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Fuel Leak

R

Rodd

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Location
Antelope, CA
Since this weekend was my time to work on the 98 burb doing the oil cooler and trying to find a fuel leak. It isn't affecting my fuel economy but it will soon. I notice it on the bell housing and drips right in the center of the truck. I checked the FFM and fuel line feeding it and they are dry. The injectors and glows are new and they are dry below where they would leak. The next step I guess is to take of the upper and lower intake to see if it is under there. Any thoughts? Am I missing something?
 
If the line going to the T-valve is leaking then it would drip in the engine valley and run down the bell housing to.

Check and make sure it’s diesel fuel and not antifreeze that’s leaking. I had one of the little freeze plugs in the head start leaking and it was running into the engine valley and down the bell housing.
 
Jaryd said:
If the line going to the T-valve is leaking then it would drip in the engine valley and run down the bell housing to.

Check and make sure it’s diesel fuel and not antifreeze that’s leaking. I had one of the little freeze plugs in the head start leaking and it was running into the engine valley and down the bell housing.
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Thanks Jaryd. It is diesel. I will check there.
 
Rodd said:
Since this weekend was my time to work on the 98 burb doing the oil cooler and trying to find a fuel leak. It isn't affecting my fuel economy but it will soon. I notice it on the bell housing and drips right in the center of the truck. I checked the FFM and fuel line feeding it and they are dry. The injectors and glows are new and they are dry below where they would leak. The next step I guess is to take of the upper and lower intake to see if it is under there. Any thoughts? Am I missing something?
Click to expand...

now is a good time to get extended bolts, and raise up the FFM above the intake runners, and replace all three fuel lines feeding the FFM... kill two birds with one stone. replace the leaking line, and make it MUCH simpler in the future to both find a leak, and fix it.
 
vstech said:
now is a good time to get extended bolts, and raise up the FFM above the intake runners, and replace all three fuel lines feeding the FFM... kill two birds with one stone. replace the leaking line, and make it MUCH simpler in the future to both find a leak, and fix it.
Click to expand...

This is my plan.
 
One other place to look for diesel fuel leaks are the injector fuel return lines, specifically the one that comes off the front of the Passenger Side head and runs across the front of the intake/valley to the "tee" on the Driver's Side where that line meets the DS line and a third line then runs back along the valley and down to return excess fuel to the tank.
 
Husker6.5 said:
One other place to look for diesel fuel leaks are the injector fuel return lines, specifically the one that comes off the front of the Passenger Side head and runs across the front of the intake/valley to the "tee" on the Driver's Side where that line meets the DS line and a third line then runs back along the valley and down to return excess fuel to the tank.
Click to expand...

I was just looking there and couldn't see anything but you can only see so much with a flashlight. I will look there in the morning.
 
I took the intake off and couldn't see anything to cause the leak. The hose to the IP was a little wet toward the top near the IP under the heat sleeve so I replaced it but the leaking continues. The FFM looked slightly wet but with the truck running I put my hand under it and it didn't get wet so It isn't there. I'm going to have to look again where Husker said. Am I missing anything?
 
after doing some more investigation the only hoses running down the center galley under the intake are the hose feeding the IP and the hose to the T valve. Neither leak. What I think is the return line is a 3 inch bent hose that goes from the center of the IP to the metal line on the front of the motor. That goes down to the left and right where the hoses from the front left and right injector hoses connect. I cant see if there are any other hoses connecting to it. All my investigating points to the FFM leaking but I can't see it or feel it. It drips one drop every 3-5 seconds at idle, so there has to be something I am missing. I am not seeing where the return line goes to the tank.
 
You said “The FFM looked slightly wet but with the truck running I put my hand under it and it didn't get wet so It isn't there.”
It could be there. With the engine running it can be sucking in at the leak. Try engine off but power up the lift pump so it pressurizes the line and keep it that way for half hour.
Spray the thing clean with brake cleaner and see if it gets wer again with diesel. If so, that is leaking. Not to say there isn’t more than one spot.

Yes the little bent hose that is 1/4” diameter is the one to swap for clear hose btw to watch for bubbles indicating air intrusion. I say do that while you are digging around. New hose clamps will cost more than the hose.

I remember a car show Camaro one time that leaked really slow but no one could see from where. Triple duece carb set up. I joked about using flour on it and looking for the wet spot. Sure enough the owner did it. He used a siphoning blowgun with air pressure down around 30 psi and turned all the chrome white. Found the leak after a few hours of sitting. Said he spent 4 hours with his compressor at 120 psi blowing the flour off the car. But where it got wet from the gas, he had to dig out “flour goop”. So if you get desperate- there’s an option. Just don’t try washing off the flour with a hose. I don’t really recommend this until you hit the panic button- it would be rough cleaning it from a dd truck.
 
NVW said:
Above the bell housing there is a 3/8" and a 5/16" hose. The small one is the return.
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Shouldn't I have seen it when I had the intake off? I was looking for it but couldn't see any other hose but the one feeding the FFM and the 2 hoses feeding the IP and the T valve. I remember replacing it on my 99 about 10 yrs ago but I'm not finding it. Where is it routed from?
 
Will L. said:
You said “The FFM looked slightly wet but with the truck running I put my hand under it and it didn't get wet so It isn't there.”
It could be there. With the engine running it can be sucking in at the leak. Try engine off but power up the lift pump so it pressurizes the line and keep it that way for half hour.
Spray the thing clean with brake cleaner and see if it gets wer again with diesel. If so, that is leaking. Not to say there isn’t more than one spot.

Yes the little bent hose that is 1/4” diameter is the one to swap for clear hose btw to watch for bubbles indicating air intrusion. I say do that while you are digging around. New hose clamps will cost more than the hose.

I remember a car show Camaro one time that leaked really slow but no one could see from where. Triple duece carb set up. I joked about using flour on it and looking for the wet spot. Sure enough the owner did it. He used a siphoning blowgun with air pressure down around 30 psi and turned all the chrome white. Found the leak after a few hours of sitting. Said he spent 4 hours with his compressor at 120 psi blowing the flour off the car. But where it got wet from the gas, he had to dig out “flour goop”. So if you get desperate- there’s an option. Just don’t try washing off the flour with a hose. I don’t really recommend this until you hit the panic button- it would be rough cleaning it from a dd truck.
Click to expand...

Thanks! I'll give it a try (not the flour) LOL
 
Rodd said:
Shouldn't I have seen it when I had the intake off? I was looking for it but couldn't see any other hose but the one feeding the FFM and the 2 hoses feeding the IP and the T valve. I remember replacing it on my 99 about 10 yrs ago but I'm not finding it. Where is it routed from?
Click to expand...
If it’s close to the factory location still then it would be running towards the bell housing under the intake to the left of the FFM and once it gets passed the FFM it turns to the driver side ( I can see and feel my return hose if I climb on top of the engine and look at the top of the bell housing where it bolts to the engine) and heads towards the tank. It’s been a while since I’ve looked at it but I’m pretty sure it runs right beside the 3/8 supply line at the bell housing and goes to the tank from there.
 
Jaryd said:
If it’s close to the factory location still then it would be running towards the bell housing under the intake to the left of the FFM and once it gets passed the FFM it turns to the driver side ( I can see and feel my return hose if I climb on top of the engine and look at the top of the bell housing where it bolts to the engine) and heads towards the tank. It’s been a while since I’ve looked at it but I’m pretty sure it runs right beside the 3/8 supply line at the bell housing and goes to the tank from there.
Click to expand...

That is what I remember when I did my last Suburban. I looked for it and couldn't see it. I'll give it another shot. I remember when it started leaking I couldn't locate it when I followed the line from the LP to the FFM. It has to be there, Although I am finding ground wires where they aren't supposed to be.
 
Rodd, you said you checked the hoses in the 'galley' (assuming Valley) but, you didn't mention if there was any diesel in the Valley itself...pooling and draining out the back. Just trying to confirm/deny areas to investigate further.
 
The return line runs between the passenger valve cover and intake manifold to the back. It may be a 1/4" line. If I remember I'll take a pic of the complete setup. I have one sitting on a bench.
 
Yeah the hose is 5/16”.

If you are able to find the hard line that all 4 injectors run to on the passenger side then you shouldn’t have a problem finding the 5/16 hose connected to the end of it unless the P.O. did something completely different with the returns from the injectors but I kind of doubt that.
 
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