compression test

[hotrodder13]

brokedown today for the first time in ages and had to call rac, he did a compression test and it was just above 100 on each cylinder, but he then squirted some oil down the spark plug hold and got it to above 140 is this ok now

(reason i broke down was the main jet had fallen out in the carb)

thanks tom

[bmcecosse]

100 is desperately low for a hot engine - did he take ALL the plugs out when doing the test ? The fact it seemed to improve when he squirted in oil (quite a clued up RAC chap there!) shows that the problem is that the compressed gas is leaking away past your piston rings - the oil temporarily sealed them up to get that slightly better (but still not terrific) reading. You need at least new rings - but most probably, a rebore and new pistons.

[hotrodder13]

it was a cold engine and no he did it one at a time and he had 2 mgs of his own and he never stoped talking

also could it be the rings havent bedded in properly

[bmcecosse]

Well - to get a proper reading you need ALL the plugs out (not-so clued up RAC chap after all........) - hot engine and fully charged battery (part of the reason for having the engine hot - the other being to have the oil thin!) - and throttle held open. Even so - the fact it increased a LOT when oil was added - does show ring/piston/bore problem................ i suggest you get hold of a compression tester (it will fare you well in future) and do a proper compression test yourself.

[hotrodder13]

thanks ill get one asap the and gve it a go and i need to change the oil as well as it does have a bit of 5w30 in which i know is wrong but its all i had

[bmcecosse]

Well - that would be hopeless in an A series! Did you imagine it was built to fine tolerances or something ?????????

[hotrodder13]

it was either that or run it 250miles on min on the dipstick im gona change it 2moro

[bmcecosse]

ASDA is 250 miles away ???????????

[hotrodder13]

i got some now anyway cant change what has been done ill tell you the results when i do the proper test also would it run properly is they were that worn