This problem is driving me crazy - if you have any suggestions please let me know.

I have a M110 6 cyl 2.8 K-Jetronic that is showing a steady 10-12 inches Hg, instead of the expected 18-20. I can't find any inlet side leak. I've pulled the hoses for the tranny and locking and capped them - no change. I've set the timing, mixture - no change.

Can worn valves produce this? A compression test reveals low-ish compression, but is this enough to give half the vacuum? Am I missing something obvious?

The car is down on power, most noticable at low revs.

Any ideas? Much appreciated.

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'79 280SE
'87 560SEL
'83 280CE
'01 Nissan Micra
'98 VW Passat
'83 911 turbo

Any time the motor is inefficient it will have reduced vacuum.

I doubt that you will find many M110 engines running with 20in of vacuum at idle. To verify whether you are running efficiently the exhaust gasses should be checked and the unburned hydrocarbons evaluated.

And double check that timing. If it ain't pinging give it another 5-10 degrees and see how the vacuum looks.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Thanks for the advice, Steve, I'll check it out! - Jack

__________________
'79 280SE
'87 560SEL
'83 280CE
'01 Nissan Micra
'98 VW Passat
'83 911 turbo