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Badly Needed Fuel Line Schematics

Donbucks

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In the last four weeks, I have experienced fuel leaking on the back side of my motor as it only drips after an hour of idling that it begins to drip. Then it drips onto my exhaust pipe that crosses over to the passenger side. After a few minutes when the truck stops running, maybe thirty minutes, then it stops dripping. I taken off my air cleaner and checked my fuel filter attachment and its bone dry and cannot see where its coming from anywhere. I really need to look up the schematics to see where the line goes from the canister on the left exhaust pipe that runs up between the firewall and the engine since I see fuel runs down on the line as well as fuel coming out of the bell housing drip hole. I hope I can get some help on some drawings from someone to understand what needs to be removed to replace this fuel leak problem. Thanks... Don

PS.... I have a 1993 Chevy Diesel 6.2
 
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Will L.

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His should be the metal rectangle box type that has 4 rubber seals on it for the 4 lines.
But it will also have the electric lift pump on the frame under door by then too.

Sorry Don, I don’t have schematic and been too many years since doing it to tell you order for sure.

All I can say is examine the 1/8” rubber return lines off each of injector, they are common culprit for engine off drips. Examine the seals on the filter also. Those are supposed to be getting harder to find from what I understand.

Two things to strongly consider
Replace the 1/4” injection pump return line with clear tubing. You’ll have to replace it every 5 years or so, but its cheap and easy. Being able to see contamination and bubbles from aeration instantly really helps diagnose problems.

Adding a fuel pressure sensor on a metal “T” where the line goes into the injection pump. Then run the wire from it to the dash somewhere and permanently mount a pressure gauge. Low fuel pressure doesn’t just make it run rough and low power, but wears out the injection pump sooner.
Db2 should be 2-5 psi and ds4 is 8-14psi.

iirc @WarWagon found some mil manuals online. Maybe those have the routing in it for the cucv ?
 

dbrannon79

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Welcome to the forum!

if any of your fuel lines run under the intake to the IP I would recommend pulling the intake and replacing them all with new diesel rated hose. the supply and return lines from the tank transition from steel line to rubber hose just behind the engine over the top of the tranny bell housing. on mine (6.5) I rerouted all the lines over the top of the intake so they wouldn't be down there in all the heat where they couldn't be seen when a leak happens. I also pulled the original fuel filter off and replaced it with an inexpensive remote filter with a clear bowl mounted to the firewall for easy access.

depending on your climate you might not be able to do the remote filter without a fuel heater installed. I live in HOT weather so it wasn't a problem for me. just something to think about.
 

Will L.

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Those square filters are notorious for leaking
That is why GM got rid of it.
I have seen many people put hoses on the lines and use inline filters until they could redo the system for a spin on style.

If you end up doing this, 5 micron is what is required. You can go smaller but if you live in a cold area where diesel fuel gels, the 3 micron and smaller plug up much more frequently from gelling.
 

Donbucks

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Thankyou all for responding. An update on return fuel lines is all injector fuel lines are replaced, and I do suspect the return line that transitions the metal line to rubber between the firewall and engine could be the culprit. This seems only to leak when the engine gets hot. I ran it for 15 minutes and not a drop of fuel leaks from the bell housing, until I shut it off. Maybe five drops was all it was after 5 minutes. But it will do a drop every second after an hour of idling and continue to drop for another 30 minutes after the engine is shut off. Heat expansion is my latest clue which worries me of the unknowns. May have to remove the intake manifold to get a closer look from the top and hopefully get lucky. I also googled on used Chilton/Haynes service manuals of a dozen stores globally, and they are all out of stock including my local city library..,, seems like people are collecting and keeping these manuals. Sheesh. I wish they would do reprints and even did online diagram search of fuel lines which was N/A page came up. Times are changing for these service manuals, hoping someone wouldnt mind selling a 1993 diesel silverado service manual on mechanical. I do have an electrical service manual tho, but it doesnt help me.
 

Donbucks

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It is a C1500 Silverado Truck , two doors with full back seat. I just rechecked the engine running for an hour and its still drips once every 20 seconds from the factory hole of the bell housing on the bottom. Leaks a little faster after its shut off the engine. I guess it runs down to the bottom faster with no parts moving then it stops altogether. All injectors lines are good along the sides, but I cannot see behind the engine, I do wonder if I should look at disconnecting the transmission and lift out the motor to do a complete checkover on all seals, exhaust manifold remove cover valves and to finally get to the root cause of the leak. I never encountered a leak from the bell housing and was hoping to see anyone has pictures, and maybe a video of what this looks like.
 

Will L.

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Ok, there is a drain hole in the valley of the engine. Any liquid that gets in the center top of the engine (valley) will drain out there. So look whatever is directly above the engine leaking.
And in your case- that big cube fuel Filter is there and gm discontinued it because this was a constant customer complaint. So start there.

A good trick if you cant see anything there, and definitely try looking before the next step——which is to begin with using a whole can of engine degreaser and clean the top of the engine really well, rinse off and let dry and cool off.

Then get a bottle of baby powder and apply that all over the engine. Usually removing the air cleaner and tape off the intake is required to get the powder everywhere. Then remove the tape and install the air filter. Start the engine and rev it up a few times. The fan will blow that crap around so the filter is needed at first- dont want the engine eating a bunch of it. Drive the truck to try to make it leak. Usually reapplying (adding a ton) of the powder is needed. You can squeeze the bottle to force it all around. Don’t be afraid to use half a bottle. Then shut it off and carefully remove air filter to not disturb any of the powder left. Look around for a wet area, the powder will make a small mud pile where the leak is.

Just rinsing with a garden hose will get rid of the rest of the powder.


There is another option, but this takes a lot more effort and expense-
Using a 1 gallon fuel can off to the side of the truck (I use a tool cart to hold it) run supply and return fuel lines from inside the bottom of the fuel can to the engine supply and return. Get everything rigged up and running with the fuel can and an external electric lift pump. Then remove the fuel can and add a whole bottle of a/c dye, close lid and shake up. put the hoses back in the fuel can and run the engine. It will take a while for the dyed fuel to get through the system and begin leaking.

Then just use the UV glasses and UV flashlight. If you are doing this outside- DO NOT use those glasses outside in the day!! Remember these are opposite of sunglasses. They amplify the uv light to your eyes. If you have to do this outside, get it going not long before sunset, then use the glasses and light after the sun is down.
Pro mechanics have a huge blanket to block all the light when using them for seeing the dye in a well lit shop.

If you have to drive the truck around to create the leak, rig the tank in the bed of the truck.
 

Donbucks

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Thankyou for the advice you all explained. I will certainly give it some thought on that and discuss this with my local buddies. I was thinking of going on Amazon to order a small camera on a long tube to run off my cell phone app...... watched a few videos to look into the tightest spots to see.
 

MrMarty51

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Thankyou all for responding. An update on return fuel lines is all injector fuel lines are replaced, and I do suspect the return line that transitions the metal line to rubber between the firewall and engine could be the culprit. This seems only to leak when the engine gets hot. I ran it for 15 minutes and not a drop of fuel leaks from the bell housing, until I shut it off. Maybe five drops was all it was after 5 minutes. But it will do a drop every second after an hour of idling and continue to drop for another 30 minutes after the engine is shut off. Heat expansion is my latest clue which worries me of the unknowns. May have to remove the intake manifold to get a closer look from the top and hopefully get lucky. I also googled on used Chilton/Haynes service manuals of a dozen stores globally, and they are all out of stock including my local city library..,, seems like people are collecting and keeping these manuals. Sheesh. I wish they would do reprints and even did online diagram search of fuel lines which was N/A page came up. Times are changing for these service manuals, hoping someone wouldnt mind selling a 1993 diesel silverado service manual on mechanical. I do have an electrical service manual tho, but it doesnt help me.
I had a Haines manual and it did not show much about the 6.5.
I do have a Chiltons book and it goes into great detail about the 6.5 engine and also the wiring diagrams are quite good too.
 

Donbucks

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I have an update on my truck as I have noticed some changes. I changed out the engine oil with 10W 40W synthetic oil and did wipe down and found that the oil leaks stopped. I noticed a much slowing down of leaks since then. I have ordered in my fuel filter and I will be changing this very soon. I do have a confession to make as I accidentally put in gasoline from the pumps and realized my mistake. I managed to drive home with half filled mix of diesel and gas and I siphoned out as much as I could out of it. I went back to the pumps to top it off with diesel once again and I think there is 10 percent gas mixed in with diesel. I presumed to think maybe the gasoline weakened my fuel filter seals since thats the only logical place that is leaking. When I use up the rest of the fuel in the tank, I will refill it once again, then I will change out the filter and I am betting that with the new oil change along with rest of the gasoline is used up. My patience in with cleaning up the truck and reading the posts has helped me understand what the engine was doing. The gasoline thinned out my engine oil and that started the premature leaking. The synthetic oil stopped all the leaks except for the fuel filter, which is`nt very much, like a teaspoon after sitting overnight. Thanks again for your support.
 

Donbucks

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I had a Haines manual and it did not show much about the 6.5.
I do have a Chiltons book and it goes into great detail about the 6.5 engine and also the wiring diagrams are quite good too.
Hello, so would you have a fuel line diagram that run up to the back of the engine and the firewall? I was wanting to see if there were connections that could be a problem. If there was a photo of that, OR, if you are interested in selling the service manual. Let me know what your thoughts on this. Thanks in advance. Don
 

MrMarty51

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Hello, so would you have a fuel line diagram that run up to the back of the engine and the firewall? I was wanting to see if there were connections that could be a problem. If there was a photo of that, OR, if you are interested in selling the service manual. Let me know what your thoughts on this. Thanks in advance. Don
I’m not sure that there will be a fuel delivery schematics in the book.
After I awaken in the morning I’ll take a peek and see if there is. If so I will post a pic in here. If there is not I will reply with a no, nope, aint no pic or schematic.
I will also get the part number for the manual that I have. I do believe that the years it covers on the front of the book is 1988 to 1998. I believe 99 is when GM made a big switchover on a lot of items and so why they cut off on the book at 98.
My truck is a 2000 K3500 crew cab and is still the same old body style so this book still cover The 2000 year model of the heavier trucks. I do believe is the last year for this body style in all the models and also the last civilian use of the 6.5 diesel engine.
 

Will L.

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I can’t remember ever seeing one.

But you could determine which line goes where by removing the filter, hold a cup under the lines & have someone power up lift pump a moment with the key. That will show which is supply to filter.
From there, use a short piece of hose and blow into that port, see which it comes out.
Basically chase the circuit like that.

iirc the two top are connected to each other and the two bottom are connected together- but it has been years since I messed with that old style filter. Most everyone replaces it with a spin on style. More than one time people had to go without a filter and shove rubber hose on the pipe nipples to bypass it a few days so they could use the truck until they could get the new filter assembly in. Often the nipple ends get damaged or the parts houses only have old filters where the rubber seals are hard and leak- and can allow sucking in enough air so the truck doesn’t run right, or not at all.

The video I posted a few years ago is on my nephews truck that filter was 30% of his problem. This was the most amount of air in a fuel system I have ever seen and the engine still run. He had to crank it like a minute and hold foot to the floor once started, and it would barely get to something like 2000 rpm.
There was also cracked rubber lines at the tank.
 
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