M923A2 Fuel Filter Change Nightmare

[NYC M923A2]

I decided to change the fuel filters on my truck this afternoon. It was the first time I undertook this service, I read the TM and printed out the applicable pages just for reference, read the different threads on the forums, bought new filters, had all the necessary tools, fresh diesel, etc.

I followed the instructions to a T. I cleaned out the filter canister in a parts washer to remove and gunk on the bottom, thoroughly washed and dried, replaced the filter, etc.

I get everything put back together, prime the fuel system with the pump next to the engine filter and try to start it. No good! Try priming it again, tried starting it again. No good! Took the engine filter off, refilled it, pumped the primer to make sure I was greeting fuel up. No good!

I tried something I didn't read in any of the TM's. I took a plastic bag, wrapped it around the fuel tank cap, stuck an air hose off a compressor, pressurized the tank, reprimed the system with the hand pump, tried starting and boom, contact, Houston we have lift off. The truck started right up. I loosened the fittings on the injectors individually to ensure any air is bled out until I got fuel to spray out.

The truck stayed running, let it run for a little while, shut it off and on a few times and then took it for a ride. No problems at all.

I wish I knew what I was doing wrong, I followed the instructions, went back to step 1 and still couldn't get it to start. Good thing I thought about pressurizing the tank.

Has anyone ever experienced this before and tried to pressurize the tank to force fuel into the system? Just curious. But this may help someone someday if they encounter the same problem.

 

[Coffey1]

Yes putting pressure in tank is a good way had to do the same to mine.

 

[73m819]

Did you get the flat washer set in the recessed space on top of the filter housing, if not, the o ring WILL NOT SEAL which means you WILL suck air.

 

[74M35A2]

Not sure if you did it or not, but the hand primer on the mechanical lift pump really doesn't work until you crack the bleed screw open on the injection pump. I did it by cracking the fuel feed line banjo fitting that feed the smaller engine spin on filter.

This was my experience anyway.

 

[allpredatorcalls]

Did you open the vent screw while you were hand pump priming? (TM 9-2320-272-23-2 dated 10 Sept 2012, , WP 0329, step 1, Fig 1, item 6 and 7)
I will be doing mine very soon..

 

[Coffey1]

Yes my o ring was right yes I open bleed valve but I still had to put pressure on tank.

 

[Suprman]

You have to push the primer pump a good 100 times if you changed the big filter. Sometimes you have to prime, start and then it will stall and you have to prime it again to get all the air out from filter changes.

 

[Coffey1]

Lol 100 times have you lost your mind. I want fuel not a heart attack.
Putting pressure is easier.

 

[Suprman]

If you don't have pressure and are relying on the primer pump only that's what it can take. You have to fill the big canister it takes a lot of pushing the primer. I've done it a few times. I do have an extra fuel cap with a wheel valve in it I normally use but it depends where you are doing it.
Will

 

[WillWagner]

You shouldn't fill the engine mounted filter. The pieces parts you can't see will f the pump up, class fit parts do not like unfiltered diesel gas. Easiest way is to put pressure in the tank, but that doesn't need to be done. Just pump the primer bulb 'till it gets firm. You will hear the overflow/check valve in the pump start to hiss. That is a sign the pump galley is full. Now, just crank it with your foot on the floor. lift your foot when it lights. Cracking injector lines is not necessary, the Bosch P, MW and A pumps are self bleeding.

 

[Suprman]

If you don't open the bleeder screw on the back of the pump it will be air bound and you can pump the primer all day long you won't get fuel to the injectors.

 

[NYC M923A2]

Thank you everyone for the replies! I was not aware of the bleeder valve, I will check it out today.

 

[NYC M923A2]

Yes the new washer was set perfectly.

 

[Warthog]

Sometimes the primer pump goes bad.

 

[jwesley74]

I agree with all the posts here. We had fuel issues (algae in the tank) drove truck 1000 miles home and did 3 filter changes along the way. I always aired up the truck before changing filters so I could pressurize the tank. We put schrader valve in our cap just for that reason. Primer pump sucks. And yes, I've hand primed too, probably 500-1000 pumps even opening bleeder screw on the pump. Really sucks. And yes, primer pumps go bad or check valve in them gets jammed open. We had issue of our truck losing prime if it sat for a day or more. Somehow it stopped losing prime on its own. Now starts everytime. Was dealing with losing prime issue for months and few weeks ago it stopped losing prime. Love it when they fix themselves. LOL

 

[DJones]

I agree with all the posts here. We had fuel issues (algae in the tank) drove truck 1000 miles home and did 3 filter changes along the way. I always aired up the truck before changing filters so I could pressurize the tank. We put schrader valve in our cap just for that reason. Primer pump sucks. And yes, I've hand primed too, probably 500-1000 pumps even opening bleeder screw on the pump. Really sucks. And yes, primer pumps go bad or check valve in them gets jammed open. We had issue of our truck losing prime if it sat for a day or more. Somehow it stopped losing prime on its own. Now starts everytime. Was dealing with losing prime issue for months and few weeks ago it stopped losing prime. Love it when they fix themselves. LOL

How much pressure are we talking about in the tank?

 

[gem1410]

If you don't open the bleeder screw on the back of the pump it will be air bound and you can pump the primer all day long you won't get fuel to the injectors.

where is the bleeder screw--

 

[SETOYOTA]

The bleeder screw is on the front of the injection pump on the inside of the pump toward the block. 10mm wrench

 

[SETOYOTA]

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.

 

[Coffey1]

I read on some post some where that the fuel hose could be bad.