L6 Oil Pumps
Originally submitted by T:
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==Oil Pump L6 Engines:==
===Operation:===The Oil Pump consists of a drive shaft, two spur gears, a pressure relief valve and a by-pass valve, all of which are enclosed in a cast-iron body.
The internal spur gears are driven by a helix gear that is mounted at the end of the pump drive drive shaft.
The helix gear is pinned on the drive shaft by a roll pin, and this in turn is mated to the gear on the camshaft.
Note The Oil Pump can be removed from the side of the engine without the necessity of engine removal
The Oil Pump assembly is mounted on the external right hand side of the Engine Block by four long bolts (5/16").
====Oil Pump:====Oil is drawn up from sump pan to the pump body, the oil passes through a wire mesh screen and a suction pipe to the oil pump via drilling's in the crank case and the inlet side of the pump assembly. From there the oil is delivered into the full flow oil filter, then the oil is directed through the filter adaptor hole and channeled through passages in the crankcase to the crankshaft bearings. The pressure regulator valve regulates the oil pressure 30 to 44 lb. sq at 1,500 r.p.m.
===By-Pass Valve===The by-pass valve is so positioned that should the full flow oil filter become some what restricted due to foreign matter, the oil distribution to the bearing will not be effected, so therfore the oil distribution to the bearings will not be effected,
Correct oil pressure:
500 rpm 10 lb. sq. in (minimum) oil temperature at approx 160 f , and increases at 1,500 rpm to 30-40 lb. sq. in
The Oil By-Pass Valve operates 9-11 lb. sq. in pressure differential, assuming that SAE 20 M.S. Grade or equivalent multi-grade oil is being used.
===Removal of Oil Pump:===First remove the full flow filter, anti-clockwise, from the oil pump adaptor, then remove the four corner bolts on the pump body assembly 5/16 in, holding the pump to the engine block.
===Disassembly:===Remove the two smaller 1/4 in screws, holding the cover plate on the pump body, now withdraw the driven gear. Remove the roll type pin from the helix gear at the end of the drive shaft
Remove the drive shaft and gear from the pump body
Slacken, then unscrew the special plug retaining the regulator spring and valve
===Inspection:===Clean up all of the parts with solvent
Inspect to see that the pump body has no excessive wear
Check and make sure the drive shaft is tightly pressed into the gear, the over-all length end to end is a distance of 4.83 in to 4.84 in
Check for looseness between the drive shaft and the housing, if wear is apparent in the shaft/housing then replace
Place the gears back into the housing as the clearance between the gear and the housing must be between .002in to .004 in (maximum)
Now check the end of gears to the pump body face, make sure the surface is clean , no gasket residue, use a straight edge , a steel rule will do, the gears must stand proud of the pump body face .002in (minimum)
Now check the gear backlash, this should be within the range of .009 in to .015 in.
Check the pressure regulator valve in the bore of the pump, it should fit freely thought the length of the bore and minimum clearance
Check the regulator valve spring to see its not worn or collapsed, the length should be approximately 2.172 in the length under load 5.12 +.40 - .20 lb. should be 1.375in.
Check the cover plate for wear so as not to permit oil to pass through the ends of the gears.
Visually inspect the by-pass valve assembly for damage or broken spring,
Finally check the helix gear for excessive wear or any damaged teeth
===Assembly:===Reverse to Disassemble, but use new roll pin, a New gasket, use the genuine GMH gasket between the end cover and the pump body to maintain the specified end clearance of the pump gears
===Torque:===The two small bolts for the cover plate pull down to 5-6 lb. ft. make sure that the drive shaft moves freely, fit New gasket and bolt the pump assembly to the engine block using the 4 long 5/16 in bolts, 17-22 lb. ft.
So in all, the workings of the oil pump is a rather an excellent design, if the oil is starved because the oil filter is blocked, due to lack of service, foreign body from say the fiber timing drive gear, sludge, carbon build up etc, the oil can still get through via the by-pass valve,
There are other ways the oil may be restricted, these can be as follows, loose bracket connection the suction pipe, blocked pick up screen, worn star gears in pump housing, no drive from helix gear, no oil in sump pan.
To gain a more insight of the oil pump workings and part names etc of the oil pump, I have some pics in my shed,
===Testing Oil Pump Pressure===The engine lubricating system incorporates a "tell=tale" which glows oil preasur drops below 3=5 lb. per sq. in. Some times the warning light might flicker or glow when idling when the engine is hot, providing it does not show when the engine speed is increased. However if the light remain illuminated while your engine speed is equivalent to 20 15mph or say 20kph ,or above in top gear, then stop engine and investigated immediately.
Note: this condition can be cased by a grounded circuit between the "tell-tale" light and switch, a defective or incorrectly calibrated oil pressure switch ,a blocked filter screen, or the oil assemble requiring over-hauling.
Above Submission by Jacks.
===Oil Pump Failures:===When an Engine has had a lot of use, the Oil Pump may leak Oil. Do not simply tighten the Bolts to stop the leak. The gaskets will have shrunk. If the Bolts are tightened the Oil Pump's internal clearances will reduce and the Pump can sieze.
The Pump should be removed, inspected and have new gaskets fitted to ensure that the gear to faceplate clearance is preserved.
Be aware that the 2 small Bolts are very lightly torqued. The 4 outer Bolts are torqued to a much higher torque. Te 2 small Bolts can strip and break if they are over torqued.
===Priming L6 Oil Pumps:===When a new oil pump has been fitted to an engine,
the dry gear teeth are not able to draw oil through them.
This is caused by the fact that excessive clearance exists between the gear teeth and the pump case. Normally this is not a problem because the oil that fills this clearance space is much thicker than air.
On Grey engines, the oil pump sits at the bottom of the sump, completely immersed in oil so priming is not a concern.
In red/blue/black 6 cylinder Engines the pump sits on the side of the Engine and at some height above the top of the oil level.
In the case of red/blue/black 6 cylinder engines the oil pump often has to be "primed" with engine oil or some other substance to allow the oil pump to prime properly.
I've never been able to get a red or black engine to prime from cranking alone. I've found that at least idle engine speed is necessary.
On red/blue/black 6 cylinder engines, taking the pump apart and flooding it with engine oil will do the trick. Some have suggested removing the oil pressure switch and pumping oil in from an oil can will also prime a red/blue/black 6 cylinder oil pump.
With red/blue/black V8 engines, grease may be required.