923A2 Losing Prime?

[Vette427]

Guys,

Fired my 923a2 up today, cranked perfect, ran fine (I pull the man throttle open to 1000 rpm for warm up), truck started to bog down and then shut off. Could not refire, although the truck did sputter and stumble like it wanted to run.

Finally got it to fire and respond to throttle, but as soon as I put it in gear it died.

Cracked open the line going into the injector pump (3/4 banjo bolt) and manually bled the system (using the manual pump) for a minute or two. There was some air in the line (foaming, spitting).

Closed the line and continued to pump and the pump got firm like it should. Also heard a sound in the injector pump, sounds like a bypass maybe? Truck fired right up and ran at idle for 10-15 min. Shut off and restarted immediately, no problem. Let it sit for about 20 min and won't start.

A couple of things unique to my situation. Truck was parked for some time uphill. Nothing major or extreme, but enough that it could be a factor. Also, I bumped the truck fuel tank bracket today with the tractor. No damage or dents to the fuel tank, no damage to the brackets, but maybe enough to jar something loose in the tank. This is why I cranked the truck initially (when I first had the problem), to move out of the way after I bumped it.

Also, I'm not 100% positive that I bled the system properly or long enough (although the truck did start and run fine for 10-15 minutes at idle and immediately restart).

The good news is that the fuel is fresh and the spin-on fuel filter was replaced last year. Not sure if being parked uphill could cause something to settle in the filter causing a blockage or cause the truck to lose prime or have a check valve or something stick.

Truck has ALWAYS started well (even in freezing weather) and ran perfect about 3 weeks ago.

Any ideas or direction is appreciated.

 

[dawico]

No clue, but I had the same issue and mine (923a2 also) was parked uphill slightly too. It only did that a few days and hasn't since. I did change parking spots but that didn't seem to be the deciding factor on needing a prime or not. Three or four starts in a row regardless of parking and it needed a prime. It hasn't done that since.

There is a bleeding bolt on the backside of the IP that works better for priming it too.

 

[Suprman]

Dry rotted lines cracked sucking air, damage to pickup tube from bumping it, bad lift pump, could be just about anything in the fuel path. You just have to start at the tank and work your way to the pump.

 

[Vette427]

Dry rotted lines cracked sucking air, damage to pickup tube from bumping it, bad lift pump, could be just about anything in the fuel path. You just have to start at the tank and work your way to the pump.

I was concerned that I could have knocked something loose internally in the tank. Which line is the pickup tube (relative to the fuel level sender). Also, im assuming that I'll need to reseal after I've removed this line to check?

 

[Suprman]

You can take off the full screen it will unscrew like the cap. Big channel locks with some duct tape on the teeth works well. Then peek in there one of the flexible cameras works well. I have had numerous fuel feed lines go bad. Something could have gotten a bit stretched and damaged.

 

[Vette427]

You can take off the full screen it will unscrew like the cap. Big channel locks with some duct tape on the teeth works well. Then peek in there one of the flexible cameras works well. I have had numerous fuel feed lines go bad. Something could have gotten a bit stretched and damaged.

I'll give that a go tomorrow along with bleeding through the bleeder on the pump. I have a camera like you're talking about. I usually park the truck downhill, but I needed to unload some landscaping blocks so I parked it uphill. I feel sure that either bumping the tank or parking the truck uphill is causing or related to my problem.

 

[Shotgun]

What Suprman said is good advise, after my 2300 mile trip bringing my truck home, I let her set for a week and could not get her to start with priming and anything else I could think of. After about 2 ½ weeks of screwing around of not getting anywhere useful and killing my batteries. Now I had to buy a jump pack for the truck another $300.00 of learning experience. I started ripping all the fuel lines out and replacing them with new ones. In the process I found one of my problems, the pick up line coming from the tank to the primary fuel filter was finger tight at the 90 degree elbow. Guess the all the vibration bringing her home loosened the nut just enough to let air in. Then the o ring was bad on the hand primer along with some cracking on the plastic primer case after taking it off and giving it a hard look. I got a new metal primer from Cummings in Phoenix and new gaskets with shipping for $80.00. Then new fuel lines with new fittings was also about the same price. Any ways it taught me to slow down and look at each part of the problem.
Hope this helps. Shotgun

 

[silverstate55]

In addition to what Shotgun mentioned above, I also replaced all fuel lines & rebuilt tank selector switch (931A2, dual tanks). And after sitting, it still lost prime.

I had a cracked return line from someone overtightening fitting into 90-degree elbow on top of one tank...I removed the elbow and found that the drop line into the tank from this elbow fitting was rubber hose, and it was disintegrating/swollen shut. I had steel tubes brazed onto brass elbows for both tanks (return lines), and haven't had a single problem since. In fact, even after a month of sitting it hasn't lost its prime.

 

[Vette427]

Guys I think I got this one beat. Found a loose fuel line coming from the big filter inside the driver's side front wheel well. It was the outside fitting (1 1/16" wrench size) and I could turn it easily by hand. It may have loosened on its own or it could have jarred loose when I bumped the fuel tank. Either way, I tightened this line and bled the system using the bleeder on the inside front of the fuel pump and the hand pump. Truck fired immediately and I took a test drive of about 5 miles and the truck ran perfect. Immediately restarted after shut down and immediately restarted after sitting for about an hour and a half. I'll check once more tomorrow afternoon, but I feel confident that I've corrected the problem.

Thanks to everyone who offered advice and suggestions.

I'll post a picture tomorrow of which fitting was loose.

 

[trackhunter]

Is it the same type of 3/8 fuel line that is coming off of the IP return.also wondering does it stop and just short of the bottom of the tank or does it curl in the bottom

 

[Shotgun]

As Silverstate55 stated, the return fuel line going into the tank on mine truck as well was a rubber hose that was falling apart and was half gone. I replace all the of 90-degree fitting’s going into the tank with new ones, as well as the new pick up tube and return tube. The one thing I am still fighting is debris in the fuel tank being sucked up and stalling the engine. I ended up making a new pick up tube with a soldered end cap on it and made it a tad longer. I then drilled a bunch of 1/8-inch holes at the bottom of it and around lower end of the tube to act as a strainer. I then put the truck at angle so the tank drain was at low point and drained it when it was about a ¼ tank low and cleaned out what junk I found. The tank is almost low enough again to drain, to see if there is still more crud in there. So far the strainer fix has been working very well. That’s about all I can for any one else having problems with keeping a prime. Shotgun

 

[Vette427]

Here's a pic of the fitting that was loose. It was loose where the 90 Deg. elbow screws onto the filter housing. This filter housing (and fitting) is located inside the front wheel arch on the driver's side on the RH (cab side) of the wheel arch. You can also see the air tube in this picture that runs from the air filter housing (under the driver's door) to the engine.

 

[Shotgun]

That’s the same connector that was lose on mine when I brought her home. That gave me 2 weeks of headache, until I started ripping out all the fuel lines and then found it was lose. Oh well now I don’t have to worry about rotten fuel lines now. Shotgun