5 Ton 923A2 Slowly ran out of Fuel

[parklandtrans]

Recently, as usual...went out and started my 8.3L Cummings to get things charged, primed up, warmed up etc etc..Last 2 years everything has been wonderful until this last time. As I sat in the Truck monitoring all the gauges ...things started to SLOW down in rpm, and slower, slower until she just stopped..!!
Total run time approximately 10-15 minutes.(again as usual every month)
Of course I tried to restart with no luck. Long story short so I don't lose some readers is...no fuel out of the fuel filter still...!! I tried priming with the OEM Block mounted prime pump to no avail. My understanding of this system is it operates on a primed system and when system loses prime...u pump...!!..until plunger gets hard, follow lines up purging air as we go until we're running again..right..?
Wrong...no start, no fuel, no purge...no nothing..??

My thought, is even if I feel a little bit of resistance in plunger I should be getting fuel...and I'm not...so at this point we will condemn the Primer Pump, we will order the correct one.(2 models available, hi and low pressure pump..?) wait for its arrival and try again. In the meantime, anyone got any other thoughts they may want to put in..??
Thanks my Fellow SS' Brothers...Bob ((PARKLANDTRANS)

 

[fuzzytoaster]

Use a 10mm wrench and open the bleeder on the back side of the injection pump and pump that button until a constant stream of fluid comes out. I recommend putting in a schrader valve on the fuel cap and pressurizing the fuel system gently to find leaks (if any) also you can avoid pumping yourself to death. Past that you should check the level of fuel in the tank, any crud in the tank, and possibly any crud clogging the filters. Since it's running for 10-15 mins it's getting fuel to it, anything much shorter would be loss of fuel prime or lack of fuel. Check the copper lines for any kinked/crushed sections as well. Anything past that you may have a bad pump but that's the worst possibility.

 

[74M35A2]

Start by replacing the flexible fuel lines on the fuel tank/pump/filter suction side. They are known leakers and only suck air so it does not show. Most have failed at this point in time. Any hydraulic hose shop can make them up for you and it is easy to change. Once done, make sure there is sufficient fuel in the tank, and then the priming process has an additional step: you need to open a bleed screw after the mechanical pump. There is a banjo fitting on the small engine mounted fuel filter hard line, and also a bleed screw the injection pump, engine side of it, front (10mmm head, best way). I crack it open when I push the plunger, and then close it before I release, then repeat. Just like bleeding brakes. Works very well and does not require 100's of pumps. Once there is air in the line, it can not be compressed enough to overcome the overflow valve pop off pressure in the injection pump, so nothing happens really except sore thumbs. Plunger will not get rock hard, you will instead hear the overflow valve in the injection pump releasing the fuel pressure with each pump. Good luck, this should take care of it. Replace your soft hose(s) or you will just keep revisiting this.

 

[parklandtrans]

Gentlemen,
Outstanding responses from both Generals..!! Last message should have included the piece of information like....all Hyd hoses have been replaced last year when this happened....and you were right on spot with the hoses being the culprit.
All the new information will be taken to the truck and applied as directed...the 10mm bolt info is new to me a will make that now part of and inserted into the procedural diagnostic tree..!!!
Thank you for the information and will pass on to the next Soldier in need...with YOU GUYS' getting the credit..!
Corporal Huke

 

[Scrounger]

You didn’t state whether you had one or the more likely two filter setup. My M923A2 loses prime every so often. It is a gremlin that I just haven’t tracked down.
What I have found that works every time to prime the system is to pump the primer on the block a bunch of time then open the bleeder on the secondary fuel filter. There will be pressurized air. Close the bleeder then repeat. It won’t take long for there to be nothing but fuel coming out. When one reaches that point you won’t need to open the bleeder anymore. Then pump the primer till you hear the fuel flowing thru the injection pump. Then it should start right up. Sometimes I give it a shot of love (ether) in the air intake tube to help out.
This method is what I use when changing filters and doesn’t require any tools.

 

[Csm Davis]

All of above is good information but when checking on a fuel problem always start at the tank. I have seen good mechanics pull their hair out until they started over at the tank. First do you have enough fuel in the tank? Make sure put at least 15 gallons in unless you have a full tank. Pressurize the tank with less than 5 psi and Crack open bleeder on first filter and see if you get fuel also check the lines from tank to filter for leaks if you get fuel at bleeder and have no leaks close it and move to next bleeder on second filter and check for leaks in between them, if you get fuel and no leaks, then move to bleeder on engine side of injection pump when you get good flow out there close it your system is primed. Start your truck. You should have found you problem somewhere along the way.

Sent from my SM-G900V using Tapatalk

 

[Swamp Donkey]

Don't forget to check the pickup tube in the tank.

 

[parklandtrans]

Always a solid piece of advice to start at the source of problem...or at the beginning of the journey..!! For all readers and responders: we have checked the tank and it had approx. 30 gallons of fuel. Also it is the (2) filter design system and we have pressurized fuel at the bottom on this filter ad well.
Update you as info comes in...!!!
bob

 

[74M35A2]

As said, pickup tube and it's connection to elbow are suspect to cracking. Remove and inspect it closely.

 

[parklandtrans]

With that being said I went out and looked at the lines going into the tank and found that the lines threads into a "Bung" and is welded to the tank..?? So short of destroying the line or the tank, how would you go about checking the line...I had one thought and it was to fill tank up as much as possible and try to get above the crack....if one is present..?? Made no difference. There are no access hole/Inspection holes evident that I can see anyway...food for thought..??
FYI .....New Primer Pump be here tommorow I hope...!!

Bob

 

[Scrounger]

A picture of the line on top of the tank would be useful. The ones that are on mine have a threaded fitting that goes into the tank with a brazed copper line going down into the fuel. The outlet is threaded for a compression fitting on a copper line that goes forward. To remove the lines on mine one has to remove the fitting from the outlet line, then using an adjustable wrench carefully unscrew the fitting from the tank. The bed will prevent the pickup line from coming out though. The options are unbolting the tank and sliding it out enough to clear the bed or bending the copper line as it comes out. Just sliding the pickup tube out a little may reveal what is amiss. At a minimum you can pressurize the line that goes forward and see if there any leaks. Also by running a pony tank from the same line you can see if the system will prime.