M1123 not running smooth starve to fuel.

[rrpakman]

Hello, I am new to Humve, and also new to this forum I have a 2004 M1123, with 6500 miles only which was running normally and perfectly fine for many months, and recently while running engine dropped its RPMs and stopped response to the accelerator, and after about 15-20 seconds it was back to normal, and kept repeating the same behavior, It looks like it had a chooked bad fuel filter I changed the fuel filter which was quite dirty, but problem stays the same. Please suggest me a solution. Thank you

 

[TOBASH]

Welcome to the forum.

You need to give us more information.

How much fuel in fuel cell? Does the problem occur with half empty tank, full tank.

Have you removed the check valves?

Have you replaced the lift pump?

Did this happen after new fuel purchase, implying bad fuel or water in fuel.

Did you purge water from filter?

Have you used the search function? This is a common issue with many posts.

Have you searched the TM’s which are posted for free.

 

[Mogman]

Welcome to the SS forums!!
The most common things that can cause this are:
Stuck check valves, if they have not already been removed then do so.
Bad lift pump.
plugged pickup sock in the fuel tank.
When was the last time you changed the fuel filter?
With the engine running if you crack the fuel filter drain and fuel does not immediately start coming out shut the valve as you likely have one of the issues above.
There are two check valves directly in front of the fuel tank, ether of these can cause issues.
If you decide it is the lift pump there are some specific things you need to know before replacing it.

 

[GuntherRommel]

Check the rubber section of hose right before the lift pump for crimping . It happened to me where it bends over the frame, loss of power going up hills

 

[rrpakman]

Welcome to the forum.

You need to give us more information.

How much fuel in fuel cell? Does the problem occur with half empty tank, full tank.

Have you removed the check valves?

Have you replaced the lift pump?

Did this happen after new fuel purchase, implying bad fuel or water in fuel.

Did you purge water from filter?

Have you used the search function? This is a common issue with many posts.

Have you searched the TM’s which are posted for free.

After the problem started I realized that the fuel filter was choking. I never replaced it before since I got it from the military, I changed the filter and the inner screen they were very bad and clogged, Thinking that now the problem was solved, No it was still the same when I stopped the engine and let it relax for about 5 minutes it starts and run normal. Is there a secondary filter somewhere in this M1123 Humvee?

No, I did not add any new fuel, no I never removed check valves, and I did not fill the tank since the trouble started, it was less than half of the tank with fuel when it started acting like this. I never replaced the fuel pump but it's making a very strong pressure, I checked by opening the water drain valve while the engine running and got a very strong stream of fuel. Yes, I have read almost all of the TM's posted so far. Realized that the fuel filter was a problem,
I have to check by removing the fuel tank cap and driving it may be a breathing issue most likely.

I thank you all for your help and support in solving my issue.

 

[Coug]

No other fuel filter, unless you count the "sock" on the end of the fuel pickup tube in the tank.

I'll agree that the fuel check valves and tank need checked. If the fuel filter had gunk in it, then the gunk had to come from somewhere.

It's unlikely, but also check the air intake system as it could cause engine throttle issues as well, though a lot less likely that they would recover like you say after a short time.

 

[TOBASH]

A lot of reasons here. It is possible your lift pump has failed. It is possible to check valves are giving you trouble. If the problem goes away when you have a full tank of fuel, it is most likely the lift pump.

 

[Mogman]

After the problem started I realized that the fuel filter was choking. I never replaced it before since I got it from the military, I changed the filter and the inner screen they were very bad and clogged, Thinking that now the problem was solved, No it was still the same when I stopped the engine and let it relax for about 5 minutes it starts and run normal. Is there a secondary filter somewhere in this M1123 Humvee?

No, I did not add any new fuel, no I never removed check valves, and I did not fill the tank since the trouble started, it was less than half of the tank with fuel when it started acting like this. I never replaced the fuel pump but it's making a very strong pressure, I checked by opening the water drain valve while the engine running and got a very strong stream of fuel. Yes, I have read almost all of the TM's posted so far. Realized that the fuel filter was a problem,
I have to check by removing the fuel tank cap and driving it may be a breathing issue most likely.

I thank you all for your help and support in solving my issue.

First you should have changed all the filters and fluids, some of those trucks have been sitting for decades, not changing all the filters and fluids can cost you dearly. You should remove the check valves they are a common issue.
You say you have good fuel flow when you open the filter water drain valve, I am assuming you are talking about when it is running good, when it is not I think that will be a different story.
One of those check valves is on the fuel tank vent and it can cause the exact issue you describe.

EDIT, again if you open the water drain valve and fuel does not immediately come out close it again as you will likely be pulling air into the fuel system.

 

[Dave2018]

Hello, I am new to Humve, and also new to this forum I have a 2004 M1123, with 6500 miles only which was running normally and perfectly fine for many months, and recently while running engine dropped its RPMs and stopped response to the accelerator, and after about 15-20 seconds it was back to normal, and kept repeating the same behavior, It looks like it had a chooked bad fuel filter I changed the fuel filter which was quite dirty, but problem stays the same. Please suggest me a solution. Thank you

My fuel supply check valve seemed unclogged when inspected. But apparently not for after removing and running rubber hose it never quits or bogs down again. Dave