Paging Dieseltech

[Bern]

Hey there Dieseltech,

I have a Deere skidsteer with a little 2.9L four-banger in it. Said engine has a Stanadyne DB4 injection pump. We were using it the other day and everything was running great. Shut it down for lunch, came back and it would barely start and run. The engine WILL run, but only at about 400-500 RPM, barely. Nothing I can do on the outside will get it to run any faster than that. I barely have enough power to lift the bucket. It acts like something came disconnected inside the pump between the throttle arm on the outside and the metering mechanism inside. I have confirmed that the lever on the outside of the pump is connected to the throttle linkage and is rotating the shaft that goes into the pump. I have also confirmed that the lift pump is still working. It will run all day at 400 RPM.

I'm far more fluent with the CAV pumps than I am with the Roosie pumps. Have you ever seen something like that before, and/or can you speculate what went wrong? I'm hoping I can simply pop the top off and fix it without having to remove the entire pump. I plan to drill out the tamper-resistant Torx screws.

Full pump number if you're curious is DB4327-5658. Attached pic is as good as I can get due to the tight space. Thanks for any help you can be.

 

[Dieseltech]

Hi Bern, How many hours on the pump? That one is built MUCH heavier inside than the other Roosa/Stanadyne pumps are. The drive shaft alone is about 300 bucks new as this model has a needle bearing/shaft drive instead of the brass pilot bushing/shaft drive. There's NO retainer ring to fail in this model pump either like the earlier pumps have. I'd first check the supply flow at the pump inlet, and if OK I'd then make sure the RETURN line back to the tank is not blocked/restricted anywhere as that would also shut the pump down, or at least limit the speed. There MIGHT be a chance the electric stop solenoid is not pulling the plunger/arm away from the metering valve as needed for the governor to have full travel, but that's not common. You might try a jumper wire on the pump hot post directly to the battery and see if that makes any change, a voltage loss through the key switch could keep the solenoid from pulling in correctly. I have the five star bolt tool and I would not try drilling the screw tops as they are very hard if I recall. Instead I'd use an air driven cutoff wheel and cut all three screw heads off to remove the cover. Screws are 10/24 thread, and HOPEFULLY they won't be stuck in the main housing as they sometimes are with dust/rust over time. Let us know what you find, there MIGHT also be broken pieces of the shaft wave thrust spring floating around inside, if so pump WILL need to come apart to repair it as I've seen that washer break before.

 

[Bern]

Hi Bern, How many hours on the pump? That one is built MUCH heavier inside than the other Roosa/Stanadyne pumps are. The drive shaft alone is about 300 bucks new as this model has a needle bearing/shaft drive instead of the brass pilot bushing/shaft drive. There's NO retainer ring to fail in this model pump either like the earlier pumps have. I'd first check the supply flow at the pump inlet, and if OK I'd then make sure the RETURN line back to the tank is not blocked/restricted anywhere as that would also shut the pump down, or at least limit the speed. There MIGHT be a chance the electric stop solenoid is not pulling the plunger/arm away from the metering valve as needed for the governor to have full travel, but that's not common. You might try a jumper wire on the pump hot post directly to the battery and see if that makes any change, a voltage loss through the key switch could keep the solenoid from pulling in correctly. I have the five star bolt tool and I would not try drilling the screw tops as they are very hard if I recall. Instead I'd use an air driven cutoff wheel and cut all three screw heads off to remove the cover. Screws are 10/24 thread, and HOPEFULLY they won't be stuck in the main housing as they sometimes are with dust/rust over time. Let us know what you find, there MIGHT also be broken pieces of the shaft wave thrust spring floating around inside, if so pump WILL need to come apart to repair it as I've seen that washer break before.

I'm unsure of the hours on the machine, it's not mine. I have plenty of pressure going in, and I have also checked the return fitting for blockage and found no problem there. Interesting theory on the shutoff solenoid, I'm going to try your direct wiring trick and see if that changes anything. The governor certainly acts like something internal is keeping the metering valve from freely moving, and I suppose a shutoff solenoid stuck halfway might do it. It'll be a while before I can get back on it, but I'll post back what I find. Thanks.

 

[Dieseltech]

I'm unsure of the hours on the machine, it's not mine. I have plenty of pressure going in, and I have also checked the return fitting for blockage and found no problem there. Interesting theory on the shutoff solenoid, I'm going to try your direct wiring trick and see if that changes anything. The governor certainly acts like something internal is keeping the metering valve from freely moving, and I suppose a shutoff solenoid stuck halfway might do it. It'll be a while before I can get back on it, but I'll post back what I find. Thanks.

Engine should be a three cylinder, DB4327 means rotor has four plungers, three outlet ports, and .270 inch plunger size. There's another thing that could cause the metering valve to stick that I ran into on a genset awhile back. The transfer pump four blade/liner set were breaking down and sending fine shrapnel directly to the fuel metering valve. Pump would need torn completely down for hydraulic head passage cleaning when that happens too.

 

[Bern]

Engine should be a three cylinder, DB4327 means rotor has four plungers, three outlet ports, and .270 inch plunger size. There's another thing that could cause the metering valve to stick that I ran into on a genset awhile back. The transfer pump four blade/liner set were breaking down and sending fine shrapnel directly to the fuel metering valve. Pump would need torn completely down for hydraulic head passage cleaning when that happens too.

You're right, it's a 3-cylinder.

Shrapnel in the metering valve, possible I suppose. I still think I'll pull the top off and investigate before removing the pump. Does the cover just lift right off, or does one need to unhook a governor spring like on the CAV pumps?

 

[Dieseltech]

You're right, it's a 3-cylinder.

Shrapnel in the metering valve, possible I suppose. I still think I'll pull the top off and investigate before removing the pump. Does the cover just lift right off, or does one need to unhook a governor spring like on the CAV pumps?

Cover will lift off without unhooking anything. It CAN be a problem putting it back on though. The BEST way to install the cover is to energize the solenoid to pull the stop arm back, using two jumper wires, one hot and other ground. If not done carefully the stop arm will go on the WRONG side of the valve control rod and lock the arm in the full load position causing engine to run away at startup. When energized the arm is pulled AWAY from the control rod allowing governor weight/sleeve full movement. When solenoid is de-energized the solenoid spring moves the arm back to push the rod to the fuel off position. Energizing the solenoid and making sure the arm is pulled IN when installing the cover makes sure that arm is away from the rod when cover is replaced straight down on pump housing.

 

[Bern]

Cover will lift off without unhooking anything. It CAN be a problem putting it back on though. The BEST way to install the cover is to energize the solenoid to pull the stop arm back, using two jumper wires, one hot and other ground. If not done carefully the stop arm will go on the WRONG side of the valve control rod and lock the arm in the full load position causing engine to run away at startup. When energized the arm is pulled AWAY from the control rod allowing governor weight/sleeve full movement. When solenoid is de-energized the solenoid spring moves the arm back to push the rod to the fuel off position. Energizing the solenoid and making sure the arm is pulled IN when installing the cover makes sure that arm is away from the rod when cover is replaced straight down on pump housing.

Thanks for the tip on installing the cover, energizing the solenoid first with jumper wires would be very easy to do.

I might have a capable student do this work for me because I have limited time. I have an older DB2 pump laying around, and thought I might have him remove that cover first for practice, and to get a good eyeball on the governor linkage and metering valve. Is the linkage and governor operation similar between the two? The number on that one is DB2825PC3742.

 

[Dieseltech]

Thanks for the tip on installing the cover, energizing the solenoid first with jumper wires would be very easy to do.

I might have a capable student do this work for me because I have limited time. I have an older DB2 pump laying around, and thought I might have him remove that cover first for practice, and to get a good eyeball on the governor linkage and metering valve. Is the linkage and governor operation similar between the two? The number on that one is DB2825PC3742.

That's the Olds diesel V-8 pump. The top solenoid is very similar to the DB4-5658 pump and the linkage/valve works the same way. The OLDER solenoids were a bit shorter and went back on easier and were less likely to jam the linkage up without energizing causing engine run away. The new LONGER solenoids are more likely to be installed wrong, but energizing the solenoid greatly reduces that from happening. With practice either one can be installed without energizing, but to be sure using two wires is the best way when replacing the cover.

 

[Bern]

That's the Olds diesel V-8 pump. The top solenoid is very similar to the DB4-5658 pump and the linkage/valve works the same way. The OLDER solenoids were a bit shorter and went back on easier and were less likely to jam the linkage up without energizing causing engine run away. The new LONGER solenoids are more likely to be installed wrong, but energizing the solenoid greatly reduces that from happening. With practice either one can be installed without energizing, but to be sure using two wires is the best way when replacing the cover.

OK, thank you sir for all of that excellent advice, and I'll be sure to keep you posted.

I do believe that it's governor related, and not inlet fuel pressure. It doesn't burp, hesitate, or misfire at all, it just sits there and runs at 400 RPM or so.