Bijur PDI pump not building pressure... help!

Hey guys!
I'm trying to troubleshoot the lube system on a 1994 Fadal VMC15, the PDI lube pump is actuating but I noticed no lube was getting to the ways. Watching the pump during it's cycle I noticed the oil line pressure is very low, like only 50PSI or so, when it should be 200+ psi. Initially I thought maybe there was a leak in the distribution system so I removed the fitting going to the distribution system and plugged it, then actuated the pump manually and I still get the same ~50PSI.

I pulled the pump apart and replaced the whole cylinder/piston/check valve unit with a new one. The seals looked ok but I figured maybe there was some issue that was only apparent under pressure so I replaced it to test. Still the same issue...

I added a small pressure gauge on top of the air piston input to make sure it was building pressure properly, and it is, it gets to full line pressure pretty much immediately.

The output filter was pretty cruddy so I pulled the filter element out temporarily in case it was blocking flow, still the same issue...

The pressure builds slowly to about 50 PSI then suddenly drops to zero every time the unit is actuated, regardless of whether it's hooked up to the distribution lines or whether the output is plugged off.

Any ideas?

Thanks,
Aaron

For anyone encountering the same problem in the future:

I finally diagnosed the problem by priming the pump (running it without output tubing attached until oil was flowing) and then having it run a cycle without the oil reservoir attached, this let me see that the 'choke valve' was basically just leaking all the oil, rather than sending it to the output.

There is a tiny rubber part inside the 'choke valve' that had been damaged. Replacing the choke valve fixed the issue and the pump now builds pressure correctly!

aarongough said:

For anyone encountering the same problem in the future:

I finally diagnosed the problem by priming the pump (running it without output tubing attached until oil was flowing) and then having it run a cycle without the oil reservoir attached, this let me see that the 'choke valve' was basically just leaking all the oil, rather than sending it to the output.

There is a tiny rubber part inside the 'choke valve' that had been damaged. Replacing the choke valve fixed the issue and the pump now builds pressure correctly!

Click to expand...

Aaron read your post and thank you so much for making this post. I am in the process of rebuilding my lubrication system on my 1998 Fadal VMC15 XT. I am really rebuilding the whole machine from ground up. Have take the Z head off powder coated it and all new parts. Had to put new Z rails on as well, still in the process of that. I do have all the Bijur part numbers for your VMC15 if you were ever to have to replace your injector parts. Way cheaper buying the cup seal and o ring than a whole new injector. Looking into a new monitor like the one you bought.

Ballistic42 said:

Aaron read your post and thank you so much for making this post. I am in the process of rebuilding my lubrication system on my 1998 Fadal VMC15 XT. I am really rebuilding the whole machine from ground up. Have take the Z head off powder coated it and all new parts. Had to put new Z rails on as well, still in the process of that. I do have all the Bijur part numbers for your VMC15 if you were ever to have to replace your injector parts. Way cheaper buying the cup seal and o ring than a whole new injector. Looking into a new monitor like the one you bought.

Click to expand...

No worries at all mate! Really glad the post was helpful!

If you have useful parts numbers please post theme here along with a short description like "bijur injector cup seal for fadal PDI pump" that way others using google to find info in the future will be able to find your part numbers!

Aaron did you replace your wipers on your machine? I have the Fadal vmc15 XT and trying to figure out what and where to find the right wipers. Knowing you rebuilt your machine figure you may have bought new wipers.

Thanks
Jeff

Ballistic42 said:

Aaron did you replace your wipers on your machine? I have the Fadal vmc15 XT and trying to figure out what and where to find the right wipers. Knowing you rebuilt your machine figure you may have bought new wipers.

Thanks
Jeff

Click to expand...

Hey Jeff!
Yes I replaced all the wipers on all 3 of the Fadals I've worked on. They were all pretty worn. I bought my wipers from ITS, the ones I used are here: Buy Fadal Way Cover Wiper Teleflex 1/2" x 8', CVR-0127 | ITSCNC

Hi Aaron, I am having that problem too. My pump does not build pressure when you say "choke valve" you mean the squarish aluminum piece that connects to the cylinder with multiple valves in it? I believe it is part number LUB-0051. Is that correct? Thank you!

Neo6 said:

Hi Aaron, I am having that problem too. My pump does not build pressure when you say "choke valve" you mean the squarish aluminum piece that connects to the cylinder with multiple valves in it? I believe it is part number LUB-0051. Is that correct? Thank you!

Click to expand...

Yep, that's the one! I got my replacement from ITSCNC and it's been working perfectly!

-A

aarongough said:

Yep, that's the one! I got my replacement from ITSCNC and it's been working perfectly!

-A

Click to expand...

Thanks bud, appreciate the help

Any time mate!

Aaron,
I had the same low pressure issue, and took the choke valve apart. The rubber seal that you mentioned being damaged happens to be the same seal used in the larger body injectors. This seal closes off the pressure relief port when the pressure cylinder is actuated. I just rebuilt all of the injectors and had a spare seal. Replaced that and everything seems normal now.

For anybody looking for PDI seals, see the part numbers below. I found these using keywords searches on the Bijur web page. I tried to get the part numbers from Bijur, but they didnt want to help. I asked them to check the detail design drawings and just get me the part numbers. They said parts are not available, and I asked about the part numbers I had found. I got this response: "BUY NEW INJECTORS". Haha. New injectors are $30 each, and I needed 15 of them. These are not hard to rebuild.

Small diameter injector (6 and 10 CC) disc seal. Bijur #: 21626

Small diameter injector O-ring, mcmaster: Buna-N standard durometer dash number 005. I ordered different durometers, and the standard part felt the most correct when compared to the old parts.

Large diameter injector (20, 30, and 40 CC) disc seal. **Also used for the bypass seal in the choke valve.** Bijur #: 21627

Large diameter injector O-ring. mcmaster: Buna-N dash number 106.

I took a video after the rebuild. The pressure struggles a bit to build. I am guessing due to oil flow to injectors, and once the injector pistons reach full stroke, flow stops, and pressure continues to climb. Can somebody confirm this is normal?