NoRice

I've had this problem for almost 2 months now. There has been a thread under PowerFC. I've determined it's not a PFC issue, so I moved it here.

Here is the old thread:

https://www.rx7club.com/forum/showth...320#post700320

Tonight I stopped by Home Depot and bought some 8 gauge wire to add an extra ground strap from the battery to the engine and the battery to the frame.

Well, when I got home, before I did anything, I turned the ignition key ON. Uh, Oh, NO Display on the Commander again. (This had been the problem until Saturday, then we thought we jiggled a wire or something because it started displaying again)

When the Commander LCD display doesn't light up, the Buttons still DO. When trying to start/crank the engine in this condition, it just cranks, NO Fuel or Spark.

I went all over the engine, fuse block, ECU wires, battery connections, I even took the Fuse box off the Positive battery terminal and used the Dremel tool on all the connectors to assure a good clean connection. I tested all the fuses with an Ohm meter.

Still NO Display on the Commander.

Well, I was about to give up after a few hours, for some reason I decided to try and Start the car. When cranking the Commander would have a black like scrolling from Bottom to Top. Kind of like the old days when the Vertical hold would go out on a TV.

Then after cranking, turning the Key off, (repeating, etc...) The PowerFC start up display would kind of come on for a second and the LCD backlight would come on.

Tried some more, then the Commander Display came ON. I then left the key ON, the Commander Display stayed ON and I noticed a Buzz or Humm from the engine bay.

Got out of the car to find the Buzz. Seemed to be coming from underneath the Upper Intake manifold. (I hope that is the what it's called. I'm talking about the thing big thing at the rear of the engine on top that looks like 4 fingers wrapping to the passenger side)

I couldn't really determine what exactly was making the noise. After a minute it just quit. Then I looked at the Commander and the display was Off again.

Played with the key again, cranking on/off, etc... Display would come on and off. The car would Just About start, backfired a few times. It seemed like when I would let the key go back to RUN, the car would immediately die out. (Which is kind of part of the original problem, it would start when Cold, then when warm it would die out when I put the Clutch IN, and then be Very hard to start or wouldn't start at all)

I also noticed that sometimes the Commander Display would be OFF, but If I moved the Key to Start, the Display would come on, or at least flicker. Then when I put it back to Run, the Display would go OUT.

So, here is my latest theory on this. It's something in the Ignition switch.

Anyone have any idea how to prove or disprove this?

Thanks in advance!

airborne

holy nuts! i've got the same buzzing and a similar problem. the buzzing from the upper intake manifold (right name!) i get exactly, also it sometimes comes on when i hook up my battery jumper. always goes off on key off. also, if you touch the UIM when its buzzing you can feel the vibration a little.
and my car won't start, or it will die quickly. no power fc problems though. i'm gonna link this in the 3rd gen section, it'll get more looks.

rotorbrain

i have heard that on my car also. i thought it to be my injectors. i heard it once when i put my new ones in and havent heard it since. i figured that it was the fuel system having airpockets in it and causing it to pulse the injectors while dry. check your fuel pump. when i replaced mine i noticed that it was in there all messed up and barely in the nozzle that it is supposed to feed fuel to. it may be running lean due to bad sealing of the pump. i have talked to others who have had their pump installed all stupid too. . . so it seems to be a somewhat common thing. you could be starving your engine of fuel. its an easy check.

airborne

haha! hey rotorbrain, you're all over this one aren't ya?

thanks, you've been hookin me up a lot lately.

whats the word on your fd? getting it fixed by a good body shop or what?

NoRice

I have the ignition switch apart. I am testing it with an Ohm meter, but not sure if it is bad or not. When is ACC or Start which leads should be shorted together?

The Shop Manual I have does not go into this, but says to refer to "1993 RX-7 Body Electrical Troubleshooting Manual"

Anyone have one of these?

Please let me know which leads should be shorted when in RUN and START.

The part is $139, so I'm not just going to Try one. Also, none of the shops has one In Stock, so I can't go Test one.


Thanks,

NoRice

I believe I can eliminate the ignition switch.

After testing and cleaning it, I put it back in the car. I turned the Key to Run, the back and forth to Start, with the Clutch OUT, so it would not start.

The display on the Commander stayed ON.

When I push the clutch IN and turn the key back and forth from Run to Start, the Commander display comes on sometimes and not others.

If I have the Key in RUN and push in and out on the clutch, the Commander Display does not change.

Also, according to the shop manual, the switch on the clutch just kills the power to the starter. Which, I've never had a problem with, it always cranks over.

Still looking. No ideas at this point.

P'cola FD

I recently had a problem with my fd bucking like mad while going down the road. The check engine light would come on, but I would get no codes. I put in a friends PFC and found out that the ecu was turning on and off while cruising around. When I hit bumps going down the road it would sometimes fix the problem. I finally broke down and replaced the wiring harness. It was a butload of money, but (knock on wood) it seems to have fixed my problem.

NoRice

Maybe it's not a wiring issue after all.

I have checked the Ignition switch, seems Ok.

I read up on the clutch switch, it only kills the power to the starter. The starter always works, so that's not it.

I cleaned all the connections (fuses/relays) that are on the Positive terminal. I pulled every fuse and relay, tested them with an ohm meter, and cleaned the leads.

I was thinking that when the Commander would not display then it must not be getting power from the one of the 4 wiring harness connections.

So, I turned the key to Run, the Commander was ON. Then I disconnected the 4 wiring connectors to the PowerFC one at a time. I found that only one of the four would cause the Commander display to go out. I figured it must be one of those wires. (This was the biggest of the 4, it has 26 connectors)

I tested voltage (while the key was still on RUN) of each lead. Then I played with the car until the Commander display went Out again. I then checked the voltages of all 26 connectors again. They were the same! I was kind of disappointed, I thought for sure that would lead me to the culprit. So, it seems like the wiring harness is not the problem?

I have the car idling Rock steady at 770Rpm, I can turn the A/C, headlights, Stereo, Fan Mod on or whatever and the Idle is like a Rock. (It was bouncing when I had it set to 950, I was hoping the higher RPM would keep it from dying out at stop lights)

I haven't driven the car for awhile. I have the front end up on jack stands in the garage for troubleshooting.

I can let the car run and run, it gets warm, the fans kick ON, then they go Off for awhile.

However, once it gets up to normal operating temps, if I turn the engine Off, I can't get it started.

I've noticed a Hum coming from under the Intake. I tried removing the intake, but even with the bolts out I couldn't move it enough to find the culprit. Note, I have the Non-Seq mod, so a lot of stuff is out of the way already.

See picture:
http://community.webshots.com/photo/...0744SrRJDeDOOk

This humming/Buzz will also come On if I leave the key in Run (engine Off) sometimes on it's own when hot. Or, if I put my Battery Charger/Starter to 125Amp Start, then the Hum/Buzz comes back.

I'm wondering if this has Anything to do with the Not starting when Hot? Another guy on the Forum has the same problem and has done troubleshooting with KDRotary over the phone and e-Mail for awhile. He finally took it to KD.

Any ideas/suggestions in the meantime would be appreciated!

Thanks in advance!