JeffWhite73

I've done some searching, just can't find the answer. Is it normal for my oil pressure gauge in my '73 to read Zero for a short period of time, then start reading?

Alan 71

Hi Jeff,
The oil pressure gauge should begin to register pressure almost immediately upon start up.
How long is the lag you're seeing? Really only a second or two would be typical.
Regards,
Alan

DUB

DEFINE: 'short period'.

And is this 'short period' when you are cranking it up after it has cooled down and not been recently driven???

And when the engine is at operating temperature...and you stop and get a bottled water or whatever..and get right back in the car...does the oil pressure show a value almost right after you crank it?

DUB

JeffWhite73

I was really watching it yesterday, just in my garage...took about 5 seconds approx. From Cold Start.

JeffWhite73

Didn't have a watch on it but around 5 seconds or so, from cold start. Had been driven the day before.
I will get to drive it this weekend and see how it acts after it is warmed up, and restarted, versus cold start.

0Willcox Corvette

I don't think 5 seconds is something to be concerned about... it's a mechanical gauge.. it takes a bit of time to build pressure.

What pressure are you running at when the engine starts and remember as the oil thins the gauge pressure will drop...

Just keep an eye on it and make sure you have pressure.

If you think the gauge bourdon tube is clogged, there are instructions on my tech site on how to clean it out too. http://repairs.willcoxcorvette.com/1...pair-cleaning/

Willcox

DUB

...5 seconds when the engine is cold and being cranked up the first time in that day is something I would not loose sleep over.

DUB

sunflower 1972

FYI, when my C3 has been sitting for a couple of days, I'll crank it over twice about 5 seconds each time BEFORE I set the choke to get an oil pressure gauge reading, then start the engine.

DUB

You are aware that performing this 'cranking method' is not doing anything beneficial.

Simply because you are still cranking the engine with the oil system not being primed. Thus..a dry start....so-to speak.

This is when a pump is needed to electrically prime the oil system WITHOUT any of the internal engine parts moving at all. And the pre-oiling system usually uses a reservoir that can hold enough oil to sufficiently prime the oil system fully and THEN you crank the engine....and then this reservoir will collect the oil needed to do it all over again...thus...the engine is NOT having too much oil in it.

DUB

sunflower 1972

I understand and completely agree with you. I know there is a film of oil still left on various vital engine parts but, it is a mechanical oil pressure gauge and it takes a little time for oil pressure to register. When I get in my 2000 Yukon with 244,200 miles on it,(electronic oil gauge) I just hit the key and go. I start my C3 that way for my own peace of mind of seeing pressure on the gauge before engine start.

DUB

If it makes you feel better doing it that way. Then it is what it is.

DUB

MISTERZ06

ACCUSUMP BY CANTON PRE-OILER HAVE IT ON MY RACE CAR

http://accusump.com/

..................................... tom

sunflower 1972

I'm familiar with Accumsump systems, having crewed on GT1 cars back in the 80's, but it's just a street car, NOT a race car.

7T1vette

Just cranking the car will generate 'some' oil pressure. With a mechanical (Bourdon tube) gauge, oil pressure should begin almost immediately. It may take a second or two to reach full pressure (for the temp oil being pumped); but it shouldn't take 5 seconds unless there is some sort of problem.

1. There could be a nearly-complete blockage in the pressure line going to the gauge. This would delay the time pressure would take to build. This condition would NOT be detrimental to the engine...it would only result in an improper pressure reading on the gauge until it reached actual pressure value.

2. There is a wear problem with the oil pump. Scoring on the side-walls of the oil pump will cause a reduction in pressure generated. If the [eventual] reading on the gauge is about the same as what you have historically seen, your oil pump is likely just fine.

3. There is a leakage problem somewhere in the oil passage system in the engine block. There are 'blind' passage plugs installed in the block following machining. If any of these has become dislodged, 'normal' oil pressure will be significantly reduced and there may be inadequate oil for the engine during operation. Again, if the 'eventual' oil pressure is similar to what you have historically seen, there is likely NO problem.

My bet is on a 'crud plug' in the oil pressure line going to the gauge.

P.S. There is no easy way of clearing such blockage without removing the instrument cluster and then the pressure line from the gauge. It would be best to just 'let it be' until you NEED to get into the gauge cluster for some other purpose.

JeffWhite73

Summer finally arrived here in the Pacific Northwest, so I have been able to get out and drive it....gauge function is intermittent, I am not looking forward to tearing anything apart on the dash!

JeffWhite73

If I were to try a mechanical gauge under the hood, do I simply remove the fitting from the location by the distributor and attach there?

DonnieP73

Yes you can. I did this very option because my oil gauge was stopped
up and didn't work at all. Just buy a cheap mechanical gauge from
auto zone, advance, or similar. I just pushed the line through the
fire-wall though a opening under the dash. Attach the line with the included
fitting at the block and I used zip ties to attach the gauge to the steering column.
This worked fine until I had time to remove the original gauge.
(Which as suggested above, was just clogged up at the gauge)
Unstopped the original gauge with brake cleaner, tested with air
pressure and reinstalled original with new line and remove temporary one.

Donnie

7T1vette

If you still have the mechanical gauge in your gauge cluster, you don't need to replace it because it has gotten 'sticky'. There should be a plastic pressure tube running from the intake manifold (near the distributor) to the gauge. If it is plastic, it has gotten hard and brittle over the years, so any activity on it should be done carefully so the tube doesn't get damaged.

You can carefully remove the nut on the intake fitting to release the tube. If you have an air compressor (even a small portable compressor is large enough), you can hook that up to the gauge pressure line...or even use an air nozzle/gun to mesh with the tube so that you can pressurize it. Set the compressor to 60-70 psi and cycle the pressure ON and OFF several times. If there is some dust/dirt in the gauge rack mechanism, this should dislodge it; likewise if it was getting a bit corroded. And, if there was a gummy oil plug in the line, this should break it up. This will not damage a Bourdon tube gauge, but it will "exercise" it. Try this and then reinstall the tube on the intake fitting. Hopefully, your problem will be solved--without having to dig into the gauge cluster.

P.S. The pressure tube does not need to be filled with oil. Pressure is pressure to the gauge; any air in the line will almost instantly compress to send that pressure on to the gauge.

JeffWhite73

I wondered if something like that would work.......

sunflower 1972

I myself personally, not knowing the age of the oil pressure gauge tubing, would screw around and attempt to clear it out. I would just bite the bullet and buy a new oil line. Just be sure the new line and the brass fittings are CORVETTE SPECIFIC, or else you'll have fun cleaning engine oil from the cockpit.