M1123 Low Power

[Hummer Guy]

There are two of them one suction and one return, they are directly in front of the fuel tank in the fuel lines with short pieces of rubber fuel line on each end, you will need some good quality rubber fuel line in 5/16" and 3/8" about a foot or so each.

Ok I see them, I notice there's another hose that makes a loop right under it, what is that hose going too?

 

[Mogman]

Might be the fuel tank vent hose

 

[Hummer Guy]

Might be the fuel tank vent hose

Hmm, mines was bent, I wonder could that be my issue.

 

[Hummer Guy]

There are two of them one suction and one return, they are directly in front of the fuel tank in the fuel lines with short pieces of rubber fuel line on each end, you will need some good quality rubber fuel line in 5/16" and 3/8" about a foot or so each.

Is there a napa number for the check valve?

 

[Mogman]

Is there a napa number for the check valve?

Not that I know of 99% just remove them you don't need them

 

[Hummer Guy]

Not that I know of 99% just remove them you don't need them

Ok, tomorrow that's my next job, I just need a 3/8 or 5/16 barb fitting to bypass it right?

 

[Mogman]

Ok, tomorrow that's my next job, I just need a 3/8 or 5/16 barb fitting to bypass it right?

No just some 5/16 and 3/8 hose, there are steel lines with built in "barbs" on both sides of the valves, just remove the valves and the short pieces of hose on each end and replace with just hose.

 

[Hummer Guy]

No just some 5/16 and 3/8 hose, there are steel lines with built in "barbs" on both sides of the valves, just remove the valves and the short pieces of hose on each end and replace with just hose.

Ok so its safe to bypass both of them? I was worried that the feeding check valve would drain fuel back to the tank and make it harder to start.

 

[Mogman]

Ok so its safe to bypass both of them? I was worried that the feeding check valve would drain fuel back to the tank and make it harder to start.

No the IP has a check valve in the return line to prevent that, the civy vehicles that used this engine did not have them.

 

[Hummer Guy]

So that hose I mention that had the a kink in it that's under the check valves, you can't tell much in this picture, but it was kinked pretty bad, Im going to get that replaced and the check valves bypassed

 

[Coug]

Ok so its safe to bypass both of them? I was worried that the feeding check valve would drain fuel back to the tank and make it harder to start.

Unless you have an air leak somewhere in the system, then there shouldn't be any way for the fuel to drain back into the tank.

 

[TNDRIVER]

Yep, did that, the tank doesn't look bad at all but there is a little dirt sitting at the bottom, I manage to get almost all of it out. I also use the power service clear diesel cleaner in the fuel that I drained out, I had the truck as reliable as a buy and drive vehicle, but now it has return back to its govplanet state, one thing breaks and then the next thing breaks

The "dirt" that you are seeing on the bottom of the tank may very well be a "biological" (I'm not allowed to call it algae on this board). It can get by the pickup sock in the tank and it grows in the fuel filter, hence pulling the filter housing to clean it thoroughly....and I might add the only way to clean the tank is with a pressure washer. It will reacurre if not completely removed and occasional fuel treatment introduced.
If you have a later model truck there is a "looped" line off two pickups that are not used, you can ignore it. Now is a good time to replace ALL the fuel lines. From your description the fuel system and the exhaust cat are about the only two gremlins to chase. My 2 cents.

 

[Hummer Guy]

Ok so Im back at it again, I bypass the check valve, and started the truck but it die in about 30 seconds, after that, I fill the filter up with diesel and then squirted some in the lines and still no start, I usually do this when I bleed the fuel system and it'll start after cranking for a little bit, but this time, nothing

 

[Hummer Guy]

I was able to get it started, I'm going to take it out for a drive tomorrow, I really hope this works. Also, I find this on top of the engine a few days ago, I don't know what it is.

I'm almost certain that my issue was that kinked hose, I decided to just blow through it and was barely able to blow out of it.

 

[Maxjeep1]

I was able to get it started, I'm going to take it out for a drive tomorrow, I really hope this works. Also, I find this on top of the engine a few days ago, I don't know what it is.

I'm almost certain that my issue was that kinked hose, I decided to just blow through it and was barely able to blow out of it.

Looks like part of a Zeus fitting that came from the rear engine cover. You found it on the back of the engine right? Those 2 fasteners turn into those fasteners and that holds it on

 

[Hummer Guy]

Looks like part of a Zeus fitting that came from the rear engine cover. You found it on the back of the engine right? Those 2 fasteners turn into those fasteners and that holds it on

Yep, in the back of the engine

 

[Hummer Guy]

So I drove it for about 4 hours today and made a few stops at some stores. When I left home, I thought for sure it was fixed, the truck had full power for the first hour I drove it, but it started to get weak again, it wasn't as bad as before but it still got weak enough where I was barely able to do 55. I'm starting to lean towards this being a vent issue. Every time I left from the store, the truck had its power back and then started to get weak after about 10-15 minutes.

Do you guys know where the fuel tank is vented at?

 

[Maxjeep1]

So I drove it for about 4 hours today and made a few stops at some stores. When I left home, I thought for sure it was fixed, the truck had full power for the first hour I drove it, but it started to get weak again, it wasn't as bad as before but it still got weak enough where I was barely able to do 55. I'm starting to lean towards this being a vent issue. Every time I left from the store, the truck had its power back and then started to get weak after about 10-15 minutes.

Do you guys know where the fuel tank is vented at?

Take the cap off and drive it.cap off should give plenty of ventilation

 

[TNDRIVER]

So I drove it for about 4 hours today and made a few stops at some stores. When I left home, I thought for sure it was fixed, the truck had full power for the first hour I drove it, but it started to get weak again, it wasn't as bad as before but it still got weak enough where I was barely able to do 55. I'm starting to lean towards this being a vent issue. Every time I left from the store, the truck had its power back and then started to get weak after about 10-15 minutes.

Do you guys know where the fuel tank is vented at?

Little white plastic thingie beside the fuel level sender . I think, but am not sure, it vents to the area behind the air cleaner ( another little silver thingie). I'm not going to suggest that you put a gallon of clean fresh diesel in a jug in the passenger floor and a hose to the mech. pump with a clean fuel filter and try driving it, might be considered by some to be dangerous. Notice how often the idea of a "clean fuel filter" keep popping up. There are a few items on these that have no substitute or NAPA number. I own two trucks and can lay my hands on 7 fuel filters, for a reason. Keep digging.

 

[Hummer Guy]

Take the cap off and drive it.cap off should give plenty of ventilation

I took the fuel cap off and still the same thing, the fuel filters are coming in today so I will change that and see what happens, the only reason I have doubts that its the filter is because the last time I took it out, the filter and the housing was still clean inside