American Bosch PSB6A-75C-3411A Injection pump, I know they're a pain

[GBman]

I have a 1954 Case 500 with the PSB6A injector system. It has worked flawlessly for the last two years. I had an issue with a plugged or a restriction that caused (I suspect in the pressure relief valve) the final filter to swell. Shutting it down immediately, change all fuel out, cleaned the tank, changed the filters, pulled and cleaned the bypass valve. Tractor starts and runs fine, but diesel is getting into the crankcase. So I shut off the fuel line to prevent this. Clearly the fuel is getting past the seal (s) between the fuel and lube oil side in the pump. I can't find a clear manual/schematic to clearly see the internal construction of the PSB6A. Everything seems to be copies of copies so you can't really see how the thing goes together. Before I send it to a recommended injector pump rebuilder I really would like to understand construction of the PSB and what seals or other are possibly compromised. Like I said, it runs fine but I know the fuel is getting by into the crankcase. So, I don't run it long and keep the fuel valve off. I don't have a back up pump and it's not something I have experience with so I've not done any exploration. At least not till I have a better understanding of what to do or not do. All help and suggestions are welcome!
Regards

 

[John Saeli]

I have a 1954 Case 500 with the PSB6A injector system. It has worked flawlessly for the last two years. I had an issue with a plugged or a restriction that caused (I suspect in the pressure relief valve) the final filter to swell. Shutting it down immediately, change all fuel out, cleaned the tank, changed the filters, pulled and cleaned the bypass valve. Tractor starts and runs fine, but diesel is getting into the crankcase. So I shut off the fuel line to prevent this. Clearly the fuel is getting past the seal (s) between the fuel and lube oil side in the pump. I can't find a clear manual/schematic to clearly see the internal construction of the PSB6A. Everything seems to be copies of copies so you can't really see how the thing goes together. Before I send it to a recommended injector pump rebuilder I really would like to understand construction of the PSB and what seals or other are possibly compromised. Like I said, it runs fine but I know the fuel is getting by into the crankcase. So, I don't run it long and keep the fuel valve off. I don't have a back up pump and it's not something I have experience with so I've not done any exploration. At least not till I have a better understanding of what to do or not do. All help and suggestions are welcome!
Regards

The problem is with the "Transfer Pump Seal". Not a big deal, do not pull the pump. The transfer pump is behind the cover with the slotted head screws. The hardest part is getting the supply lines out of the way. Pull that body out and behind the gear is the seal. We stock them here. If the shaft is grooved from wear, I have a simple solution for that also.

 

[GBman]

The problem is with the "Transfer Pump Seal". Not a big deal, do not pull the pump. The transfer pump is behind the cover with the slotted head screws. The hardest part is getting the supply lines out of the way. Pull that body out and behind the gear is the seal. We stock them here. If the shaft is grooved from wear, I have a simple solution for that also.

Thank you John, I'll call you tomorrow. If I didn't get a response on here you were going to be my next call!

 

[DanielW]

As John says, common problem and easy fix - takes about 5 minutes and done with the pump still on the tractor. Take a look at my response in this thread (link below) where I give a parts breakdown and say what seal number to order. Any industrial supply can get one. Same seal for a 4 or 6. Attached pic below shows cover you take off and seal circled.

L

Thread 'Psb injection pump seal kit'

Aug 27, 2025

I have a Cockshutt 550 with a psb injection pump.

I am looking for the seals. Either orings or the square rings to seal the hydraulic head.

Does anyone know where I can get them?

Thanks
Lloyd

• ljm
• Replies: 5
• Forum: Tractor & Farm Talk

 

[GBman]

As John says, common problem and easy fix - takes about 5 minutes and done with the pump still on the tractor. Take a look at my response in this thread (link below) where I give a parts breakdown and say what seal number to order. Any industrial supply can get one. Same seal for a 4 or 6. Attached pic below shows cover you take off and seal circled.

L

Thread 'Psb injection pump seal kit'

Aug 27, 2025

I have a Cockshutt 550 with a psb injection pump.

I am looking for the seals. Either orings or the square rings to seal the hydraulic head.

Does anyone know where I can get them?

Thanks
Lloyd

• ljm
• Replies: 5
• Forum: Tractor & Farm Talk

Thank you Daniel! Very much appreciated! Thank you for the clear diagram!!
GB