Maintence, Install And Repair Guides

Forum dedicated to Polarstar Airsoft Guns.

Moderators: THE ARCHANGEL, Archer

Post Reply
User avatar
MAA Member
Posts: 702
Joined: Sun Aug 14, 2011 7:42 pm
Location: Eagan, MN

Maintence, Install And Repair Guides

Post by Archer » Wed Feb 19, 2014 9:16 pm

This is a listing of various Maintenance, Install and Repair guides for the PolarStar Fusion Engine, The Polarstar FCU, and other components of the PolarStar guns.

FCU Installation into M4/M16 style Buffer tube:

Polarstar M4 to MP5 Ver 2 Fusion Engine Conversion

Polarstar FCU Power Lead Repair and Heat Shrinking Tutorial ...

Lubricating PolarStar Fusion Engine Nozzles ... e-nozzles/

FCU Wire Coding guide
FCU Rev 1 wires:
White = nozzle solenoid (-5v)
Yellow = poppet solenoid (-5v)
Blue = +5v (for solenoids)
Black = trigger switch (connects to purple/red when pressed)
Grey/Green = full auto switch (connects to purple/red when pressed)
Purple/Red = -5v (for trigger/auto switch)

FCU Rev 2 wires
Yellow = common ground
Green = trigger
Blue = full auto
Black = poppet
White = nozzle

Thank you Rudy with Bingo Airsoftworks for this! :)

Note, Gen1 V2 Fusion Engines use Rev1 FCUs, Gen2 V2, Gen3 V2, V3, M249 and M240B Fusion Engines use Rev2 FCUs
Nozzle Not Moving Troubleshooting Guide
Polarstar nozzle not moving

1. First make sure your battery is charged. A bad or low battery can cause all sorts of problems.

2. Try resetting your FCU settings back to default and see if it works. (The Fusion Engine FCU may be returned to the factory defaults by holding in the programming button while plugging in the power supply.)

3. Try turning your psi up to 80 to 120 psi. (For those that run a lower psi than P* recommends.)

4. If none of the above works then:
Disconnect the air line. Open up the fusion engine panel on the side and test fire with the battery plugged. You should hear both solenoids clicking. If you can't tell, unplug one of the solenoid connectors and test fire. Do it again for the other. Both solenoids should click in at least one of the sockets on the trigger board, other wise you have a dead solenoid, or your wiring is messed up.

Swap the solenoid connections around and retest to figure out if your wiring is messed up or if a solenoid is dead. If a solenoid works on one plug, but not the other, your wiring's messed up. If it doesn't work on either, then it's a dead solenoid. One of the solenoid plugs should be marked with a thin black line, and one of the sockets should be marked with a thin black line as well, so you can figure out which one goes where if you forget.

Always make sure that your nozzle and poppet valve have proper lubrication as well.
General Fusion Engine Maintenance And Troubleshooting Tips from "Bingo" of Bingo Airsoft Works
I (Bingo) thought it might be helpful to have a thread on Fusion Engine Maintenance and Troubleshooting Tips, so here's a few things I've learned by working on the Fusion Engine:

1. You pull the trigger and the poppet valve sticks open, blowing air out the nozzle. You have to disconnect the air line to reset the "stuck open" condition.

This is usually caused by one of two conditions. First there could be dirt in your Fusion Engine. If you aren't careful with the QD connectors and you manage to get dirt into the FE, the dirt can cause your poppet value to stick open or jam up your solenoids. I recommend that you have a nipple cover for your QD connector (gun side) and have it covered any time it's not connected to your air line. To fix this condition, you will need to open up your Fusion Engine poppet valve cylinder and clean out any dirt you may find in there. Also you should remove the solenoids and take a look at the input ports (they are on the top of the solenoid with little metal screens). If there is dirt there, vacuum it out or tap the solenoid upside down to try and clear the dirt. Don't blow air through it as it will just force more dirt into the solenoid valve. If your solenoids are leaking (likely due to dirt), you can spray a little silicone oil into the input port, reassemble the FE and fire it several times. This will push the oil through the solenoid and hopefully flush out any dirt. Usually this is "dust" type of dirt and it should blow through the nozzle and poppet valve, but it would be wise to clean those areas too if you have this problem.

The other condition is the poppet valve nozzle O-ring is worn or the wrong size. In some early Fusion Engines, there is a small chance that the nozzle O-ring in the poppet valve the incorrect size (this is the o-ring inside the poppet valve cylinder). If this o-ring is worn or the wrong size, when the poppet valve is triggered, nozzle air (that fires the BB) leaks back through the o-ring, and then pressurizes the poppet valve (pushing the poppet sail), causing the valve to stick open. This is usually the case when you pull the trigger and the gun fires, but the air continues to leak from the nozzle. If you disconnect the air line, it resets and all is fine, until you fire again. The fix for this condition is to replace the o-ring (size 011-70D) or lubricate it so it makes a better seal.

2. The nozzle does not return to the firing position quickly, or it is sluggish to return to firing position. This can result in a lot of BB jams or multiple BB feeding through.

This is likely caused by no lubrication on the nozzle. The nozzle is supported by 3 o-rings. There is a o-ring inside the nozzle, an o-ring at the base of the nozzle, and a o-ring inside the front cylinder. If there is no lubrication the nozzle can get stuck or move very slowly, causing all sorts of problems. I'm actually surprised at how dry the nozzle area can get. I've opened up several Fusion Engines to fine the nozzle o-rings are bone dry. If this is the case, use TechT Gun Sav and lubricate all 3 o-rings. This is probably the most important periodic maintenance you can do with your Fusion Engine. Keep that nozzle nice and lubricated.

3. BBs jamming up in the BB feed tube. The nozzle may not be pulling back far enough to allow the BBs to feed. Or you have a bad BB jam in the hopup, and you need the nozzle out of the way to clear the jam.

(with gen1 FCUs) You can temporarily force the nozzle to retract and stay retracted by momentarily connecting the WHITE wire on the FCU to the RED/PURPLE connector on the FCU. This will power thenozzle solenoid and pull the nozzle back. You can then check and see if the nozzle is being pulled back far enough, or have it retract so you can clear a jam. I would not recommend leaving the nozzlepowered for a long time (I only momentarily touch the wire to the connector, I never "clamp" the wire). If you are having BB jam problems due to the nozzle not retracting far enough, then there is analignment or nozzle length issue. This will require shimming the Fusion Engine so it sits farther back, or changing the nozzle length. Both require a bit of caution and tinkering as you don't want to jeopardize the air seal with the hopup. You can use this same technique to test the poppet solenoid. If you connect the YELLOW wire to the RED/PURPLE connector, you will trigger the poppet and air should blow through the nozzle. Unfortunately you can't easily do this with gen2 FCUs. You can instead check by removing the nozzle spring and manually pushing the nozzle all the way back, then reassemble the gun and look to see that the nozzle has cleared the BB feed tube.

4. Testing for proper air seal between hopup and nozzle.

One of the really nice features of the Fusion Engine is the nozzle air seal within the Fusion Engine cylinder is 100% (otherwise you would hear hissing from a leak). This can help when testing for an air seal between the nozzle and the hopup/barrel. With the gun disconnected from the air supply (never do this test when there is air connected to the gun), you can blow down the barrel. If you have a perfect air seal you will feel no air leaking. If air is leaking, then air is escaping between the bucking and the nozzle. A little air escaping is not a problem, as it will not affect your FPS too much, but if you can blow relatively easily through the barrel, then you are not getting the performance you can out of the Fusion Engine and the bucking needs to be changed and/or the nozzle position needs to be checked. If you can't access the end of the barrel easily (by either removing the inner barrel from outer barrel, or removing the flash hider), you can use a short piece of tubing (macroline works well, maybe a straw) and insert it into the barrel end, of course be aware you may have an air leak from this tube, but account for that when testing this way.

5. Solenoids not triggering but the FCU seems to be working correctly (it shows FIRE when trigger pulled, the full auto select shows AUTO)
First check the battery and make sure it's fully charged (or use a battery that you know is working on another P* gun). The solenoids need 5v to activate, but the FCU board will still operate at lower voltage. So if your battery is weak, it would appear that the FCU is running fine but the gun isn't shooting. If you have access to another FCU, try connecting another FCU to the wire harness and test. If it works using another FCU, then reset the original FCU (plug in the power while holding the button down) and test again. If this doesn't help, then the FCU may be bad. If using the second FCU didn't help, and swapping the battery doesn't help, then it's likely a broken wire or connection in the wire harness, so the wire harness should be replaced.

6. Nozzle is not retracting (or only retracts sometimes), but air is being fired through the nozzle

First make sure you have enough psi. Run the gun at 100 psi and see if that helps. If it does, then the nozzle might need to be lubricated and/or the gun needs to run at a higher psi. If the nozzledoesn't retract (or especially if it only retracts sometimes), but it does retract when not in the hopup (e.g. remove the upper receiver on an M4) then it is likely a problem with the nozzle o-rings. They may be worn out and leaking. An easy way to test for this is to access the fusion engine and fire the gun on full auto with the air connected. If the nozzle is moving, try pinching it with your fingers. If you can stop the nozzle by simply pinching lightly, then air is leaking and the 3 nozzle o-rings should be replaced. If the nozzle is moving when out of the hopup, but does not move reliably when in the hopup, it may be out of alignment and rubbing or binding in the hopup. Paint the tip of the nozzlewith a sharpie pen, about 1/4" all around the tip. Assemble gun and attempt to fire on full auto, then check the nozzle and see where the ink has rubbed off. If there is significant ink missing or gouging on the nozzle, then the alignment needs to be check and/or shimmed.

7. Avoid using a 11.1v lipo with a DN setting greater than 17
This may result in inconsistent firing. Click here to see my post regarding this.

8. Avoid using a 9V batteries to power the Fusion Engine.
9V batteries can often not provide enough current to power the FCU and solenoids. Save yourself a lot of troubleshooting headaches. DO NOT USE 9V batteries.

9. Always test and troubleshoot using a freshly charged battery
The first thing to test when troubleshooting your Fusion Engine is to make sure you have a freshly charged battery. Your battery may have enough power to operate the FCU, but not enough to trigger the solenoids. When in doubt, start with a verified fully charged battery. And as mentioned in #8, don't use 9V batteries.

10. NEVER leave your battery attached to the FCU overnight.
Leaving your battery connected to the FCU overnight will likely result in the battery being completely drained (esp. if you are using a small lipo). If using a lipo battery, that will damage the battery and not make it usable any longer. The sleep mode of the FCU will still draw power. Just make it a habit to always disconnect your battery at the end of the day.
All credit for this goes to Bingo for this nice write up.

Rear Solenoid Leaking Problems & Possible Solutions
Some solenoids that leak can be fixed by spraying a little bit of silicone oil into the engine through the air line, point the engine upward, so the oil drains toward the solenoids, and fire on full auto for a bit. This will work the oil through the solenoids and help oil the o-rings and possibly pull out any dust/dirt that might have gotten in there.

If possible, I would recommend doing a short burst right into the macroline connector on the FE and fire full auto for quite a long time to let the oil work it's way through the solenoids. Hooking up to a home compressor helps when you need to burn through a lot of air. I don't know what that is in drops, since it takes quite a bit to make it down the back of the cylinder and into the solenoids.

Another option would be to take the fusion engine solenoid manifold off and pull out the solenoids, then you can put a few drops directly into the intake on the solenoids. It will be the hole at the top with a small metal screen in it. Be careful not to lose the small o-rings that are attached to the manifold and the cylinder. Then you can fire it a bit to work the oil through.

It may or may not solve the problem, it depends on how bad the solenoid is leaking and if it's dirt causing the problem. If it's really hissing badly, I'd recommend contacting P* about it. If it's just very lightly crackling, you can just try running with it for a bit and see if the problem goes away. It's relatively little air that is escaping.

This and more possibilities are on here: ... enoid+leak
Task Force Echelon - Click and like our facebook page!
OP IRENE X - T.F. Ranger - Charlie Company 1-3 Medic
OP IRENE XI - Somali Freedom Fighters 3-1 Medic
TCA Giant Airsoft Game I & II - Midwest Alliance General

Posts: 4720
Joined: Fri Jul 13, 2001 3:01 am
Location: Richfield, MN

Re: Maintence, Install And Repair Guides

Post by Downtown » Mon Feb 24, 2014 4:44 pm

Smitty had one Selenoid go bad on his unit. If they do go bad and it is within the 1 year, you are covered. If not, it is about a $90 repair. There are 2 different units (they are tuned differently). One operates the poppet and the other operates the nozzle. So it is important to know which one is the one that is shot.
TEAM LEADER - Blacksheep Airsoft(MN)
MAA Member Number: 5
OP: Northern Light CO
OP: The Ohio Project CO

Post Reply

Return to “PolarStar Forum”

Who is online

Users browsing this forum: No registered users and 1 guest