Vacume

usma41 · Post by **usma41** » Tue Mar 27, 2007 11:06 am

Wes, I have 15lbs of Vacume, taken from the wiper supplie side, is this correct?

Post by **wesk** » Mon Apr 02, 2007 11:13 pm

At what throttle setting (RPM)?

maeserik · Post by **maeserik** » Tue Apr 03, 2007 12:25 am

i have 17 just behind the pcv valve on ± 650 rpm, it is the highest steady vacuum possible, reached wihile adjusting timing and no pinging during acceleration. i have average fuel use 14-15 liter for 100 km = 3.7 usgallon for 62 miles

maybe this info can help

usma41 · Post by **usma41** » Tue Apr 03, 2007 3:15 pm

Can't say what RPM but it was at Idle.

maeserik · Post by **maeserik** » Wed Apr 04, 2007 12:03 am

you must adapt the vacuum gauge direct at the intake manifold without with no influence of the vacuumpump on the fuelpump

if you have 15 lbs and the needle is steady everything is OK

eventualy advance the timing a little more to get a bit more vacuum

if the jeep drives fine without hesitating leave it that way

Post by **wesk** » Wed Apr 04, 2007 10:01 am

The detailed answer is in TM 9-8012 for the M38 Page 80, Paragraph 79c6.
Idle 650 RPM vac at manifold elbow 18 to 21" at sea level (subtract 1" of vac for each 1000' above sea level.

For the M38A1 use TM 9-8014 page 103 paragraph 107 which shows 17 to 21" at sea level.

artificer · Post by **artificer** » Fri Apr 06, 2007 2:02 pm

Nice to see others using a vac gauge to its full potential. Here is a good link
http://www.secondchancegarage.com/public/186.cfm