Air intrusion | Replace the olives or replace steel lines

[John_piv]

Hey y'all, she's sucking' air...
I've got a clear line on my return line coming from the injection pump and I see little bubbles as the trucks running. She idles fine, runs a little rough, but refuses to idle after running; that makes me think it's somewhere in the return lines. I'm steadily replacing the injector O-rings since they're cheap insurance for about $6, so next I want to tackle the olive seals.

From what I can gather, any of the LOW PRESSURE steel lines can be replaced with rubber hoses. It also looks like enough rubber to redo my intake and return lines are cheaper than 2 of these olive seals!

Would I be better off replacing those steel lines with rubber or buying olives and keeping the steel? I've also seen guys use the rubber hose AS and olive seal, but I'm not sure I trust that. I run about 80/20 WMO and would be worried about the pressure. Anybody tried that quick fix on WMO?

Thanks!

 

[Jesus Freak]

You can't suck air on the return side. What do you have for a fuel pump? Electric or the stock mechanical? The common way to start checking for air leaks is to attach a hose to your fuel pump and put the other end of the hose in a bucket of diesel fuel and see is that stops your air intrusion. Between your engine and fuel tank there's a couple places that are common problems like the fuel tank selector valve or the water separator that might still be on your truck.

 

[John_piv]

You can't suck air on the return side. What do you have for a fuel pump? Electric or the stock mechanical? The common way to start checking for air leaks is to attach a hose to your fuel pump and put the other end of the hose in a bucket of diesel fuel and see is that stops your air intrusion. Between your engine and fuel tank there's a couple places that are common problems like the fuel tank selector valve or the water separator that might still be on your truck.

Right now I have the stock mechanical pump. Your saying to test it you just bypass the whole tank system and just throw a hose in a 5 gal diesel can?

 

[chillman88]

Leaking return lines will not cause a drivability issue. They will cause STARTING problems. Once it's running and has refilled the feed side you will be fine.

Yes, just bypass the whole tank and run directly from a bucket of diesel straight to the fuel pump.

 

[John_piv]

Leaking return lines will not cause a drivability issue. They will cause STARTING problems. Once it's running and has refilled the feed side you will be fine.

Yes, just bypass the whole tank and run directly from a bucket of diesel straight to the fuel pump.

What are some of the main problem areas on the feed side? Lot of guys say fuel heater, but my 6.9 doesn't have one. Lines going to the filter/lift pump? Lines to injector pump? Or literally every hose or pipe from the tanks?

 

[Jesus Freak]

Pretty much all the hoses and pipes from the tank. The tank selector is notorious.

 

[franklin2]

What are some of the main problem areas on the feed side? Lot of guys say fuel heater, but my 6.9 doesn't have one. Lines going to the filter/lift pump? Lines to injector pump? Or literally every hose or pipe from the tanks?

It hasn't sunk in yet. You do not have a problem on the pressure side of the pump. Air is not going to be able to get in when it's pumping fuel, even if you did have a leak. It's going to leak fuel, not leak air. The only way you are going to continually get air in the system is on the suction side of the pump. I would not be surprised if you had rust pinhole in your sending unit on top of the tank. I had that problem. I just took the quick connect plastic line off, got some rubber fuel line and slid it up over the pin hole to cover it up with a hose clamp, and then slid the original plastic line up in the rubber hose with another hose clamp.

 

[Jesus Freak]

It hasn't sunk in yet. You do not have a problem on the pressure side of the pump. Air is not going to be able to get in when it's pumping fuel, even if you did have a leak. It's going to leak fuel, not leak air. The only way you are going to continually get air in the system is on the suction side of the pump. I would not be surprised if you had rust pinhole in your sending unit on top of the tank. I had that problem. I just took the quick connect plastic line off, got some rubber fuel line and slid it up over the pin hole to cover it up with a hose clamp, and then slid the original plastic line up in the rubber hose with another hose clamp.

Yeah, that's another common thing.

 

[IDIBRONCO]

Lot of guys say fuel heater, but my 6.9 doesn't have one.

If you still have the factory steel line from the lift pump to the fuel filter it has one. There's a wide spot in that line. That's the fuel heater. The originally had a wire running to that wide part. A lot of those wires have been cut off by now.

 

[chillman88]

What are some of the main problem areas on the feed side? Lot of guys say fuel heater, but my 6.9 doesn't have one. Lines going to the filter/lift pump? Lines to injector pump? Or literally every hose or pipe from the tanks?

Main problem areas would be any joints, all the quick disconnects have o-rings in them. Just because it's not leaking fuel out, doesn't mean it's not sucking air in. The WMO could be making the problem worse, a slightly thicker fluid takes more effort to pull through the lines which will put more stress on any potential leak points.

 

[Old Goat]

Here is what you need to run a rubber Hose from the Filter to Injection Pump.

Filter to IP Hardline Delete Kit

russrepair.com

Goat

 

[John_piv]

Main problem areas would be any joints, all the quick disconnects have o-rings in them. Just because it's not leaking fuel out, doesn't mean it's not sucking air in. The WMO could be making the problem worse, a slightly thicker fluid takes more effort to pull through the lines which will put more stress on any potential leak points.

Just tried the jug of diesel straight to the pump, and lo and behold that fix the bubbling. Problem is that means it's somewhere in between the tanks and the pump...

Went ahead down to the selector valve, but I'm not seeing any rings whatsoever inside of the quick disconnect. Have you got a picture of what they're supposed to look like or where I can find them?

 

[chillman88]

Have you got a picture of what they're supposed to look like or where I can find them?

I didn't, but I was home doing nothing so....

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No idea what size they are, sorry. I've never replaced them myself. If I have to I usually just replace the quick disconnects themselves. I'm sorry that doesn't help a whole lot though. I'm really not sure how to best isolate which one could be the issue when it's pulling air in. Fuel leaks are easy to find....

 

[John_piv]

I didn't, but I was home doing nothing so....

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No idea what size they are, sorry. I've never replaced them myself. If I have to I usually just replace the quick disconnects themselves. I'm sorry that doesn't help a whole lot though. I'm really not sure how to best isolate which one could be the issue when it's pulling air in. Fuel leaks are easy to find....

No, that helps. I was expecting it to be where it seal under the clip, not up inside the clip. Your dead right about finding a fuel leak. When it started surging on both tanks, I was hoping for a visual leak; but no luck.

I'll probably start out by replacing all 6 disconnects just to be safe, I had taken them all off recently to check the switch. Where can you get them from? I see straight ones online, but I'm not seeing the 90° ones this'd need.
(Thanks for the pictures by the way!)

 

[chillman88]

I'm not really sure, last time I needed some I bought them locally. Looks like Napa has them?

https://www.napaonline.com/en/p/NOE7306759

I'm sure you know but just in case, feed is 3/8 return is 5/16 and each tank has a pair of quick disconnects too.

Of course you're going to start somewhere and not just do everything but I wanted to cover all the bases.

Honestly I'd just do the feed ones for now. I don't see why you'd need to mess with the return fittings.

It's always POSSIBLE it's internal to the FSV as well, just food for thought if all else fails.