Responses to last 4 posts...

Thanks, to spooledUP7 for the clarification on the TCA vacuum side. That tidbit was not posted or doced anywhere I could find.

When I did static tests on all the lines they all initiatlly passed. In the case of the TCA I could hear it change position during the static tests with nominal vaccum -OR- pressure when tested individually.

When I tee'd into different lines and road tested them for some reason I didn't test the vacuum side of the TCA so I don't know if that solenoid is opening or not. I'll be testing the resistance and activatipm of all the solenoids on the bench and go from there.

I'm replacing the lines with Viton as I go.

I was just thinking that someone needs to go beyond the static vacuum line diagrams in describing what goes on when. Derek's information at
http://home.istar.ca/~dvandit/TurboT...shooting.shtml
is very useful and way more detailed than any of the information I had before (I wish I had seen known about it a week ago as I would have saved a not of abstract thinking time decucing how this stuff is supposed to actually work).


Jon

 

After much distraction (business trips and medical issues), I finally got around to getting the solendoid rack out yesterday. Sadly, all the solenoids function at room temperature and have ohm readings ranging from 36.5 to 37. Same goes for the TCA solenoid mounted on the ACV. Since all the connections hold vacuum/pressure and the TCA pressure solendoid is directly connected to the pressure tank, I am at a loss as to why I'm not getting pressure on the TCA line unless the solendoid is not opening because of a problem with the wiring harness itself. I've got the wiring diagrams so I guess I'll pull the ECU and test from the connector next.

If the harness passes muster, then I'm at a loss as to where to go next. Not finding direct cause and effect leads me to believe that even after replacing all the hoses if and when I put this back together I probably will have ended not effecting the symptoms.

 

Just to reveiw:

unless I'm missing something there are only a handful of causes for no secondary boost:

1) Venting CRV - You've checked all this except the hose from the secondary to the CRV. You definately HAVE to pull that sucker off to check it, I split mine right up the side but the split faced the turbos so I never could see it.

2) Non actuating TCA - You only "heard" it move. Climb under the car pull off the pressure hose (it's the main central one on my car it was the only one I could clearly see.

Hook up a hand pump through a check valve and slowly pump it until you see the actuator move. Make sure it moves the whole way. Once it's fully engaged, release the pressure (open the check valve) you should see the TCA slide back. This is a double check.

Forget vacuum side. It could be totally stuffed but your TCA should still move (albeit slightly slower) and engage the secondary.

You can double check that the system doesnt have any leaks by hooking your boost gauge into the pressure chamber. At switch time (4500+) you pressure should drop slightly and then recover. My bet is that it falls on it's ***.

3) Pressure leak:
LOTS can go wrong here:
* loose / open BOV
* leaking x-over
* leaking IC end tanks ( I think Jspecracer had this)
* leaking couplings (the engine moves AWAY from the IC under heavy load)

4) starvation:
(pretty unlikely)
*jammed secondary butterfly
* blocked filter
etc

-pete

 

rpm_pwr, you've been a help in my boost problem thread (see https://www.rx7club.com/forum/showth...hreadid=123500). I decided to get more specific here with a new post.

I've been completely through all the boost problem diagnostic procedures (or so I led myself to believe) and tore into the car a week ago. I have yet been able to find a specific cause.

Every line/componet passed in static tests. I tee'd into lines with a pressure gauge and did road tests. I went through the connections in order of complexity of access (wastegate, prespool, CRV, secondary Y and finally, TCA lines).

It all passed muster until I found I was getting 0-0-0 on the TCA pressure line under all conditions. At that point I believed the problem was obvious that the solenoid was bad because the pressure tank (a direct feed) was holding plenty of pressure.

Unfortunately, now that everything is apart I find the solenoid works with a 9v battery and the resistance is nominal (36.7 ohms). So now I believe I'm looking at either a short in the circuit or a bad harness connection to the ECU. That's why I want to understand the specific differences I'm seeing in the different type of solenoids since the TCA vacuum solenoid and the TCA pressure solendoid share the activation circuit from the ECU (a PowerFC in this case).

In hindsight, if I had known up-front that the TCA pressure and vacuum solenoids shared the same activation circuit from the ECU I would have continued the road-tests to see if in fact I was getting 0-0-0 on the TCA vacuum line too. Both solendoids failing on a chassis with only 33K miles is a little bit of a stretch.


Jon

 

I feel your pain Jon. The whole system can be quite frustrating to troubleshoot. I'm starting to think "FD" must be the abbreviation for "Boost Problem" in Japanese

If you're really interested in checking the wiring, you could try to ohm out the wire that goes from the ECU to the Turbo Control solenoids. It looks like you should be able to read a short between one of the wires on each turbo control solenoid plug, and terminal 4R (page Z-38 and Z-41) of the ECU harness. The drawing on the page looks like it shows the terminals on the ECU itself, which will be like looking at the back side of the cable plug. Remember to reverse things if you're looking at the front side of the plug. You should probably also check from this wire to ground, since the wire could be cut and shorting to the chassis somewhere. From what I understand, you would get a fault code on the stock ECU if this wire was broken, but not on your PFC.

I don't know much about the PFC, but I wonder if it has a test mode to allow activation of various solenoids. That would really be the ticket for testing this.

Good luck,

 

Yeah certainly sounds like the wiring. Dont worry about pulling it all apart though because if the wiring is split you would have had to do it anyway.

Dont forget to post what you find.

-pete

 

Ahh...ditch the seq system. I'm making more hp at 4k than a stock fd peak. Making as much peak torque as a stock car by 3,600. (Actually, I'm comparing my car nonseq, vs my car with a down pipe, and intake running seq.) Not to mention, you'll never have to deal with those pesky boost problems again.

CJ

 

Try heating up the TCA vacuum solenoid, and see if it still works with voltage.

 

Thanks for the thoughts guys. I'm on the road all week (first chance to check the thread). I've got the wiring diagram manual as a guide.

One thing I did learn since my last post is that the TCA vacuum solendoid does not have the same electrical properties as the TCA pressure solenoid. It has different resistence specs (32 ohms -vs- 37 ohms) and, at least in my case, the multi-meter says it dead shorts internally (although it does activate). Since the two solendoids chare the same circuit from terminal 4R (Y/L color code), one can effect the other in various ways.

Overall it appears when they designed the 13B-REW that the TCA envioronment we modded after the initial prototypes to include a vacuum line to speed up the transition (hence the placement and different specs for the the two solenoids).

I hope to have some time this weekend to work on it. I'll let you know.

Jon

 

I assume you'll be interrogating the original engineers soon. If you find the guy who designed this, smack them once for me too

Kidding of course. BTW- neat info. Good luck this weekend.

Cheers,

 

Exactly! Ask them why they didn't make the TCA actuator a magnetic solenoid much like a starter solenoid. Bastards, I bet the FD engineers had poll running on who could engineer a car with the most three nipple solenoids. If you look at any early (1970), and late model Mazda, you will find at least 2 or more of the exact same solenoids as used in all 3 generations of the RX-7.

 

I forgot to provide an update from last weekend.

The continutity of the 4R circuit on the harness between the ECU and the solendoids checked out fine. I went ahead and spliced a tap wire into the line near the ECU to allow monitoring of voltage/continuity of the circuit during road tests in the future.

In the meantime, after heat and cold soak tests I'm convinced the TCA vacuum solenoid is a lying sneak and a flake (if that reminds you of anyone you know, I'm sorry). Off the car I've gotten readings ranging from dead short at room temp to conitinuity of 55 ohms at 200F. Rest assured is being replaced.

While things are apart I'm upgrading the injectors and replacing the FPD as well as all the other work related to the hose lines and solenoids. Considering the status of parts orders and my available time I'll be lucky to be back in operating condition by the 16th. I'll give an update when things are rockin again.

Jon

 

Just a bump for anyone still monitoring.

The new 850cc injectors (primaries) just arrived today two weeks later after I ordered them. I hope to be running this weekend with new solenoids and hoses to boot.

Jon