Compression test

[EuroDat]

Don't keep pumping the gas peddle between tests.

throttle open or closed does not matter with fuel ratio. Its the plunger that keeps discharging extra fuel for acceleration. That happens ever time you pump the gas peddle. Engines with downdrafts are effected most because gravity helps the fuel flow to the engine. Sidedrafts have less trouble because they dont have the velocity to pull the fuel into the engine when cranking.

[LeonV]

I don't think there is much risk of flooding regardless of the throttle position. I don't think it matters.

The carbs supply fuel proportional to the air flow and inversely proportional to the venturi area. If you've got the plugs pulled, then you'll have minimal air flow. The only cylinder that would be pulling any air in through the carb will be the one currently under test. The other five will be huffin-n-puffing through their spark plug holes.

I'm thinking that even if you do manage to pull any fuel into the one cylinder under test, it'll dry out as soon as you move to the next cylinder?

I agree, I don't think flooding is a concern. I should have said, keeping the throttle closed (on a carburetted engine) while doing a compression test will suck more fuel into the cylinder. Whether that floods the cylinder or not depends on how long it takes the operator to perform the comp check.

throttle open or closed does not matter with fuel ratio. Its the plunger that keeps discharging extra fuel for acceleration. That happens ever time you pump the gas peddle. Engines with downdrafts are effected most because gravity helps the fuel flow to the engine. Sidedrafts have less trouble because they dont have the velocity to pull the fuel into the engine when cranking.

EFI and round-top SUs will not care how many times you pump the pedal between tests. Triples, 4-barrels and other carbs with accel pumps will...

[71Nissan240Z]

Different guages will give you different readings. The important data from your test is how close the numbers are together. I remember I got 185-190 on each cylinder l28 flat tops.