Compression Test Tool...will this work or
 

am I about to set off a bomb?


Kevin

How is the guage going to hold the pressure to let you read it?

well...
 

I guess someone will have to crank the engine while someone reads the gauge. It really needs a check valve or something like that doesn't it?

Kevin

yes....thats exactly what it needs...becasue I am not sure you could get an accurate reading without it.

Even if you could get a decent reading, the reading would not be correct due to the volume of the piping to the gauge. This increases the cylinder volume significantly. The only way to get a true reading is to have a check valve very close to the glow plug hole. Additionally, the inside diameter of the pipe should be small to cut down on the volume. You then must crank the engine through several cycles to compress the air in the pipes a little bit each cycle until the pressure in the pipes gets close enough to the pressure in the cylinder. After enough cycles, the gauge will stop increasing in value. That's fairly close to the actual cylinder compression.

I couldn't read the gauge too well, but you had better hope that its at least over 300psi. otherwise, BOOM!

I have exploded one.
 

In my early diesel days, I used a hand-held Craftsman compression guage (the kind with the rubber tip) designed for gasoline engines. It only took 1 attempt when the guage went "boom" in my hand. Fortunately I wasn't hurt, but it was enough for me to purchase a real diesel compression guage.

SteveM.

As for the gauge...
 

It registers 1000 p.s.i. and I may just go ahead and purchase the real deal.

Kevin

With a compression ratio of 22:1, you would need a gauge capable of 22* 14.5 = 320psi.
The selection of a gauge of 1000psi seems a little high, but much better than one of 300 psi ;)

the compression in a diesel will
 

be wayyyy over 320 PSI, could be enough over to blow up a 320PSI gauge.

As long as the tubing can withstand the pressures, your contraption should work with a check valve thatr is

mercedes 300td compression
 

has anyone made a hollowed out injector to use with a differential compression tester like they use on small aircraft engines? to check for individual cylinder component failure; with each cylinder checked at tdc on compression stroke.

I was not saying the Combustion pressures!

Our diesels typically have a compression ratio of 22:1 - correct?

Air pressure is around 14.5 (or is it 14.7 I can't recall)

Thus, the compression pressure in the cylinder (without fuel injection) WILL be compression ratio times air pressure. ie 14.5 * 22 = (Do your own maths here!)

Am I missing something?

Carefull
 

I'd be more afraid of the brass piping and connections holding the pressure. That could really be a bomb.

Hmmm
 

Compression readings.

400 to 420 PSI is normal

With blown intake turbo seals you can get 500 or higher = bad news.

Whunter, surely the Turbo wouldn't make any difference when cranking the engine for a compression test? All injectors out, only the pressure gauge & adaptor connected.