first 5 ton m931, will take advice!

[OkieM1008morrison]

so I finally managed to finagle and horse trade to get my first 900 series 5 ton, this is uncharted waters for me, the cummins is also new to me. the truck came from a rural fire department that accessed the truck from the forestry department. long story short I am the new proud owner, it is a low mile truck at 1250 miles and is painted ugly red. formerly desert tan and a quick paint job at that. so last week I went and picked up the truck, had to be slave cable jumped because the 4 hawker battery's were completely dead. the truck was 'idling' when I got there, it would rev up to about 1100 rpms and then go down to 400 rpms and almost die then back to 1100...the cycle went on and on. I get in to drive it the 40 mile trip home and push the pedal..it does nothing and then 4 seconds later it picks up and im driving away. feels as if it has no power on the way homeruns 50-55 the whole way home. but real laggy...and lethargic. on arrival I let the truck sit and idle, I went ahead and filled both tanks to the top with new diesel. its still idling exactly the same as it did before after about 30 minutes of idling like that it died and would not start. I managed to track down a small leak on the tank selector valve and ended up replacing 2 rubber lines because they were stamped 1988. also I replaced the filter and put in new o rings on the filter housing bolt and underneath the rim. filled it with fuel and pumped the primer and it fired up within 2 seconds and ran great for 2 minutes, idled at a smooth 600 rpms and then died, wouldn't start after that. I pulled the filter and it was only 1/8 full. so I took my air chuck and blew backwards through the lines to see if I had a blockage, but everything was free flowing. I filled the filter back up and pumped the primer and it started and ran again for another 2 minutes at the smooth 600 rpms. then idled up to 800 rpms and died...

what could I do to figure out my problem? how do I tell if the IP is going out? it draws the fuel correct?

 

[MtnSnow]

Sounds like it is still sucking air somewhere in the fuel system. They are so air in the fuel sensitive!

 

[dawico]

Not a bad looking truck and it is a m939 series truck BTW.

Good luck with it. I can't help you much with that one.

 

[R Racing]

Could be a bad line or bad O rings in your tank selector valve. I just went through tis on my m816 . replaced all lines. still did the same. ended up finding a broken o ring in the selector valve.

 

[OkieM1008morrison]

theres only 2 lines coming off that tank selector valve that aren't new at this point. so I guess I will replace those as well..better safe than being on the side of the road mad. is there a way to tell if that tank selector valve is leaking? I will take a look at it tomorrow to see if there are any obvious sighns. I just hope my IP pump isn't going out. im a newbie on 5 tons. especially with the cummins, but im a quick learner. thanks for the ideas

 

[Warthog]

The tank selector valve needs a rebuild. Not hard but time consuming.

 

[OkieM1008morrison]

well I guess its not a bad thing I have replaced dang near every single rubber fuel line! im going to pull the tank selector valve tomorrow and see what I can do with it, I mite know where I can get one for cheap that's NOS. thanks for the advice you guys know it all!

 

[Warthog]

All it takes is a couple of o-rings and some steel wool. I'll see if I can find the print numbers. I got mine at Ace hardware.

 

[wheelspinner]

A 939 with the NDT tires would normally not have the ABS MWO applied as radial tires were part of that upgrade. Might want to make sure you have them.

If not there were folks selling the entire upgrade kit for cheap money.

 

[OkieM1008morrison]

The super singles were switched for the NDT's right before I picked up the truck. It has the abs mwo in the cab and clearly marked. I have a brand new set of michelins on super single rims I'm getting ready to throw on it!

 

[Warthog]

All it takes is a couple of o-rings and some steel wool. I'll see if I can find the print numbers. I got mine at Ace hardware.

Here is the Selector Valve Rebuild thread

http://www.steelsoldiers.com/showthread.php?76086-5-ton-fuel-tank-selector-valve-cleaning-rebuild

 

[61sleepercab]

Hope you have fuel problem licked by now. You might try Divide and Conquer ...... part system at fuel filter and run off can to check engine itself, then run fuel from selector from can ......check out fuel lines.... Watch for little stuff, wore spots from line vibration on frame. cut O rings, split in fittings. 5 ton are fun when running well. Have fun Mark

 

[OkieM1008morrison]

so today I went ahead and disconnected the tank selector valve completely from the bottom of the cab, took it apart and found the big o ring was completely smashed, and was still an o-ring but wasn't sealing much. the small one was weathered, to say the least. I also decided to replace the two remaining hoses that I hadn't replaced yet. so now all are new. I found it much easier to pull my snorkel off from the air filter of the truck. made quick work of loosening all the lines going to the tank selector valve. now for the bad, I managed to "over tighten " the brass fitting to one of the 1/2 inch lines....heard a snap and I cracked the hose fitting plum in two. didn't hurt my new hoses. but now I haft to head to the hydraulic and fuel specialty store in Tulsa to get the fitting I need. I plan on doing that after I get off shift from the fire station Thursday...I was so close to getting it all hooked up and running!!!

 

[OkieM1008morrison]

Good news! I rebuilt the fuel selector valve through and through and now all the hoses coming off are brand new. One of the o rings on the selector valve was obviously old and compressed to a thin layer. I'm almost shure it was most of the problem, but I had two hoses that we're starting to dry rot so I killed 2 birds with one stone! Truck has never idled and ran better! Man I love this 5 ton!

 

[Motorcar]

Thanks for the follow up report, so many times threads end when the problem gets fixed but the OP never posts. Makes the "search" a pain when you chase dead ends, congrats on your success.

 

[Warthog]

Glad you got it running. Good job

Like I said rebuilding the selector valve isn't hard just time consuming. Hardest part is getting all the other parts out of the way.

Compressed and dried out orings can sure make a truck run bad. Amazing how a simple item can deadline a truck.

 

[Artisan]

Glad your joined the club....lots O fun ahead!

...but there is no such thing as a "900" series.

M939 Series, I do believe, is more like it...

 

[OkieM1008morrison]

once I removed the snorkel from the air filter canister, it made life so much easier! I was able to access the bottom of the tank selector valve with ease. i'm kicking myself because I wish I would of done that first thing. the O-rings in all cost 55 cents, im amazed how such a little thing can affect the truck so much. I was able to start all of the brass fittings with ease without cross threading them! I managed to find another muffler for the truck since the one on the truck decided to blow out of the bottom when I was messing with the fuel air leak. it blew out due to rusting from the inside out. the straight pipe sounds good, but I prefer to be able to think while im driving down the road. thanks for all the advice on my new truck, you guys are great! I wish I was working on the truck now! but its 28 degrees in Oklahoma, and I was up all night last night due to a storage building fire....it never ceases to amaze me how much CRAP people pay to store in a storage unit!

 

[dmetalmiki]

Well done you accomplished that task well so you deserved the end game. And as mentioned previously thanks for running the thread right through to conclusion, a refreshing change that.