On the dyno with a friends race car and we could not get it to kick into vtec. Replaced the selenoid, no change. Checked the oil pressure at the vtec selenoid check port and it was over 70lbs with the selenoid activated. The car uses a Speed Pro which does not control the vtec so the msd is used for activation. Measured the signal at the selenoid and it fires at the proper rpm as controlled by the pill in the msd box. So it seems like all the elements are there for it to work...but nothing. Can something fail in the head to mechanically stop the engagement. We took the whole rocker arm assembly apart looking for anything unusual and nothing.
Ideas?

 

****, I can't remember what they're called, but there are some dowel pin like things inside the rockers...I think those have to be there for vtec to work

 

remember, the vtec solenoid activates when its grounded, so make sure that the window switch or whatever you are using to activate the vtec solenoid is grounding it and nnot trying to send a 12v positive signal to it

 

We had the same problem at the shop once.
We took the head apart and everything seemed fine, until we used an air gun to blow the oil pasages and found an air leak due to a mising little bolt that didn't let built enough oil pressure to activate vtec. Everything looked fine from the outside, the selenoid had the right pressure, wiring was right, but the real problem was inside the head itself after the selenoid thanks to 10mm bolt from the rocker arm assembly.
Hope you find it helpfull.

 

i'm probably not very helpful here.... but i'd take that MSD box out..... see what happens then.

I agreen w/ wantboost... maybe its gettin a signal, just not the right one.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by wantboost &raquo;</TD></TR><TR><TD CLASS="quote">remember, the vtec solenoid activates when its grounded, so make sure that the window switch or whatever you are using to activate the vtec solenoid is grounding it and nnot trying to send a 12v positive signal to it</TD></TR></TABLE>I will check that. The thing is that it was working fine and then it just quit working.

 

is the Vtec check port before or after the solenoid valve? I'm just wondering if you know for sure the solenoid turns on and the valve is open... I think that should be investigated further

 

Thats odd. We had the same problem on our Turbo car except it was intermittant. We thought we dropped, or bent a valve because we heard this loud ticking. Turns out the solonoid was turning on and off, slamming the pins in and out of the rockers. Switched to a JDM solonoid and no problems since.

 

Every vtec solenoid I've seen required +12v NOT ground to engage. The solenoid is in contact with the block, which provides the ground source. The ECU provides +12v to turn vtec on.

Be careful about running the vtec solenoid off a MSD window switch without a relay. The solenoid is a fairly beefy piece, and probably creates some nasty inductive feedback. Honda uses a diode AND a beefy as **** FET driver (Sanken SK5151) to drive it. Without a diode or two, I'd worry about cooking your MSD switch.

You can always test vtec solenoid operation by running a wire from the hotside of your battery direct to the solenoid. If you do this at idle, you should be able to notice the difference in the motor if vtec engages properly. You might need to rev the motor up a little bit off idle to get enough oil pressure.

Good luck.

 

im having the same problem, i read that u should check ur LMA (Lost Motion Assembly) i havent gotten around checking mine yet but just thought i'd give u a heads up.

 

It worked fine for 3+ years. It is activated by a rpm activated switch(msd) and a relay is used to cahanged it to 12v+. The port is after the vtec solenoid, and the vtec was tried with a hotwire, still no change over. Vtec is locked permanently on the car now. Just couldn't figure it out.