Your best analysis based on vacuum readings will come from your own experience, however.
Current the options are: How Will a Compression Test Help? It might be worth reviewing at this point how an engine actually works. The inlet valve opens allowing air and fuel mix through the carbs into the cylinderthe piston draws down at this point creating a vacuum to suck the mix in.
At the correct point in time hopefully!!! Then as the piston rises in the cylinder once more, the outlet exhaust valve opens to blow out the spent gases.
At each point the correct things must be satisfactorily sealed — The pistons must be sealed against the inside of the cylinder at all times or gases will leak past.
As the bore is circular the piston head has a series of o-rings around it to achieve seal. The valves must also close properly against their seats at the correct points in the cycle or gas will rush past. These seats in particular need to be watched in older cars such a the MG as the engineers relied upon lead in the petrol to lubricate the process.
If the engine has been run on unleaded pertol without a lead substitute the seats can wear and recess into the head and breaking the seal with the valve. The valve seats and the piston o-rings seal the moving parts, but additionally cylinder head must be sealed against the cylinder block by means of the head gasket.
By measuring maximum pressure at the bang point we can get some idea about the effectiveness of the seals, and with a bit of know-how we can get an idea about which seals are the problem. To do measure this we use a hi-gauge compression tester — a device which fits into the spark plug socket.
Performing the Compression Test In practice performing the compression test is easy — remove all the spark plugs so the engine turns more easily under the starter motor screw in the tester to the cylinder you want to check and turn the engine.
Repeat for each cylinder noting your results as you go, this is the dry test. Repeat again having squirted engine oil into each cylinder the wet test — the oil acts as a seal on the piston, so problems with the o-rings will result in a significant rise of compression between wet and dry tests for a given cylinder.
First up draw up a grid, one column for each cylinder and two rows dry and wet: The compression tester — as I said get hold of one with a 14mm thread for the MGB, there are quite a few on ebay and Amazon.
Your spark plug spanner of choice, and oil can with engine oil in it. A bit of paper, masking tape and pen.
You might also like to use a remote starting kit the type that lets you turn the starter motor with a button while working in the engine bay I just went back and forth between the engine and the cab and used the key like the pleb I am.
Labeling the leads — I also leave a tally mark as well as the number, in case of smudging. Labeling the leads The labels were to allow me to re-attach the leads in the correct order, because I like to be able to start my engine. The spark plugs removed.This information describes how to test engine vacuum and what to expect in results when testing.
It notes common faulty readings and the possible causes. Gasoline Engine Vacuum Testing & Specifications How to Test Engine Vacuum on Gasoline Engines. How to Perform a Static & Dynamic Compression Test.
In this video, . A vacuum test is one of the simplest and most effective diagnostic weapons the shade-tree mechanic has in his arsenal. With an inexpensive gauge, you can gain insight into the symptoms of vacuum leaks, incorrect timing, low compression, sticking valves and more.
Engine Testing with a Vacuum Gauge Vacuum gauges have been a valuable tool to mechanics for years. Even with modern computer controlled engines a vacuum gauge is still a valuable tool for diagnosing engine and transmission problems.
Compression Testing; Leak Down Testing; If you hook a Using a Vacuum Gauge to Check Engine Performance up to an intake vacuum source, it can tell you a lot about your engine’s health.
For now you can use this next test to see if you have and exhaust restriction. It’s a pretty cool test, I . Engine Performance Testing with a Vacuum Gauge.
You can determine the location of the leak by doing a compression test. Remember, engine problems can affect transmission performance. If you suspect an engine problem, connect a vacuum gauge to the intake manifold. Note the location and action of the vacuum gauge needle, and .
Two Stroke Vacuum/Pressure Testing ¶ A Two Stroke Engine must have compression above and below the piston rings. We all know about taking engine compression readings from the spark plug hole but a lot of people seem to forget that a two stroke engine must have a sealed bottom end that will hold both compression and vacuum.