Help with compression testing...

[salty_dog_68]

So, my reliable old Westerbeke 58 has started blowing white smoke with the exhaust and there is a gurgling sound coning from the raw water siphon break. I want to do a compression test on the cylinders to see if it yields any clues. I have done compresskon testing on a gasoline engine but neber diesel. So, I purchased a diesel compression testing kit with the glow plug adapters. However it looks like I will have to remove the fuel lines or possibly even an injector or two to get the glow plug adapters into the glow plug holes.

My question is this: If I have to unhook the fuel line from the injector will I get an accurate reading or will there be some blow back through the injector giving a false low reading?

I have scoured the interweb looking for a video tutorial on marine diesel compression testing but have not been able to find anything. Does anyone have a link to a compression testing tutorial?? Thanks in advance for your input.

[delmarrey]

I've always tested thru the injector hole, which gives you a slightly lower reading due to the injector missing (adding more air space).

But I'd connect hoses to the injector tubes and run them into a fuel can. And crank over the motor, with the glow plugs out, for a little while to make sure it will NOT start.
I would think if the motor starts with the gauge attached it may BLOW the gauge APART! ��
If you were to disconnect the main fuel line, the Injector Pump (IP) would run dry. The IP requires fuel as a lubricant. As well, you would probably have to prime it to get going again.
With a common rail/electronic injector system you could just disconnect to wires to the injectors and/or the pump itself, depending on design?

You may want to consult with Westerbeke as to RPM and pressure. And they may even have a procedure for glow plug hole testing. (508) 823-7677

[Dymaxion]

In addition to basic compression testing the is leakdown testing that is done using an air compressor and the engine fixed at TDC one cylinder at a time. Leaks via valves show as noise at intake or exhaust (and bubbling), noise heard at oil filler if rings, and bubbling into coolant system if head gasket. Helps clarify things. HTH

[DougR]

The basic steps for your test are:
- run the engine to warm it up
- remove all of the glow plugs in the engine, and remove any high pressure fuel lines as necessary for access to the glow plug position
- the injectors need to be in the cylinder in question or there won't be any compression
- if your stop solenoid is "energized to stop" , tie the solenoid in the "no fuel" position with string or wire....if the solenoid is "energize to run", disconnect the wire from the solenoid. If you have a manual stop cable, pull the cable out and leave it out. In all of these cases you are preventing fuel from being injected. There will be plenty of fuel in the injection pump to do your testing without hurting anything
- insert the glow plug adapter in one cylinder and connect the gauge to the adapter
- crank the engine 4 or 5 compression strokes until the gauge stops climbing or the recording arm stops moving on the recording card
- record the reading if you're using a gauge, then release the pressure in the gauge and move the gauge and adapter to the next cylinder and repeat the process

There won't be any blowback thru the injector. Typically opening pressure for injectors for your engine will be somewhere between 2500 & 3500 psi, and the compression you will be measuring will be running between 350 and 400 psi.

DougR

[olaf hart]

Originally Posted by DougR

The basic steps for your test are:
- run the engine to warm it up
- remove all of the glow plugs in the engine, and remove any high pressure fuel lines as necessary for access to the glow plug position
- the injectors need to be in the cylinder in question or there won't be any compression
- if your stop solenoid is "energized to stop" , tie the solenoid in the "no fuel" position with string or wire....if the solenoid is "energize to run", disconnect the wire from the solenoid. If you have a manual stop cable, pull the cable out and leave it out. In all of these cases you are preventing fuel from being injected. There will be plenty of fuel in the injection pump to do your testing without hurting anything
- insert the glow plug adapter in one cylinder and connect the gauge to the adapter
- crank the engine 4 or 5 compression strokes until the gauge stops climbing or the recording arm stops moving on the recording card
- record the reading if you're using a gauge, then release the pressure in the gauge and move the gauge and adapter to the next cylinder and repeat the process

There won't be any blowback thru the injector. Typically opening pressure for injectors for your engine will be somewhere between 2500 & 3500 psi, and the compression you will be measuring will be running between 350 and 400 psi.

DougR

Thanks Doug.
How would you test an engine with no glow plugs, like a 2000 series Volvo?

[DougR]

For many years Volvo Penta has offered a German compression tester called a Moto-meter as a special tool. This tool has a paper card which records the compression pressure of each cylinder and thus provides a written record of the test. Very clever device....

Each engine type has an adapter for the Moto-meter which fits that particular engine, either in the injector opening or the glow plug opening. In the case of the 2000 series the adapter resembled an injector. To do a test on a 2000 series engine, all the injectors are removed and the adapter is placed in the first cylinder, and the test performed. Then the adapter is moved to the next cylinder, and so on until all the cylinders are tested.

DougR

[skipmac]

Hi Eric,

Don't know if I mentioned this or you already know but the W58 just a Perkins 4.154 with red paint. The only difference is how Westerbeke sets up some of the heat exchangers and maybe the manifold.

A lot easier to get info and parts searching under the Perkins model.

[salty_dog_68]

Thank you for the responses. I started my troubleshooting at the raw water circuit and my problem turned out to be a piece of pencil zinc stuck in the outlet hose barb on the heat exchanger. Always a blessing when a problem looks serious but ends up being something simple. I can go back to referring to my auxiliary power as my "trusty old westerbeke".

[delmarrey]

Yep! Most motor problems usually come down to lack of a scheduled maintenance program.

I credit the Navy for leading the way in my stewardship on small boats!