[T3] No oil pressure
Jim Adney
jadney at vwtype3.org
Sat May 11 22:17:22 PDT 2013
On 10 May 2013 at 8:40, David Sanderson wrote:
> I'm seeking some help as I have run out of ideas regarding my newly
> built motor - a motor with no oil pressure.
There are a couple things to check. Mainly that the holes in the pump
body match up to the holes in the case. The early large hole cases
made circa 1970 had hole positions that were later changed enough
that they won't work with the later pumps. Proper pumps for those
cases were discontinued long ago. If that's your problem, you might
be able to find a decent used one, or it might be possible to modify
the case and/or pump to work together.
Other possibilities:
The drive gear is slipping on it's shaft. It's just a press fit.
That's usually enough, but sometimes this fails. The press fit also
makes it possible to adjust the length of the input shaft to make
sure you have plenty of, but not too much, engagement with the slot
in the camshaft.
You should always put some oil in the pump when you install it, The
oil helps the edges of the gears seal well, so that the pump can
prime itself. Otherwise, air can just slip past the edges of the
gears and you'll never develop enough vacuum to draw the first oil
into the pump. And, like all the other moving engine parts, it's
always best that they be pre-lubed for the first startup.
Speaking of dry startup, one thing that lots of people miss is to
install the crank seal dry. All oil and grease seals, and their
mating surfaces should always be lubricated when installed. It only
takes a few seconds of dry running to ruin one.
One way to test that the pump is working, before you actually start
the engine, is to remove the oil pressure sender and install a long
plastic tube using a 1/8" NPT plastic fitting. Run the tube back to
the oil filler pipe, so you won't make a mess, then crank the engine,
with the spark plugs and pushrods out. You should feel air coming out
of the end of the tube and then watch oil come thru.
Testing with a tube like this prevents air pressure from being built
up in the oil galleys ahead of the incoming oil. This also helps the
pump prime itself, by removing the need to overcome that pressure.
Finally, sometimes the problem can just be in the pressure switch.
I've had engines where the sender choose that time to die, just from
sitting around for a couple months. But ISTR that you said you tried
a different sender.
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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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