2003 1078 A1 derated ether start

[MGVFD]

Hello,

Our VFD received this truck just a little bit ago through a DOD grant. Truck ran and drove fine. The kids at the HS painted the truck. They didn't do anything engine wise just the cab and bed.

The truck wouldn't start today without either. Even then it wouldn't stay running. We lifted the cab and primed the fuel system and the truck started. It stayed running, but the check engine light was flashing once every ten seconds. The truck wouldn't go over ten mph. We are looking for someone with a code reader. I think the fuel problem may be the fuel feed line bleeding off. If you let the truck sit for tens or so you'll have to prime it again.
The batteries were low. We had to jump start the truck. The alt had the two green lights and the voltage gauges read good voltages.
Thank you for any input.

 

[fuzzytoaster]

Check the following:

1. All 3 soft fuel lines for cracks
2. Visually check for wetness on fuel filter and fuel/water separator
3. Remove separator bowl and inspect plastic bowl for cracks, fatigue, etc as well as condition of o-ring
4. If able, prime the fuel system with no more than 5 psi of air and inspect fuel system for leaks, hissing, etc (black primer bulb especially)

I'm in DFW and have the ability to read codes. My semi is dropping off a 5 ton in Sulphur Springs, TX on Monday next week. He could bring it back to my shop for inspection and etc. There may be more going on since you said it only does 10 mph which is odd. Typically bad fuel delivery leads to no start situations, not slow driving.

 

[GeneralDisorder]

Just replace the fuel hoses - they are rotten and sucking air. This is real common on surplus FMTV's.

 

[Ronmar]

What fuzzy said, the bleed-down of the primary fuel system indicates a leak somewhere. If it is leaking it IS sucking in air! There is a primary fuel pressure test port between the HEUI pump and the filter on the side of the head. sucking air will show as dips/fluctuations in primary pressure.

you will need a reader to diagnose the Check engine light, but it may be related to a missfire/rough run/hampered ability to maintain commanded RPM with the inputs the ECU is giving to the injectors Ect.

baseline fuel pressure is the foundation of engine performance. Always surprised that most EFI systems don’t even monitor it…:0

here is what an air leak looks like on a primary fuel gauge. Pressure should be steady, 25@ idle ramping up to 60PSI by peak torque RPM. If yours is leaking down in minutes it will look a whole lot less stable than this video I think…

 

[MGVFD]

We replaced the main fuel feed (tank) line and put in new fuel filters tonight. We couldn't get it to start on fuel. We tried the primer pump no luck. We capped the tank with rubber and pressurized it and took the fuel line coming out of the filter with the glass bowl. We were able to get fuel to come through. We haven't changed the fuel line going to lift pump yet. That will be next on the list.

 

[Ronmar]

If the primer is working you should feel it moving fuel on a completely dry line in ~17-18 pumps. Here is how you test the primer and clean the bypass valve…

 

[MGVFD]

Ty you for the video. Cleaned out the primer and replaced the hose to the injector pump.

 

[MGVFD]

Can I get the correct name for the fuel cutoff solenoid? The black and red wire off of the fuel transfer pump. Need a part number and troubleshooting guide. It is intermittent. Since I have the primer button fixed and new filters/fuel lines. I can get the truck to start. I have to wiggle the wires on the solenoid as the start is intermittent.

 

[MGVFD]

I have another question. The air over hydraulic pump wouldn't shut off. I think the switch is broken. Ran out of time before I could trouble shoot it. Is it just the button or is there another controller somewhere?

 

[Ronmar]

I have another question. The air over hydraulic pump wouldn't shut off. I think the switch is broken. Ran out of time before I could trouble shoot it. Is it just the button or is there another controller somewhere?

Just the button air valve for the AOP control… You looking for the start-run solenoid on the back end of the governor? #1 in this pic? Google 1255772…

 

[MGVFD]

I am waiting for a new hydraulic pump so I can lift the cab. I have been looking for a Fuel Shutoff solenoid. I found the part number as being 3116. Since I can't access the solenoid till I can lift the cab. I have found a ton of these solenoids. Is there a correct one? I found the two post but mine had a connector. Is there a difference in design or a recommended Fuel shutoff solenoid that y'all can suggest?

 

[Ronmar]

The one on my LMTV has two terminal posts… on the A0 they chained the ground connection on over to the water separator bowl heater. The other terminal is also tied into the STE wiring, up to that large cannon plug under the drivers dash…

 

[MGVFD]

The fuel shutoff on mine has a two wire connector. It is a 2003 A1 I believe. I was getting voltage to the fuel shutoff solenoid. It is intermittently working though. I believe it is either the connector or the solenoid. If you tap the solenoid it'll start quickly. That you for the diagram.

 

[Ronmar]

OK, I completely lapsed on the fact we are talking about an A1 here... Must be getting old

A1's(3126/C7) are Hydraulic Electric Unit Injectors(HEUI) so are EFI... They do not have or use a governor or a run solenoid. The ECU simply stops firing the injectors to shutdown just like any other EFI... Now you undoubtedly have sensors on the High Pressure Oil Pump(HPOP) located where the governor is located on a 3116 mechanical engine, but what is leading you to the conclusion you have some issue there?

 

[GeneralDisorder]

The fuel shutoff on mine has a two wire connector. It is a 2003 A1 I believe. I was getting voltage to the fuel shutoff solenoid. It is intermittently working though. I believe it is either the connector or the solenoid. If you tap the solenoid it'll start quickly. That you for the diagram.

2003 does NOT have a fuel shutoff solenoid. Please post a picture of the thing you should not be beating on.

 

[MGVFD]

2003 does NOT have a fuel shutoff solenoid. Please post a picture of the thing you should not be beating on.

I am not beating on anything. I was talking with the mechanic from A&M where these trucks come from. He suggested we had a fuel shut off solenoid issue. When I get the cab lifted again I'll take a pic and posted it up. It was over by the injector pump above the compressor. It has a two wire connector. It seemed to start after I disconnected and reconnected this solenoid.

 

[Ronmar]

I am not beating on anything. I was talking with the mechanic from A&M where these trucks come from. He suggested we had a fuel shut off solenoid issue. When I get the cab lifted again I'll take a pic and posted it up. It was over by the injector pump above the compressor. It has a two wire connector. It seemed to start after I disconnected and reconnected this solenoid.

well the only solenoid involved in the HEUI system is a pressure regulator needle valve. The ECU monitors pressure and modulates the needle valve to regulate the HPOP engine oil pressure between ~500 and 3000 PSI. The piston relationship in the HEUI injectors multiplies this HPOP pressure 7X into the fuel they pump, So the ECU can control final fuel injection pressure between ~3500PSI - ~21,000PSI. Or if its on the HPOP pump, it could also be a pressure sensor. There are other pressure and temp sensors spread around the head. you need Cat ET, or someone with it, to talk to the ECU and diagnose what is actually going on… what could be happening is unplugging the sensor is allowing the engine to start in limp mode but once it starts reading a failed sensor it faults again. You might find that it starts with the sensor disconnected… but again, you need to get in on the couch Sigmund…

 

[GeneralDisorder]

I would lay odds that the truck needs a new HEUI pump and possibly injectors. Probably also an engine oil pump. That is the typical symptom of HEUI pump failure. Disconnect the IAP sensor or the IAP solenoid and that seems to put the ECM into some kind of first-time calibration procedure where it probably moves the solenoid through it's entire range or has to relearn the correlation between the solenoid and the sensor and that gets them working again for a while. This was exactly the scenario on the last two 3126 HEUI pump failures I've worked on.

That is THE REASON most of us rank the A1/3126 trucks at the bottom of the desirable list. 75% of the one's I have been involved with needed a new pump sooner or later. They are - surprisingly - not very robust. Lots of soft yellow metals in the tiny pistons and cylinders inside. They seem to be either severely affected by age or they were just problematic and never got changed to newer updated parts due to the military not putting any significant miles on them. The failures I have seen are either age related or crib deaths. Not that it matters much - but the 1999 to 2004 trucks with the 3126 are just crazy prone to this failure mode.

Wait till you see the price of the parts! Let alone the labor if you are paying for it. It's a decent sized job.

And whoever "A&M" is - their mechanic needs some CAT HEUI engine and or FMTV remedial training because he sent you on a goose chase for a device your truck never had. Disregard any future "ideas" this guy has.

 

[MGVFD]

I would lay odds that the truck needs a new HEUI pump and possibly injectors. Probably also an engine oil pump. That is the typical symptom of HEUI pump failure. Disconnect the IAP sensor or the IAP solenoid and that seems to put the ECM into some kind of first-time calibration procedure where it probably moves the solenoid through it's entire range or has to relearn the correlation between the solenoid and the sensor and that gets them working again for a while. This was exactly the scenario on the last two 3126 HEUI pump failures I've worked on.

That is THE REASON most of us rank the A1/3126 trucks at the bottom of the desirable list. 75% of the one's I have been involved with needed a new pump sooner or later. They are - surprisingly - not very robust. Lots of soft yellow metals in the tiny pistons and cylinders inside. They seem to be either severely affected by age or they were just problematic and never got changed to newer updated parts due to the military not putting any significant miles on them. The failures I have seen are either age related or crib deaths. Not that it matters much - but the 1999 to 2004 trucks with the 3126 are just crazy prone to this failure mode.

Wait till you see the price of the parts! Let alone the labor if you are paying for it. It's a decent sized job.

And whoever "A&M" is - their mechanic needs some CAT HEUI engine and or FMTV remedial training because he sent you on a goose chase for a device your truck never had. Disregard any future "ideas" this guy has.

We haven't fully accepted the truck. We can still reject it. I'll have to give a reason. We do not have the funds for a expensive rebuild. If we get stuck with the truck it would sit for 18 months till we receive the title and we would sell it.

 

[GeneralDisorder]

We haven't fully accepted the truck. We can still reject it. I'll have to give a reason. We do not have the funds for a expensive rebuild. If we get stuck with the truck it would sit for 18 months till we receive the title and we would sell it.

If you can do that then DEFINITELY DO IT. Get a C7 truck instead (2004.5+).