6.9 idi air intrusion!!!

[The_gestach]

Hello! New to the form! I’m 20 years old building a 6.9 idi with a HX35 turbo! I am having issues with the fuel system getting air intrusion! I have bypassed the light pump and have a electric fuel pump with filter on it. I have bypassed the water fuel separator too. I have gone as far as bypassing the main fuel filter by cutting the line for the intake to the injection pump! I have also replaced all the return lines as well as the supply lines. I cant seem to find where the air is coming from! I have a clear hose for the return line from the IP and seeing air come through! Full tank of fuel as well I’m in such a head ache please if you know anything else that can cause it please let me know! Thank you!!

 

[Farmer Rock]

If you haven't already, I would suggest replacing all the low pressure fuel lines first. They commonly get pin holes that aren't visible, but cause what you describe. The metal lines are the worst. That's cheap insurance anyway. Also, you should get at least the primary fuel filter back on there soon.


Rock

 

[ROCK HARVEY]

The low pressure steel lines (not the ones from the IP to the injectors) also have rubber olive seals on each end that harden and fail. The ones on my truck were basically gone; I don’t think they had ever been replaced. I found viton replacements: Parker vibra-lok 60VLV-5 (5/16” size) and 60VLV-6 (3/8” size). My truck took 2 of each, but I think some trucks only need 1 of the 3/8” olives. I also believe that some trucks use 1/4” olives. Just measure the OD of the steel line and buy the olive in that size. The 1/4” ones would be 60VLV-4. The non-viton ones are a little cheaper, and are what came in the truck originally. They are 60VL series instead of 60VLV, but the size numbers will be the same.

 

[The_gestach]

Thank you rocky for the response but I have barley any steel lined anymore I have replaced a lot of it with rubber because it had rubbed through. I am not keeping it that way I just would like to get it running good before I buy any replacement kits. There should be no more olive seals left except if there is one on the injection pump feed line from the filter because I had cut off the fuel filters fitting line going to IP. And yes I will be getting a filter in it but I’m trying to relocate the fuel filter for more space inside the engine bay. I can take pictures tomorrow and upload them so you know that I’m working with. Thank you!!

 

[ROCK HARVEY]

Do you still have the steel return line from your injection pump back to the tank? It runs straight front to back down the driver side of your engine, under your injector hard lines. At the back of the engine it has a fitting where the rubber return lines connect to it. Some trucks have a different setup, but I believe the 6.9s came with this steel line. On my truck the olive seal in that fitting was so far gone the fitting wobbled around loosely on the steel line.

 

[Farmer Rock]

One detail we need is, does the air intrusion cause your truck to start hard or to just run like crap? If it's only when running, look at the return lines, if starting hard, then look at fuel supply system.



Rock

 

[The_gestach]

Thank you rock! I’ll take a look at the return line olive but i see the air coming out of the injection pumps return line, also my truck does numerous of things it hard starts when cold starts good when warm, while driving it runs lean once warmed up and only starts getting air intrusion when warm, it smokes a bit of white/blue but goes away once warm so I think that is more because of timing but I could be wrong! Thank you!

 

[Farmer Rock]

Thank you rock! I’ll take a look at the return line olive but i see the air coming out of the injection pumps return line, also my truck does numerous of things it hard starts when cold starts good when warm, while driving it runs lean once warmed up and only starts getting air intrusion when warm, it smokes a bit of white/blue but goes away once warm so I think that is more because of timing but I could be wrong! Thank you!

I would have to think the smoke on startup is related, unless it is just a coincidence and out of time like you said. One of my trucks has a real bad case of air intrusion, and is good for smoking out mosquitoes on startup,lol. That truck has 2 cross threaded injector lines that don't seal correctly thanks to the PO. if everything else checks out, look at the hard lines up top, and make sure all the retainer clamps are still on. If they are not on it cause the injector lines to vibrate bad and get rubbed through, so lookout for that.



Rock

 

[ROCK HARVEY]

You could also try running the engine using a hose from a jug full of diesel to your electric pump. If it runs good then you know the problem is somewhere between your tank and your pump. On another truck I had a steel line come out of its holder and vibrate against the frame until it wore a hole through itself.

 

[Farmer Rock]

You could also try running the engine using a hose from a jug full of diesel to your electric pump. If it runs good then you know the problem is somewhere between your tank and your pump. On another truck I had a steel line come out of its holder and vibrate against the frame until it wore a hole through itself.

I had that happen to my 87. I took me quite a while to find it because it rubbed through on top of a bend in the line. No fuel ever leaked out but it would surge something terrible, and drove me crazy so I pulled all the lines and later found it because of that.



Rock

 

[ROCK HARVEY]

After re-reading your first post, I realized that if you bypassed the fuel filter by cutting the steel line from your fuel filter housing to your IP, you still have the olive seal in the fitting where the steel IP intake line attaches to the IP. I bet that olive seal is bad and is the source of your problem. If you run the engine from a jug of diesel and you’re still seeing bubbles on the return line from the IP, there’s no where else they could be coming from.

 

[riphip]

Does your truck still have the water separator hooked up to the feed hose??

 

[The_gestach]

Hey rock! I had took the IP inlet line off yesterday and wouldn’t you know the olive was bad!! I had my daily driver at a tire shop so I wasn’t able to go get a new olive from a dealer so I used some 5/16 hose and made a new olive. No noticeable air in fuel anymore. But I found a way of slowly bring up RPMS and at a point the RPMs will spike and go higher without me moving the pedal. the truck is still doing that now so I’m just going to test the truck doing the bucket of fuel way to be safe and make sure not any of the metal lines are rubbed through without me knowing or seeing! And RIPHIP no I have bypassed the water separator.

 

[OlKoot]

I just did my return line, pulled it, and made sure all thee lines were new, and tightened. sure enough, the rear fitting had to be rubergreased, and tweaked. New clamps,

 

[The_gestach]

You must be registered for see images attach