Compression Figures?

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pos

pos

Well-Known Member
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3,685
Location
West Yorkshire
Hello,

I am going to perform a compression test on my 200TDi, does anyone know what the compression readings should be, or be around?

Thanks
-Pos
 
not sure where the disco bloke gets his figures from ?

i'd be expecting something over 400psi - but it's the relative results you need to consider, LR recommend not more than 70 psi difference between any cylinder
 
Cheers Sean. No doubt the garage will have some sheets or at least a spec page in a booklet that will provide the factory fresh pressures. Also, do you know what psi my turbo should be producing as standard?

Cheers
-Pos
 
The Mad Hat Man said:
wot yu gonna check compression with? It will need to be a special diesel tester, coz normal petrol ones may not go high enough.
Click to expand...

My local specialist has a diesel compression tester :) Is there a difference between a compression tester and a cylinder leakage tester?

-Pos
 
yes cylinder leakage is external compressed supply that tests valve and ring blow by and also headgasket.

Compression tester will only tell you what compression an engine can generate
 
Thanks for the info. Well I know that they have a diesel compression tester of some shape or form. They also have a different bit of kit that connects up to an air line, is that a leakage tester or is it likely to be a different compression tester?

-Pos
 
The Mad Hat Man said:
thats a leakage tester. they set the piston to TDC and then put 100PSI (nom) into the cylinder and see what it settles to when the air supply is shut off. see here
Click to expand...

Well that sounds like a better bit of kit then :) I'll opt for that me thinks. So it basically forces air into the cylinder and then displays how much air is being lost? I think that their bit of kit is only a single gauge tester.

-Pos
 
hughesy said:
Oy pos you should have stuck to your old 2.5 n/a this tdi you've got sounds like a pile of ****e:D
Click to expand...

I think it's alright, I just want to make sure that the bores are sealing as well as eachother. When i had the head off a few months ago the bores were in good condition with the cross hatching still clearly visible, no glazing and no scoring. It is possible that there will be some leakage from the valve seals, but they're easily replaced.

I also noticed today that when removing the fuel filter, it wasn't holding much fuel. The central cavity (where fuel is drawn towards the injection pump from) was empty but there was plenty of fuel in the filter matrix around the outside of the cannister. The filter is brand new - and is not clogged. I also fitted a new Delphi lift pump, but when the engine is turned over it doesn't launch fuel at the bonnet, it kind of "blubs" out to about the same height as the glow plugs, that isn't right is it? The lift pump on my N/A would launch it at the bonnet and all over the engine bay.

-Pos
 
big ad said:
how much is the test going to cost as i might get that done on mine soon.
Click to expand...

Don't know. My local specialist will charge an hour for it so about £40 plus VAT, but I might be able to do it myself (if I can borrow their kit) - I do them plenty of favors!

-Pos
 
Well I did a leakage test on it today and managed to pull three glow plugs apart in the process :eek: The good news is that each cylinder is running at or around 95% efficiency, which is quite good me thinks :) I also double checked my lift pump which was doing bugger all in the way of lifting fuel, there wasn't a drop being pumped through and i only put it on a few weeks ago. I took the pump off to fit another pump only to find that after I'd put a new pump on my old one was working again, so i swapped them back and put the old one back on. I can only assume there was some dirt in the spring mechanism that had been dislodged when I removed it and manually pumped the cam lever (not the front priming arm). Now it needs the fuel knocking up very slightly and I think it's as good as it was. It still seems to have a bit of a flat spot, but I'm guessing that is the fuel pump being restricted when the pin hits the cone on the boost diaphragm?

Just to add to the fun, when I was leaving my engine just stopped. It didn't wobble or judder, just a clean cut stop. Stop solenoid I thought straight away and rightly so, the wire had snapped nicely in two :doh: Fixed that and it's running again now but I'm still not 100% happy. I shall have to find some tinker time over the weekend.

-Pos
 
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