ONGOING MAINTENANCE

 

RECOMMENDED SCHEDULED MAINTENANCE INTERVALS AND FLUID RECOMANDATIONS:

 

FUEL REQUIREMENTS
 
The 4 cylinder, non supercharged engines, can operate on 87 octane car gas, or 100LL with the recommended amount of Marvel Mystery Oil added as shown on the can label.

Six Cylinder engines are high compression engines and therefore MUST use high octane fuel (91 octane or above)  100LL is also good if Marvell Mystery Oil is mixed with the gasoline.  This requirement is also for any turbo or supercharged engine.

Oil, for all engines should be 5W30 or 5W40 weight.  Use regular or semi synthetic oil if you use 100LL fuel and not full synthetic oil.  You can use synthetic oil, after a 100 hr brake-in period but only if you do not use 100LL fuel. 

The ideal gasoline mix is 91 octane auto gas with 20% 100LL to elevate the octane even further. With this mix you can use 100% synthetic engine oil.

Please read and understand all operating instructions for this engine in the Subaru maintenance and vehicle operations manual.

Change spark plugs                        100hr

Change engine oil & filter                 50 hr
        Non synthetic for the first 100 hr - 5w30
        Non synthetic for anyone using 100LL (Semi Synthetic OK)

Change PSRU oil                            50 hr

 

PDF on adjusting the DOHC valves

PDF on changing the DOHC timing belt

 

CHANGING THE OIL:

After removing the filter, check that the hex nut (1 1/8" socket) holding the aluminum filter mount ring onto the engine has not come loose.  Otherwise, you can get oil leaks at the top of the filter mount ring.

Overtightening the filter will also cause a leak.  Be careful to only go 3/4 turn past the first "touch point".  It is recommended that the oil filter be safetied.  One technique to do this is to put a large hose clamp onto the filter, then safety the screw housing portion of that clamp to a fixed point.  Of course, always make sure you are safetying in the "tightening" direction.

Always start the engine after oil changes and test for leaks. 

When you change your PSRU oil, examine the amount of particulates in the drained oil.  Always check the clarity of the oil in the sight tube.

 

FUEL PRESSURE REGULATOR INSTALLATION

SUBARU H-6

Text Box: Old Regulator

 

 

INSTALLATION:

  1. Disconnect the return hose and vacuum line from the old regulator. Remove old regulator from fuel rail. Drill through the regulator flange side opening (The one where the O-ring is located) using a sharp 7/32 drill. This will remove the regulating function of the valve by opening it. Use a drill to clear out any shavings from each of the two openings and blow through with compressed air and/or carburetor cleaner spray. Lubricate the O-ring with a little oil and reinstall the old regulator onto the fuel rail.
  2. If you have a fuel bypass bleed line is installed, remove it, as the new fuel regulator assembly includes a bypass bleed.
  3. Install bleed hose and new regulator assembly and clamp to engine mount structure. Secure one hose end to the old regulator on the fuel rail using Oetiker clamp. Shorten the existing return hose and install to the new fuel regulator assembly using another Oetiker clamp. Install vacuum hose to new regulator assembly.
  4. Turn on fuel pump and read the fuel pressure on the EIS instrument. Adjust the regulator screw to 30 PSI. Tap the EIS fuel pressure transducer to verify accurate and stable pressure reading. Turn the pump off and watch that the fuel pressure drops to 0 PSI in about 5 seconds. Make sure that the pressure goes to 0. If not, tap the EIS pressure transducer again to verify operation. Your fuel pressure is only as good as what the gauge is displaying so this back and fourth procedure is important. All pressure adjustments are done with the engine off initially to get close, then at idle, with the vacuum hose disconnected from the regulator and the hose to the engine plugged with a screw.
  5. The pressure at Idle, with the vacuum hose reinstalled should be about 30 PSI and must be higher than the setting of the automatic pressure switch. At full power, the vacuum in the manifold goes towards 0, just as if the hose was off, and you should read 30 PSI during cruising flight. Watch to see if the backup pump engages at lower power settings or on the ground due to the two pressures getting very close.
  6. Starting the engine will take a few more blades of cranking but it’s worth the safety and economy that this bleed valve / lowered pressure regulator offer.
With the vacuum hose connected, the pressure will drop to 23-28 during idle operations.

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