pinto head gasket gone?

[sarkie83]

I just want to check my thinking is correct, as I've not used a compression tester before...

a few weeks ago the Capri died, and wouldn't re-start. I checked out the ignition and found a lot of burnt/corroded bits, so replaced it all thinking that was the cause of my problem. anyway, I'm getting a good spark, fuel to carb, checked pressing the throttle and get a spray down the venturi's, so the last thing I could think of was to do a compression check...

so each plug out, compression tester in, and turn the engine over for 5 secs or so...

each one reads around 25 psi! am I correct in thinking I would expect to see more like 120-150 psi on a healthy engine? also, as I got an identical reading on each, I assume that does point to head gasket failure rather than a ring (as in that cause I would see one cylinder with a reading dramatically difference from the rest?)

The Capri in question...

[cobblers]

Did you hold the throttle wide open when testing the compression? It would be very odd to see all 4 cylinders as low as that.

[Granadaman72]

IIRC a headgasket tends to blow between 2 cylinders, so 2 would be low and 2 normal. Have you checked the timing belt?

[sarkie83]

no - i didn't hold the throttle open when I did it...excuse my ignorance - how does that effect the compression?

ok, so from the sounds of it, those readings don't sound right, so I've probably done it wrong...

nadaman72 - I did look at the timing: rotor arm was at 1, bottom pulley at 8 deg btdc and the camshaft triangle wasn't at 6 oclock, more like 5 oclock. I discounted it as the problem as the head hasn't been off/i've not changed anything...so surely nothing could have changed.

[unitybonez]

If by ''the camshaft triangle isnt at 6" you mean that the pointy bit on the pully doesnt align with the dot on the timing plate looks like your belt slipped, which is something that recently happened to me too, and like you i had spark n chaged all ignition bits to no avail.

[colnerov]

Hi, A headgasket can blow between 2 cylinders = 2 low readings adjacent. Or blow into a waterway = 1 low reading or 2 not next to each other. Hold the throttle open as said, the pressure reading will go up in steps, keep turning until it stops rising. If all the readings are low and they improve with some oil down the bore then it indicates rings are worn.

However it sounds like the belt has jumped (Not unknown) so you will need to correct that. It could be your problem.

Good luck.

Colin

[nomad]

Hi,

May 26, 2013 14:54:17 GMT sarkie83 said:

I just want to check my thinking is correct... as I got an identical reading on each, I assume that does point to head gasket failure rather than a ring (as in that cause I would see one cylinder with a reading dramatically difference from the rest?)

Not quite - if it's worn bores (engine is due a rebore) expect to see all readings about the same but low.
If it's a headgasket gone expect the (1 or 2) cylinders which have blown to be low.
Most garages have a "sniffer" they can dip into the radiator to see if hedgasket has blown, very quick n easy. (thinking about it - not sure how the water would show if the headgaskert hasn't blown into a waterway??)

May 26, 2013 15:36:15 GMT sarkie83 said:

no - I didn't hold the throttle open when I did it ... how does that effect the compression?

Carbs have 2 butterfly's (1 choke + 1 throttle) to "strangle" the airflow, your choke has been removed (fine) but if you don't hold the throttle open when checking compression no air can get in - so there's very little air in the cylinder to compress - so you show low compression (even on a good engine)

[sarkie83]

Well i went out today, loosened the belt tensioner, moved the cam round slightly so all my marks lined up, retightened and it fired up straight away :-)
So i guess the belt had slipped after all..
Nomad - thanks for the explanation, that now makes sense!