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My guess NC after reading that. Thanks SD.
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M923A2 Starts only with Ether, and stalls when put into gear
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scrump
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Hello All,
Happy Memorial Day, remembering my step dad and squadron mates who passed in the line of duty or after their service ended.
Regarding the M923A2. Working hard to absorb as much and execute as much of the sometimes conflicting advice (all of it totally appreciated!) as best as possible.
Thought was if I could fix the transmission issue, starting with ether is no big deal...I could do my Memorial Day events. That ship has sailed.
My big focus would be to at least to be able to get the truck to MOVE (other than in reverse) so I could actually take it somewhere to get it fixed if all else fails...she's on top of a 300' hill right now.
I'll execute as per the guidance above...fuel pressure, fuel line, check the lock up solenoid operation...but not sure how that matters:
Back to the lock-up solenoid since it is already out now. While you have it off, see whether it is in the open or closed position. Then supply 24v and a ground to the proper wires and insure that it changes positions. My fear here is that removing the solenoid and capping the ends has placed the torque converter in permanent lock-up. This would explain the new "lurch" after removal, which is also a symptom of a stuck shifter button. A stuck shifter button or grounded wires presents with a lurch then an engine stall.
I'm told that exact opposite is what happens...removing the solenoid and capping the ends of the transmission lines simply makes it NA, and since I don't need to switch the transfer case on the fly, nor use a PTO function, getting rid of it was the advice of Memphis Equipment who seems to know what they're taking about.
However, I'll follow the advice of the previous post to test it...this is what I'm talking about, conflicting info running me in circles which gets me in "trouble" on this forum.
Post 7, I'll follow that advice, with fuel pressure and timing. No I did not check those things specifically but how is there low fuel pressure when it can run up to 2500 RPM, and how is the timing potentially bad when it purrs like a kitten after a tiny shot of ether? But I get it, perhaps the low PSI prevents the start (the primer pump was replaced, and still needs ether, manual prime does not help it start). How does timing and pressure just go bad? Hard to conceive but I'm going to simply follow orders cuz you guys are the experts!
I have to go to work for the next four days, so my responses will be slow...but in the meantime can someone please tell this newbie what NC and NO mean? No Change? Not Operational?
thanks,
mark
Happy Memorial Day, remembering my step dad and squadron mates who passed in the line of duty or after their service ended.
Regarding the M923A2. Working hard to absorb as much and execute as much of the sometimes conflicting advice (all of it totally appreciated!) as best as possible.
Thought was if I could fix the transmission issue, starting with ether is no big deal...I could do my Memorial Day events. That ship has sailed.
My big focus would be to at least to be able to get the truck to MOVE (other than in reverse) so I could actually take it somewhere to get it fixed if all else fails...she's on top of a 300' hill right now.
I'll execute as per the guidance above...fuel pressure, fuel line, check the lock up solenoid operation...but not sure how that matters:
Back to the lock-up solenoid since it is already out now. While you have it off, see whether it is in the open or closed position. Then supply 24v and a ground to the proper wires and insure that it changes positions. My fear here is that removing the solenoid and capping the ends has placed the torque converter in permanent lock-up. This would explain the new "lurch" after removal, which is also a symptom of a stuck shifter button. A stuck shifter button or grounded wires presents with a lurch then an engine stall.
I'm told that exact opposite is what happens...removing the solenoid and capping the ends of the transmission lines simply makes it NA, and since I don't need to switch the transfer case on the fly, nor use a PTO function, getting rid of it was the advice of Memphis Equipment who seems to know what they're taking about.
However, I'll follow the advice of the previous post to test it...this is what I'm talking about, conflicting info running me in circles which gets me in "trouble" on this forum.
Post 7, I'll follow that advice, with fuel pressure and timing. No I did not check those things specifically but how is there low fuel pressure when it can run up to 2500 RPM, and how is the timing potentially bad when it purrs like a kitten after a tiny shot of ether? But I get it, perhaps the low PSI prevents the start (the primer pump was replaced, and still needs ether, manual prime does not help it start). How does timing and pressure just go bad? Hard to conceive but I'm going to simply follow orders cuz you guys are the experts!
I have to go to work for the next four days, so my responses will be slow...but in the meantime can someone please tell this newbie what NC and NO mean? No Change? Not Operational?
thanks,
mark
normally open/closedHello All,
Happy Memorial Day, remembering my step dad and squadron mates who passed in the line of duty or after their service ended.
Regarding the M923A2. Working hard to absorb as much and execute as much of the sometimes conflicting advice (all of it totally appreciated!) as best as possible.
Thought was if I could fix the transmission issue, starting with ether is no big deal...I could do my Memorial Day events. That ship has sailed.
My big focus would be to at least to be able to get the truck to MOVE (other than in reverse) so I could actually take it somewhere to get it fixed if all else fails...she's on top of a 300' hill right now.
I'll execute as per the guidance above...fuel pressure, fuel line, check the lock up solenoid operation...but not sure how that matters:
Back to the lock-up solenoid since it is already out now. While you have it off, see whether it is in the open or closed position. Then supply 24v and a ground to the proper wires and insure that it changes positions. My fear here is that removing the solenoid and capping the ends has placed the torque converter in permanent lock-up. This would explain the new "lurch" after removal, which is also a symptom of a stuck shifter button. A stuck shifter button or grounded wires presents with a lurch then an engine stall.
I'm told that exact opposite is what happens...removing the solenoid and capping the ends of the transmission lines simply makes it NA, and since I don't need to switch the transfer case on the fly, nor use a PTO function, getting rid of it was the advice of Memphis Equipment who seems to know what they're taking about.
However, I'll follow the advice of the previous post to test it...this is what I'm talking about, conflicting info running me in circles which gets me in "trouble" on this forum.
Post 7, I'll follow that advice, with fuel pressure and timing. No I did not check those things specifically but how is there low fuel pressure when it can run up to 2500 RPM, and how is the timing potentially bad when it purrs like a kitten after a tiny shot of ether? But I get it, perhaps the low PSI prevents the start (the primer pump was replaced, and still needs ether, manual prime does not help it start). How does timing and pressure just go bad? Hard to conceive but I'm going to simply follow orders cuz you guys are the experts!
I have to go to work for the next four days, so my responses will be slow...but in the meantime can someone please tell this newbie what NC and NO mean? No Change? Not Operational?
thanks,
mark
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NO means Normally Open when at resting position. NC means Normally Closed when at resting position. So an actuated valve, whether operated by air, electric, hydraulic, etc., will start in one of those positions. When it is activated it changes to the other position, or it may have multiple positions. The NO and NC just describes the resting or starting position of the valve before it's activated.
Low fuel pressure can still be on the table because you can't put a load on the engine without stalling it out. The pressure could be enough to idle and rev the engine without a load but not enough to maintain a load.
Maybe someone else can explain the timing a little better but I seem to remember reading that the gear is on a tapered shaft without a key. The gear can loosen and move, effectively changing the timing.
Happy Memorial Day to you and thank you for your service.
Low fuel pressure can still be on the table because you can't put a load on the engine without stalling it out. The pressure could be enough to idle and rev the engine without a load but not enough to maintain a load.
Maybe someone else can explain the timing a little better but I seem to remember reading that the gear is on a tapered shaft without a key. The gear can loosen and move, effectively changing the timing.
Happy Memorial Day to you and thank you for your service.
Sounds like the tranny is in 5 locked. There is no way you will overcome the gearing and 5th gear clutch pack.... it will simply kill the engine with very little movement. It's like putting a manual tranny car in 5th gear and trying to start out. The reason it works in reverse is the gearing....much much lower....but it's still slipping the TC lock up clutch when it shouldn't.
We need a hydraulic diagram of the tranny to know if the valve is dumping hydraulic pressure (releasing the TC clutch) or is passing it to the piston, which then applies pressure and locks it .
Since you have the valve out, lets check it for NO or NC. With no electric applied, can you blow from port a to port b?? If you can blow through it, it is normally open (NO). If you apply 24vdc it should shift and you cannot blow air through it.
If it is normally closed (NC), you will not be able to blow air through it. Then when you apply 24 vdc, it shifts and you can blow air through it.
You may need to put the valve back in and just unplug the electric or devise a union for the two lines so they let fluid flow (not blocked)(if it is NO).
I'm going searching for tranny hydraulic diagrams.
We need a hydraulic diagram of the tranny to know if the valve is dumping hydraulic pressure (releasing the TC clutch) or is passing it to the piston, which then applies pressure and locks it .
Since you have the valve out, lets check it for NO or NC. With no electric applied, can you blow from port a to port b?? If you can blow through it, it is normally open (NO). If you apply 24vdc it should shift and you cannot blow air through it.
If it is normally closed (NC), you will not be able to blow air through it. Then when you apply 24 vdc, it shifts and you can blow air through it.
You may need to put the valve back in and just unplug the electric or devise a union for the two lines so they let fluid flow (not blocked)(if it is NO).
I'm going searching for tranny hydraulic diagrams.
sandcobra164
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Just read this and figured I'd chime in some off the wall information which may help or may help nothing at all. The only reason I say this is because I had this very similar experience with an M936A2 Wrecker that I used to operate with the National Guard back in the days of yore. It did not need ether to start but that's the only thing not similar. It would start up and run just fine, rev up and so on. As soon as pulled into gear it would lurch slightly and stall. Did not try to release the brake to see if it made a difference. Problem was the PTO for the wrecker body was engaged while the transmission neutral which is normal for wrecker body operation. Disengaged the PTO and the truck was fine and could move. I posted earlier thinking I figured out why the solenoid would be normally open or closed. Now my head hurts. Disclaimer; I'm not an engineer. Hopefully one will come along soon and explain it for me. It was a great truck and it even stayed in my front yard for a while until it went to it's "forever" home.
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scrump
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Hello TobyS,
IMO, the tranny is not locked in 5th. Why not? When it was up on blocks, and put into gear, the RPM was 1500 and the "forward speed" was only 7 mph.
I would think with that RPM in 5th, the speedometer would indicate a much higher speed because of the much higher speed of the tires.
mark
IMO, the tranny is not locked in 5th. Why not? When it was up on blocks, and put into gear, the RPM was 1500 and the "forward speed" was only 7 mph.
I would think with that RPM in 5th, the speedometer would indicate a much higher speed because of the much higher speed of the tires.
mark
scrump
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The transmission is an Allison transmission, model MT564CR.
I do not have power take off in this truck.
The way I read the below quoted section of the maintenance manual: The valve is NORMALLY CLOSED. When the solenoid "is activated" it directs main oil pressure of transmission to the transmission governor system. Therefore, removing the switch and capping both ends of the oil line keeps it in it's NC position and has not added problems.
Does anyone read the below paragraph differently? "TRANSMISSION 5TH-GEAR LOCKUP SOLENOID VALVE -Activated by transmission control
switch and transfer case switch, the 5th-gear lockup solenoid valve directs main oil pressure of
transmission to the transmission governor system. This puts transmission in 5th-gear, creating less
drag on transfer case synchronizer which permits smoother shifting from one transfer case drive
range to another."
I do not have power take off in this truck.
The way I read the below quoted section of the maintenance manual: The valve is NORMALLY CLOSED. When the solenoid "is activated" it directs main oil pressure of transmission to the transmission governor system. Therefore, removing the switch and capping both ends of the oil line keeps it in it's NC position and has not added problems.
Does anyone read the below paragraph differently? "TRANSMISSION 5TH-GEAR LOCKUP SOLENOID VALVE -Activated by transmission control
switch and transfer case switch, the 5th-gear lockup solenoid valve directs main oil pressure of
transmission to the transmission governor system. This puts transmission in 5th-gear, creating less
drag on transfer case synchronizer which permits smoother shifting from one transfer case drive
range to another."
sandcobra164
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Thinking about it more, the torque converter may be the culprit for some of your issues. I'd try removing an axle shaft on each rear axle and the caps off of the front axles and see what happens when you put the truck in gear. They normally have open differentials on the axles, the transfer case would still be in play as if the truck were complete. The driveshaft coming from the rear of the transfer case should be spinning but since the axles are open differential the truck could sit still against the parking brake. The engine should stay running and that would be a much safer test. I know your truck is not a wrecker variant and your lockup solenoid is removed and capped off. I posted thinking it might be a wiring issue as these trucks have interlocks in both the motive power section and the electrical section. I should have been more clear in my post.
Yes, the speed would be higher....I'll stay subscribed, but am out of ideas. Good luck
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If timing slipped, there is usually white smoke involved, but not always. He needs to do as Simp or SD have suggested. Split the issue in half, troubleshoot the engine, check timing and fuel pressure. If the engine is not doing what it is supposed to do, the trans can't do what it needs to do because it has no/low power driving it. If all is good on the drive end, then jump to the driven end.
scrump
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Gentlemen,
When I get back home, I'm going to focus solely on the "drive end"...perhaps that may fix the driven end. Perhaps not. Not much left to check on the driven end.
Perhaps the injector pump is failed, if there's fuel pressure, and timing, then that pump probably needs to come off...I can see that as the only remaining reason the engine will only start with the boost of ether, no fuel in the cylinders when it initially cranks...
I have a new injector pump, but need to get the back half modified to match the existing pump specs.
Thanks!
When I get back home, I'm going to focus solely on the "drive end"...perhaps that may fix the driven end. Perhaps not. Not much left to check on the driven end.
Perhaps the injector pump is failed, if there's fuel pressure, and timing, then that pump probably needs to come off...I can see that as the only remaining reason the engine will only start with the boost of ether, no fuel in the cylinders when it initially cranks...
I have a new injector pump, but need to get the back half modified to match the existing pump specs.
Thanks!
scrump
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Truck won't even start now. Fuel injection pump removed for replacement or repair. Hopefully this will fix the driven end.
scrump
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Hey Guys,
I have a new fuel injection pump. The old one was a bear to get out (access to one bolt on the backside of the pump was very difficult).
However, the new one is about to go in. It's the same pump with a slightly different governor but the guys at Diamond Diesel in Oakland Ca compared all the specs and seem to think it'll be just fine. I had them do an ops check on it (for a cool $425!...and I thought aviation was expensive).
Anyway, I don't see a way to bar the motor to TDC. No access to the flywheel to turn the crank...can I simply turn the alternator to get the TDC pin to align or is there another way to turn the crank so I can align the TDC indicator pin before I put the pump in? Thanks...
I have a new fuel injection pump. The old one was a bear to get out (access to one bolt on the backside of the pump was very difficult).
However, the new one is about to go in. It's the same pump with a slightly different governor but the guys at Diamond Diesel in Oakland Ca compared all the specs and seem to think it'll be just fine. I had them do an ops check on it (for a cool $425!...and I thought aviation was expensive).
Anyway, I don't see a way to bar the motor to TDC. No access to the flywheel to turn the crank...can I simply turn the alternator to get the TDC pin to align or is there another way to turn the crank so I can align the TDC indicator pin before I put the pump in? Thanks...
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Yeah, you can use the alt to bar the engine, but it will only turn reverse rotation. That is OK. OR, just use the damper bolts to turn it. Be careful, you can shear the pin if you turn the engine too fast.
Did the pump shop stand check you old pump? What do you mean by "different governor"?
Did the pump shop stand check you old pump? What do you mean by "different governor"?
scrump
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Hi Will,
Thanks for the advice,...yes, go slowly or the plastic pin can break for finding TDC...
The "damper bolts"...where are they? On the front of the flywheel? If so, they're not on center but I guess I could get them to rotate the crank if that's what you're talking about.
Stand check my old pump...no, didn't want to spend the money, troubleshooting the existing pump would have cost the same as the new one. (Got a GREAT deal on ebay on this pump...well, it'll be a great deal if it works, but it did test good
Different governor: The front of the pump has a data plate, the back end of the pump has a data plate on it. That's the governor data plate, and the tech looked up the specs, it has a slightly higher idle and a higher top end (2400 RPM vs. 2100)
Thanks for the advice,...yes, go slowly or the plastic pin can break for finding TDC...
The "damper bolts"...where are they? On the front of the flywheel? If so, they're not on center but I guess I could get them to rotate the crank if that's what you're talking about.
Stand check my old pump...no, didn't want to spend the money, troubleshooting the existing pump would have cost the same as the new one. (Got a GREAT deal on ebay on this pump...well, it'll be a great deal if it works, but it did test good
Different governor: The front of the pump has a data plate, the back end of the pump has a data plate on it. That's the governor data plate, and the tech looked up the specs, it has a slightly higher idle and a higher top end (2400 RPM vs. 2100)
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Damper bolts are on the nose of the crank. They hold the vibration damper on.
So the governor is NOT different, just the governed speed.....only ask because there are different governor TYPES that go on the pump, RQV, RQVK, RSV, etc. Some are for stationary power things like pumps and generators, generators are usually governed at 1800 unless it is a funky Hz like 600 or something like that for aircraft use. You need to make sure you get an automotive governor and NOT a stationary power type, it will make it so the truck is not too fun to drive, if drivable at all.
So the governor is NOT different, just the governed speed.....only ask because there are different governor TYPES that go on the pump, RQV, RQVK, RSV, etc. Some are for stationary power things like pumps and generators, generators are usually governed at 1800 unless it is a funky Hz like 600 or something like that for aircraft use. You need to make sure you get an automotive governor and NOT a stationary power type, it will make it so the truck is not too fun to drive, if drivable at all.
scrump
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I found the location to bar the engine. It's on the back of the engine block, at the flywheel, on the right side of the engine.
There's a plastic cover plate, pop that off, but in the geared tool ($95, thanks to the guys at Diamond Diesel in Oakland for lending it to me!) and find top dead center by barring the engine and pushing down the pin located below the fuel injection pump. There are other techniques when putting the pump back on so the timing isn't changed when cranking down the pump (which drives the tach as well BTW).
Truck started and moved immediately with the new pump...
So yep, a fuel problem...all the other stuff was a waste of time other than it convinced me (and others here, who said from the get-go that it was a fuel problem.
I also got to learn my truck's systems during the troubleshooting (which didn't really cost much but time).
The fuel pump was $500 and testing it another $420 (on a $100K Bosch test stand)
Hopefully she'll continue to behave like this, holding the prime, no ether required, drives nicely...
ONLY problem that still exists with the truck is that if I start at the bottom of a hill the RPM does not build to climb that hill...I need a head start to get it up over 1000 RPM or so and then she'll accelerate...Ideas ?
Thanks all for the help and advice, hopefully I can be helpful in the future with such stuff now that I'm an "expert"...HA!
There's a plastic cover plate, pop that off, but in the geared tool ($95, thanks to the guys at Diamond Diesel in Oakland for lending it to me!) and find top dead center by barring the engine and pushing down the pin located below the fuel injection pump. There are other techniques when putting the pump back on so the timing isn't changed when cranking down the pump (which drives the tach as well BTW).
Truck started and moved immediately with the new pump...
So yep, a fuel problem...all the other stuff was a waste of time other than it convinced me (and others here, who said from the get-go
that it was a fuel problem. I also got to learn my truck's systems during the troubleshooting (which didn't really cost much but time).
The fuel pump was $500 and testing it another $420 (on a $100K Bosch test stand)
Hopefully she'll continue to behave like this, holding the prime, no ether required, drives nicely...
ONLY problem that still exists with the truck is that if I start at the bottom of a hill the RPM does not build to climb that hill...I need a head start to get it up over 1000 RPM or so and then she'll accelerate...Ideas
? Thanks all for the help and advice, hopefully I can be helpful in the future with such stuff now that I'm an "expert"...HA!
scrump
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Oops, re-reading my above post, the location to "bar" the engine is on the LEFT side of the engine, at the back, behind the primer pump.
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That's where the "proper" barring spot is. Great job on getting it up and going. As for your issue on getting a head start, the only thing I can think of, without putting test equipment on it, is to make sure the throttle lever is hitting the stop for full throttle. If the arm is hitting the stop, there is an adjustment in the governor/AFC housing that can be made so the rack goes to full fuel earlier.