M923A2 Fuel Filter Change Nightmare

[SETOYOTA]

The hoses are my next step. They all look new but I know they could still be cracked. Truck was rebuilt in 2012 I think 700 miles but you never know.

 

[DeeMan6996]

When I bought my truck I had mine shipped to me. I've been working on cleaning the fuel system on my truck as it had been sitting for three+ years. I drained 80 gallons of diesel, replaced the filter, Cleaned the Injectors (Since I did run my truck with the bad diesel) Then Pressure Washed the inside of it. Part washed my tank and put everything back together. Filled the canister with diesel and Primed the pump with the hand pump. Cranked and Cranked and no start. So had a friend put a little of ether in the intake and it tried to fire then just spun and spun. So I knew I was sucking in air someplace. After a couple of short days of trouble shooting I finally figure out that my truck was sucking in air from the petcock right before the fuel filter/canister. I replaced it with a new one and boom it fired right up! Those pesky Petcocks like to suck air after a while of sitting!

 

[doghead]

where is the bleeder screw--

http://www.steelsoldiers.com/showthread.php?124962-m939a2-wont-start-after-fuel-filter-change/page3

Post # 11 has a real picture of the bleeder.

Also, http://www.steelsoldiers.com/showthread.php?130322-M931A2-Fuel-prime

 

[tbar123]

2 ?'s If your pressurizing the tank is it a good Idea to have the bleeder valve open and have someone close it once the air gets out? Would a spritz of oil on the primer pump lubricate it enough to work? I have drained my filter and pumped that primer for 5 minutes straight with the petcock open and nothing!

 

[rosco]

Yes, an the 1st. But theses trucks are too new for me - haven't moved up yet, but in the old days here, the M37's & M211's were fitted with a primer pump on the dash, to assist in cold starts, same as some small aircraft. They had a leather pump washer inside, which would dry out - then it wouldn't pump. If you unscrewed the packing gland, you could take out the pump shaft & massage/oil/even spit on the pump washer, and it would pump again.

 

[doghead]

They have O-rings and check valves.

They do fail from sitting for years or even decades with no use.

Disassemble, clean and repair as needed.

 

[jwesley74]

My truck will lose prime if it sits 2 days without driving. I did the filter change. Bled the system with hand pump. Drove it to the ga rally with no issues. Now if it sits 2 days I have to bleed. The washer is new and properly seated. I'm not sure where air is getting in. Any ideas. I wish mind would fix itself.

Pressurize the tank and see where the fuel leaks from. 20-30 PSI will do the trick.

 

[Tow4]

Pressurize the tank and see where the fuel leaks from. 20-30 PSI will do the trick.

I think about 5 psi will be better unless you are trying to make the tank round. It doesn't take much to show the leaks.

 

[allpredatorcalls]

2 ?'s If your pressurizing the tank is it a good Idea to have the bleeder valve open and have someone close it once the air gets out? Would a spritz of oil on the primer pump lubricate it enough to work? I have drained my filter and pumped that primer for 5 minutes straight with the petcock open and nothing!

??? If you are talking about a M939A2 series truck wouldn't you want the drain closed and then open your bleeder (pictured) while pumping.

 

[70deuce]

Check out this post. The rubber line coming from the hard line on the frame rail to the lift pump/primer pump on the block was shot even though there was only 11,000 miles on it since rebuild.

http://www.steelsoldiers.com/showthread.php?124955-939A2-keeps-losing-prime-no-leaks-evident/page2

 

[chadande]

Here is a pic of a schrader air valve in a fuel cap. Very easy way to pressurize the fuel tank and fill the large canister / bleed the system.

 

[tbar123]

??? If you are talking about a M939A2 series truck wouldn't you want the drain closed and then open your bleeder (pictured) while pumping.
View attachment 524073

My truck is a M923 84' it doesn't have what is in your picture.
Another question If I may, What kind of seals are in the older style hand primer pump? rubber,cork, round flat? My truck is a few miles away so I want to have a good assortment of the correct style seals when I head out there. Thanks for any and all advice.

 

[juanprado]

My truck is a M923 84' it doesn't have what is in your picture.
Another question If I may, What kind of seals are in the older style hand primer pump? rubber,cork, round flat? My truck is a few miles away so I want to have a good assortment of the correct style seals when I head out there. Thanks for any and all advice.

You have a primer pump with a handle and a drain petcock. The primer pump takes 2 standard type orings maybe 1/2 if I remember correctly. Easy to dissasemble and rebuild. The clear fuel line in mine was aged and did not look good. maybe 1/4.

 

[dikwks]

I was using this thread to help find out why my truck quit. It was losing prime sitting still and would cut off idling in the driveway. I got a schrader valve and added it to the fuel cap, put a little pressure on the system and found this hole on the bottom side of the filter that was added into the line supplying the fuel lift pump. Wouldn't show up without the pressure. Just another thing to look out for. Hope the picture loads...

 

[jcollings]

**** all these problems, I got my truck at add fuel conditioner and algicid with about an eighth tank, filled the tank up have had no problems no starting problems never touched anything, it makes me wonder if I should do anything or not. I'd hate to have problems on such a good running truck.

 

[WV New Guy]

My truck is refusing to get going when I'm at the bottom of a hill and start out I'm gonna change both filters and see where that goes . Today I was in back yard which is sloped and had to floor it and after about 1-2 minutes it started climbing out . Truck runs just fine on the road pulled fine with 5 tons of gravel in the back no issues seems like only issue is a hill from a dead stop . Can a fuel issue be the cause?

 

[Suprman]

Does it rev up or bog when trying to go up the hill? How much of a hill are we talking? The truck weighs 21000 lbs. It wont like going up a really steep incline unless you are in low range. If its bogging it could be a fuel starvation, air starvation or sucking air into the fuel system. Does the turbo spool right up?

 

[WV New Guy]

Seems bogged down only does it off road slight incline doesn't seem like air could be turbo but last time I was down the bottom of the property I was in low and the turbo spooled up and up it went but even in low in 1st gear it didn't want to go . Air cleaner was just changed so I know it's not that unless I take it out and see if it's really restricting it that much. Seems like it takes a while for turbo but I could be wrong . I'm off to work tomorrow so I won't get to work on it till Tuesday if I'm lucky maybe I can get the wife to take video and send it to you.

 

[WV New Guy]

So I gave the fuel filter change a try cause I was sick of looking at filters on the work bench. Glad I did as there was black gunk in the big filter . Despite going back and reading this entire tread and trying everything but new fuel lines no go truck will not fire.

 

[doghead]

Did you bleed the injector pump?