bikedaft
Well-known member
3gm30f has 3, one for each cylinder
Compression testing. Is this a thing?
- Thread starter IanCC
- Start date
IanCC
Active member
I have been shown this from a thread on Facebook. It's bottom half of a 3gm30 injector with compression guage screwed in. And holding plate fits as well!
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IanCC
Active member
So get old injector, pull guts, weld up fuel inlet. Drill and tap fuel return hole to take pipe fitting you want for guage.
DinghyMan
Well-known member
Because not all sizes and types can be bought off the shelf as most kits seem to assume you have a vehicle engine with glow plugs
Same as the injector removers, easy if you have a vehicle but we make the Volvo TAMD removal tool as they are uncommon, and a tad pricy for the genuine Volvo tool
scottie
Well-known member
how much specialist time can you buy for £20 plus cost of old unit
IanCC
Active member
Specialist diesel injector shop pop tested 3 injectors, reshimmed all 3,with print readouts of pressures before and after. £20 cash. I know.
IanCC
Active member
If only i knew which yanmar tractor was the equivalent.
COMPRESSION TEST ADAPTER - SMALL
Also Kiene Diesel Tool part no. C3083 i believe is correct for anyone passing this way.
DinghyMan
Well-known member
If you can send me some dimensions from your injector I can make a dummy injector with a PCL line fitting on or similar?
scottie
Well-known member
Yes you won a watch there but perhaps stole a deal
sleep well
IanCC
Active member
PM sent
DinghyMan
Well-known member
And responded
rogerthebodger
Well-known member
If you do a leakage test you may find out what the exact issue is leakage test
Leakdown Test
The leakdown test measures how well the cylinder is sealing. This is done by inserting compressed air (around 100 psi) into the cylinder at TDC and then measuring how much is lost from the seals (there will always be some). This is done by two gauges on the leakdown tester—see the photos for more information on how to use the tester.
As with the compression test, you want the numbers to be within a percentage of each other. The leakdown test can also help you pinpoint the problem before tearing down the motor by listening for the air escaping the cylinder. Once the cylinder is pumped up, listen for air escaping from the cylinder and where the sound is coming from. Here is a list of what to listen for:
Air escaping out the PCV, road draft tube, oil dipstick, or oil cap: indicates that the piston rings in that cylinder are worn and pressure is getting past them, or that the cylinder itself is scored or damaged.
Bubbles or pressure in the coolant: indicates that the head gasket has been compromised or the cylinder head is warped or cracked.
Hissing or whistles from the intake: indicates that the intake valve seat is not seating properly or there's a bent valve.
Hissing or whistles from the exhaust outlet or manifold: indicates a worn exhaust seat or bent valve.
Sounds from a cylinder adjacent to the one you are testing: indicates a bad head gasket or warped head.
If you find that the cylinders are making and holding compression, it lets you know that your power issues are one of the basic three things needed to make power: fuel, air, or spark. These generally tend to be much cheaper than a problem in one of the cylinders, which usually leads to a teardown and rebuild. The compression and leakdown tests can tell you the health of the inside of the engine without a computer and without a teardown.
Leakdown Test
The leakdown test measures how well the cylinder is sealing. This is done by inserting compressed air (around 100 psi) into the cylinder at TDC and then measuring how much is lost from the seals (there will always be some). This is done by two gauges on the leakdown tester—see the photos for more information on how to use the tester.
As with the compression test, you want the numbers to be within a percentage of each other. The leakdown test can also help you pinpoint the problem before tearing down the motor by listening for the air escaping the cylinder. Once the cylinder is pumped up, listen for air escaping from the cylinder and where the sound is coming from. Here is a list of what to listen for:
Air escaping out the PCV, road draft tube, oil dipstick, or oil cap: indicates that the piston rings in that cylinder are worn and pressure is getting past them, or that the cylinder itself is scored or damaged.
Bubbles or pressure in the coolant: indicates that the head gasket has been compromised or the cylinder head is warped or cracked.
Hissing or whistles from the intake: indicates that the intake valve seat is not seating properly or there's a bent valve.
Hissing or whistles from the exhaust outlet or manifold: indicates a worn exhaust seat or bent valve.
Sounds from a cylinder adjacent to the one you are testing: indicates a bad head gasket or warped head.
If you find that the cylinders are making and holding compression, it lets you know that your power issues are one of the basic three things needed to make power: fuel, air, or spark. These generally tend to be much cheaper than a problem in one of the cylinders, which usually leads to a teardown and rebuild. The compression and leakdown tests can tell you the health of the inside of the engine without a computer and without a teardown.
IanCC
Active member
That's amazing, a whole new world opens up.
I guess there is no "petrol or diesel" leakdown testers, unlike compression testers, because they all operate at circa 100psi. Is that right?
rogerthebodger
Well-known member
Amazon.com
You may need an adaptor to fit your injector hold which you are talking about to DinghyMan
You may need an adaptor to fit your injector hold which you are talking about to DinghyMan
DinghyMan
Well-known member
Probably going to go with Euro Air Line fittings on the dummy injector so that they will work with both compression testing and leak down kits
May also need an injector puller as well
oldharry
Well-known member
I never bothered with compression testing a diesel. It only tells you there is or isn't a problem. Leak down tests tell you so much more.
IanCC
Active member
Hmm, but surely no point in doing leakdown if compression good?
rogerthebodger
Well-known member
If a diesel runs it ha enough compression to start it may lose power due to leakage via the valves piston rings etc when running
A leakdown test will show you this where a simple compression test will not
You can do both if you wish but the leak down test will show you where the fault is where a compression test will not
AntarcticPilot
Well-known member
A thought, but couldn't you do something similar without compressed air or anything but the engine? Turn the engine MANUALLY until it's at as high a compression as you can manage, and simply hold it there. If the force required to hold it diminishes, then the compression is being lost, and all the other symptoms you describe can be looked for. On most older engines with relatively low compression, you might actually be able to turn it through maximum compression, in which case holding it just before that point would do the trick.
This is a thought experiment - I haven't actually tried it except to get a general idea as to whether the compression on all three cylinders on my VP2003 is about the same. But you could go all scientific and use (for example) an old-fashioned torque wrench (the kind with a pointer moving over a scale) to see if the torque required to hold against the compression remains constant when holding the crankshaft at a specific angle.
I'm in Hong Kong, 5913 miles or so away from Capricious as the crow flies , so I can't try it!
rogerthebodger
Well-known member
Well In thory you could do that may be an a single cylinder but on a multi cylinder the other cylinders would interfeat with the test and the friction would ffect the resistance.
The ait need continuous fees so yon can lisson for where the leakage is going
The ait need continuous fees so yon can lisson for where the leakage is going