I did some compression tests yesterday but didn't follow the correct procedures. I did them with a cold engine, took only one spark plug out at a time, tested and put it back, and I didn't do anything with the throttle while performing the dry and wet tests and the battery was not fully charged the entire time. I got some crazy numbers (surprise, surprise) so I want to do it again.
My "results" PSI:
#1-dry-131-wet-300
#2-dry-100-wet-212
#3-dry-129-wet-240
#4-dry-128-wet-190
Are the results from a compression test on a cold engine are useful? How long after a wet test can a dry test be done? Do I need to get it running to get the engine warm? Thanks for the help-Jason
Cold compression test?
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- Posts: 1833
- Joined: Wed Mar 24, 2010 10:45 pm
- Your car is a: 1975 Spider
- Location: clermont fl
Re: Cold compression test?
ok, loaded question but. a charged battery, a wide open throttle and all sparkplugs out at one time, is the only true way to compression test a motor in my opinion. now by adding some fluid for a wet test, was the amount of fluid measured or just poured in. the numbers that you show are not that bad for a cold engine though. what type of problem are you searching?
Automotive Service Technology Instructor (34 year Fiat mechanic)
75 spider , 6 Lancia Scorpions, 2018 Abarth Spider, 500X wifes, 500L 3 82 Zagatos. 82 spider 34k original miles, 83 pininfarina, 8 fiat spider parts cars
son has 78 spider
75 spider , 6 Lancia Scorpions, 2018 Abarth Spider, 500X wifes, 500L 3 82 Zagatos. 82 spider 34k original miles, 83 pininfarina, 8 fiat spider parts cars
son has 78 spider
Re: Cold compression test?
No, the amount was not measured, about a cap full? I'm trying to evaluate the car as a whole....I paid $500 for it, put in a clutch cable (PO was driving when it broke) and got it started. It has a brake booster leak, tapping valves, and runs rough in general. I drove it home, parked it and have been able to start it since. I haven't tried to hard though, just evaluating what I got and what it needs. It's a 77 5speed 1800 with a mechanical choke Holley Carb and points.
Re: Cold compression test?
I did another round of "cold engine" compression tests today, throttle wide open, all plugs out, wet and "dry"-I did a wet test 24 hrs prior to this "dry test". here's the numbers:
#1-----d-130----w-300 and d-240----w-238
#2-----d-100----w-212 and d-160----w-240
#3-----d-130----w-240 and d-130----w-150
#4-----d-130----w-190 and d-150----w-160
#1-----d-130----w-300 and d-240----w-238
#2-----d-100----w-212 and d-160----w-240
#3-----d-130----w-240 and d-130----w-150
#4-----d-130----w-190 and d-150----w-160
Re: Cold compression test?
What you are looking for is about the same reading all four cylinders. Cold is fine, as long as all cylinders are cold
Not a fan of "wet" compression tests.
Seems you consistantly get a lower reading is #2, so that is reason for concern, BUT that is not causing your no start. Get it running, get it warm, and check it again.
Keith
Not a fan of "wet" compression tests.
Seems you consistantly get a lower reading is #2, so that is reason for concern, BUT that is not causing your no start. Get it running, get it warm, and check it again.
Keith
- 124JOE
- Posts: 3141
- Joined: Fri Jun 24, 2011 7:11 pm
- Your car is a: 1978 124 fiat spider sport 1800
- Location: SO. WI
Re: Cold compression test?
yes anything under 80 may have problems
yours is fine
fuel and spark next,or again
yours is fine
fuel and spark next,or again
when you do everything correct people arent sure youve done anything at all (futurama)
ul1joe@yahoo.com 124joe@gmail.com
ul1joe@yahoo.com 124joe@gmail.com