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What should the compression reading be

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Firing order for rocam1.6

A six cylinder in-line engine has a power impulse every 720 degrees/6 i.e. 120 degrees of crankshaft rotation. The crankshaft has six crank-throws placed at 120 degrees out of phase with one another, which can be arranged only in three planes. Therefore, the crankpin phasing is arranged in pairs. For heavy-duty diesel engines, seven journals and bearings are provided, at each end and between adjacent crankpins. For petrol engines only 4 or 5 main journals are provided. The firing order with the crankshaft arrangement shown in the attached figure is considered. With piston 1 at the top of the compression stroke, its opposite piston 6 is at the top of its exhaust stroke. Rotation of crankshaft through 120 degrees brings pistons 2 and 5 to their TDC and either one of these can be arrangement to complete a compression stroke. If piston 5 is arranged to be at the end of compression and at the start of its power stroke, then piston 2 must be on its exhaust stroke. Rotation of crankshaft through second 120 degrees positions pistons 3 and 4 at the TDC, so either one of these can be on the compression stroke. If piston 3 is made to be on compression, piston 4 must be on its exhaust stroke. A third rotation of 120 degrees brings pistons 1 and 6 back again to TDC, where piston 6 is arranged to be on the compression and piston 1, therefore, be on its exhaust stroke. A fourth 120 degrees rotation brings pistons 2 and 5 to their TDC. Piston 2 is now on its compression and piston 5 on its exhaust stroke. Rotation of crankshaft through fifth 120 degrees brings piston 3 and 4 to TDC. Piston 4 is on compression and piston 3 on its exhaust stroke. Final rotation of 120 degrees completes the 720 degrees displacement of crankshaft and brings the pistons into positions for the next cycle. This cycle provides a firing order of 1, 5, 3, 6, 2, 4. If the phasing of paired crank-throws 3 and 4 and 2 and 5 are interchanged, then a second equally suitable firing-order of 1, 4, 2, 6, 3, 5 is achieved. This arrangement provides excellent dynamic balance and evenness of torque, and is preferred for engines larger than 2.5 liters provided length is not a prime consideration.

Sep 28, 2016 | Cars & Trucks

1 Answer

How many pounds should the compression tester read?

There is no set amount of compression that is correct as it depends on atmospheric conditions, engine wear, etc. The important thing is that each cylinder tests within 10% of all others. Readings should be taken with throttle held wide open, and for most modern engines 120 to 150 PSI is ok. 90 psi or less usually indicates a problem. Crank engine over 4 or 5 times for reach test, with full battery and all plugs removed.

Mar 09, 2016 | Cars & Trucks

1 Answer

What is the compression for a mazda 1989 b220 0 133.0 engine

good engine condition 155 lbs/sq inch to 165 lbs/sq inch( dry)
no more than 10% variation between cylinders
compression readings of around 120 wet indicate a worn engine

May 19, 2015 | 1989 Mazda B-Series

1 Answer

What is the compression readings for a 1979 c10 i6 250

normal compression readings will be in the 150-165 psi range
There is a permissible 10% differences between adjacent pistons
anything below 120 psi is considered worn engine
really low readings on 1 cylinder indicates
broken ring
scored bore
bent valve
burnt valve
loose valve seat insert
low readings between adjacent pistons indicate a head gasket

Mar 17, 2015 | Cars & Trucks

1 Answer

How can check compression for ford escort 1989 1.9 4 cls

Hi there, I'm AL the owner of Big As Auto Repair.

When performing a compression test on each cylinder they must be within 25% of each other or this will cause the engine to run bad. However, if you have a compression reading of say 120, 125, 115, and 120 PSI then you have something else causing the engine to run bad. If you need further assistance go to my website below. Have an awesome day! Auto Repair

Feb 22, 2015 | 1989 Ford Escort

1 Answer

03 hondaCRV won't start

ok more info... good.
ok , compression is #1 , no amount of spark or fuel makes a dead engine good. (the 120 is low x4 but i bet you didnt do it WOT like the
instructions stated. most cars can do 150 easy. , all my 1.6L do 180.
the reason i ask is the cam belt slips after 50miles and all 4 jugs
drop from 180 to 120 or lower. so did you block the throttle open.
my wild guess is compression really is good and the belt never slipped. yet. (interference engine they are) all of them
so backup and read my post, did you check spark yet.


Jan 09, 2014 | 2003 Honda Civic

1 Answer

I have a mit challenger 2.8 turbo 1997 what should the compression reading be on the pistons

compression readings will be the same as a natural aspirated engine readings Lowest will be 120 psi the highest around 170psi but what ever you get there should not be any more than 10% difference between readings. The turbo doesn't come into it as the compression test is done with no plugs in and at crank speed

Jan 07, 2014 | Mitsubishi Pickup Cars & Trucks

1 Answer

Knocking at upper left front of engine or # 4 cly. Compression on #2 and 3 cly. 210 psi. #1 180 and # 4 120 psi. Thanks, Larry

I think with the lower pressure reading that the knocking will be coming from a broken compression ring or cracked piston. There is only 10% difference allowable between pistons in a compression test.. However check that the valve train is not causing you problems with a failed rocker or cam shaft bush gone.

Mar 31, 2013 | 2002 Saab 9-3

1 Answer

Car wont start, replaced fuel pump. Now I havefuel to cyls, spark @ plug but no ignition, maybe flooded? Any ideas? Please?

you need to do a compression test on all cylinders. All cylinders should have about the same amount of compression with a minimum of 120 psi.
if there is a major drop of compression in a cylinder that means there is a malfunction in that cylinder(bad valve, broken rings, etc
if there is a major drop in compression between 2 cylinders then that means you have a bad head gasket.
if all cylinders read 0psi then you have a broken timing belt
If all cylinders read about the same then you need to check the timing and make sure the cam(s) and crank shaft are still at top dead center (TDC)

Nov 16, 2011 | 1995 Mazda MX-6

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