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JLTV 1278 questions

Mekanik

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Ohio
I’m not too sure on where to post this thread because I couldn’t find any sections for a 1278 so if I’m in the wrong spot I apologize.
Anyways I have a 1278 JLTV in my bay that was brought in for a wiring harness due to a couple of codes being thrown on the DSDU. It did not run when it was brought in, we thought it would after replacing the harness. That did not work, there are no longer any codes on the dsdu. I follow the TM for engine crank but no start and it tells me to replace the engine. There are only 176 miles on this vehicle, is it possible the engine is no good? Is there switches on the inside or outside of the cab that I’m not seeing? It is not in tow mode and the manual fuel priming pump is in run mode. When I do turn it over it tries to start but does nothing I get a little smoke out of the exhaust. I’ve cracked the injector lines to make sure I’m getting fuel there which I am. I have drained the fuel tank and put new fuel in it still the same result. Any help will be appreciated.
 

DeMilitarized

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Need to test actual fuel rail/ line pressure to see if it meets the proper pressure spec for the engine that is in the vehicle. If the pressure is too low then a pickup tube could be clogged or a line or the injection pump be bad. Also it could cause the injectors to not fire properly on some cylinders.
 

GeneralDisorder

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Give it a whiff of ether and see if it kicks off for a second - make sure it's a very small amount. If it does then chances are there's some computer lockout or wiring issue that's not enabling the fueling.

I'm no expert on the JLTV.

Also I have to say - having looked over a JLVT - WAY too complex. PVT Snuffy going to hit the wrong button and eject the warp core. o_O
 

Mekanik

New member
7
2
3
Location
Ohio
I’ve checked the fuel pressure at the rail it’s good, I also tried to use ether and it’ll run for about 3 seconds then shut down. I’m assuming it is a wiring issue and as much as I don’t want to I’m ordering a main engine wiring harness for it, once it comes in and I replace it I’ll post an update. Thank you guys for your help
 

Sixgun_Symphony

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Colorado
Any updates?

I try to reach out to guys that might have been working around the new trucks. If I can ask, what are your impressions on the truck? ... I'm ex-Army here (11B, 1-5CAV, and 2-8INF), got out in 2012... Iraq 06 again in 09 and then Afghanistan '11... I got to work with the Oshkosh MATV a lot there, I've been following the development of the JLTV and am mildly obsessed with it now lol... Wish I could have played around with it or still had access to the nerdy technical stuff. I've heard both really good things about it, and some not-so-good things. Still wish we would have had this earlier in the GWOT
 
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Mekanik

New member
7
2
3
Location
Ohio
Any updates?

I try to reach out to guys that might have been working around the new trucks. If I can ask, what are your impressions on the truck? ... I'm ex-Army here (11B, 1-5CAV, and 2-8INF), got out in 2012... Iraq 06 again in 09 and then Afghanistan '11... I got to work with the Oshkosh MATV a lot there, I've been following the development of the JLTV and am mildly obsessed with it now lol... Wish I could have played around with it or still had access to the nerdy technical stuff. I've heard both really good things about it, and some not-so-good things. Still wish we would have had this earlier in the GWOT
Sorry for the late response, but in my opinion the JLTV could be a very useful piece of equipment if there wasn’t so much electrical problems with them. We haven’t received the engine harness for the truck mentioned above so I have no updates with that but so far every jltv my coworkers and I have worked on have had electrical issues that leads to a no start. They are very temperamental for instance I had to pull one into my bay for an annual service, it was covered in snow but it started up no problems at all. No codes being thrown and for the temperature outside it started instantly. It was in my bay for about 4-5 days while I was doing the service. The snow had melted and I was finished with the service, went to start it and now I have a jltv that cranks but no start. There aren’t any active codes and I’ve reset the service life on the computer but still nothing. So like I said, in my opinion, they are garbage lol.
 

Sixgun_Symphony

New member
2
1
3
Location
Colorado
Sorry for the late response, but in my opinion the JLTV could be a very useful piece of equipment if there wasn’t so much electrical problems with them. We haven’t received the engine harness for the truck mentioned above so I have no updates with that but so far every jltv my coworkers and I have worked on have had electrical issues that leads to a no start. They are very temperamental for instance I had to pull one into my bay for an annual service, it was covered in snow but it started up no problems at all. No codes being thrown and for the temperature outside it started instantly. It was in my bay for about 4-5 days while I was doing the service. The snow had melted and I was finished with the service, went to start it and now I have a jltv that cranks but no start. There aren’t any active codes and I’ve reset the service life on the computer but still nothing. So like I said, in my opinion, they are garbage lol.
Oh yeah, of course always some bugs to work out still, but for sure what youre saying seems to be a common thing I've heard. Electrical and the suspension.. I've gotten to briefly speak with a few different ppl about the truck. I'd say the reception has been overall positive however.

Some other complaints are things like the vehicle taking a long time to turn on because you have to turn on the batteries and computer system and stuff before starting the engine and shut them off before turning the truck off. Or the loud whining noise, which just from viewing in video I can hear. To me it sounds like so many different things lol. Like drive belts, straight cut gears in the differentials or something, maybe the hydraulics. Besides the electrical stuff and whatnot how are the Duramaxs holding up??? What about the other hard parts of the powertrain?

This has been online for a bit... I find so much of it interesting https://imlive.s3.amazonaws.com/Federal Government/ID262475967522175197973698392766791648919/03 Appendix 1_ JLTVA1 Maintainer Training POI.pdf
 
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