The hunt for air begins...

[N.E fjord-by-fjord 2fiddy]

So, after installing a new return line kit... Improvising and routing around my turbo (because i was given a non turbo kit and didn't have the time to swap it out...), and then adding an extra o-ring to the top of every cap under the fuel line nuts to ensure they were all seated well...

There still seems to be air getting in. The problem of hard starts is vastly improved since the kit install, but could be better, I had to cycle the GP's about 5 times before the kit, and then drain my batteries half way just to get it to life... Now, 1 glow plug cycle, and two cranks at about 30 degrees, and she wakes up. Still smoky though, and a rough idle for about 5-10 sec. This is after 1-2 days of sitting. I get a solid start if i run it again soon after, but depending on how long, varying degrees of smokiness...

After warm, restarting:
<2 hrs: quick start, no smoke
<5 hrs: quick start, a few intermittent puffs
<8 hrs: lazy start, 5 sec smoke
12-18 hrs: 2 cranks, 5 sec smoke, rough idle for 10 sec
24+ hrs: 2 cranks minimum, 10 sec smoke, rough idle for 20 sec

I don't know if that helped, but I figured I'd write it anyway. Can't hurt, right? Also... all of that is 1 GP cycle, and 30 degrees... Been like that here for days.

All that being said, I guess my question(s) is this...

Where in the fuel system should I start first? I assume that working my way systematically line by line/part by part all the way back to the tank sender would be my logical course,,,

But are there any "typical spots" that I don't know about that I might check first and possibly save myself some time?

In another post recently, I heard someone mention some o-rings on the heater above the fuel filter that can let air in,,, I'll start with that, and wait to hear from you guys about my "procedural method"...

As always, thanks to anyone and everyone in advance,

Cheers!

 

[theguruat12]

Looking at the times you posted (VERY helpful), you have what appears to be a sloooooooooooooooooooooow air intrusion leak. Mine would literally take a full minute to start if it sat for more than 10 minutes. First guess is fuel heater o-ring, as you said. Excellent write up on FTE about replacing it. Orrrrrrr you can just install a Duralift electric pump and not worry too much about hunting down the leak. Great write-up on THAT in our tech articles.

If fuel heater o-rings don't fix it, check the olive seals on both the filter inlet and outlet, and the IP inlet. They look like little sections of hose, and they are known to dry out and leak. I replaced mine and it helped a lot.

 

[79jasper]

Also replace the rubber line at the lift pump.

This could very well just be from your gp issue.

Sent from my USCC-C6721 using Tapatalk

 

[JSVD]

Tygon f-4040-a is a clear yellow tube which is rated for diesel line. Buy some off the internet and use it to test, or put short pieces in after problematic areas.

 

[N.E fjord-by-fjord 2fiddy]

You say the rubber line at the lift pump... That's the one down low, correct? Front passenger side...? Will do O-rings today... Thanks again guys.

 

[79jasper]

Yes.

Sent from my USCC-C6721 using Tapatalk

 

[riotwarrior]

as far as I know...leaks occur @

return lines/caps

return lines from rear brass fitting back to tank...rubber to plastic line

Olives = ONE 3/8" from lift pump to filter head AT the filter head fitting only...TWO 5/16 from filter head to IP

The factory 6.9 early style return system has a dedicated return line from the IP that attaches to a 4way union, for IP return and right/left bank injector return, at the back of the engine. That attachment point is where the mysterious 4th olive is located.

Fuel heater O ring as stated

Lift pump fuel inlet line at frame

fuel filter it self can leak too!

Schrader valve in filter head and the fuel filter warning light sending unit

now this is all off top of my head and about sums it up...there could be more but I don't recall any more...


E D I T
Add correct size and number of olives to post.

Also those whom use worm gear screw type clamps on return lines are asking for trouble...the nice red spring clamps are the best for this IMHO

Oh as well as making sure return line caps are smooth inside, ensure no cast flash on hose nipples that can cut hose as well.

E D I T 2

You must be registered for see images attach

Crude, but works.

Had to add this in!!!!

Hope that helps

 

[ZWilson07]

as far as I know...leaks occur @

return lines/caps

return lines from rear brass fitting back to tank...rubber to plastic line

Olives one pair from lift pump to filter head one pair from filter head to IP NOT SURE if two pair or one and a third olive...

Fuel heater O ring as stated

Lift pump fuel inlet line at frame

If 6.9 water separator on firewall another olive located here too apparently.

fuel filter it self

Schrader valve in filter head and the fuel filter warning light sending unit

now this is all off top of my head and about sums it up...there could be more but I don't recall any more...

Hope that helps

Jeez now I see why it's always being posted about. There are a lot of things that could allow air in especially when dealing with these being older trucks.

 

[icanfixall]

One correct ion about the olives before the filter head. On that 3/8 inch steel line from the lift pump to the filter head we have only one 3/8 inch olive. Its at the top fitting and its the brass fitting. The bottom fitting on that lift pump to filter head has a flaired fitting. Now as for the filter to injection pump. Yes, it has 2 olives and they are 5/16 for that 5/16 inch line.

 

[riotwarrior]

One correct ion about the olives before the filter head. On that 3/8 inch steel line from the lift pump to the filter head we have only one 3/8 inch olive. Its at the top fitting and its the brass fitting. The bottom fitting on that lift pump to filter head has a flaired fitting. Now as for the filter to injection pump. Yes, it has 2 olives and they are 5/16 for that 5/16 inch line.

Edited list to correct the olive parts...Gary do you know the size and location of olive on fuel/water separator for 6.9's on firewall? Maybe we can get a picture from a member and get make a list all nice and clear with photos etc and get it made into a sticky etc.

Would be ideal IMHO to have a simple concise post with all parts portrayed and pictured and where etc...

JM2CW

 

[Agnem]

Extra O-rings under the caps... may not be a good idea. These caps are meant to sit just so. Trying to push them down harder may actually allow air in, instead of doing what your hoping, which is keeping it out. The lower O-ring sits at about .020 thousands larger diameter than the upper one, and the cap is held in place by a detent molded into the cap which captures the upper O-ring. Pushing the cap down further, may cause the cap to bell slightly, reducing the tension on the lower O-ring. Your best bet is to put a piece of clear vinyl tubing on the line from the filter head to the injector returns. This will allow you to determine from what direction your air leak is coming from.

 

[N.E fjord-by-fjord 2fiddy]

I did think about that... will give it a shot. Now she's not starting at all after a fine start last night, and colder weather! In between then and now, I checked the steel line that goes from supply pump to filter, and there was NOTHING in it...... To me that says my leak is @ the supply pump? Now this is becoming an urgent problem, since I have to leave tomorrow @ noon.... Sweatin'...

 

[N.E fjord-by-fjord 2fiddy]

I have a second set of hands coming home soon.... If i hold down the air release valve on the filter head while she cranks the engine, will this aid in getting the fuel up to the filter/rails if the problem is indeed a weak supply pump? I'm beginning to think it is......

 

[riotwarrior]

Just jump the starter solenoid with it in N or P and you are golden to do it on yer own!

Just sayin...

I carry a remote start switch JIC it's ever needed ROFL.

Al

 

[TahoeTom]

There are no olives on the 6.9 water separator on the firewall, just fuel hose and clamps. I just tossed mine or I would post a picture. There are two sets of hose and clamps from hard lines to separator.