Very odd compression readings!

[hollowaykid]

I have a 1.6 pinto in my capri. After having stronger firing on no.1 and 3 i thought id get my hands on a compression tester after changing plugs and leads to see if it was that but nothing.

 

Anyway the readings i got are strange but seem oddly correct!

No.1 i got 125psi

n0.2 90psi

no.3 125psi again (thinking ok somthing was wrong with no.2)

no.4 90psi

 

this seems really odd too me is anyone able to shed any light on this?!

 

thanks, Stu

[supersport]

was that a dry test? try doing it again with a bit of oil down the plug hole.

[hollowaykid]

i did put a drop down there. seems really odd

[w p e]

throttle wide open aswell.

[hollowaykid]

what shall i open it?!

[72mk1escort]

yes mate get someone to press the trottle to the floor when you do it or pull the cable or carb linkage under the bonnet.

 

If when you do it with a bit of oil down the bores it increases that means either your rings are shot or the bores or knackered or a bit of both.

 

Hope this helps you mate

[hollowaykid]

How does it make a difference with the throttle opened? Not critising just curious because wouldn't the valves be shut anyway?

[vibrating_Cake]

is it running twin carbs? or single?

 

i had readings like this when i had a floppy butterfly (dont know the technical term, but it was "too closed" in the throat on zero throttle, the clearances were wrong. giving low readings on closed throttle on that cylinder.

[hollowaykid]

What do you mean by too closed?

I've got a brand new 32/36 dgv like on the 2.0l.

[vibrating_Cake]

ahh its alright then, that wont cause it.

on twin carbs you have 1 butterfly per cylinder, and if one is too closed it lets less air in, therefore lower compression test readings.

but on a single carbie this doesnt matter, so cant be that, hmm.. are the tappets/valve clearances right on all4?

i forget what these are called on the older engines now lol

[bortaf]

when closed the throttle flap will still be (or should be) open enough to let air through to idle, with twin side draughts there is one throttle per cylinder and if one is restricting the air then less will get into the cylinders to be compressed but with you twin choke this wont be a problem, it's just best to have the throttle wide open to let as much air in as possable to get an acurate reading.

If that's a wet test and the reading were the same dry i'd say you have a valve sealing problem like over tight tappets of recessed valve seats/burnt valve seats, if it was lower when tested dry i'd say the rings have gone or you have bore wear on those 2 low reading cylinders

 

 

Drat beaten to it whilst spell checking

[hollowaykid]

O right! I'm away this week on work but my dads a mechanic so I'll give home a ring and get him to check it all out! (I'm only 19 and using this engine to learn as much as possible on!)

Thanks all for the information! It's so useful!

[oliwally]

Check valve clearances.

cant remember the settings off the top of my head but the adjusting of them can be a little tricky as the nut can move the adjuster as you tighten it.

easiest way is get the sizes either side of the one you need and adjust it so the bigger size dont fit while the smaller one falls through.