am I about to set off a bomb?


Kevin

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

__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
---------------------
Section 609 MVAC Certified
---------------------
"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

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.

__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
---------------------
Section 609 MVAC Certified
---------------------
"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

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!

__________________


1980 500SE/AMG Euro
1981 500SEL Euro
1982 380SEL
1983 300TD
1983 500SEC/AMG Euro
1984 500SEC
1984 300TD Euro
1986 190E 2.3-16
1986 190E 2.3
1987 300D
1997 C36 AMG
2003 C320T 4matic

past: 1969 280SE 4.5 | 1978 240D | 1978 300D | 1981 300SD | 1981 300SD | 1982 300CD | 1983 300CD | 1983 300SD | 1983 380SEC | 1984 300D | 1984 300D | 1984 300TD | 1984 500SEL | 1984 300SD | 1985 300D | 1986 300E | 1986 560SEL | 1986 560SEL/Carat | 1987 560SEC | 1991 300D 2.5 | 2006 R350

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.

__________________
'93 190E/D 2.5 Turbodiesel 5-speed (daily driver)
'87 190D 2.5 Turbo rustbucket - parts car
'84 Dodge Rampage diesel - Land Speed Record Holder
'13 Ram 2500 Diesel
'05 Toyota 4Runner

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

__________________
Tony from West Oz.
Fatmobile 3 84 300D 295kkm Silver grey/Blue int. 2 tank WVO - Recipient of TurboDesel engine.
Josephine '82 300D 390kkm White/Palamino int.
Elizabeth '81 280E, sporting a '79 300D engine.
Lucille '87 W124 300D non-turbo 6 cylinder OM603, Pearl Grey with light grey interior


Various parts cars including 280E, 230C & 300D in various states of disassembly.

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

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?

__________________
Tony from West Oz.
Fatmobile 3 84 300D 295kkm Silver grey/Blue int. 2 tank WVO - Recipient of TurboDesel engine.
Josephine '82 300D 390kkm White/Palamino int.
Elizabeth '81 280E, sporting a '79 300D engine.
Lucille '87 W124 300D non-turbo 6 cylinder OM603, Pearl Grey with light grey interior


Various parts cars including 280E, 230C & 300D in various states of disassembly.

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

__________________
1984 280SEL, 62,000 miles
Euro model in the USA
1983 300D (Totaled out 10/2004)
New Factory Mint Green paint
Palomino int
1982 240D (Steak dinner for two)

Compression readings.

400 to 420 PSI is normal

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

__________________
ASE Master Mechanic
asemastermechanic@juno.com

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D
1984 190D
2003 Volvo V70
2002 Honda Civic

https://www.boldegoist.com/

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.