Failed 26 year old original db2, what’s inside? What goes wrong?

Thewespaul

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The torque screw basically is an adjustable stop for the metering valve, limiting how much fuel can get through the mv and into the charging ports in the head.
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The leaf spring is an adjustable limit to your plunger stroke, it compresses as you tighten the screw which causes the edges of the spring to move further out due to its moon shape. It limits how far the plungers move out in their bores, which is also controlled by the metering valve’s ability to adjust how much fuel enters the pumping chamber through the .094” fill port when it registers with the charge port in the head, that volume determines how far out the plungers move. The cam ring determines the timing, firing order, cylinder count and most importantly how far the plungers move into their bore when the rollers come across the peaks.
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Thewespaul

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Here’s how the cam ring, cam pin and advance piston interact. As the advance piston moves in its bore it changes the relationship of the cam ring to the rotor attached to the driveshaft, changing the injection timing by 10-12* by its function alone.
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Thewespaul

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Yes, a steel sleeve is a cheap upgrade and a sleeved advance bore is the only way to build a reliable db2 anymore, the steel sleeve although an improvement over bare aluminum will still wear out the advance piston and lead to transfer pressure issues down the road. My solution (we're getting into part 2 thread material now) is a ceramic sleeve that basically eliminates wear on the advance piston. Here’s a 90cc pump that was wrecked by a gas station with a diesel tank full of gasoline, head and rotor seized and driveshaft snapped, but the advance piston bore was undamaged with minimal scratches on the advance piston. This is the only pump I have seen yet that has managed to show any visible damage on the advance piston.

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Thewespaul

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To add to my comments on rotor workings, here is a .310 rotor cut in half with an EDM machine. You can see the pumping chamber at the top, below that the two fill ports, below that is the delivery valve location and single discharge port.
 

Farmer Rock

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Thank you Wes for taking the time to share this information.Very good write up!




Rock
 

chicken bones

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I am still running the 1994 factory sealed turbo Stanadyne DB2 Injection Pump , 400000 + KM . I know its way over due for a rebuild , recently my Truck does not go to high idle at least not right away as it use to . I thought it would be the sensor / switch by the thermostat, just have not got around to changing it yet. But could this be a sign that my very high mileage Injection Pump is failing ? I have always added lubricating to my fuel , stock fuel filter set up. I would love to see you disect my Pump one day , guess we need to talk about my replacement. Thanks for educating us on these old Trucks.
 

Kevin 007

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I am still running the 1994 factory sealed turbo Stanadyne DB2 Injection Pump , 400000 + KM . I know its way over due for a rebuild , recently my Truck does not go to high idle at least not right away as it use to . I thought it would be the sensor / switch by the thermostat, just have not got around to changing it yet. But could this be a sign that my very high mileage Injection Pump is failing ? I have always added lubricating to my fuel , stock fuel filter set up. I would love to see you disect my Pump one day , guess we need to talk about my replacement. Thanks for educating us on these old Trucks.

That's impressive mileage on a DB-2. Nice work. What lube additive do YOU use? (not trying to start a additive debate everyone)
 

Laine D

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I was thinking the other day about how cool it would be to be able to dial in the torque screw on the fly. It would be even cooler on your larger pumps where you can control the fueling. I know that they have some AFC tuning things for the cummins trucks, but I think it would be much more simple on these.
 

IDIBRONCO

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I was thinking the other day about how cool it would be to be able to dial in the torque screw on the fly. It would be even cooler on your larger pumps where you can control the fueling. I know that they have some AFC tuning things for the cummins trucks, but I think it would be much more simple on these.
It seems like it would be fairly difficult to me. The torque screws have a locking nut to hold them in place. You'd have to get around that. Plus you'd have to have some kind of linkage that ran from inside the cab to the torque screw in order to do any adjusting while on the fly. Maybe I'm wrong here since IPs and injectors are not on my list of anything that resembles expertise. My only reference here is a manual choke carb on a gas engine. I do have one of those on the Red Truck and I do LOVE it. I've had it on several different engines and in 5 or 6 different vehicles.
 

chicken bones

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I have used a few ,but mostly Stanadyne & PS Diesel Kleen. lately the PS Diesel Kleen , every tank full gets a dose. Also I have never turned up the fuel or done anything with the pump. Dont run my tanks below 1/4 tank , for the most part. Also still running a Machanical lift pump.
 

nelstomlinson

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The torque screws have a locking nut to hold them in place. You'd have to get around that. Plus you'd have to have some kind of linkage that ran from inside the cab to the torque screw in order to do any adjusting while on the fly.
How about remove the lock nut, connect the end of the screw to a little 12VDC gear drive motor which makes two or three RPM. Have a switch in the cab that can power the motor in either direction. You would just have to put in positive stops to make sure you didn't let it turn too far.
 

Laine D

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It seems like it would be fairly difficult to me. The torque screws have a locking nut to hold them in place. You'd have to get around that. Plus you'd have to have some kind of linkage that ran from inside the cab to the torque screw in order to do any adjusting while on the fly. Maybe I'm wrong here since IPs and injectors are not on my list of anything that resembles expertise. My only reference here is a manual choke carb on a gas engine. I do have one of those on the Red Truck and I do LOVE it. I've had it on several different engines and in 5 or 6 different vehicles.
if we could figure out the lock nut aspect of it, the linkage would be the main issue. On my 110 I feel like a full rotation on the torque screw makes a significant difference. I’m not sure if every pump is like that though. I adjust it with a flexible Allen/screw driver thingy. If you could somehow incorporate the tool I use with like a 4 position rotary switch, obviously mechanical, you might be able to actually see a difference in fueling. I’m not a very good explainer LOL. If I had a pump not on my truck I would love to try and make something like this.
I’m basically picturing these 2 images mixed together. Not sure if you guys will catch my drift or not.

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Thewespaul

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The lock nut has to stay to retain the o ring against the housing and seal the torque screw. Y’all can experiment with electric control if you like, but I plan to keep electronics off my db2s indefinitely. It would be more difficult to do with the smaller pumps like 90 and 110s because of the retained light load advance but locked timing pumps I have external controls available for anyone who wants to have the ability to adjust power on the fly with my 130 and larger pumps, all done mechanically with control in the cab. We are going to be showcasing it on a project I’ll be making a thread for once it hits the dyno.
 

Thewespaul

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I have used a few ,but mostly Stanadyne & PS Diesel Kleen. lately the PS Diesel Kleen , every tank full gets a dose. Also I have never turned up the fuel or done anything with the pump. Dont run my tanks below 1/4 tank , for the most part. Also still running a Machanical lift pump.
That’s very good, although turning the pumps fuel delivery up won’t have any negative affects for reliability, in fact you can often cheat a bit more life out of a worn pump by turning the fuel up. Your high idle issue is likely unrelated to the pump, it’s probably an issue with your high idle solenoid, if it’s getting erratic I sell them on my website.
 

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