# Diff. Pressure Checker

Derek Pulvino dbpulvino at hotmail.com
Fri Apr 9 11:59:39 EDT 2004

```John,

Thanks for the info.

Actually, based on your description, it does sound to be the same thing.
One side to compressor, with a gauge to measure input pressure and another
gauge to measure the pressure the cylinder holds.  Then from the pressurized
cylinder, you can also listen to the crankcase breather, exhaust, and intake
to see where the air is leaking out.

The other puzzle I've got to solve is finding tdc on each cylinder.  My
guess is find tdc for cylinder 1, then tdc for the other cylinders will be
72-degrees off...of course following the firing order.

Are we looking more for deviations from cylinder to cylinder or for an
absolute number?  If for the second, can the number be derived from the
acceptable compression numbers given for the 3b in the Bentley?

Thanks again, and hope you don't mind that I sent this back to the list.

Derek P

> > Can anybody tell me whether or not a "differntial pressure checker" is
> > what's used to perform a "leak-down test?"
> >
> > Based on the description -two pressure gauges with a pressure regulator
>in
> > between, inlet hooked to compressor, outlet to the sparkplug hole- it
> > sounds
> > to be.  Somebody I know has an airplane and uses it regularly to
>diagnose
> > engine condition.  Also, assuming I can find the right adapter for the
> > spark
> > plug size, what would be the PSI setting I'd want to use?
>
>Derek, a leakdown tester is a tester just for leakdown and not related to
>differential pressure checker.  Different leakdown testers probably vary
>some from brand to brand...some of them use two gauges, some just
>one...either one does the same results.  Mine has just one gauge...with my
>gauge I need a minimum of 100 psi from my compressor.......plug in one hose
>from the compressor to the tester and...again with mine, others could be
>already have the short hose screwed into a plug hole and after setting the
>gauge to 100 psi I then make the last connection...between the "other side"
>of the gauge and the hose to the plug hole and then note what the drop in
>psi is to that cylinder.  by using 100 psi I can directly relate that to a
>certain percent of leakdown......if it now reads 90 psi I have 10% leakdown
>etc.
>Using the leakdown does take longer than a compression test but the good
>side, it will put you closer to the problem area while with compression all
>you know, there is a problem somewhere.
>
>My leakdown tester came with two spark plug size fittings which so far
>covers everything I need it for.........I haven't messed with those big
>18mm
>Ford plugs for a looong time!
>
>I've used mine for many years on customers VW's and Toyotas and do prefer
>it
>over a compression test
>
>John Gourley

_________________________________________________________________
Is your PC infected? Get a FREE online computer virus scan from McAfee®