At 4:36 PM -0400 7/8/05, ROBERT DONALDS wrote:
>I think the vac pump and the oil pump are driven by the same shaft
>so they may not be spining at first start up. the timing  belt may be oil
>soaked does the intermediate shaft pulley run off the smooth side of the
>belt ?
>me thinks it does time to pull the timing cover off
>Bob

To me it seems odd that the vacuum is not coming up.
It should take the vacuum some time to fill up the reservoir anyway.
Are you sure the vacuum buildup is different when the oil pressure
comes up normally?

The reason I ask is that I've seen this unprimed oil pump problem on
two 50 degree gas engine installs. One was a older 1.8L motor and the
other was my 2.0 ABA that didn't start having the problem until
recently. It now has 80K hard miles and I'm replacing it.

The 1.8 motor, oil pickup and pump were replaced (used motor) and it
still had the problem.

The gas engines run the oil pump off the distributor shaft so I know
the oil pump is turning in them. Yet they still can have trouble
coming up to pressure.

On the 1.8L motor the problem was solved by adding a accumulator type
pre-oiler used by racers. It pressurizes the system as soon as the
key is turned on and in doing so primes the pump. On the 2.0 I just
start it. If the pressure does not come up right away I hold it at
2500 rpm and it comes up within 10 seconds. Heck, It was time for a
new engine anyway.

I have read somewhere that the lack of a windage tray in the 50
degree installations allows the oil to froth and that contributes to
the pump losing prime.

So I don't know if we have similar or different problems, but it does
not seem uncommon.

Do you rev your engine pretty high? In both these cases the engines
tend to see 5K to 6K rpm range. One particularly stubborn time of no
prime the 1.8 wouldn't prime was after parking after a climb to
Tahoe. This could point to a oil frothing connection.

hth,
--
  -Otmar-
82/86 Stretch Vanagon Westfalia GTI. "Power of two" Soon to be TDI.
http://www.evcl.com/vw
1 914 EV, 1 Insight Hybrid