hello ya'll!

Since rebuilding my JDM DB8 I have a problem with my Vtec not engaging..

First I checked all electronical bits.. (I have no Vtec oil pressure switch)

-the ECU is giving de 12v signal to the solenoid at 5500rpm
-the solenoid clicks when I apply 12v to it
-solenoid gives 17+ ohm at 1pin connector
- No CEL codes

So today I decided to check the oil pressure at the vtec port left on the head and on the block at the oil pressure sensor.

At the block I got a nice 20psi at idle and 70psi at high rpm.

At the Vtec port I only got 20psi at 5500rpm.. I used both methods; first applied 12v from battery to solenoids 1pin connector.
Also had the car on jack stands in gear at rpm to make sure solenoid is getting 12v.

So the question is; What are the possible causes for the low oil pressure when vtec is supposed to engage?

Thanks

 

Did you take apart the head?There are these little o-rings under the cam caps that sometimes are forgotten.Atleast in my motor there are I am not 100% sure if you have them but check.They cause oiling issues.The solenoid also has a small screen that needs to be checked it can become clogged.I am guessing this may not be the problem but you might as well check to make sure.

 

I did take the head apart yes. Will check that o-ring tommorow!
The screen and solenoid gasket are brand new.

Thanks

 

Just took the Nr3 camcap off and found the O ring being completly flat/flush with the head.
I assume this is not what its suppose to look like?

some pics to ilustrate:

 

Uhh there should be two of them - both should be a snug fit in their respective holes...

 

I think what you are reffering to is the Vtec rocker shaft orifices.. which are located on the belt side of the engine on the intake and exhaust side.

This is the O-ring underneath the nr.3 camcap, of which there is only one

 

Oshizz, I think I left mine out too...!

 

Cams aint gonna like that!

Just replaced mine.. Still no Vtec.
What's next? Im kinda out of ideas

 

Check in this thread maybe something in here will help?

https://honda-tech.com/all-motor-nat...-port-2486207/

 

Thanks, but unfortunately that thread doesn't come up with a solution, like all treads about vtec oil pressure problems..

I was thinking.. Could it be because of a bad oilpump? It does give proper pressure at the block but maybe its a little worn and cant get the pressure to the head anymore.. Just guessing here.

 

Is there any way you can get some air pressure in that passage to check flow?

 

good idea, gonna give that a try! I assume I can use the same port as where the vtec oil pressure is checked? thanks

 

Anytime man good luck.

 

I think it might be possible to put the oil control orifice on backwards or to accidentally leave the oring off provided you removed it when you were fiddling with the head.

 

I've checked/replaced the orifices and O-rings but all seems in place and in good condition.

Will do the air-pressure test up next.. If all seems to work ok I'm just gonna start replacing s**t! starting with the solenoid

Thanks for the input guys

 

What ecu ?

 

stock P73 ecu obd2a

 

Please post up when you get it figured out.

 

will do!

 

So I may have found the problem!

Today I did the Vtec airpressure test.. put something like 70Psi of pressure on the check port. huge leak between the first rockers!..

Video: (not blocking the little hole here cause oil would have been hitting my phone if I would, but it shows the leak)


Vtec piston stuck or worn?

 

Glad to hear you figured it out.

 

The piston of the Vtec rocker nearest to the solenoid was lying loose in the head!

I seriously F***d up when assembling the head..
Glad the little piston didnt do any damage tho!

Thanks for the help y'all!

 

Whaaa?!

It wasn't even inside the rockers?

 

nope! the middle piston was loose in the head underneath the right rocker and next to the LMA
Dont know how I managed to do this.. maybe a loss of concentration after re-assembling the head a million times due to errors..