M923a2 no start question

[86m1028]

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.

Again, thank you for mentioning this as a possibility.

EDIT: I did just confirm tach does register about 200rpms when cranking,
have not checked with either yet (need to go get some).

 

[snowtrac nome]

the injection pump is a bosch p7100, used in lots of equipment 4 b cummins to big john deere sixes. they are a good bullet proof pump with some high delivery rates, that's why the pullers love them so much. The only weakness is the gear to pump connection that can slip. I had a 4b 2 summers ago a mechanic had pulled the pump to change the shut off solenoid, and didn't torque it right. The same symptom you have now they had, I had to retime it and torque it properly.

 

[86m1028]

the injection pump is a bosch p7100, used in lots of equipment 4 b cummins to big john deere sixes. they are a good bullet proof pump with some high delivery rates, that's why the pullers love them so much. The only weakness is the gear to pump connection that can slip. I had a 4b 2 summers ago a mechanic had pulled the pump to change the shut off solenoid, and didn't torque it right. The same symptom you have now they had, I had to retime it and torque it properly.

I was told by a Bosch dealer that it's an "MW sieres" pump.
Is he incorrect ? This is on an A2 with the 8.3 cummins.

 

[Tornadogt]

Keep It SIMPLE. Open the Bleeder valve on the front inside of the pump (between the injection pump and the engine, it takes a 10mm wrench. Open it 1-1 1/2 turns. Separate the air intake at the rubber 90deg turn on the driveside (close to the PCM box) you can roll the window down and spin the engine over with the switches and spray either into the intake at the same time, when it starts keeping it running at a low-idle RPM with small squirts of the either until it bleeds the air out of the injection pump/lines/injectors and runs on its own. It may take up to 45sec-1min to bleed. Close the bleeder valve on the injection pump once the engine is running on its own. let it run for a while and before shutting it down open the bleeder again to purge more air. You may have to do this a few times over the course of a couple days to get all the air out.... Good luck and keep us updated...



Just to explain a bit: It sounds like it has air trapped, Spinning it over with the starter will not spin the injection pump fast enough to overpower the air lock and get fuel to the injectors. the engine running at 500-700 RPMs will.

 

[86m1028]

Keep It SIMPLE. Open the Bleeder valve on the front inside of the pump (between the injection pump and the engine, it takes a 10mm wrench. Open it 1-1 1/2 turns. Separate the air intake at the rubber 90deg turn on the driveside (close to the PCM box) you can roll the window down and spin the engine over with the switches and spray either into the intake at the same time, when it starts keeping it running at a low-idle RPM with small squirts of the either until it bleeds the air out of the injection pump/lines/injectors and runs on its own. It may take up to 45sec-1min to bleed. Close the bleeder valve on the injection pump once the engine is running on its own. let it run for a while and before shutting it down open the bleeder again to purge more air. You may have to do this a few times over the course of a couple days to get all the air out.... Good luck and keep us updated...
Just to explain a bit: It sounds like it has air trapped, Spinning it over with the starter will not spin the injection pump fast enough to overpower the air lock and get fuel to the injectors. the engine running at 500-700 RPMs will.

I understand what your saying & will give it a try but I have even removed all 6 lines at IP & cranked it over... nothing.
Ive removed the return line & check valve, when cranking fuel flows out the return.
Ive clamped off the return line thinking it might help force fuel up into the lines & still got nothing.

Will try try those suggestions & post back tomorrow.

 

[WillWagner]

It's an MW with an RQVK governor.

The reason I asked about lines off and for a pic is that what you describe can be caused by the return check valve being installed into the inlet port...yup, it happens, they are the same size fittings. Looks like yours is good. If there is zero delivery, the fuel shut off lever is going to the open position, it is most likely a pump. But, you need to troubleshoot it. You need to check the pressure in the pump and make sure the shut off is not being pulled too far up, there is a measurement for how far the lever needs to travel for the rack to move to the proper position to allow injection. I posted the measurements somewhere here, search for all my posts. It was just a few months back.

Even if the gear moved on the shaft, there would still be fuel delivery

Yes, cranking the engine at 150 RPM is indeed enough to purge air from the system without cracking lines, that is one of the beauties of bosch inline pumps, they do purge nicely, no mess.

 

[74M35A2]

the injection pump is a bosch p7100, used in lots of equipment 4 b cummins to big john deere sixes. they are a good bullet proof pump with some high delivery rates, that's why the pullers love them so much. The only weakness is the gear to pump connection that can slip. I had a 4b 2 summers ago a mechanic had pulled the pump to change the shut off solenoid, and didn't torque it right. The same symptom you have now they had, I had to retime it and torque it properly.

Not a P7100, just looks like it. Same inline pump assembly, and same gear attachment mechanism (taper). Pump shaft has key slot, but key is not used.

He could remove the governor cap and see if the governor weights/springs are spinning around at a good pace when cranking to check if taper is slipping, but tach drive probably keys off center of shaft anyway?

 

[86m1028]

Keep It SIMPLE. Open the Bleeder valve on the front inside of the pump (between the injection pump and the engine, it takes a 10mm wrench. Open it 1-1 1/2 turns. Separate the air intake at the rubber 90deg turn on the driveside (close to the PCM box) you can roll the window down and spin the engine over with the switches and spray either into the intake at the same time, when it starts keeping it running at a low-idle RPM with small squirts of the either until it bleeds the air out of the injection pump/lines/injectors and runs on its own. It may take up to 45sec-1min to bleed. Close the bleeder valve on the injection pump once the engine is running on its own. let it run for a while and before shutting it down open the bleeder again to purge more air. You may have to do this a few times over the course of a couple days to get all the air out.... Good luck and keep us updated...
Just to explain a bit: It sounds like it has air trapped, Spinning it over with the starter will not spin the injection pump fast enough to overpower the air lock and get fuel to the injectors. the engine running at 500-700 RPMs will.

Ok, grabbed a can of either @ the auto parts store today.
It will fire on either but there is no fuel going to the cylinders.
I.P. is getting fuel & it is returning to the tank thru the IP & out the return line.
Pulled all 6 injector lines OFF at the top of the IP & cranked it. No fuel out the ports, just returns to tank.
So I guess I'm down to a stuck rack or bad governor ???

 

[snowtrac nome]

sounds to me like a problem in the pump I would pull it out and have it rebuilt

 

[86m1028]

sounds to me like a problem in the pump I would pull it out and have it rebuilt

Thanks
I was hoping there was an easy fix, guess not.
Now to decide if I want to fix it or part it out.

 

[MtnSnow]

Pinch off the return fuel line and crank it (the MW pump needs to have at least 15psi of internal pressure before it will push fuel to the injectors. I had this problem due to a faulty check valve at the fuel return line..

 

[86m1028]

Pinch off the return fuel line and crank it (the MW pump needs to have at least 15psi of internal pressure before it will push fuel to the injectors. I had this problem due to a faulty check valve at the fuel return line..

MtnSnow
You already taught me that trick on a recently purchased m936a2.
Which by the way DID fix the loss of prime issue on it.
Thanks again for the help on that one.

I have tried that & it made no change.
As far as I can tell something is stuck in the IP preventing fuel from going to the cylinders
It just bypasses to the return or when pinched just dead heads at the IP.

 

[Tornadogt]

If I understand what happened correctly, the truck was in good running order until you changed the fuel lines and now you have this problem? Is it possible that some debris from the inside of the new lines made its way into the injection pump and is preventing fuel from getting to the injectors but not preventing fuel from coming out the return line? Maybe someone with more knowledgeable about the inner workings of the pump could let us know of something that can be checked.. maybe a screen filter or small orifice inside the injection pump somewhere? Please let us know when you do find out and good luck.

 

[86m1028]

If I understand what happened correctly, the truck was in good running order until you changed the fuel lines and now you have this problem? Is it possible that some debris from the inside of the new lines made its way into the injection pump and is preventing fuel from getting to the injectors but not preventing fuel from coming out the return line? Maybe someone with more knowledgeable about the inner workings of the pump could let us know of something that can be checked.. maybe a screen filter or small orifice inside the injection pump somewhere? Please let us know when you do find out and good luck.

Yes, truck was in running driving condition.
Pulled rubber fuel lines, truck sat about 2 months with out lines attached but fittings were covered.
Replaced fuel lines, still need to do engine mounted fuel filter but don't see the point now.
Truck has always started instantly !
Ip is getting fuel but it goes straight out the return line, even when all cylinder lines are removed at the IP.

I dont see how anything could have made it past the fuel filter.

 

[Tinstar]

I'm just shooting from the hip,
but what about pressurizing the tank?
Not a lot of course.
Just enough to help maybe push past whatever is possibly causing a blockage.

 

[86m1028]

I'm just shooting from the hip,
but what about pressurizing the tank?
Not a lot of course.
Just enough to help maybe push past whatever is possibly causing a blockage.

Thanks for the suggestion, I have pressurized the tank to help prime it.
I have pinched the return line & cranked it, just not getting fuel out the top of the IP.

Maybe some loving TAPS with a 16lbs sledge hammer ???
Just kidding, maybe, maybe not !

 

[WillWagner]

OK, here's something that I remember. When the FSOV shuts off, the rack returns to the zero delivery position, which is toward the governor portion of the pump. This puts a slot in line with another slot that shunts the fuel back into the gallery, IIRC, the rack is helped to be held at zero delivery with a magnet. I have seen a few times that an engine wouldn't start until the throttle was depressed. In the post that you put up with the picture, you stated that the throttle linkage was off because the ball joint broke. It wouldn't happen to still be off would it? If so, go out and manually hold the throttle wide open and have someone crank it.

 

[Docuscg]

I had the same truck and same problem. Did all that you tried and more. Truck would start and run as long as you sprayed ether. Had a old -old -old friend who was a truck mechanic come by and said to check the pick up tube for cracks in the fuel tank. So I pulled the pick up tube out and blew air in the tube holding closed one in and air bubbled out of the soldered joint at the top. There is a brass tube that is soldered to the 90 degrees fitting that screws in the top of the tank. So I heated the joint and took it apart. Cleaned it and soldered. Never thought that little bit of a air leak would kept my engine from running. But hit the starter and VVAAARROOOOMMMMMM! Never had a problem with it to this day! Hope this helps you. Good Luck.

 

[86m1028]

OK, here's something that I remember. When the FSOV shuts off, the rack returns to the zero delivery position, which is toward the governor portion of the pump. This puts a slot in line with another slot that shunts the fuel back into the gallery, IIRC, the rack is helped to be held at zero delivery with a magnet. I have seen a few times that an engine wouldn't start until the throttle was depressed. In the post that you put up with the picture, you stated that the throttle linkage was off because the ball joint broke. It wouldn't happen to still be off would it? If so, go out and manually hold the throttle wide open and have someone crank it.

Yes, throttle linkage is still off, haven't found the ball & joint yet.
Ill give that a try tomorrow & report back.

 

[86m1028]

I had the same truck and same problem. Did all that you tried and more. Truck would start and run as long as you sprayed ether. Had a old -old -old friend who was a truck mechanic come by and said to check the pick up tube for cracks in the fuel tank. So I pulled the pick up tube out and blew air in the tube holding closed one in and air bubbled out of the soldered joint at the top. There is a brass tube that is soldered to the 90 degrees fitting that screws in the top of the tank. So I heated the joint and took it apart. Cleaned it and soldered. Never thought that little bit of a air leak would kept my engine from running. But hit the starter and VVAAARROOOOMMMMMM! Never had a problem with it to this day! Hope this helps you. Good Luck.

My truck has a brass fitting & copper tubing in the tank.
All of the fuel system is good, this is NOT a loss of prime issue.
This is an issue INSIDE the IP not letting fuel to any of the injector lines.

Thanks for your suggestion though.