M1123 Power Loss

SamB

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Help! I'm 11 months into trying to get my M1123 to run properly. To start off, it's a 2004 M1123 with the NA 6.5 and 4L80E.

When I got it, I couldn't get it to start. Took it to a mechanic and the mechanic said the fuel inside of it was likely bad and allegedly drained the tank, replaced the fuel filter, and got it started up.

It had a hard time starting especially when cold, but I was able to get it started and drove it about 250 miles in a day with no issues. Then all the sudden I had loss of power. I was driving 55-60mph and the truck slowed down to about 30mph with the gas peddle to the ground. I pulled off to the side of the road and when I got to about 5-10mph with the foot off the accelerator it stalled and the "TRANS" light came on. I let it sit for a minute and started back up. Had no problem getting back up to about 25mph and couldn't go any faster with the engine roaring. I pulled over again, once I took my foot completely off the accelerator it died again and the transmission light came on again. I was frustrated but relieved it happened in a highly populated area with mechanics near by. I live 120 miles away in a town with a year round population of 77 and the next town is 52 miles away. Anyway... I figured it must be a transmission problem. Maybe the transmission isn't shifting and that'd explain the transmission light.

It went to a transmission shop and they told me the transmission looked like it matched the odometer (5k miles) and was pretty much a brand new transmission (no issues).

So I had it towed to a diesel mechanic who was open to working on military vehicles. The mechanic ended up deciding the problem was the Fuel Injection Pump. He replaced it with a new FIP bought off of eBay. He also had to make an adjustment to the Throttle Position Sensor. This took 10 months for him to find parts and time to work on my HMMWV.

Last week I went and picked it up, it had a hard time starting, but once I got it started it made the 120 mile drive home just fine.

Yesterday I replaced both my batteries, installed the supplemental grounding harness, and replaced my glow plugs. Started it up and it didn't even hesitate! Started up right away like a brand new truck. I then drive it to a friend's how's to pick up a BBQ Grill. Drove 17 miles, picked up the grill, and went to head home. I made it 1 mile from his house and pulled over to check a suspicious bungee cord holding the grill down. Hoped back in and went to drive off. Got up to 40mph and couldn't go any faster. Slowly lost speed (going down hill) until I got to 30mph. With the accelerator to the ground I could only go 23-30mph depending on the grade (all of which were downhill grades the whole way home). If I pulled over then it was the same problem. I get down to about 5ish mph and I loose power steering and the truck stalls. From looking in my sideview mirror while driving I could also intermittently see smoke and smell unburnt fuel. I think the smoke was white but I was driving into the sun and having a hard time telling with lighting at the time.

I'm no mechanic. I spent a lot of time in Humvees in Iraq but I was a dumb grunt. Not a mechanic. Please give me some advice! Curious if anyone has had any similar issues. Thank you.
 

Mogman

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Well the first thing I would do is make sure you are getting fuel to the IP, with it running open the water drain valve connected to the fuel filter and see if you have fuel pressure there.
You also seem to be having TCM issues
 

diesel_dave

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Utah
Help! I'm 11 months into trying to get my M1123 to run properly. To start off, it's a 2004 M1123 with the NA 6.5 and 4L80E.

When I got it, I couldn't get it to start. Took it to a mechanic and the mechanic said the fuel inside of it was likely bad and allegedly drained the tank, replaced the fuel filter, and got it started up.

It had a hard time starting especially when cold, but I was able to get it started and drove it about 250 miles in a day with no issues. Then all the sudden I had loss of power. I was driving 55-60mph and the truck slowed down to about 30mph with the gas peddle to the ground. I pulled off to the side of the road and when I got to about 5-10mph with the foot off the accelerator it stalled and the "TRANS" light came on. I let it sit for a minute and started back up. Had no problem getting back up to about 25mph and couldn't go any faster with the engine roaring. I pulled over again, once I took my foot completely off the accelerator it died again and the transmission light came on again. I was frustrated but relieved it happened in a highly populated area with mechanics near by. I live 120 miles away in a town with a year round population of 77 and the next town is 52 miles away. Anyway... I figured it must be a transmission problem. Maybe the transmission isn't shifting and that'd explain the transmission light.

It went to a transmission shop and they told me the transmission looked like it matched the odometer (5k miles) and was pretty much a brand new transmission (no issues).

So I had it towed to a diesel mechanic who was open to working on military vehicles. The mechanic ended up deciding the problem was the Fuel Injection Pump. He replaced it with a new FIP bought off of eBay. He also had to make an adjustment to the Throttle Position Sensor. This took 10 months for him to find parts and time to work on my HMMWV.

Last week I went and picked it up, it had a hard time starting, but once I got it started it made the 120 mile drive home just fine.

Yesterday I replaced both my batteries, installed the supplemental grounding harness, and replaced my glow plugs. Started it up and it didn't even hesitate! Started up right away like a brand new truck. I then drive it to a friend's how's to pick up a BBQ Grill. Drove 17 miles, picked up the grill, and went to head home. I made it 1 mile from his house and pulled over to check a suspicious bungee cord holding the grill down. Hoped back in and went to drive off. Got up to 40mph and couldn't go any faster. Slowly lost speed (going down hill) until I got to 30mph. With the accelerator to the ground I could only go 23-30mph depending on the grade (all of which were downhill grades the whole way home). If I pulled over then it was the same problem. I get down to about 5ish mph and I loose power steering and the truck stalls. From looking in my sideview mirror while driving I could also intermittently see smoke and smell unburnt fuel. I think the smoke was white but I was driving into the sun and having a hard time telling with lighting at the time.

I'm no mechanic. I spent a lot of time in Humvees in Iraq but I was a dumb grunt. Not a mechanic. Please give me some advice! Curious if anyone has had any similar issues. Thank you.
When it slowed down to 5 mph at the end, was the engine still "roaring" rpm-wise or was it sputtering? A video of this behavior might be helpful.
 

TNDRIVER

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Cleveland,TN
Help! I'm 11 months into trying to get my M1123 to run properly. To start off, it's a 2004 M1123 with the NA 6.5 and 4L80E.

When I got it, I couldn't get it to start. Took it to a mechanic and the mechanic said the fuel inside of it was likely bad and allegedly drained the tank, replaced the fuel filter, and got it started up.

It had a hard time starting especially when cold, but I was able to get it started and drove it about 250 miles in a day with no issues. Then all the sudden I had loss of power. I was driving 55-60mph and the truck slowed down to about 30mph with the gas peddle to the ground. I pulled off to the side of the road and when I got to about 5-10mph with the foot off the accelerator it stalled and the "TRANS" light came on. I let it sit for a minute and started back up. Had no problem getting back up to about 25mph and couldn't go any faster with the engine roaring. I pulled over again, once I took my foot completely off the accelerator it died again and the transmission light came on again. I was frustrated but relieved it happened in a highly populated area with mechanics near by. I live 120 miles away in a town with a year round population of 77 and the next town is 52 miles away. Anyway... I figured it must be a transmission problem. Maybe the transmission isn't shifting and that'd explain the transmission light.

It went to a transmission shop and they told me the transmission looked like it matched the odometer (5k miles) and was pretty much a brand new transmission (no issues).

So I had it towed to a diesel mechanic who was open to working on military vehicles. The mechanic ended up deciding the problem was the Fuel Injection Pump. He replaced it with a new FIP bought off of eBay. He also had to make an adjustment to the Throttle Position Sensor. This took 10 months for him to find parts and time to work on my HMMWV.

Last week I went and picked it up, it had a hard time starting, but once I got it started it made the 120 mile drive home just fine.

Yesterday I replaced both my batteries, installed the supplemental grounding harness, and replaced my glow plugs. Started it up and it didn't even hesitate! Started up right away like a brand new truck. I then drive it to a friend's how's to pick up a BBQ Grill. Drove 17 miles, picked up the grill, and went to head home. I made it 1 mile from his house and pulled over to check a suspicious bungee cord holding the grill down. Hoped back in and went to drive off. Got up to 40mph and couldn't go any faster. Slowly lost speed (going down hill) until I got to 30mph. With the accelerator to the ground I could only go 23-30mph depending on the grade (all of which were downhill grades the whole way home). If I pulled over then it was the same problem. I get down to about 5ish mph and I loose power steering and the truck stalls. From looking in my sideview mirror while driving I could also intermittently see smoke and smell unburnt fuel. I think the smoke was white but I was driving into the sun and having a hard time telling with lighting at the time.

I'm no mechanic. I spent a lot of time in Humvees in Iraq but I was a dumb grunt. Not a mechanic. Please give me some advice! Curious if anyone has had any similar issues. Thank you.
I would be surprised if it was not a fuel issue. REMOVE the fuel filter from the truck and post pictures, bet it's ugly. The trans light is probably from low pressure from the engine not turning fast enough to keep up the trans pump pressure as it stalls. Algae grows in diesel fuel and if the tank and fuel system is not CLEANED thoroughly it will grow back quickly. I've had the tank OFF of one truck twice and the other one once. Add POWER SERVICE BIO KLEEN with each fueling.
 

Mogman

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There are two check valves in the fuel lines directly in front of the fuel tank, they are problematic and should be removed and bypassed.
 

SamB

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Well, I paid a mechanic to flush the fuel system and he allegedly replaced the fuel filter. However, that clearly didn't happen! Look at what I found! Thank you TNDRIVER! I didn't bother to check because I trusted that it had been replaced...

Is this inner fine filter supposed to be green? Or is this what allege growth looks like?

Also, my mind is blown that the second mechanic who had it for a long time and replaced the fuel pump never checked the fuel filter...

I just ordered a replacement filter. When I get it replaced I'll let you guys know how it runs. If I still have the same problem I'll record a video as diesel_dave requested.

Thank you again everyone. First posting on SteelSoldiers. You guys were very quick to give advice to a stranger. Much appreciated!

IiIMG_1255.jpgIMG_1254.jpg
 

TNDRIVER

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Well, I paid a mechanic to flush the fuel system and he allegedly replaced the fuel filter. However, that clearly didn't happen! Look at what I found! Thank you TNDRIVER! I didn't bother to check because I trusted that it had been replaced...

Is this inner fine filter supposed to be green? Or is this what allege growth looks like?

Also, my mind is blown that the second mechanic who had it for a long time and replaced the fuel pump never checked the fuel filter...

I just ordered a replacement filter. When I get it replaced I'll let you guys know how it runs. If I still have the same problem I'll record a video as diesel_dave requested.

Thank you again everyone. First posting on SteelSoldiers. You guys were very quick to give advice to a stranger. Much appreciated!

IiView attachment 868250View attachment 868251
BAD NEWS........... you are not through...... if you have the square panel with 4 screws in the bed of the truck you need to remove the panel then the fuel sender (round thing with 5 or 6 screws 2 wires) and have a look inside the tank. If the bottom looks anything like your filter removal and cleaning is in order. If not your second filter will look like this one in short order.The green tube is a water seperator , fuel passes water does not. It can be rinsed and reused(someone will have something to say about that). The anti siphon valves that Mogman speaks can become clogged also. Pick up sock in the bottom of the tank can become clogged. Good time to replace all the fuel hose while its apart. Congratulations you are about to become a mechanic, the joys of owning a HMMMWV . Don't forget the POWER SERVICE. Keep the pictures coming.
 

SamB

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BAD NEWS........... you are not through...... if you have the square panel with 4 screws in the bed of the truck you need to remove the panel then the fuel sender (round thing with 5 or 6 screws 2 wires) and have a look inside the tank. If the bottom looks anything like your filter removal and cleaning is in order. If not your second filter will look like this one in short order.The green tube is a water seperator , fuel passes water does not. It can be rinsed and reused(someone will have something to say about that). The anti siphon valves that Mogman speaks can become clogged also. Pick up sock in the bottom of the tank can become clogged. Good time to replace all the fuel hose while its apart. Congratulations you are about to become a mechanic, the joys of owning a HMMMWV . Don't forget the POWER SERVICE. Keep the pictures coming.
Oh man... Well, thank you. I've got some work ahead of me for sure. I'll take pictures and keep you guys posted. Going to go take a look in the tank today and start figuring out what all parts/supplies I need to order to get this taken care of. I won't forget the power service.

Thanks much.
 

Mogman

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I would also look closely at the IP to see if that was actually replaced, if not time for small claims court at least.
EDIT, I understand it was the first mechanic that supposedly replaced the fuel filter, but no REAL mechanic would replace the IP without replacing the fuel filter no matter what the customer said, it would be a requirement and is the required by every diesel injection service that has ever rebuilt a pump for me even though I do not need to be told.
 
Last edited:

Mogman

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Unfortunately you cannot trust anyone unless you KNOW they are trustworthy, but there are precious few out there, not sure where your truck came from but there are folks out there that you can trust, one right there in CA where many trucks come from.
Unless you are willing to become a mechanic I would solicit comments on folks you can count on from the other board members here that may be closer to you than CA.
 

TNDRIVER

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Oh man... Well, thank you. I've got some work ahead of me for sure. I'll take pictures and keep you guys posted. Going to go take a look in the tank today and start figuring out what all parts/supplies I need to order to get this taken care of. I won't forget the power service.

Thanks much.
Let me add a PS. If you did not remove the fuel filter canister from the fire wall you should pay special attention to the cavity in the bottom of the filter housing where it accumulates water. This needs to be cleaned thoroughly. This housing can be a real PITA to replace, comes off pretty easy, not so easy to replace, especially for a non mechanic type.Please post us some tank pics when you get that far . Depending on what is there I'm sure there will be some ideas here.
 

Action

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If you think a part will get replaced, put a scratch or similar on the item before service. If scratch is still there, the old part is still there.

The fuel tank access panel is in the bed between the rear seats. Maybe 8” x 5”. Remove that and the round level sender under it. You should be able to clearly see the bottom of the tank. The “sock” at bottom of puckup tube is white when new.
 

Retiredwarhorses

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Well, I paid a mechanic to flush the fuel system and he allegedly replaced the fuel filter. However, that clearly didn't happen! Look at what I found! Thank you TNDRIVER! I didn't bother to check because I trusted that it had been replaced...

Is this inner fine filter supposed to be green? Or is this what allege growth looks like?

Also, my mind is blown that the second mechanic who had it for a long time and replaced the fuel pump never checked the fuel filter...

I just ordered a replacement filter. When I get it replaced I'll let you guys know how it runs. If I still have the same problem I'll record a video as diesel_dave requested.

Thank you again everyone. First posting on SteelSoldiers. You guys were very quick to give advice to a stranger. Much appreciated!

IiView attachment 868250View attachment 868251
Filter probably did get replaced, but unfortunately the mechanic did not address the algae issue.
AFAIC, this can only fully addressed with the full R&R of the fuel system. Replace the fuel tank, filter, fuel lines, at times, even the lift pump becomes contaminate. You have to continually treat the fuel with Biocide.
This algae will, not if, but will kill your new injection pump in short order….
while treating your fuel with Biocide, you will need to replace your filter often….
 
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