[KeepItCrunk96ZJ]

Just as it says. I put new connector tube o-rings on friday, a new bluechip injector pump this morning, and there are no leaks on the high pressure side. My tank was full of black diesel, and i'm at a total loss for a reason why. So i took then airdog off, checked filters, checked check-valve, dropped the tank, and blew out all the hoses. Both the airdog check valve and the one on the return line of the pump are functioning.

where in the HELL could i be getting a leak from?

Literally, every single piece or part on this truck, that in any way shape or form carries diesel fuel, was taken off, inspected, and re-installed. I have no puddles or drips ANYWHERE, and theres no fuel in my oil.

This truck is giving me hell lately, and i'm losing my patience. I've been on the phone daily with Chip Fisher of BlueChip Diesel and even he is stumped. Can someone please think of soemthing i may have missed? Something you saw or heard somewhere? Anything?

:S:

 

[Jimbowe]

Have you checked everything on the return line all the way back to the tank?
How about the banjo at the rear of the engine on the return line?
How about the torque on the hp lines to the injector connector tubes, too much will warp and crush the fitting while too little will leak.
Have you had your injectors out and if so are you absolutely sure one or more of them are not slightly out of allignment with the connector tube causing a leak?
At the moment thats about all I can comeup with off the top of my head.

 

[KeepItCrunk96ZJ]

Yes, i had that return line off and blew it out and its not leaking a drop.
Yes, the banjo bolt/check valve is working fine and just as it should.
The truck is not leaking fuel anywhere, nor is it running in a way that would point towards a cyl not getting proper fuel delivery.
And yes, i've done the injectors before and am positive that theres making good connections with the connector tubes. I took out the tubes on friday and re-saeted with new o-rings just to make sure.

I forgot to say, it seems to like to start only if its pointing downhill, the more angle the better. This is showing me the problem is on the low pressure side, as far as i can tell. But everything on the low pressure side is functioning properly...

8 years as a diesel mechanic, and go figure my own truck is the only thing to stump me.

 

[Jimbowe]

Boy that's a tough one for sure.
Since you havn't been able to determine whether the leak is on the feed side or the return side, how about putting in a section of clear fuel line at the high point on the feed side and see if air shows up before the vp44?
Just a thought.

 

[blackcloud98.5]

im stumped lol you can put a 8-10" lift springs or a block in it??

 

[Explosives87]

Did you check the pick up in the tank.

 

[KATOOM]

Since I cant remember what your truck is doing, refresh me. Why do you think its loosing prime?

 

[KeepItCrunk96ZJ]

blackcloud98.5 you made my morning, good one.

 

[nickg]

I've seen the fuel cap (vacuum valve) stick and cause the tank vacuum suck the fuel back to the tank after sitting for a while, actually saw aq GM metal tank collapsed so bad it could only hold 1/2 its fuel capacity.

try leaving the cap loose.
I gutted the vacuum vale on mine, its the black button in the center of the fuel cap

heres an unmolested cap

and a molested cap

 

[patracy]

You've definitely got a low pressure side leak. Visual inspection won't always point you to the leak though. You could have a pinhole leak that seals under pressure (lift pump working) but allows air back in when not under pressure. Do you have 1/2" lines? You'll need to check/re tighten every fitting.

 

[nickg]

with a gutted cap in the event of an roll over it will leak fuel, you can also see if its stuck by depesssing the button with your keys or a screwdriver, it should move easily, I replaced my cap with a new one and it edventually stuck as well , so then I gutted the cap

 

[dozer12216]

O'K, I'm on a brain fail mode.
Find a old fuel cap and gut it. Put a whell valve stem in the cap. (After gutting and drilling hole to accept the metal threaded type valve stem. Take a tire pump with gauge and pump the tank up with """"""" 3 """""""" PSI pressure. Let it set until you find the fuel leak. Theat should be the point that allows the fuel to siphon into the tank.

 

[KATOOM]

Is the vent on your fuel tank capped?

 

[Sandman76]

You could do a pressure leak down test on different section of your fuel system to try and issolate the problem area. Could be as simple as the relief valve on the VP44 sticking open or not seating properly and the fuel system will get the air from the tank on the return line and allow the supply line to leak back to the tank and robbing your VP44 and supply side of fuel?

 

[KeepItCrunk96ZJ]

The tank cap was another thing i thought of, but i switched it and its venting perfectly. Actually, a haze of white steam comes out of it beucase its been really cold but himid here lately, so that alone showed me it was fine.

When i dropped my tank yesterday, i took off every line and every fitting. I reinstalled them all and dont have a single leaky one. Not to say i dont have a pinhole in my lines, but i've installed a complete 1/2 line kit as well and its maybe 18 months old. Id want to say im safe, but then again, my airdog failed in 17 months... so who knows.

And i did switch return line banjo bolts with a friend and there was no change, so thats not it either. Its actually really rare that those fail, from what ive been told by most mechanics i've talked to, its usually further down the line.

Patracy, i think your onto something tho. Thats where i'm currently at with what could be wrong.

And Dozer, im going to make one of those on monday. I've done that on man larger duty diesels, but never had to do it on a 1 ton. I have a few different caps, beucase thats actually how i bled hydraulic pumps at my last job.

ty part is, the black fuel. I dont know how the fuel in my tank is so dirty. I mean, its battleship gray in a 3/8ths fuel line thats clear. In a bucket its black. The connector tube o-rings are like 50 miles old. Only thing i could think of otherwise would be the injector o-rings on the body. But that would mean i'd have diesel in my oil, which i changed last night, and there was certainly no fuel in it. It was thick and still sticky like Rotella T is, 15-40 btw.

This dirty fuel may be causing the check valves to stay open just a slight bit. But, after putting fresh fuel in it and cleaning it out as much as i did last night, i know the system as clean as it could possibly get, and it still didn't start unless i was facing downhill.

Im starting to get bruises from

 

[Jimbowe]

ty part is, the black fuel. I dont know how the fuel in my tank is so dirty. I mean, its battleship gray in a 3/8ths fuel line thats clear. In a bucket its black. The connector tube o-rings are like 50 miles old. Only thing i could think of otherwise would be the injector o-rings on the body. But that would mean i'd have diesel in my oil, which i changed last night, and there was certainly no fuel in it. It was thick and still sticky like Rotella T is, 15-40 btw.

This dirty fuel may be causing the check valves to stay open just a slight bit. But, after putting fresh fuel in it and cleaning it out as much as i did last night, i know the system as clean as it could possibly get, and it still didn't start unless i was facing downhill.
QUOTE]

I think you just identified the source of the leak with the dirty fuel.
If one of the injector O rings is damaged it will allow oil to get passed and drain into the fuel return line.
That don't mean there will be fuel in your oil though unless the connection between the connector tube and the injector is not sealing.
Remember the fuel return line is not under pressure.
When the engine is off the oil around the O ring gets sucked into the drainback in the head and into the fuel return.
When the oil is all passed the O ring then air from inside the valve cover gets passed the O ring and into the fuel return line and you lose prime.
I know it's a pain in the a$$ job but if it was me I would replace the injector O rings and copper washers. I'll bet it solves the problem.

 

[KeepItCrunk96ZJ]

Well im certainly going in there and checking that next. What sucks tho, is that this never happened before. Then my injection pump computer died, right after my airdog failed, and when i replaced those two things is when all this stuff started happening, its like one thing after another, this black fuel is just another finding. I still don't know how im losing prime.

When this is sorted out, this truck will be de-tuned and put up for sale, just putting the word out!

 

[KATOOM]

Well im certainly going in there and checking that next. What sucks tho, is that this never happened before. Then my injection pump computer died, right after my airdog failed, and when i replaced those two things is when all this stuff started happening, its like one thing after another, this black fuel is just another finding. I still don't know how im losing prime.

When this is sorted out, this truck will be de-tuned and put up for sale, just putting the word out!

Have you tried unplugging your Airdog's fuse BEFORE turning the truck on? If you unplug the Airdog before it has a chance to prime the fuel system and the truck starts fine, your new VP has a tight pintle valve. Just make sure to plug it back in right after it starts.
But this is just a shot since you claim it starts only when pointing down hill.

 

[jason]

I have had the exact same problem for 2 years and have not found it yet. Glad my driveway is steep.