I've had many 2nd gen RX7s and they all have the same warm start problem. the typical starts right up with no help when its cold and not when its warm. I know I don't have a motor problem because this engine in my TII swap is brand new and broken in with perfect compression. Yet it too has the same problem where it starts fine in the morning (cold) and I have to switch the ECU pin 3B (starter signal) off and then it will start. Everything under the hood is replaced and all my sensors check out fine according to the FSM. For some reason my friend's GXL doesn't have this problem and his is an 88' like mine. This swaped 88' of mine used to be a NA GXL and it had the same problem, now with the new Turbo engine, ECU, and senors it still has the same problem. I thought the new engine and sub parts would fix this but nope. The car runs perfect after its running.

Anyone have an idea on how they fixed this problem. I know practically everyone has had this problem and maybe still does, what have you guys done?

 

mine went away when i installed a microtech,did put back in the stock one for a short time(just testing) and the problem came back,swap in again the micro and no problem,so in other words my problem was a bad ecu

 

Hot start issues are often related to low compression in the motor. Have you checked to compression in you new motor to make sure it is good?

I have seen some kind of a mod to the ECU to help with this issue before as well. IIRC you need to put a different resistor in or something along thoes lines. I believe it was on this forum but i'm not 100% sure.

 

i had a thread about this problem...my fix was a starter relay rewire and changed the brushes in my starter ...it spun the motor real fast that it had no chance to flood ...in my thread there was alot of differant fixes ...ive built alot of motors and its not low compression ..if your motor spins fast enough you ecu cant put you in flood condition ...ive been there done that.....when sensors fail and the ecu fails it will shoot more fuel ...but in my case it has no chance to flood...flood freeeeeeee

 

Perfect compression, over 85 psi all rotations front and rear. 85 is brand new in my high altitude and especially on a S5 Turbo engine.

Microtec huh? I'm pretty sure its a factory ECU problem cause my friend has about 60 psi compression on his TII (ya thats low compression to the max) and me has a Rtek 2.1 and his starts right up at any temp and runs fine. So first fix is... 1. ECU

New starter maybe. I haven't put a new starter in it so maybe its not spinning fast enough?? ok next fix... 2. faster starter

I think aaroncake did a fix where he put a resitor inline with the temp sensor wire that fooled the ecu into giving out less fuel and that fixed the hot start problem but made it a little more difficult to start in colder conditions...

Keep the ideas coming guys, I have tried different new and used TII ECUs both N332 and N333 but the same problem came up...

 

mine runs rough on hot starts because of intake temp sensor heat soak

 

hmm intake temp sensor... I've replaced mine with another known good used one and a brand new one. same issue though. I haven't tested those wiring harness wire though. I should check the leads to it when I have some spare time

 

As soon as I went standalone, the car has never flooded. I can start it, move it in the driveway for 20 seconds, then cut it off, and it always starts up the next time. Now I have clean injectors and a healthy motor so that helps.

 

All you have to do to see if the water thermosensor is working or not, is to backprobe its input to the ECU when the engine is cold, and watch the voltage drop as the water heats up with the engine running. It should drop to approx a half volt when fully hot.

See the remarks about the after market ECU's and how they have no problem? What they've done is eliminate the stock ECU Start Map and substituted a different amount of fuel during Start.

Buy a RTEK2.1 and you can eliminate any hot/cold/whatever start problems .....without using a fuel cut switch (what a drag).

 

yup. Rtek 2.1 is pretty much the next thing I'm getting done for my TII swap. I should have mentioned that I have a Rtek 2.0 on my 88 AE and it doesn't have the hot start problem, it did when I had the stock ECU in it though. I'm just wondering what Mazda was thinking when they made crap startup maps and not the maps found in standalone ECU's like the Rtek ECU. In the long run it would have been better for them cause their rotaries would have run longer without having to replace the engine due to lower compression and no start. Like I said, my friend has about 60psi compression on his TII and won't start at all with the stock ECU... you put his Rtek 2.1 in and it starts every time

 

Its not the issue of a old one. Its the placement of it. The closer it is to the engine, the more chance it will get heat soaked after the warm engine sits for a while. This might not be your problem, but its the problem with mine and a few other people Ive seen. I run a megasquirt stand alone, so its not hte issue of having an aftermarket ecu. Here is what mine does, you might or might not have the same problem. BTW my temp sensor is on the elbow right off the throttle body, I will probably relocate to my intercooler piping soon

When i drive my car, it starts up fine. I drive to full warming temp, and if I start my car up within 5 minutes, my car is fine, but if it sits for more than 15 minutes, my car has trouble idling. It gets really lean a/f ratios hitting 15:1 or leaner. It usually causes my engine to idle rough and eventually die out. I have to keep a little throttle to keep the engine alive. after 3 minutes, the a/f ratios go back to normal. It might or might not be your problem, this is what Ive experienced

 

Ya I relocated my temp sensors ( I have 2, one for the ECU and one for a digital Intake temp gauge) one to the elbow like yours and one on my intercooler piping. Both locations give just about the same readings and the same issues... Both sensors are N326 they say on the side, I have a N332 or N333 (turbo) ECU, is there a N332 or 33 Intake temp sensor and are they different? Maybe that?? After all this is a swaped TII engine so it has my NA intake temp sensor...

 

The air intake temp sensor is NOT used for starting a RX-7.

 

Didn't think so hailers. Its all about the water thermo sensor, altitude sensor, and the internal fuel map... It was worth a shot though...

 

Now I know there are resistors I can put inline with the water temp sensor that fool the ECU into thinking the engine is hotter thus giving it less fuel at startup. I remember in the past where one of the moderators built a device that was a solenoid activated by the starter impulse that added a resistor inline with the water temp sensor and then back to no resistor when the starter impulse was gone (engine running) I'm trying to look for that thread right now... Does anyone remember what resistor that was? above all I could experiment with that slightly and find the right resistor so that the ECU would think the engine is hotter than it really is and lean the startup map a little so it actually starts normally. Maybe I can remake the solenoid resistor design to perfection so that there would be no cold start issues that the first design had...

 

My stock ECU/engine has no problems starting up cold or warm, let alone un-flooding. (Go go gadget S5)

 

I wrote about using a resistor at one time, then in the same thread changed my method to using a Voltage Switch Kit made by JAYCAR (Aus). It, the voltage switch, kept the Start signal to the ECU up intil the time the water thermosensor reached a temp of somewhere around 110-120*F, whereupon at that figure the voltage switches relay pulled in and kept the signal from 3B reaching the ECU.

So at that temp and above, the ECU used the afm for fuel delivery at startup and not the Start Map inside the ECU anymore.............til the water temp fell down below the 110-120*F.

That setup worked like a charm. Since then they came out with the RTEK2.1 with a feature where YOU can set the ms the injectors stay open during Start. So the JAYCAR got removed and the RTEK2.0 got a new chip to update it to a RTEK2.1.

JAYCAR is Austrailian and it's catalog is online. It is a KIT. It needs to be soldered together and then you have to adjust it to fit your needs/trigger.

Anyway, the resistor idea was ...........not that good an idea. It would have been better to just have put a switch inbetween 3B and the ECU than rig a resistor. Bad idea.

http://www.jaycar.com.au/productResu...p?FORM=KEYWORD The universal voltge switch in that site.

 

Ya thats the trick. Right now... I have a switch in between 3B and the ECU.... Kind of a drag when I want my girl to drive the car somewhere, she's got the hang of it now but still I'm looking for a cheap and automatic alternative to switching the circuit. It makes me wonder.. did this car ever start right from factory?? Everything is new in it...

Thanks for the info Hailers. This RX7 isn't my primary RX7 or else I would have bought the Rtek for it already. The discomfort of a switch is better than ~$400 right now I guess; That money could go towards stuff in my AE right now instead