Oil pressure gauge needle bouncing?

[hobbes_the_cat]

This is a problem that I have had ever since I swapped in my new (to me) motor. The oil pressure bounces about 10-15 psi all the time; idle, revs , whenever. I talked to the guy who built and raced the motor and he said the oil pump had a lot of races on it and that it was probably wore out, so today I swapped in another used pump that I know is good and my gauge does the same thing! So I put the original pump back in and took a vid of the problem. It has a home- built oil pan that has had lots of races on it so I assume it was built right. don't think I am low on oil, the dipstick actually reads a little high because I put half a qt. extra to try and cure the problem. The motor is a LZ21 (Z22 block, L20 crank, L-head.) any ideas???

[datzenmike]

The stock gauge is damped so it takes 10-15 seconds for it to rise from 0 to 40 pounds. This is so owners don't flip out when the gauge briefly drops from a hard corner or stop. For all I know this is perfectly normal... pressure goes up, relief valve opens... pressure goes down... repeat. Did the same with two gauges so probably normal unless the after market sender is weird.

[hobbes_the_cat]

Well I had the same gauge on my l18 and it was always smooth and steady and this is a mechanical gauge. The pressure relief valve explanation makes sense tho...

[bananahamuck]

but if it was a pressure relief , how come it always drops 5 psi no matter what the pressure..?? i.e. If it was a set pressure it would go back to that pressure not just drop 5 ...right?

[datsunaholic]

How many filters have you tried? Only time I've ever seen anything like that was low oil. Heck, could be harmonics.

[hobbes_the_cat]

I thought low oil too, but the PO said the dipstick was accurate. The filter is new but nothing special, not a fram tho! Do you think it's cavitating or something? Maybe I will try a better quality filter like a k&n...

[wayno]

That is annoying, it's as if the oil pickup tube has a hole in the side of it, and it keeps sucking air, but the hole isn't big enough to stop it from continuing to pick up oil.

Do you have another oil port to put the oil pressure hose, maybe farther away from the oil filter.

[EricJB]

Sorry cant watch the vid while I'm at work. Is the gauge electric or mechanical? If it's electric, check your ground strap from the motor to the chassis.

[hobbes_the_cat]

That is annoying, it's as if the oil pickup tube has a hole in the side of it, and it keeps sucking air, but the hole isn't big enough to stop it from continuing to pick up oil.

Do you have another oil port to put the oil pressure hose, maybe farther away from the oil filter.

I have the line hooked to the same port everyone else uses, is there another please to hook it up?

Sorry cant watch the vid while I'm at work. Is the gauge electric or mechanical? If it's electric, check your ground strap from the motor to the chassis.

The gauge is mechanical and worked fine with the previous motor.

[Z-train]

Worked fine before means nothing.Stupid stuff first:

 

1)borrow another guage to varify

2) the filter

3)relief valve

4) pump

[datzenmike]

Worked fine before means nothing.Stupid stuff first:

 

1)borrow another guage to varify

2) the filter

3)relief valve

4) pump

 

A different pump was used... no change.