New engine rebuild, NO OIL PRESURE!!

[Gearhead1956]

Just rebuilt my Robbins 295 4 stroke 1996

Fired it up with valve cover off and noticed no oil flowing.

pulled oil pressure sending unit and sure enough no oil. started engine NO oil.

Loosened bolts holding oil pump, (thinking maybe I had them two tight) no oil

Pulled oil pump, looks ok.

With inner rotor shoved into outer rotor at one end I have .005 clearance 180 out between inner and outer. I would think that would be good?

Block was cleaned and all passages was blown thru with compressed air.

Is there any way to prime this oil pump? The engine did run for about 30 sec. 2 or 3 times! Think I should of had oil by then. ??

[clr.R4tch3t]

Old hot rod trick is to pack the pump with peterolium jelly. It will lube it up, gives it some body to creat suction in the pick up tube, and it will break down in the oil eventually so you don't have to worry about it.

[Spicyunicorn]

With valve cover off put a shop vac over the oil supply passage (fan side) and turn motor over had this same issue a month ago and the vacuum helps prime the oil pump

[sonnyk]

After rebuilding aircraft engines, we would remove a pipe plug on an oil gallery, and connect a pressure pot to prime until we saw oil coming out at some other location on the engine.
Some folks would just motor the engine with the top spark plugs removed until oil pressure shows up on the cockpit gauge. If the pump is having trouble picking it up, the first method I described always works.

[sonnyk]

Not familiar with this engine myself (new guy here), but the sending unit port would work, assuming it is a pipe thread.

[Gearhead1956]

I did the petroleum jelly packing, After reading that I do remember hearing that back in the 60's. I also poured oil down the sending unit hole.

That worked! Got oil to shoot out of the top of the head. Thanks Guys!

I have put about 4 miles on it now and the oil light still comes on at idle. Checked E-bay for a new pressure sending unit, they wanted $40 for a $9 switch! LOL

I now know you this thing had a rod knocking when I got it! Someone has messed with the governor. I will GPS it, But I sure I was doing 30-35 MPH. I was able to catch car in the subdivision.

[clr.R4tch3t]

And to think I was born in 87 and still knew about it. Just proves that you can learn a thing or two about a thing or two if you know the right people and ask the right questions. Haha

[Gearhead1956]

Originally Posted by clr.R4tch3t

And to think I was born in 87 and still knew about it. Just proves that you can learn a thing or two about a thing or two if you know the right people and ask the right questions. Haha

Yea, I have reached the age where I have now forgot more then I know! LOL

Sad thing is, its the truth. CRS

[dundeebarnbuggy]

Before you buy a new sender, why not check the actual pressure at idle? Even a dial type tire pressure gauge will work for testing. Usually low pressure at idle is a sign of too much bearing clearance or worn pump. What was the clearance between the gears in the pump and the housing? End play can be reduced by carefully sanding the pump body on a flat surface, wear inside can't.

[Gearhead1956]

Originally Posted by dundeebarnbuggy

Before you buy a new sender, why not check the actual pressure at idle? Even a dial type tire pressure gauge will work for testing. Usually low pressure at idle is a sign of too much bearing clearance or worn pump. What was the clearance between the gears in the pump and the housing? End play can be reduced by carefully sanding the pump body on a flat surface, wear inside can't.

I agree on the bearing clearance on low oil pressure.

But this engine has no rod bearings and what we would call the mains are roller bearings on the end of the crank.

Now the oil pump cover had a dent in it, witch was odd given the fact there is no way to get to that cover with the fan and shroud on the engine.
I took the dent out and smoothed out the inside of the cover 800 grit paper.

These rods were machined in CHINA!!

The clearance in the pump with inner rotor shoved tight at one end and measured 180 degrees from that point was .005, which should be good.
Outer rotor to housing is to close to measure.
The pump housing is made into the engine cover and what they want for the oil pump, cover and sending unit is just crazy!
I may try a direct gauge. but first I think I will change the oil. I used 5w30, thinking I may go to 10w40