M923A2 Fuel Issue

[ebs]

Hello, I am new here and still getting familiar with how to use this site. Please be patient. My quick account: I have a1991 BMY HARSCO FLATBED CARGO TRUCK, M923A2, CUMMINS 8.3 with about 12,000 miles on it. A couple of months ago it ran fine. I went to start it about two weeks ago. It would turn over but not fire off. I checked the fuel and found it to smell bad, almost like bad gas, i.e. shellac or turpentine. Fuel if getting up to the brass screw behind the injectors but none to the injectors themselves. I drained over fifty (50) gallons of the fuel and cleaned out the fuel system, then filled the filters with red heating oil fuel and pumped the new fuel through the lines. I am now getting the new clean fuel at the line into the injector pump and the return line. Still no fuel out of the injector line. Can anyone help me, please? Am I doomed to an injection pump re-build? Thank you for any assistance!

 

[simp5782]

Is the fuel shut off solenoid pulling back when the ignition is hit? Or if the solenoid is missing then is the arm on the pump turned as far up towards the motor that it can go?

 

[ebs]

Yes, it does pull back/up.

 

[74M35A2]

Pinch the return line closed with Vice-Grip needle nose pliers, and try again. Report back. Don't run it long if this works. It is just a diagnostic indicator only to check/test/field clean the overflow valve at the return line outlet banjo fitting. Sour fuel could have sludged it in the open position.

Very rare for one of these injection pumps to go bad. I think we've only seen 1-2 max of members here that have said so.

Best to tie back or simply remove the fuel cut solenoid until you have this figured out. It can pull back when first cranked, and then slowly extend during cranking that you will not be able to see from the cab. This is very common with aged batteries, even when they are cranking strong (fast voltage drop).


Next step would be to use a clear piece of hose on the return and look for air in the flow. You could also remove one of the governor caps and verify the injection pump is actually rotating.

 

[ebs]

Thank you very much for the input. I have four (4) new batteries and keep them on trickle charge. I had a friend watch the solenoid for me while I tried but I will wire the valve open. I work another twelve (12) hour shift tomorrow but will try your suggestion later in the week.

 

[TedCat]

Did you get your truck to start?

 

[ebs]

It is definitely getting fuel up to the IP but still no luck.

 

[ebs]

I finally got a day to work on the beast. I pulled the return line off and plugged it temporarily. Still no luck!

 

[TedCat]

Would fuel exit the return regaurdless of IP condition or does the IP have to rotate/function to send return fuel?

 

[74M35A2]

Fuel should likely exit anytime the pressure exceeds the overflow valve spring pressure. This is the squeak you hear when pushing the primer on a non-running engine.

 

[ebs]

Some additional observations: with the plug in the return line, pressure builds and very small amount weeps out of the banjo while turning it over; with the plug out, a little fuel flows out of the return hose when the turning over ceases.

Do you think that heat would help at all?

 

[ebs]

Greetings! STILL working on this problem. I pulled the injection pump off and cleaned it as much as I could without disassembling it. Put it back on but NO luck. Nothing coming out of the top!

Any suggestions on a place to get a new pump OR send mine for a rebuild?

Thank you in advance!

 

[silverstate55]

When have the fuel filters (primary/secondary) been changed? How old are the fuel hoses?

I had this problem with mine; air was getting into the fuel lines due to age & dry-rotting/cracking, enough fuel was struggling up to the IP to make it seems like it should start, but the engine was still too fuel-starved to start. Replaced flexible fuel lines and once primed it fired right up.

It happened again about six months later...this time I had to disassemble the fuel tank selector (I have a 931A2 tractor with dual tanks, I know you have a 923) and replace the O-rings.

6-8 months later it happened again, but only with one tank (down in AZ helping member 98G): the tank was full, but upon further investigation the fuel pickup tube had broken free from its solder joint and fallen into the darkest, deepest depths of the fuel tank...thank God I had dual tanks!

About a year afterwards, same problem with no start from either tank....I traced it to fuel primer pump on the side of the engine, once replaced it fired right up after priming. It’s been a few years now and everything is still running fine, but there were many frustrating days of head-scratching before I figured it all out.

If you’re sucking any air into that fuel system, it won’t fire....it will seem like there’s enough fuel dribbling out when priming or cranking, but there’s not.

Please post results when you get a chance.

 

[ebs]

davidb56

Thank you for your reply! Fuel is flowing heavy into the fuel injection pump. It is also coming out just as strong from the return side. It just isn't coming up through the top.

We have tried several different tests. I pressurized the tank in order to gain fuel flow. I also plugged the return side in an attempt to force some fuel upward. Still no fuel to top injection outlets.

Do you still think that it could be air?

Thank you again for any and all suggestions.

Bud

 

[Elijah95]

Floor the truck during cranking procedure, and make certain the fuel shutoff arm is properly in position. These things are KISS and very black/white


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[ebs]

Floor the truck during cranking procedure, and make certain the fuel shutoff arm is properly in position. These things are KISS and very black/white


Sent from my iPhone using Tapatalk

Thank you. I have tried that but I am willing to put the pump back on and try again.

Bud

 

[Crf450x]

Floor the truck during cranking procedure, and make certain the fuel shutoff arm is properly in position. These things are KISS and very black/white


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Agreed. Even with the pump not spinning, with the injector lines off you should see fuel flowing through the pump and coming out at least one port.

 

[ebs]

Hello, Just wanted to get back to you. I had someone take the IP apart. Internally, there were a few bent rods on the governor system and one of the rods fell off due to being bent. How this happened, I have no idea? Did not get the pump back on yet. Thanks again.