compression tester

[Batista230]

Hi
I have been locking for a compression tester for diesel engine on ebay
The ones marked for diesel seam to go for big money
But the one that say petrol, start at a tenner

http://cgi.ebay.co.uk/PETROL-ENGINE...t=UK_Hand_Tools_Equipment&hash=item19c0fdcb76

http://cgi.ebay.co.uk/AUTOMOTIVE-CO...iagnostic_Tools_Equipment&hash=item230c744e07

I seams that you thread the test into where the spark plug threads
there are several kinds of threads for spark plugs and my question is; is there a way of getting these compression tester to fit and seal into where the injector goes into a diesel engine

Thanks
James

 

[Tmoose]

I think a diesel's cranking compression would exceed the gage's capacity, and might even damage the one-way valve, hose and fittings.

 

[potteryshard]

Could easily damage the operator as well; we're talking some serious pressure here. Having to pull the gauge needle out of one's forehead is annoying.

 

[Batista230]

What kind of PSI are we talking about here for diesel engines

 

[patprimmer]

over 300 psi I would expect or 20 bar.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[catserveng]

There are two issues with finding a compression tester for diesel engines.

First the pressures are higher than those found in a spark ignited engine, some diesel engines I'm familar with have a cranking compression pressure of nearly 400 PSI.

Next, gas engines use spark plugs, usually 14 or 18 mm threads, so a couple of adaptors will allow a pretty broad use of the test tool. For diesel engines you typically need to remove an injector or nozzle, and the test adaptor needs to be the same size/shape as the removed component. No standard for most engines, every manufacturer has their own injector, hard to find a one size fits all tool for that.

You can likely make an adaptor from an old injector if you carefully gut it and have a good fabricator make up your adaptor for the check valve and gauge. But make sure it fits well and is well made, as you could up end with an unwanted addition to your forehead, as pointed out above.

Hope that helps, Mike L.

 

[BrianPetersen]

For VW engines you use the glow plug hole, not the injector hole.

The glow plugs on a VW TDI are M10x1.0 which are the same as most modern motorcycle engines use for their spark plugs, so that's the adapter you use.

And don't forget to find a way to disable fuel supply prior to cranking the engine to check the compression ...

 

[Batista230]

For Mikes idea of making the attachment from an old injector
This could be done I suppose, taking the inners of the injector out and cutting a thread inside it
But I need a pressure gage of up to 400 psi right not 300
So what I need to do now is find a pneumatic gage of 400 psi
And find a thread cutter with the same thread on as the end of the gage

Thanks
James

 

[thruthefence]

I would also suggest that you use a better quality hose than that which is supplied with a 'cheap' gasoline engine compression tester.

 

[dgallup]

By the time you upgrade the hose & gage, make adapters, etc. you could probably just buy the correct tool and be done with it.

 

[evelrod]

Might I suggest simply doing a leak down test if you are diagnosing a compression problem. Same adapters as stated above but less drama.

As to the pressure...What's the problem with only 400psi? Right tool for the job too expensive? I've got IC race engines that are pumping 250 plus and I use a regular gauge that reads to 400.

Rod

 

[Batista230]

Well as you can see the injectors are out and are somewhat grubby
Just I though if I cleaned them up put them back on would the engine fire much easyer

As dgallup says this is quite a farce
If i threaded a nut onto the fuel inlet of the injector as seen in the photo and threaded a reducing bush inside the nut to thread onto the end of the gage tester or visor versor
That would allow me to put the compression tester stright onto the injector without removing the injector only to remove the compression nut from the injector pump
I cant find my fella gage so I dont know what size thread it is
It looks to course to be pipe thread but if it was I would say 1/4 BSP /NPT
Could be metric course though
Only way to find that out is with micrometers and fela gage??

Rod
For I leak down test dont I need the following
2 x gages
pressure regulator
and an orifice?

Thank
James

 

[Batista230]

Hear I have found a pressure gage

http://cgi.ebay.co.uk/63mm-Hydrauli...174?pt=LH_DefaultDomain_3&hash=item3a614da71e

I have bough gages from this firm in the past for pressure washer on cleaning plants
The gages worked well
However the gage is for hydraulic and dose not state pneumatic
So how do you think it would work with air as opposed to liquid??

 

[evelrod]

I have no idea how difficult it is to order from the U.S. but if it is anything like when I order from the UK...

A couple cheap alternatives for the DIYer...It's not Snap On, but it gets the job done at a quarter the price.

http://www.harborfreight.com/automo...iece-diesel-compression-tester-set-46800.html

http://www.harborfreight.com/automo...e-diesel-engine-compression-tester-93644.html

http://www.harborfreight.com/automotive-motorcycle/diagnostics/cylinder-leak-down-tester-94190.html

http://www.harborfreight.com/automo...r-fuel-injection-pressure-test-kit-97706.html

Rod