Oil to Camshafts but none to Gauge. Why not?

[TroonSprint]

After 50 years of working on engines, my Sprint twin-cam has me puzzled. The engine has been reconditioned and carefully assembled. About two weeks ago I went to start it for the first time in 38 years. After cranking it with the plugs out for an age, there was no reading on the oil pressure gauge. I took the end plate off the new pump and squeezed some petroleum jelly in there, and after that it was OK. The engine started and had an oil pressure reading of around 40 psi. Great.

I haven't tried to start it again until this morning. As before I took out the plugs and cranked it on the starter motor, but after repeated attempts, again there is no reading on the gauge. So I removed the gauge pipe and adapter from the side of the block and cranked again. No oil came out of the hole.

Looking through the oil filler cap it seemed quite oily in there, so I have removed the cam cover and cranked it on the starter again. Lots of oil is finding its way up to the camshafts and small puddles are forming around the cam followers, so there must be oil pressure. And yet no oil at all, not one drop, has come out of the hole in the block where the gauge plugs in.

I'm baffled. What the heck is going on? How can there be sufficient oil pressure to push it up to the head and yet apparently none in the side gallery? All suggestions gratefully received as always.

Mike
I now understand why one of the correspondents on this site has the by-line "Sometimes my Lotus makes me cry"!

[promotor]

The side gallery is where the oil for the crank main bearings, jackshaft and ultimately the camshafts get their oil supplied from - so if the cams are getting supplied then HOPEFULLY your crank is getting oiled. That would be a major concern for me! However, it may not be as simple as that.

Looking at the engine from the drivers side - from the top of the oil delivery passage (from the oil pump) the oil normally takes a turn left to the rear of the engine and also right to the front of the engine. It's possible you have a blockage between where the oil leaves the delivery passage from the oil pump and the gallery up to the pressure sender take off where the oil turns right. Something to consider is maybe the engine has residual oil in the galleries that is getting pumped out up to the camshafts but the engines ability to pull up oil from the sump is being hampered. If this is the case then maybe you don't have a blockage and you have an oil pump suction problem due to a pickup pipe blockage etc.

I would want to check that oil is being pushed out of the 1/8" NPT plug that is situated under the passenger side engine mount (if you can get to it without too much issue and providing it's not seized in or too tight!!) as the hole under that plug is part of the main oil feed from the oil pump and sees the freshly pumped oil before the crankshaft main bearings do. I would hope that is an easier starting place than taking the engine out!

[TroonSprint]

I understand what you're saying. I have Miles Wilkins engine book and have been studying the oil diagram at the front. But there isn't a hope of removing that small screw plug on the exhaust side without removing the engine mounting, and even then it's painted over. I have probed with fine wire in both directions from the oil gauge take-off point and can find no obstruction. Neither should there be - this engine was thoroughly cleaned, and is as clean inside as it is outside.

I'm not sure how to proceed - I really, really don't want to take the engine out! What is extremely puzzling is that two and a half weeks ago it was running and the gauge was working. In the intervening time I have been building up the doors and haven't touched anything under the bonnet. So why can't I get the gauge to work now?

Keep the ideas flowing please.
Mike

[AHM]

The small puddles on the cam followers are always there - designed to lubricate the cams before you get oil pressure.

If it has been standing it can take a long time for oil pressure to build if you are only cranking - you can hear the note change when it does finally build pressure.

[TroonSprint]

OK, thanks guys for your comments. Here's where I am now. I took the face plate off the brand new pump again this afternoon and saw that it was very oily in there. Oil dripped out. Anyway, I pushed some more petroleum jelly into the spaces round the rotor and re-assembled. Turned the engine on the starter once more, and within 10 seconds the gauge was reading 40 psi. I turned it over for several short bursts and can see that the camshafts are being well lubricated with plenty of oil oozing out from all the journals. Pressure on the gauge was steady at 40 psi. I have one of those modern pre-engaged starters, so it turns over very smartly.

Why the oil didn't get to the gauge earlier is a mystery. Let's see how it is tomorrow. Time to go indoors and start cooking dinner.

Mike

[AHM]

If you start the engine you get oil pressure instantly, just cranking takes much longer.

It may have taken most of your afternoon, but better to play it safe.

[Gordon Sauer]

When I was getting my car back on the road last year, I cranked and cranked and cranked it with the starter and never got oil pressure or oil coming out of the gauge tube. I was frustrated and wasn't sure what to do but I knew when I put the car up everything was fine (22 years earlier!) so I started it, had immediate oil pressure and been fine ever since. I've always questioned whether you can really get oil pressure to show on the gauge just by starter cranking; (Starter cranking is also insufficient to let you know if your headlight pods will pull down with vacuum!) I don't have anything but the original starter so slower cranking speed. Gordon Sauer

[mbell]

I get pretty similar behavior out of mine. If it hasn't been run in a while it basically won't build pressure unless you run it. Goes straight to 40+ PSI when running

I've had some partial success by reverse priming the system using a weed spraying bottle to pump oil in the pressure gauge take off. Once I've been able to use this measure to get it to build pressure on the starter but it hasn't always worked. It at least ensures there is some fresh oil at the bearings when the engine is started.

Due to re-start mine soon so expect to be breaking out the weed sprayer again.

[tonyr27]

I had the opposite earlier in the week, insufficient power in the battery to start the engine but the oil pressure gauge indicated pressure when cranking the engine!

TonyR

[toomspj]

Do you have an oil cooler - these can easily get blocked and can give intermittent flow. If you do, I'd replace it pronto! If you don't just ignore my comments.

Paul