How to compression test diesel engine ?

[rdp50734]

I want to compression test my engine, I have borrowed my mates kit.

Where do I do the compression test?

 

On my old petrol engines I tested through the spark plug but with the diesel and the injectors being inside the rocker cover I'm not sure...

 

Do you test through the glow plug hole? 

 

I have on glow plug that is useless with a replacement on the way.

 

I have the 1.4 tdi 80 bhp estate BNV engine code.

 

Thanks.

[coskev]

Yeah glow plug hole.

What size threads are in your kit?

[hutchysrs50]

I needed a special kit for testing my PD engine, mostly because of how narrow it goes where the glow plugs are. So It can be tricky...

Edited 11 February, 2016 by hutchysrs50

[mogwye]

Me too.

 

DB.

[rdp50734]

Thats great thanks!

 

In the kit there is M10 x 1, M10 x 1.25, M12 x1.5 and M14 x 1.25.

 

It has dummy injectors but I don't think I need them? M20 x 1.5 and M24 x 2.0

 

I do have a faulty glow plug too, which a new one is on order.

[coskev]

You might aswell fit a set of glow plugs,seeing as they are all coming out anyway and don't cost a lot

IIRC the thread size is M10x1

Have you ever fitted glow plugs before?

[rdp50734]

I've never fitted glow plugs no. I did order just one but yeah would make sense to change them all.

 

From the glow plug description it was M10 x 1

 

I have the torque setting for them and know how to use it lol.

 

Do you start the engine or not when compression testing as I'm doing it by myself so not sure I'll see the gauge from the cabin.

[hutchysrs50]

You don't want the engine starting at all!

Disconnect the injector loom on the right side of the block, the big round plug with a red tag on.

[coskev]

As above,injector plug is the easiest way to stop it starting.

I wouldn't torque the glow plugs,but interested to know the figure you've got?

They are a tapered thread,so they seal,so you need to be careful when fitting them that you don't overtighten them

[rdp50734]

Is that this one? 

 

 

also here is the torque figure from the haynes manual.

 

[hutchysrs50]

Yep that done.

Iirc the torque figure is usually writen on the side of the box the glow plugs come in, have for me anyway but will depend what kind you get.

It's a low figure around 5nm off the top of my head though. Just checked the picture, 15nm will be correct then

Edited 12 February, 2016 by hutchysrs50

[rdp50734]

Right just taken it off to try it and make sure the engine doesn't start and now after putting it back on I have a flashing coil on the display!

 

Any ideas what that is?

[SuperbTWM]

Right just taken it off to try it and make sure the engine doesn't start and now after putting it back on I have a flashing coil on the display!

 

Any ideas what that is?

If you have turned over the car without the injectors plugged in it will have logged a fault code for the injectors

[rdp50734]

Yes, Ive been out and reset it. The unit I have though doesn't give an error code.

 

Just out of interest what psi should I be seeing on testing.

 

I know its more important that they are all balanced but still would like to know.

 

Also, if one is down/up is that when you do the lash adjustment or something else?

[sepulchrave]

Yes, Ive been out and reset it. The unit I have though doesn't give an error code.

 

Just out of interest what psi should I be seeing on testing.

 

I know its more important that they are all balanced but still would like to know.

 

Also, if one is down/up is that when you do the lash adjustment or something else?

 

Lash adjustment is for the injectors, not the valves.

 

If you have a cylinder down then you'll have to take the head off and reseat the valves.

[SuperbTWM]

What were your results?

[rdp50734]

I haven't done it yet.

 

Just getting info right in my head before I do it this weekend or next.

 

Reseating a valve sounds involved.....

 

Fingers crossed they are fine!

[mogwye]

When I compression tested my 80 bhp TDI after it had had new valve guides, valves lapped and a new head gasket; with a cold engine it recorded.

 

Cyl 1 - 445

Cyl 2 - 445

Cyl 3 - 460

 

DB.

[rdp50734]

Thanks mogwye!

 

Its been running a bit rough lately and sluggish to pull off but 1 minute in and it runs fine.

 

I also have the BNV engine but there doesn't seem to be much info on that engine even in the haynes manual.

[mogwye]

I think the Haynes manual was published way before the BNV engine came along, maybe the MK2 Fabia Haynes will have the relevant info - Can anyone confirm this ?

 

DB.

[mogwye]

Thanks mogwye!

 

Its been running a bit rough lately and sluggish to pull off but 1 minute in and it runs fine.

 

I also have the BNV engine but there doesn't seem to be much info on that engine even in the haynes manual.

 

Have you carefully checked that the Torsion Value is set exactly at 00:00 - Makes a big difference to performance and MPG.

 

DB.

Edited 12 February, 2016 by mogwye

[rdp50734]

I haven't checked the torsion value. 

 

I do want to do it but I have a mac so can't use vcds to check on a computer and physically Im unsure where it actually is.

 

I have read the guide but Im weary about messing it up.

[corndog]

You can use virtualbox to virtulalise windows on your mac to use VCDS. Works great

[rdp50734]

Nice to know, I do have bootcamp but I had read that it doesn't work properly.

 

Will give virtual box a try! Thanks.

 

Do you take all 3 glow plugs out or just the one that you are compression testing?

[sepulchrave]

All of them so the engine spins freely.