M923a2 no start question

[86m1028]

I have an m923a2 that has never not started.
From day 1 this truck has started instantly.
Truck has been parked for awhile, I replaced all fuel hoses from tank to engine primer. It has fuel to the I.P.
I have removed the stop solenoid & use the emergency stop cable.
Enigne is getting fuel
Truck cranks fast enough to build oil pressure
What am I missing ?

Can the pcb go partially bad ?
Main batt switch still functions
Start switch works, it cranks !

What else could it be ?

NOTE:
I have noticed it does not do the self check on the ABS, could that have anything to do with it ?

 

[BenRoberts]

I know you said it's getting fuel but acts like it has a bad prime.

 

[BenRoberts]

My PCB is bad and will sometimes not do the check for the abs. I will also loose power to the cab as well when it does that

 

[86m1028]

Yes, it is getting fuel.
Check valve in return line seems to be working.

I have disabled (unplugged) the ctis, should not matter but thought I would mention it. It is unplugged for other reasons than truck not starting.

I have power to the cab & it cranks when I hit the starter.
It just won't start.

 

[Jbulach]

Did you make sure your getting fuel to the injectors by cracking the injector lines open?


Sent from my iPhone using Tapatalk

 

[Tinstar]

Will a small shot of ether make it fire?

 

[86m1028]

Did you make sure your getting fuel to the injectors by cracking the injector lines open?
Sent from my iPhone using Tapatalk

Not at the injector lines but I do have fuel coming in & going out the I.P.
I did try pinching the return line.

 

[86m1028]

No, I haven't tried either yet.
Ill have to go get some.

 

[snowtrac nome]

crack the fuel lines it will tell you if the rack is moving I'm working on an Isuzu right now with a fuel rack stuck in no fuel.

 

[86m1028]

crack the fuel lines it will tell you if the rack is moving I'm working on an Isuzu right now with a fuel rack stuck in no fuel.

Well snowtrac nome it looks like you are right.

Any way to unstick it, other than rebuild ?
I guess it sat too long without fuel in the IP.

 

[74M35A2]

Zip tie back the stop solenoid. Dollars to donuts, this is the issue (low batt voltage). Cranking speed stays consistent as voltage drops to where solenoid extends to stop position.

 

[86m1028]

Zip tie back the stop solenoid. Dollars to donuts, this is the issue (low batt voltage). Cranking speed stays consistent as voltage drops to where solenoid extends to stop position.

Thanks
But stop solenoid has been removed.
I'm using emergency stop to kill the motor
& yes it is flipped back in the open position.

I wish that was the problem.
Was wondering why there was so much fuel pressure @ the fuel inlet on the IP, when I was priming the fuel lines, now I know why.

 

[Jbulach]

It's likely just air... Crack all the lines at the injectors, then crank for a bit, have soldier B watch for bubbles and fuel, then start tightening the lines as they purge out.

 

[86m1028]

It's likely just air... Crack all the lines at the injectors, then crank for a bit, have soldier B watch for bubbles and fuel, then start tightening the lines as they purge out.

No fuel at the injection lines, lot of pressure at inlet to IP.

 

[WillWagner]

No fuel at the injection lines, lot of pressure at inlet to IP.

Hmm, there shouldn't be that much pressure there. Maybe 25 psi if all it does is crank. Can you take a picture of the side of the pump where the fuel enters the pump? You say it sat with no fuel in it, was the pump off or were lines removed?

 

[snowtrac nome]

either return issue or stuck fuel rack

 

[74M35A2]

Sorry I may have missed. Did you confirm it will fire on ether?

One member had the shaft strip out on the connection to the stop lever. His would not shut off, but yours could be failed opposite? Just another thing to check.

If OK, then it looks like your pump has something funky going on. Is your tach showing cranking RPM (to at least indicate front gear drive in tact)? Will be OK if fires on ether.

Working 8.3L Mil eBay pumps can be had for I think $250 or less. Easy to install and time (push pins on pump and engine).

Pump internals may be messed somehow, not allowing fuel rack to rotate plunger barrels to above stop condition. I have not messed with the injection pump much, but perhaps you could remove the rear cover and see if you can move the rack somewhat easily in and out? Rack travel is a tension fight between pedal request and governor fighting back. But with engine stopped, and move the throttle request shaft, it should be easy to move the fuel rack. May have to assist it by hand? I may not be calling this the right part, but it should have a threaded end with a nut or two on the back side of it.

 

[86m1028]

Hmm, there shouldn't be that much pressure there. Maybe 25 psi if all it does is crank. Can you take a picture of the side of the pump where the fuel enters the pump? You say it sat with no fuel in it, was the pump off or were lines removed?

Not a LOT of pressure but around 25psi. Relief valve in return line opens, returning fuel back to the tank.
I can remove the return fuel line & pump fuel out with primer.

When I say it sat with no fuel in it, I mean supply hose from primer was left off it & I'm GUESSING it dried out.
IP was NOT removed from engine, nor were the lines to the injectors removed.
Note: this truck has ALWAYS started INSTANTLY from day 1.

Please note in pic that throttle linkage is removed.
The ball on the fuel lever broke & im trying to locate a new one.
Also elec fuel shutoff solenoid has been removed & not in pic.

 

[snowtrac nome]

a good point has been made there is a cover on the front acc drive cover screw it off, on your truck you should have a tach drive on it with an inspection mirror check and see if the nut spins with the gear. the gear mounts to the pump with a taper it takes about 130 ft pounds to torque the nut on the end of the pump. The p7100 pump is known for coming loose and loosing timing especially if the pump is pushing a lot of volume. if some one changed the pump and didn't torque it right it may have lost time or come loose, yes I have seen this before.

 

[86m1028]

Sorry I may have missed. Did you confirm it will fire on ether?
One member had the shaft strip out on the connection to the stop lever. His would not shut off, but yours could be failed opposite? Just another thing to check.
If OK, then it looks like your pump has something funky going on. Is your tach showing cranking RPM (to at least indicate front gear drive in tact)? Will be OK if fires on ether.
Working 8.3L Mil eBay pumps can be had for I think $250 or less. Easy to install and time (push pins on pump and engine).
Pump internals may be messed somehow, not allowing fuel rack to rotate plunger barrels to above stop condition. I have not messed with the injection pump much, but perhaps you could remove the rear cover and see if you can move the rack somewhat easily in and out? Rack travel is a tension fight between pedal request and governor fighting back. But with engine stopped, and move the throttle request shaft, it should be easy to move the fuel rack. May have to assist it by hand? I may not be calling this the right part, but it should have a threaded end with a nut or two on the back side of it.

No, I haven't confirmed if it will start on either yet.
Did verify that stop shaft is rotating freely.
I haven't located a good detailed exploded view of this pump.
I ASSUMED the fuel rack is near the plungers ???
Did remove plug on top of IP & internal throttle linkage SEEMS to be moving correctly
(I have never been into an IP before).

Have searched a lot & just can't seem to find any good info on this MW IP.
Pretty much any good info has been on SS.

Are there any good pics of governor & rack ???

Thanks to all that have offered help.