Topic: Rebuild 750k4- no oil pressure

[lash]

Completely stumped on this one. On the engine stand with oil tank hooked up for an oil pressure test. Ran with the starter several times and no pressure on the gauge. Pump has been primed in an oil bath and all the air out of the pump. Tried pouring about 2 qts. of oil down the cam chain hole to fill up the oil pan- still no luck. Changed the oil pump to a different one- nada. Remove the filter and there is no oil getting that far from the pump. The oil gallery from the pump to the filter is clear but no oil has come through it.
Hopefully someone has seen this before and has a solution!

[Ujeni]

I haven't had this issue, but I have built these engines many times. Here's what I would do if it happened to me.

• You have tried two oil pumps. I assume both pumps are assembled properly and in good working condition. I will also assume that all seals and collars are all installed properly when mounting the oil pumps. If that is all true, then it is safe to say that it isn't your oil pump. Honestly, that was my first thought though. I would have taken out the pump and rebuilt and tested it. Moving on...
• Are your oil lines from the tank allowing oil into and out of the engine? If they are clogged somehow, then even the two quarts of oil you poured into the pan might not be enough to build oil pressure. I could be wrong about that as I have never had this issue. Its worth inspecting your oil tank and lines to make sure they are clear.
• Tell us about what you did to the engine cases. Anything that could clog them if missed during cleaning? It might be worth tracing the oil path through-out the entire engine to make sure all oil gallies are clear.

[BenelliSEI]

That is very strange. Any chance the line from the tank to the suction side of the oil pump is air locked? With the pump removed, does oil flow from the tank out the suction port?

[PeWe]

Air bubbles must be helped out of the pump when priming.
The pressure relief valve keep air if not opened when priming. Remove the nut, prime and see the bubbles coming out when rotating the sprocket.

Rotate the sprocket while blocking one of the 2 holes for oil lines with a finger. You'll feel a hard underpressure when pump is working. Like blocking a vacuum cleaner.
Then rotate in the other direction and blick the other hole. Try the other direction or block other hole if not working at all.
If no underpressure, air is in there.
My pumps had air blocked by relieve valve.

Really thin oil in pump must be easier to prime.
I flushed pump with naphta in the 80's to clean it. Never an oil pressure issue.
I just started it and saw oil pressure lamp shut off very quick.

[lash]

John, you’ll never guess what engine this is! I have tried all the above and still nothing. Next will be to try a different oil tank and lines to see if that has any effect. I will re blee d the pump like Pewe suggests and see what that does. The galleries are open at least to the main one that crosses the engine where the pressure switch is, as I have a gauge installed on the end and I can read pressure on it if I blow air in the filter hole. Out of town today so I won’t be able to do anything but will post the outcome this week.

[newday777]

Lash
Did you bead blast the cases?

[BenelliSEI]

John, you’ll never guess what engine this is! I have tried all the above and still nothing. Next will be to try a different oil tank and lines to see if that has any effect. I will re blee d the pump like Pewe suggests and see what that does. The galleries are open at least to the main one that crosses the engine where the pressure switch is, as I have a gauge installed on the end and I can read pressure on it if I blow air in the filter hole. Out of town today so I won’t be able to do anything but will post the outcome this week.

Dwayne….. Petty sure I guessed! I’d check the obvious first.
1. Hook up a hose to the back port that supplies the pump. Is the port clear to the pump pick up. Put some air on it or pour some oil through (pump removed)
2. Is the pressure port from the pump to the filter open test with air.
3. Are the  pump drive gears properly aligned and pump is spinning?
Assuming the pump is bled of air, oil should move! I’m sure you figure it out!

[lash]

The cases were vapor blasted and washed thoroughly. Ran a tap through all threads. There is no oil coming through the gallery from the pump to the filter so it has to be the pump or the tank, or both.

[BenelliSEI]

The cases were vapor blasted and washed thoroughly. Ran a tap through all threads. There is no oil coming through the gallery from the pump to the filter so it has to be the pump or the tank, or both.

Agreed. Possibly the hose from the tank. The supply hose is on the rear engine port?

[lash]

Rear is supply. Going to try different tank and hoses.

[BenelliSEI]

Rear is supply. Going to try different tank and hoses.

Good Luck!

[Bodi]

The pump inlet comes direct from the tank, so putting oil in the sump won't help and may overflow the tank once you start the engine and the scavenge pump does its job.
It takes some suction to open the antidrainback valve in the pump to open. And that might be stuck closed. Did you check them on your pumps? The oil pump is not a good vacuum pump. Filling it with thick oil (90wt?) before instlling one will help it pull air to open that valve. Or you can remove the piston and spring, get oil pressure, then put them back in. Messy and a PITA but if desperate?

[lash]

60 psi on the starter! Finally! After taking the oil pump out so many times I think I have more oil on the floor than in the engine, but at least now success . Another air purge in the oil bath and a change of oil lines and tank fixed whatever problem I was having. I also know I am getting oil flow to the cam towers so the valve cover can go on and I can get this finished.
Thanks for all the replies and ideas.

[Ujeni]

Glad you got it working! I'm still betting it was your oil lines. Don't use the old ones in your next build until you confirm they are ok!

[lash]

That is probably what the problem was, however the lines I used the first time were brand new steel braid lines made by a forum member. They had flow but obviously not enough. Second time around I used an old set and that worked.

[HondaMan]

I am finding in nearly all of the pumps in the last few years that the shaft seal must be replaced, due to the age of the neoprene - it is getting stiff. The worn rubber lip on this seal only makes sealing pressure once the main PSI is over 5 (to squeeze it shut), so when the scavenge chamber (on the other side of the seal) is empty or full of bubbles there is no pressure differential to make the old, stiff rubber press closed on the shaft. For the last 18 months I've had to change the seal on every pump, even very low-mileage ones, because the seal rubber won't flex anymore. As soon as I change it things work perfectly, so it's worth the extra effort, IMHO.

[lash]

For sure on my next one but how to you get that little sucker out?

[BenelliSEI]

Well that’s all good news! It’s going to look good in my K6. Well done. J.

[HondaMan]

For sure on my next one but how to you get that little sucker out?

Oddly enough, I use a tiny screwdriver from one of those sets of 'jewelers screwdrivers' I got at Ace Hardware. It is hardened and tiny, lets me get into the edge of the seal and bend it inward. Then I nab it with some [also tiny] aggressive needlenose pliers and pull it in, then it curls up and comes right out. Afterward I use 2000 grit emery to smooth out any divots. The new ones go in about halfway, then they need to be tapped down and seated. For that I use one of the larger jewelers' screwdrivers, or sometimes a cut-off nail I made (no point or head) for this purpose, that fits in between the seal and the inner metal edge. Two or 3 taps and it's home!