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New to me M923A2 - A couple of questions

FFRCobra

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"Long time listener, first time caller..." And first MV to boot.

I've tried to search on this but it seems advance search (where I can narrow down to this sub forum) finds every post with any keyword in the search text as opposed to weighting on the most keywords that match (any ideas on that would be helpful as well).

I've read the -10 and tried to navigate the field maintenance manual but can't find or I flat missed explanations to these couple of items:

- When I first picked up the truck from the PO a few weeks ago, it would start right up easy as can be. Now if it sits for more than a day or two I have to pump the accelerator several times to get it to start. Starts right up if it's been started in the last day or so. Otherwise it's a lot of cranking and pumping of the pedal. I suspect losing prime in some way? No obvious fuel leakage anywhere I can find. Any ideas besides losing prime? The TM says on A2s you should start to crank and then floor it until it fires (if I'm remembering correctly) but the PO said "no way, it's fuel injected" which I would tend to agree with on any other FI vehicle. Regardless, that leaving it on the floor doesn't help, just pumping the pedal does it if it's sitting for a few days.

- Yesterday I had it running for a while with the hood up as I chased some air issues (horn, some CTIS air leakage, etc). It was mid 80's and in the shade but after idling for about an hour the cooling fan still never kicked in. I looked at the temp gauge but it doesn't move a lot anyway. Beginning to suspect the gauge as well. My experience with diesels is they run much cooler than gas anyway but I would think I would get some heat in it after an hour requiring the fan to come on. Any thoughts on what is normal temp and fan activation in a similar situation?

- When I shut it down after the hour or so, I heard something clicking for about 5 minutes intermittently (maybe more). Both switches (battery and start/run) were off and when it clicked, the gauges would bounce with the clicks. Very odd. I don't think I understand what all the battery switch actually kills. Evidently not a lot.

I have to say it's fun tinkering with it and researching the minor issues with the truck. Horn was an easy fix as were some rear light wiring issues. First time with anything with air brakes so I've been reading a ton on that as well as learning to live with the CTIS quirks. Besides the issues previously mentioned my next priority is the lack of any buzzers or lights for low air on start up and parking brake. I'm afraid its the module that controls those items since it's so many related items ($$$) but we shall see.

Thanks in advance for any wisdom guys!
 

MuleMac01

Military vehicle collector
Steel Soldiers Supporter
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The cooling fan comes on about 190- 200... you will hear it when it does :p The radiator is made so big and over designed on these trucks they sometimes never come on when your driving unless your in 100+ temps or climbing a hill or a mountain.
 
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Suprman

Well-known member
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You are loosing prime somewhere there is probably a small air leak. It has an injection pump. The fan comes on around 200 degrees there is a shutterstat control on the upper radiator hose. Get an ir thermometer and measure if you think something is not right. Did you check the coolant level? The clicking and Gage's jumping is indicative of an electrical issue. You can download the p2p guide it will help you. Maybe a defective power switch.
 

FFRCobra

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Location
Raleigh, NC
Thanks for the tips guys. TM says to purge the fuel/water separator each day which I missed previously. (I need a nice easy chair with no interruptions to read that thing cover to cover!) Might be part of one of the issues. Does everyone actually do that every use? I do it on my daily driver diesel about once a month max.

P2P application is awesome by the way. Definitely helped see the gauge components that are affected by a potentially bad switch. That seems even more likely as when I went to fire it up to day both switches on yielded no ABS test. Flipped the ignition switch off and on again and got the ABS self test and CTIS lights. Probably the culprit.
 

FFRCobra

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Location
Raleigh, NC
Tm says to drain air tank petcocks every day, after use, to keep water out of the air system.
Yep, got that one. And it makes sense. What I missed the first time and find a little overkill is this one from the -10, 119-6:

FUEL FILTER/WATER SEPARATOR
1. Service Operation.
a. The fuel filter/water separator (Figure 5, Item 2) is located under left-front fender on M939/A1 series
vehicles, and attached to left side of engine on M939A2 series vehicles, and requires daily maintenance.
 

FFRCobra

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Location
Raleigh, NC
Hey FFRCobra, this is the ORGINAL FFCobra! I'm Bill P, the guy who started FFCobra and I also have an M923A2. So who are you? :)
Hey Bill! You're like a bad penny! :razz:
I just went by name in FFCobra, Sean Teague. Built a MkII but did some heavy mods to get a 4.6 DOHC shoehorned into it. She's still running strong! Haven't been on that site in a while. How long have you had your [insert cool name for the 5 ton here].

"Deuce" has a cool name to it, wish we had one for the 5 ton. "Double Deuce" sounds cool but is only 80% accurate :)
 

bricksrkids

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Acworth, ga
Hey Bill! You're like a bad penny! :razz:
I just went by name in FFCobra, Sean Teague. Built a MkII but did some heavy mods to get a 4.6 DOHC shoehorned into it. She's still running strong! Haven't been on that site in a while. How long have you had your [insert cool name for the 5 ton here].

"Deuce" has a cool name to it, wish we had one for the 5 ton. "Double Deuce" sounds cool but is only 80% accurate :)
Hey Sean... great to see you here. These things are a blast!
 

FFRCobra

Member
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Location
Raleigh, NC
Just kidding. But, your skin does need a minimum thickness to live here.....
No worries, as long as everyone can take it as well as they can dish it out here we will all be just fine.

Now back to the original station programming... How often are you guys draining the water separator? Certainly not on every use like the TM said.
 

FFRCobra

Member
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6
Location
Raleigh, NC
I think I found the losing prime issue. A few pumps of the primer button and fuel was pouring down from the seal of the fuel filter. Started to tighten it and it sounded gritty so I'm off to find an FF834 fuel filter.
 
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