TheSamba.com :: View topic - Pre-oiling and sudden no pressure. And asking for reasons why?

Sun Dec 07, 2025 3:01 pm

I've run into yet another hickup in the ongoing saga of my 1776 build.

First off, as I write this, it occurs to me that I need to state that this has been one very helpful community and for that and everyone I've engaged with, thank you. I'm on other forums for other cars I have, none are as responsive as this one.

So, for a reminder on what the motor is (probably doesn't matter on this topic but here goes), 1776 build on a new autolinea magnesium dual relief case. Engel W100 cam, stock rods, lifters, rockers, autolinea dual port heads, stock valves.

Ok...so I wanted to pre-oil the motor so I could spin it before first fire up (and without grinding on that new cam till its ready) to lube the oil passages, get it on TDC #1 and set up static timing with the distributor, and then spin it with the starter to check function and pressure of the new untested fuel pump. I'm running dual 34 PDSIT's and they are picky on the pressure I am told, I don't want to be dealing with over-filling carbs and flooding it while breaking in the cam. So I have that set up with a pressure gauge in-line.

Anyway, pre-oiling went great. I built a pressure pot as suggested by Glenn in this post

https://www.thesamba.com/vw/forum/viewtopic.php?t=807079

I am running a remote full flow filter, so I set up with the pressure pot feeding the line from the filter to the motor, with an oil pressure gauge installed into the oil sending unit port. I did it this way, because 1) I wanted a gauge installed in the sender port, and 2) I didn't want to push oil backward through the filter.

This worked well. I had the pot at 25 PSI using a bicycle pump, and the oil pressure gauge read 25 PSI also. Great. You could hear the oil working its way through the motor. One tip, make sure you don't let the pot run dry or you will blow compressed air through the oil passages, effectively un-doing the oiling you just did!

When I had it sufficiently filled, I pulled the spark plugs and and took the rocker shafts out, removed the pushrods (marked to their positions so valve lash will remain unchanged on reassembly) so I could spin the motor without cam contact. I was pleased to see they were all well oiled! total lubrication to the rocker assemblies was achieved oiling it this way, and zero cam or bearing wear.

The pressure oiling works like a dream.

I manually filled the hose from the motor to the filter. Rotated the motor backward by hand slowly, watched the pump draw the oil down in the line. Awesome...confirmation the pump is doing its thing. Rotated forward a little, watched it push the oil back up in the hose.

Put that back together and filled the filter.

Rotated to #1 TDC, set static timing on the distributor to fire at 7.5 degrees BTDC

Decided to engage the starter now to see how much oil pressure it would build, and test the starter engagement, to prime the fuel system to see what pressure it would build also. Enaged the starter, no oil pressure. Quickly pulled the dipstick to see the oil a little more than 1/2 a litre down from where it was...so oil pump is picking up/moving oil...where is the pressure? Hmm...

Checked the obvious, no leaks anywhere.

Disconnected the oil feed line and reinstalled the pressure oiler. Drained the oil from the motor and re-filled the pressure pot, fed it in as I did last time. But this time, no oil pressure.

The oil gauge I have for breaking in motors is old, and I noticed that it had become dislodged from its face. Ok, gauge is likely bad. Bought another.

Hooked that up, started filling with the pressure pot (20 psi), no pressure on the new gauge. You could hear the oil going through the motor again! but no pressure.

Took the gauge off. blew out the tube with air, no blockages, put it back together. Fed in some more oil...no pressure. Took it off again, the tube had no oil in it.

hmmm again! So the gauge is not getting any oil to measure pressure.

Leaving the oil sender port open this time, I pulled the trigger on the oiler and fed more oil in at 20 psi. I got a gentle trickle out of the port. I should have squirted right out of there. So, oil is getting to the top of the motor, but not building significant pressure to register on the gauge or force itself through the tiny tube that feeds it.

So...what could change to where the pressure oiling no longer produced pressure, and neither does a working pump when spinning with the starter?

The only thing that changed was taking the rocker shafts off and pulling the pushrods. Yes, doing this keeps you from grinding away on that new cam until you're ready. But I think it also dislodges the lifters sufficiently to where it can no longer build pressure. I'll put it back together and re-test with the pressure pot...if I am correct, it will build pressure once again on the gauge. But if this is correct it means there is no way I can test the fuel system ahead of time, I will have to just pray its all good and I don't have to interrupt cam break in.

I thought I would share as I had read many posts from folks who like to pull the rocker shafts and plugs, and crank the engine, to save cam wear on a new cam. For those who do, please understand that if I'm right, then you're not building any pressure. You're not pushing oil where it needs to be, and so any benefit you think you are getting from doing it is not there.

I'll report back what I find when I reinstall.

Anyone have any other ideas how to test and adjust what pressure a new fuel pump will build, without endlessly cranking on a new camshaft?

Mon Dec 08, 2025 2:00 pm

How old was the case ? Are you sure that the pressure relief plunger was free to move and return? If that sticks down you will loose pressure : possibly with the engine running, that plunger would have "floated" with the oil flow and returned to rest in the right place .

Without pushrods and rocker arms there would be some oil coming through the cam followers where they would be feeding the rocker arms through the pushrod. That might account for some loss of pressure.

I would not be surprised that if you had just put the engine together, primed the oil pump or just overfilled it so the oil runs into the pump, and started it without taking so much care, you would never have had any problem.

Mon Dec 08, 2025 5:14 pm

So, tonight put the pushrods and rocker arms back in - instantly the oil pressure returns on the gauge when using the pressure oiler.

So, for those who, as practice, pull the rockers off to save the cam while you mess about, you're doing so with no oil pressure and risking running the bearings dry.

mikedjames - the case is brand new.

You're right, I agree it likely would not have had an issue (in oil pressure) by just running it. But if you've ever wiped a new cam, you gain an appreciation of how easily (especially today) it can be done. So I pre-oil with pressure however possible. First VW engine build, but it deserves no less than what I give other motors. Yeah, it would likely build pressure quickly, but it costs nothing to do the extra step.

When breaking in a new cam I don't like messing with unknowns in fuel, spark, etc. so I like to get that all sorted out ahead of time. Usually on other motors, I have trusted components on hand and will do the break in with them. On this one, being the only VW I've ever done, I have new parts and no way to really test them, so I was hoping that pulling out the rocker shafts and backing the lifters away from the cam woudl let me spin it as much as I needed to check the fuel system and pressure (and carbs x 2 for sticky floats) while leaving the cam alone. I now know, you can't do that, you'll do more damage than good. Glad I had a gauge connected to realize it quickly!

Mon Dec 08, 2025 7:07 pm

Talk about the oil pump. New? Did you happen to deadhead it at any point?

Tue Dec 09, 2025 5:22 am

New oil pump. Installed correctly, and primed and tested. Not dead-headed.

The rockers/pushrods provide resistance to flow as oil moves through the lifter and up the pushrods. Taking those out eliminates the restrictions that build pressure, so the oil can just leave the lifters and dump straight into the sump. So to be more accurate, it will build enough pressure to get that far into the motor, but its not enough to register on a gauge (less than 5-10 lbs in my case)

Some also asked about the relief valves, they're good. Have had them out and checked to ensure they don't stick, and they don't. smooth operation without binding but not slopping or leaking past either.

So its just that simple...no pushrods, no pressure. Condition corrected immediately when they were put back in.

Today 6:31 am

Update..,I have seen several YouTube videos of people pulling the pushrods and still getting pressure readings. It makes me suspicious of my conclusion from above.

What can be reasons why removing the pushrods results in no readable pressure, reinstall brings it back?

Oil pump is good, and moves oil (remote oil filter, took off hose and checked action while cranking by hand). Motor is new, case is new, was thoroughly cleaned and rifle-brushed. Dual relief case, new relief pistons and springs, piston action checked, they do not bind. These are the "solid "pistons not the ones with the notch in the side.

With the pushrods installed, my hand pump oiler can maintain 20 PSI and send oil all the way out the pushrods and coat the rockers wonderfully. I pushed 3L of oil through the motor this way.

There are no leaks anywhere.

So...my engine seems to be unable to build pressure without the pushrods, others (very reputable folks) seem to have no problem here and now I see video evidence. It occurs to me that I should solve this before firing it up.

What else could prevent building oil pressure, related to pushrods being removed? I feel like there's something needed to be understood here, and the only thing I know for certain is removing pushrods eliminates oil pressure, bringing them back fixes it, but others have video of achieving oil pressure without pushrods...

Today 7:31 am

its simple, resistance = pressure and Boyle's law.
you removed a good portion of the oiling system there by reducing resistance, less resistance means more flow and lower pressure. theres not much information out there that ive found on a vw oil pump's volume but someone mathed it for a 26mm pump @ 6 GPM, a Porsche's 36mm pump was rated at 12GPM so id figure that 26mm rating is probably realistic.
can your pump up garden sprayer produce 20 psi at even 3 GPM, let alone 6? I highly doubt it.
you maxed out its flow capacity

Today 7:35 am

Thanks...and that's my logic also. I was satisfied with that...until I saw others doing it and achieving pressure anyway, 20-30 lbs based on videos I've seen.

With so many people saying "crank until you have pressure with the pushrods out"...I would have assumed if you cannot actually develop pressure this way, then someone would have noticed a long time ago. Its making me question myself...wondering what else I can check.

Today 9:26 am

If you have normal oil pressure with the pre luber, there is nothing to be gained by solving your mystery

Ive had oil pressure without pushrods on a new motor. It was less than normal than with pushrods.

Cranking rpm , oil viscosity, temp, lifter position , gauge accuracy will all factor in .

Fire it up!

Today 10:07 am

Thanks chrisflstf

So, that's the trick. I do have normal pressure with the pre-luber, but only with the pushrods/rockers in. Take them out, and it also goes to zero.

When I say zero, I mean too low to measure on the gauge. If I pull the gauge out, oil will dribble from the oil sender port. But a dribble is not pressure.

Again I was satisfied that the pushrods being absent was the problem. But then when I see others getting at least some pressure, it makes me go back and wonder.

My motor won't be any different internally than others in terms of oil passages. I considered maybe the pickup tube was an issue, but if I hand crank the motor I can push oil out of the hose to the filter right from the first turn.

I went back and looked at my notes and photos from the build and confirmed that I did put in the block-off plug from the pump outlet (needed for full flow remote filter oiling).

All I really know is I don't want to start cranking it with the pushrods in to discover that there is something else after all. Only thing I can think of is relief valves but they only drop pressure if they get stuck open, mine move freely and the springs in them are new, it takes a reasonable amount of force to compress them.

So, this is me being double (triple) sure that I haven't overlooked something (probably something simple), and if not then I guess just my particular motor with tolerances in the particular parts in that case, has that result.

Today 10:47 am

Pressure readings when pre-oiling is not important. 2psi or 50 psi makes no difference except that the rate of flow is different is all. It's about the passages get filled. Once they are filled and you start the engine you should have instant oil pressure. That is the whole reason for the pre-lube exercise. That is the point when the pressure reading is important.

Today 11:40 am

When I pre-oil, I have the strainer plate plate off and a clean oil pan under. I run the oil through 2 times and then close it up and fill to the mark.