B20 Valve timing, passes leakdown, failed compression

 
Old 01-03-2019, 08:37 AM
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Default B20 Valve timing, passes leakdown, failed compression

https://photos.app.goo.gl/iozvAz1GcgxkZ79MA

On a 2000 1st gen CRV EX, running with no compression in 1 and 4.
A leak down test pressurized 1 and 4.

Timing appears to be close, maybe one tooth retro. I have a link to a video above. It shows the deflection on the timing belt belt. If you can see the video, is this deflection of maybe 1/2" between the cams acceptable? It seems that the timing belt is in good condition. Alt, AC and PS belts are old.

The cam in the video are pinned at TDC. Valve lash is not correct, but in adjusting it, for example, on #4 exhaust, I couldn't get the 0.18 mm gap called for between the camshaft lobe and the rocker. The leak down tester was just a compression tester adapted to accept an air compressor hose fitting so there is no differential pressure reading.
Valves appear to move freely.

One theory is the 1&4 intakes are not opening so the compression will not build while running. What do you think?
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Old 01-03-2019, 10:25 AM
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Default Re: B20 Valve timing, passes leakdown, failed compression

Just to confirm, you had a dual gauge leak down tester? One gauge shows input pressure and the second gauge shows cylinder pressure (loss pressure)?
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Old 01-03-2019, 01:24 PM
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Default Re: B20 Valve timing, passes leakdown, failed compression

Originally Posted by TomCat39 View Post
Just to confirm, you had a dual gauge leak down tester? One gauge shows input pressure and the second gauge shows cylinder pressure (loss pressure)?
Not a 2 gauge test. The tester used for the leak down test was your screw-in type compression tester with one gauge and a 't' with a male fitting for an air hose.

Last edited by nooboo1; 01-03-2019 at 01:26 PM. Reason: Spelling
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Old 01-03-2019, 02:53 PM
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Default Re: B20 Valve timing, passes leakdown, failed compression

I'm not sure the accuracy of a 1 single gauge setup but it obviously holds some of the constant pressure being applied.
Was this done with the piston TDC or BDC?
If TDC did the piston not shoot to the bottom when air was supplied?

Compression is a moving process while the leak down is static. I would start with checking your mechanical timing.
I suspect a tooth or two off.
Not enough for contact but enough to prevent compression when in motion.
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Old 01-03-2019, 06:57 PM
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Default Re: B20 Valve timing, passes leakdown, failed compression

Originally Posted by TomCat39 View Post
I'm not sure the accuracy of a 1 single gauge setup but it obviously holds some of the constant pressure being applied.
Was this done with the piston TDC or BDC?
If TDC did the piston not shoot to the bottom when air was supplied?
Nope, none of them, 1 and 4 are the 'bad cylinders'.

Compression is a moving process while the leak down is static. I would start with checking your mechanical timing.
I suspect a tooth or two off.
I had a B20 that was a tooth off and ran like this one. I did not check compression, it might have been instructive! [/QUOTE]

Not enough for contact but enough to prevent compression when in motion.
Sounds good and my question is: is the slack between the cams normal as in the pic below or video at the top?

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Old 01-04-2019, 01:10 PM
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Default Re: B20 Valve timing, passes leakdown, failed compression

Originally Posted by TomCat39 View Post
I'm not sure the accuracy of a 1 single gauge setup but it obviously holds some of the constant pressure being applied.
Was this done with the piston TDC or BDC?
If TDC did the piston not shoot to the bottom when air was supplied?

Pistons 1&4 were TDC with allen keys locking the com vertically. The pistons stayed put.

Compression is a moving process while the leak down is static. I would start with checking your mechanical timing.
I suspect a tooth or two off.
Not enough for contact but enough to prevent compression when in motion.
Maybe the belt is stretched?
One tooth off might keep the valves from opening, maybe?

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Old 01-04-2019, 07:03 PM
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Default Re: B20 Valve timing, passes leakdown, failed compression

Originally Posted by TomCat39 View Post
I'm not sure the accuracy of a 1 single gauge setup but it obviously holds some of the constant pressure being applied.
Was this done with the piston TDC or BDC?
If TDC did the piston not shoot to the bottom when air was supplied?

Compression is a moving process while the leak down is static. I would start with checking your mechanical timing.
I suspect a tooth or two off.
Not enough for contact but enough to prevent compression when in motion.
The cams were pinned TDC for 1&4... only those two were checked.
The pistons stayed TDC.
I was preparing to take the head off but if the timing belt will fix the problem...rt?
Tried to attach a picture of the slack between the two overhead cams but I don't have enough privilege.
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Old 01-04-2019, 08:09 PM
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Default Re: B20 Valve timing, passes leakdown, failed compression

I see the pic, I don't have personal experience with b series. It seemed to me like it looked slack but I've seen other ppls photo's and they look similiar to your pic and they've been fine.

Did you check your mechanical timing?

I was thinking if valves opened improperly so that the upstroke can't build pressure. But now thinking about it, I would think you'd have to be nearly 180* out for that to happen. You'd need valves open at BDC and close up on the upstroke but close up late.
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Old 01-05-2019, 08:14 AM
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Default Re: B20 Valve timing, passes leakdown, failed compression

Would you pull the head or just install a new timing belt and adjust valves and timing? Or get a double gauge leak down tester?
Please excuse the multiple posts.
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Old 01-05-2019, 04:16 PM
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Default Re: B20 Valve timing, passes leakdown, failed compression

I would set mechanical timing, which in the process would also set timing belt tension and then I would see about compression testing on all 4, dry then wet.

After that, I would have a better idea of how to proceed.

Do you have the factory service manual for the engine?
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Old 01-05-2019, 07:30 PM
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Default Re: B20 Valve timing, passes leakdown, failed compression

Originally Posted by TomCat39 View Post
I would set mechanical timing, which in the process would also set timing belt tension and then I would see about compression testing on all 4, dry then wet.

After that, I would have a better idea of how to proceed.

Do you have the factory service manual for the engine?
I don't have a Honda manual so I am using our library 'Motor' and AutoZone seems to have good step by steps.

I'll get the timing set with the new belt, adjust the valves then do a compression test...a Leak down test, rt?
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Old 02-11-2019, 07:31 PM
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Default Re: B20 Valve timing, passes leakdown, failed compression

you NEED to properly adjust valve lash before doing ANY form of pressure testing. if lash is too tight to a point where it holds valves open even the littlest bit, it will have a drastic impact on leakdown test. If the lash is uneven between any of the cylinders even the smallest bit, it can cause a DRASTIC difference in compression test results.
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