Compression test results seem way too low?
#1
Canned. I got CORNED!
![](https://www.rx7club.com/images/misc/05_year_icon.png)
Thread Starter
iTrader: (5)
Join Date: Mar 2007
Location: Appleton, WI
Posts: 1,029
Likes: 0
Received 0 Likes
on
0 Posts
Compression test results seem way too low?
13b, 1986. Unknown mileage believed to be 50k-60k ish.
When I first got this motor, I tested it and I believe the results came back ~100psi each rotor. I had it in a car that ran great, got 22mpg-ish, decent power for N/A, ran strong. I pulled it out, transplanted it into a GXL and it's sat for a couple of months. I got it running, ran some water through it to clean it out and now I get 6 strong exhaust pulses, not 5. A seal must have been stuck or something.
I've had the car around the block once or twice and it seems to still be in good condition, albeit a large vacuum leak preventing it from idling.
I tested the compression last night and I dunno if it's my $7 harbor freight tester or what, but I got 90 front/65 rear While holding the pressure release button, the needle didn't even really move.
Would the car even run with compression that low? What's going on?
When I first got this motor, I tested it and I believe the results came back ~100psi each rotor. I had it in a car that ran great, got 22mpg-ish, decent power for N/A, ran strong. I pulled it out, transplanted it into a GXL and it's sat for a couple of months. I got it running, ran some water through it to clean it out and now I get 6 strong exhaust pulses, not 5. A seal must have been stuck or something.
I've had the car around the block once or twice and it seems to still be in good condition, albeit a large vacuum leak preventing it from idling.
I tested the compression last night and I dunno if it's my $7 harbor freight tester or what, but I got 90 front/65 rear While holding the pressure release button, the needle didn't even really move.
Would the car even run with compression that low? What's going on?
#4
Josh
#5
Canned. I got CORNED!
![](https://www.rx7club.com/images/misc/05_year_icon.png)
Thread Starter
iTrader: (5)
Join Date: Mar 2007
Location: Appleton, WI
Posts: 1,029
Likes: 0
Received 0 Likes
on
0 Posts
I didn't think 5 pulses would make sense either, but I'm positive it did make 5 pulses at one point. I have video of it somewhere. Perhaps it was a side seal or something.
It's very possible that the injectors are leaking (probable, actually) and that makes alot of sense, I don't know why I didn't think about it. Thanks for the help.
It's very possible that the injectors are leaking (probable, actually) and that makes alot of sense, I don't know why I didn't think about it. Thanks for the help.
#6
Canned. I got CORNED!
![](https://www.rx7club.com/images/misc/05_year_icon.png)
Thread Starter
iTrader: (5)
Join Date: Mar 2007
Location: Appleton, WI
Posts: 1,029
Likes: 0
Received 0 Likes
on
0 Posts
Oh, yes, it's the same compression tester. I don't think I can remove the valve, it's really cheap.
I'm looking to sell this motor which is why I want concrete numbers. Motor runs great and pulls strong but I don't want to mislead anybody.
I'm looking to sell this motor which is why I want concrete numbers. Motor runs great and pulls strong but I don't want to mislead anybody.
Trending Topics
#10
dont hold down the release valve. that'll give incorrect readings. if u cant remove the valve then just do the test without holding it down and at least u will get an accurate reading of the strongest side.
#11
Canned. I got CORNED!
![](https://www.rx7club.com/images/misc/05_year_icon.png)
Thread Starter
iTrader: (5)
Join Date: Mar 2007
Location: Appleton, WI
Posts: 1,029
Likes: 0
Received 0 Likes
on
0 Posts
I'll pull off the intake manifold and see if I can find another vacuum leak and wet test it and post the results.
#12
oh my bad. well considering how much the numbers have dropped, that sucks. well a wet test will always return back stronger numbers so dont be surprised if ur back up to 100. how is the charge in ur battery? if the battery was at full charge when u first tested it then that could explain the stronger numbers. battery voltage will also change readings but that doesnt explain the difference between the front and rear. best of luck.
#13
Canned. I got CORNED!
![](https://www.rx7club.com/images/misc/05_year_icon.png)
Thread Starter
iTrader: (5)
Join Date: Mar 2007
Location: Appleton, WI
Posts: 1,029
Likes: 0
Received 0 Likes
on
0 Posts
ah, haven't charged the battery in awhile either, I'll throw it on there right now and report back when I test it tonight or tomorrow.
Should I pull both trailing plugs out when I test it or just the side I am testing?
Should I pull both trailing plugs out when I test it or just the side I am testing?
Thread
Thread Starter
Forum
Replies
Last Post
trickster
2nd Generation Specific (1986-1992)
25
07-01-23 04:40 PM
LunchboxSA22
2nd Generation Specific (1986-1992)
37
10-26-15 10:53 AM