SpeedracerRX7

Just today I lost my secondary boost. It doesn't transition at all and I only get like 4 psi after 4500 RPM. I have narrowed it down to two solenoids that have been common problems in the past. The only problem is how do I test them. I am figuring that it is either the Turbo Control Solenoid or the Charge control. If I have searched and found out correctly, the Charge Control should be closed while the ignition is off and then opens when the ignition is turned on. Is this correct? I am pulling the upper intake manifold tomorrow and I would like to test them all while I'm under there but I don't have a mighty vac. Can I run a positive and negative lead from a battery and jump the terminals on the solinoid to test if it is open or closed relative to where it started? Let me know.

I have done a lot of searching on this but with so many threads to work through I was beginning to get confused. This is just one more reason why I'm working toward the single.

jeffrored92

You'll want to get a mityvac. I tried troubleshooting using a bike pump to supply some pressure, but I had no accurate gauge and couldnt use it to create a vacuum.

Yes, you can connect 12V across to the solenoid terminals to test them. But simply applying 12V to the solenoid and verifying that you can blow air through it doesn't guarantee the solenoid is OK. Sometimes they can stick when under operating conditions, for instance the TCA pressure solenoid has the pressure tank pressurizing one of it's ports. When you supply 12V to the solenoid, this pressure can cause the solenoid to *stick* making it take longer to open than it should (if it opens at all).

If you're going to remove the UIM, I say get a mityvac or similar product and test things properly. You'll want the one that does both pressure and vacuum.

EDIT: Yes, the charge control solenoid should be off with the ignition OFF. In this sense, off means no voltage applied to it and no air passing through it. With the ignition ON it should be activated (12V) and it allows vacuum (from vacuum tank) to chamber A of the charge control actuator, pulling the actuator rod in.

If you don't already know about this site, go here http://www.autosportracetech.com/RX-7/rx7stuff.htm It has some simple tests described that can help you determine if you're charge control solenoid is working OK.

books

iTrader: (8)

An alternate method to removing the UIM is to remove the ecu. You can test each solenoid by grounding the appropriate female slot on the ecu harnesses. After you remove the ecu you’ll need to have the ignition turned on to supply 12 volts. Just listen to hear the solenoids click. In order to hear the solenoids better, you can solder a long wire to a sewing needle. Place the needle in the harness slot and ground the other end in the engine bay where you’ll be able to hear the solenoid.

jeffrored92

Good advice also. I did this, with a needle and long wire, and it worked quite well. My only concern is that I could only seem to hear one click when grounding the ECU output for the TCA. As you know, that output drives two solenoids. Back when I did this, I didn't have a mighty mityvac. Also remember - hearing a click doesn't guantee the solenoid will function with pressure/vacuum applied, and at engine compartment temps.

However, I suppose it would be possible now to get my mityvac onto the respectives lines at the TCA, then manually ground the solenoids using a needle/long wire. Doing that, I should be able to determine if they are both functioning correctly. I have been a bit apprehensive to remove the UIM so I might try this method again now that I've got the mityvac. If I still can't nail the issue, then I'll bite the bullet and get that UIM off.

Looks like through trying to help, I have been helped myself - cheers big ears

books

iTrader: (8)

I was referring specifically to the solenoids not the actuators; this was an electrical test. The test does more than just test the solenoid it verifies the integrity of the wiring. To confirm the solenoids actually worked under high temps, I eventually pulled them all out and heated them in an oven and tested them by applying 12 volts and pressure to the ports.

jeffrored92

Didn't mean to make it sound like I was correcting you champ - testing the integrity of the wiring is an important step. I was just making sure that he (and others) knew that that test, on it's own, is insufficient to rule out the solenoids as a problem.

books

iTrader: (8)

I appreciate your response, hopefully our replies will help others.

SpeedracerRX7

Just a real quick question reguarding the turbo control solenoid(s). What do the two different solenoids do? I mean one is at the top of the Lower intake manifold and one is like the third back in the rats nest.

Julian

iTrader: (14)

Look on http://rx7.voodoobox.net/ click "how-to" and "Solenoid Valve Test"

jeffrored92

The Turbo Control Actuator is operated by both pressure and vacuum. With pressure applied to one side of the actuator, and vacuum to the other, it operates nice and fast.

One turbo control solenoid supplies the pressure (from pressure tank) and the other turbo control solenoid supplies vacuum (from the vacuum tank.)

Both solenoids are controlled by a single ECU output, see the wiring diagram for info on that. Below 4500rpm this output is off, and both turbo control solenoids are off. After 4500rpm, these solenoids are turned on by the ECU, routing pressure and vacuum to opposite sides of the actuator causing it to snap into the open position.

Have you checked out that link I posted before? All this info and more is on that website.

I can't help you with where the solenoids are located - check a vacuum diagram or search the forums for more info on that

KevinK2

"proper" test is in an oven at 200F, with pressure or vac from a tank on supply nipple, and gage on output nipple with a dummy actuator tee'd in, cycling on and off with 12V supply (radio shack, or just battery). simple cold elect test is not sufficient to screen a solenoid that needs pressure and/or heat to malfunction.

Knowing that, I just had them change the TC and CC solenoids when I had a rebuild installed. Included the attached hoses. Subtle hot boost control problems that had been evolving went away.

dgeesaman

iTrader: (7)

Following the suggestions on Dave Disney's site, this is what I did with the solenoids out of the car:

1) Tested each nipple for leakage in both pressure and vacuum with no voltage applied.

2) Measured coil resistance both hot (250F) and cold.

3) Using a battery charger, I applied 12V power and tested the solenoid to function (click) and hold up to 25inHg and up to 15 or 17psi, both cold and hot. A 'failing' solenoid will not vent the air immediately or will remain stuck - you need to repeat the test at incrementally higher pressures to see how high each will go. This is the test outlined in the link. The trick is verifying that the solenoid releases immediately when pressure is loaded on the outlet side - the solenoid spring needs to overcome the pressure to release. I repeated the test hot also. At the very least, conduct this test on both TC solenoids, and make sure the TC pressure solenoid releases well under pressure - swap one that performs better from the rack if needed, or buy new. I replaced both TC solenoids new since they tend to wear out.

Some solenoids made a buzz sound some of the time when under 12v and full pressure - I believe this is not a problem, but I'm not sure. It only tended to happen when I was testing them at artificially high pressures like 15 or 17psi - at 10-12 the noise was small or none.

(It may have been result of the charger's DC rectifier, but I'm a mechanical engineer, not electrical) . I also noticed that if you have any items like an R/C car controller, it will hold 8 AA batteries in series that might make for a much safer and better DC 12v source. I didn't use the car battery since a short would be very dangerous.

4) I will be testing the harness soon also - you can see in the FSM page F-56 when the solenoid connector should be on/off.

I strongly recommend the Mityvac Silverline Plus model. It's only $20 more, and it reaches higher pressure than the plastic model and it also has a built-in gauge to know what you're doing. With the plastic model you'll need to tee in another gauge like you saw on Disney's site. As well, if you're having trouble generating pressure with the Mityvac, I found it performs much better with a couple extra drops of silicone oil in the chamber. Out of the box they seem underlubricated and don't generate pressure consistently.

Regarding the cold and hot, they will cool quite quickly, so I pulled them out of the oven one-by-one so each was reasonably hot. It also helped me to put a piece of white electrical tape on each and write down the results and notes about it using a superfine Sharpie pen. The tape got soft in the oven but was ok.

Dave