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Normal vacuum gauge reading?

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scott_duerring

Regular Contributor
What is considered a "normal" vacuum gauge reading for an 8.2 MPI Crusader engine? Both of mine read 14-15 at idle with the gauge plugged into manifold outlet for the fuel regulator.
 
Thanks for the replies. Originally I thought it was a little low as well but I got a "curb side" opinion that for these 8.2 s it is in the normal range because of the fact they are put together a little "looser" (my term) than the smaller 7.2 s and such.
I know these gauges are amazing cheap but effective diagnostic tools, is there a way to use them to determine if you have a dead or dying cylinder? Say in a situation where you get a good compression reading but it may be masked because of oil leaking past the oil ring? I know the unplugging the spark plug wire step but was just wondering if a vacuum gauge could be an easier way to see if the condition exists.
 
As long as it is consistent (steady) I'd say you are at the low side of ok (GM service data says 15-20 in Hg at ECU set idle )...

Which ECU do you have? The newer ones have a diagnostic called a cylinder power balance test that will quickly point you down that path (ID the "problem cylinder")... a leakdown test may still be needed for additional insight.
 
makomark said:
As long as it is consistent (steady) I'd say you are at the low side of ok (GM service data says 15-20 in Hg at ECU set idle )...

Which ECU do you have? The newer ones have a diagnostic called a cylinder power balance test that will quickly point you down that path (ID the "problem cylinder")... a leakdown test may still be needed for additional insight.
Click to expand...

If I understand your question, I have the Gen. 3 program. I had sent the ECUs into Pleasurecraft in 2008 and they "updated" some of the programming to get better performance but do not think they changed the basic program of the gen. 3 .
 
They likely did NOT change the program, only the points in the fuel map and/or the timing curve....

I checked my Rinda manual. It says the cylinder power balance test started with the MEFI-4 ECU's... :-(
 
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