How To: Bleed 6.5L Fuel System - Diesel Bombers



Chevy/GMC 6.2L and 6.5L Discussion of Chevy and GMC Trucks with 6.2L and 6.5L Diesel Engines

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Old 10-16-2012, 02:41 PM
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Default How To: Bleed 6.5L Fuel System

Im just going to do a quick write-up of how to bleed the fuel system on a 1999 6.5L turbo diesel. The process should be similar for most 6.5L, but may vary. This is a pretty simple process, but its always nice to have pictures when you are doing it your first time. (Which is what i would have liked, since i am also new) I would like to thank Mayhem for his advice throughout the past week. Without further ado, onto the topic.

This first picture is just a view of the engine bay from the drivers side fender.


Next up, you want to find your fuse box. For those of you that dont know where thats at, its right next to the brake master cylinder.


Now take the cover off the fuse box. After that, you have to remove the Fuel Pump Relay. On mine, this was the black relay at the bottom left corner.




Now that you have found the relay, and remove it, you need to open the breather on your fuel filter. Just a few quick turns to the left (Lefty Loosey, Righty Tighty) and it will be open.


Now find a peice of wire you have laying around. Doesn't need to be anything special. I used a two inch peice of 18 gauge.


You are now going to jump the fuel pump relay with this piece of wire. I tried to take a picture of the two sections to use your wire on, but it was kind of hard. So, if you look at the fuse like a U, you need to put on end of the wire in the top right, and the other end in the bottom left.


You should be able to hear the lift pump working. If you don't, you either have a wiring problem or your lift pump is shot. If you do hear the pump, within a few seconds (depending on how much air is in there) fuel should start coming out. Stop jumping the fuse, and tighten down the breather on the filter.

Your half way done! *Hopefully*

Now find the T-handle. It is located to the left of the Oil fill/cap.



Now just like the filter, your going to turn this a few turns to the left to open it up, and then go back to the fuse box and jump the relay the exact same way you did the last time. Soon you should hear fuel coming out. If its like my case, you'll hear it dripping on the ground. This is because Chevrolet put a drain hose on it.

The final picture is with me laying on the ground looking up. You can kind of see the drain hose. In the picture, its right above the two little bolt looking things in the middle

You may have to repeat this whole process to get it perfectly bleed. Hopefully this helps at least one person!

Good luck, and Happy trucking
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Old 10-24-2012, 12:33 AM
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A short note to make life easier for you.

On 96+ you should find a red wire with an insulator over it very near the back of the underhood fusebox.
Simply apply 12v to that wire to activate the LP for filter priming-no need to remove the relay.

Your process is exactly right for pre 96 though except the relay is found on the firewall on the passenger side,although that can also be circumvented by applying 12v power to the ALDL pin G under the dash to activate the LP for filter priming.

Another note is that you should be opening the water in fuel drain valve with the engine running- it is also a good test for LP operation then-if the truck stalls LP diagnosis is required.

Last edited by racer55; 10-24-2012 at 12:35 AM.
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Old 10-24-2012, 08:31 PM
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Quote:
Originally Posted by racer55 View Post
A short note to make life easier for you.

On 96+ you should find a red wire with an insulator over it very near the back of the underhood fusebox.
Simply apply 12v to that wire to activate the LP for filter priming-no need to remove the relay.

Your process is exactly right for pre 96 though except the relay is found on the firewall on the passenger side,although that can also be circumvented by applying 12v power to the ALDL pin G under the dash to activate the LP for filter priming.

Another note is that you should be opening the water in fuel drain valve with the engine running- it is also a good test for LP operation then-if the truck stalls LP diagnosis is required.
Thanks for the added tips. The 99 is the only one i have worked on. Im glad someone else had some key points to share!
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Old 10-28-2012, 04:27 PM
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On my '96 all I have to do is leave the bleeder open on top of the filter and then turn key to the on position so the lift pump primes the system. after fuel comes out i close the bleeder and start the truck. Most easy way i can think of doing it.
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Old 10-28-2012, 07:12 PM
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Originally Posted by JorgeNY View Post
On my '96 all I have to do is leave the bleeder open on top of the filter and then turn key to the on position so the lift pump primes the system. after fuel comes out i close the bleeder and start the truck. Most easy way i can think of doing it.
You only get about a 3 second LP run that way and then you tend to make a mess.
If the LP is already running when you open the bleeder you are also in the best position to close the bleeder before fuel goes everywhere.
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Old 10-28-2012, 07:16 PM
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Quote:
Originally Posted by racer55 View Post
You only get about a 3 second LP run that way and then you tend to make a mess.
If the LP is already running when you open the bleeder you are also in the best position to close the bleeder before fuel goes everywhere.
I just lay an old towel in the area to soak up fuel.
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Old 10-28-2012, 08:18 PM
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On OBD I trucks you can run a wire from a positive terminal on either battery the the G terminal on the ALDL port under the dash and that will power up the LP it is a good way to check wether or not the LP is functioning
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