good cleanup to remove the compound, I reinstalled it. To much surprise and pleasure it was sealed! I have never had so much trouble getting the hardlines to seal, and just this small bit of "lapping" managed to solve the leak.

Maybe this will help someone in the future, I was expecting to have to find a used rail and new hardlines! Very pleased with the fact it worked!


I've reclaimed some lines over the years too, it's about a 50/50 chance.. but it's worth the try!!
I took the adapter fitting out of the injector... then clamped the line in vice. put the adapter in a hand drill, and used valve compound to 'lap' in a new surface.. clicking forward and reverse every couple seconds... The ones that wouldn't 'come around'.. were from a distorted/cracked nut..
Yeah, I've saved a few hundred bucks over the years!! 8)
Author:  Sir Sam [ Mon Aug 27, 2018 3:12 pm ]
Post subject:  Re: "Lapping" fuel lines to rail to fix leaks.
In this case I determined it wasn’t the lines that were the issue, 3 and 4 would not seal at the rail even if I swapped lines from 1 and 2.

1 and 2 always sealed fine, so I was thinking I might need a new rail, turns out new rails are NLA. And being a non moving part I can understand how it would be a very low failure item.

It would be nice to have the tool or a tool you could attached to the drill to lap the inside of the rail seat if needed. The injector adapter makes a nice lapping tool for the lines, but at least we can still buy new lines........for now.
Author:  GordnadoCRD [ Mon Aug 27, 2018 7:00 pm ]
Post subject:  Re: "Lapping" fuel lines to rail to fix leaks.
Nice fix!

I guess if it works for air through the valves, it should work for diesel through these!
Author:  APC9199 [ Mon Aug 27, 2018 7:50 pm ]
Post subject:  Re: "Lapping" fuel lines to rail to fix leaks.
My only concern here is the use of lapping compound on fuel system components. Most lapping compounds are silicon carbide (nearly diamond hard) and are designed specifically to abrade material off of whatever they touch. If ANY of that gets into the injector system it is going to do immediate damage to the valve seat or orifice. Make sure that you do not allow any compound into the actual rail or lines. Or, if you do, clean it like your life depends on it before reassembling anything.

For background...I have had conversations with machine shop owners who used lapping compound to repair spindle tapers and didn't clean the residue off completely and found a few weeks later that their spindles and tool holders were completely worn out from lapping each other thousands of times a day for days on end. I've also heard of fluid pumps wearing out the impellers from copious amounts of lapping compound running through them.

I don't think any of this isn't extremely obvious to most people, but I thought it could use some clarification for those who are not familiar with the way our high pressure injectors work.
Author:  WWDiesel [ Mon Aug 27, 2018 10:33 pm ]
Post subject:  Re: "Lapping" fuel lines to rail to fix leaks.
APC9199 wrote:
My only concern here is the use of lapping compound on fuel system components. Most lapping compounds are silicon carbide (nearly diamond hard) and are designed specifically to abrade material off of whatever they touch. If ANY of that gets into the injector system it is going to do immediate damage to the valve seat or orifice. Make sure that you do not allow any compound into the actual rail or lines. Or, if you do, clean it like your life depends on it before reassembling anything.

For background...I have had conversations with machine shop owners who used lapping compound to repair spindle tapers and didn't clean the residue off completely and found a few weeks later that their spindles and tool holders were completely worn out from lapping each other thousands of times a day for days on end. I've also heard of fluid pumps wearing out the impellers from copious amounts of lapping compound running through them.

I don't think any of this isn't extremely obvious to most people, but I thought it could use some clarification for those who are not familiar with the way our high pressure injectors work.

I totally agree, any lapping compound getting into the wrong places could be totally depremential to high tolerance parts especially like injectors.
We used to send parts out to be ultrasonic cleaned after using any abrasive compound on them to ensure total cleanliness and that no residue remained.
Author:  Sir Sam [ Mon Aug 27, 2018 10:43 pm ]
Post subject:  Re: "Lapping" fuel lines to rail to fix leaks.
No idea what the compound I used contains for grit, it was green and came with a dremel set.

That said I rinsed the lines and rail out throughly to make sure there wasn't any grit left.
Author:  rancherman [ Tue Aug 28, 2018 9:55 am ]
Post subject:  Re: "Lapping" fuel lines to rail to fix leaks.
Sir Sam wrote:
No idea what the compound I used contains for grit, it was green and came with a dremel set.

That said I rinsed the lines and rail out throughly to make sure there wasn't any grit left.


depending on how 'green' yours was, 600-1200 'grit'
Chromium oxide... excellent for ultra hard surfaces; chrome, stainless, diamond..
Author:  mrhemi [ Tue Aug 28, 2018 12:33 pm ]
Post subject:  Re: "Lapping" fuel lines to rail to fix leaks.
rancherman wrote:
Sir Sam wrote:
No idea what the compound I used contains for grit, it was green and came with a dremel set.

That said I rinsed the lines and rail out throughly to make sure there wasn't any grit left.


depending on how 'green' yours was, 600-1200 'grit'
Chromium oxide... excellent for ultra hard surfaces; chrome, stainless, diamond..


Or Crest Toothpaste. You said it was from a Dremel kit.
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