Car won't start. Please help.
 

So I have a '91 RX7 with a TII swap. For the first couple of weeks after I got it running it seemed fine. Then it developed a starting problem. I knew i had fuel pressure, spark, and air so I couldn't understand why it wouldn't start. I even hooked it up to a car to make sure it had plenty of power. But no luck.

However when I try to start it my fuel pressure is about 30 psi and it holds that fine. However I unhooked the fuel pump and tried to start it and while doing so it still held about 30 psi.
Correct me if I'm wrong but I would think with the fuel pump unpluged and trying to start it, that the fuel pressure would drop some due to fuel being injected.
This led me to believe that it wasn't injecting fuel.
So I checked the voltage at the 3W, 3X, 3Y, and 3Z ECU terminals and they read 12 volts. So I checked the voltage at my primary injectors, about 12.5 volts. And checked the resistance of my injectors, about 14.5 Ohms. All are within spec so I'm not sure what to do now.
So please let me know if you have any ideas.

Thanks a lot, Ben

Anyone got any ideas? I'm willing to try almost anything. I've been dealing with this for over a month and need to get it fixed.

Check the Air Flow Metter. It couls also be a timing issue, check the CAS.

if it was previously running and it just started
check ur clutch sensor
check ur fuel rail
try priming the fuel system with the papper clip trick
also could it b that its flooded????

last try timing

Thanks for all the suggestions. I tried a few of them but I was thinking that it wasn't injecting fuel when it was trying to start and I just confirmed that today. I zip-tied the primary injectors to the fuel rail and added enough fuel hose to move the rail to where I could see the injectors. Then I attempted to start it while watching the injectors. And they were not injecting/spraying fuel. I had about 30 psi of pressure.

So knowing that and knowing that the injectors are getting the correct voltage and that the voltage at the ecu terminals is correct and that the injector resistance is right, I would think that the only other answer is that the injectors are not being grounded.

So my new question is where does the ground wire for the injectors lead to? I believe it's the black & yellow wire. I've looked at some wiring diagrams but have not been able to work out where I need to look.

All help would be appreciated! Thanks a lot, Ben

The ECU provides the ground signal on the Light Green wires.

So does that mean that there is not a physical ground which I can check? And the wierd thing to me is that, IF I get it started it runs fine, until I shut it off and it gets cold again.

Yeah if you take an LED light and place the negative wire of the light into the back of the pin at the ECU dealing with a primary injector and the positive LED wire into the back of a pin which has power on it when the key is to on and then start the car and the light would flash indicating a ground signal being sent to the primary injector.

I got an led last night and tried that today with no luck. And what I don't understand is that you said that the light green wires carry the ground signal, but at the ECU I have a constant 12 volts on all four of the light green wires for the injectors when the key is in the ON position.

So what does the black and yellow wire at the injectors do? Is that the source of voltage to drive the injectors? And is it possible that I have a loose or bad ground somewhere that could cause this?

You have either a bad ground or a bad ECU.
Are you getting spark?

Yep. I have spark. The thing is that once it's running it's fine. It's just getting it started that's the problem. And now I know that it's because it's not injecting fuel. So I don't think that the ECU is bad. I'm going to check some of the grounds tomorrow and see what I can find.

I wonder who did the swap... If they didn't ground the main injector ground under the vacuum rack then it would act like you are saying...Or if the ground wire to the firewall worked loose.

That'd be me. Second engine I've put in the car. And I checked both of those grounds. I cleaned them and reconnected them. Still no luck. With the key in the on position I have about 13V at the black/yellow wire on the fuel injector connector. And between 5-7V on the light green wires. What I'm trying to understand is how it grounds the injectors. I figure my problem has to be a faulty connection either in the wiring or ECU because it seemed to start when it started getting colder. So maybe there is a bad connection and the metal is shrinking with the cold and looses contact. I don't know.

Still haven't gotten this figured out. Replaced a few grounds following Aaron Cake's writeup on his website. I checked and cleaned the one at the firewall. And replaced one of the ones that grounds under the vacuum rack.
Still no luck. Going to replace a couple more tomorrow and see where I get. I would take it somwhere but I don't know that there's anyone around here I trust. So I guess it's up to me. Let me know if you have anymore advice.

Thanks, Ben

It's like this: the black/yellow wire supplys power to the injectors.

That power passes through the internal coils of each injector and goes back to the ECU on the light green wires. THAT is why you see batt voltage on the light green wires.

The light green wires circuit goes to an internal ECU device and THAT device PULSES a gnd to each injector to make them open and shut........in miliseconds.

So its normal to see batt voltage on the injector clips and also see voltage on the light green wires at the ECU (same source of power).

So now you know how the injectos work. Power to each injector on the black/yelllow and then the ECU pulses a gnd to the light green wires to each injector at the right time.

Look at your tach. Key OFF. Now stare at the tach needle. Turn the key to just ON. Tell us......did the tach needle make a small movement each time you turn the key from off to ON or not? IF the answer is no.........then that's too bad. You have a problem. Electrical in nature.

No tach needle movement also means you have no bannanas.....well no spark is what I mean. No spark.......means no injector action.......means it ain't a gonna start til it's fixed.

Normally if one suspects the injectors not working, he proves it by spraying a two-three second spray of starter fluid into the air filter and then trys to start it. IF it starts then, that means the electrical side of life is good and it's just a fuel problem of some sort.

Series five ECU gnds are in several places. One near the ECU itself and one or two others on the engine block. Sad to say on series five they colored then black/white. Not good thing to do since there are several black/white wires on the EM harness on the engine that are power wires. Dumb move on their part.

FED-EX the car to me and I'll fix it.........humor

The gnds that run b/t an area near the wiper motor to the engine/transmission don't do much of anything in life that makes starting the car happen. The black/white ECU gnd wires do have a bunch of stuff to do with making the ECU/injectors/coils work. The large gnd wire near the starter has a lot to do with making the car work but you KNOW that is good 'cause the starter is turning over. See manual for the ECU gnd points.

Actually you can prove if the ECU gnds are good. Just key ON and then jumper the fuel pump check connector. If the pump works.........then more likely than not the ECU gnd is good. That's on a NORMAL stk RX. If it's been fiddle fucked with then that might not apply especially is someone has rerigged the fuel pump wiring. I KNOW your pump works, but does you pump work with key to ON and the fuel pump check connector jumpered?

That said, if you put the key to ON and the pump runs continuously............then the fuel pump wiring has been fiddle with and my test above does not apply to your situation. Pump should NOT run continuously with the key to just ON/engine off..

Also FYI: The lead and trail coil ASSY's must be bolted to the chassis with at least one fastener. The coil assy's internal gnd circuit is in the bond b/t the coil assy body and the chassis. No paint allowed b/t the two items. I really does not take much contact b/t the two items to let the coils work. I've even just laid the coil assy on the attach studs and the car will start and idle. While its idling you can lift the coil assy up off the attach studs and the engine will die and you WILL get a bit of a shock if one hand touches the chassis and one hand holds the coil assy while doing that.

Ok thanks. That does help me understand the injector system. Now to answer your questions. Yes the tach needle bums slightly when turned to on position. And yes it will fire if I spray starter fluid in a vacuum line that feeds the intake. But as soon as the starter fluid is expended it dies.
And yeah I noticed that with the wire colors. I've checked the one right by the ECU and ran new ones for a few of the other ECU grounds.
And FED-EX is too expensive. How about priority mail flat rate? lol. I SO wish that was possible.

And yes the fuel pump works with the key on and the yellow check connector jumpered. And as far as mods that have to do with fuel and such, I have a Walbro 255 and an rtek 1.5. But I did not rewire the fuel pump.
And no it does not run continuously with the key on and the engine off.

I'm so totally at a loss. I'm sorry I'm so difficult. All help is VERY much appreciated.

Thanks, Ben

Since you have spark (tach needle bumps up a tash when turning the key to ON)........I'd assume the ECU gnds are not the problem.

The fuel pump check connector jumpered causing the pump to run constantly also means the ECU gnds are good.

So you've got spark and the car runs if starter fluid is sprayed for a moment into the airfilter. Injectors are not pulsing a gnd on the light green wires when they should. Sounds like a bad component in the ECU.

It'd help if you could borrow another series five ECU and give it a try.........but if you could you woulda by now.

Maybe send the ECU/RTEK chip back to Digital Tuning and ask them if it's functional?

IF the ECU was pulsing a gnd for the injector wires .......then when you tried the LED light in an earlier post it should have blinked each time the key was just turned to ON ......just like the tach needle bumps each time the key is turned from off to on.

IF the LED light had blinked when attached to one of the light green wires in the ECU plug (plug connected to the ECU doing that)............then I'd have said it was mechanical in nature.....as in the fuel lines crossed/blocked/something of that nature.

FEDEX would probably not have worked. They want a signature when they deliver I would probablY been off somewhere else and missed the delivery.

Maybe I'll think of something else later........for right now it seems to be the ECU to me. Why the injector drivers would have gone tits up is beyond me. Never had that type problem ever myself.


Might try this IF the intake is off the car right now. Pressurize the fuel rail. Then pick out one of the injector wires at the ECU. Put a piece of wire in the back of the light green wire you selected. Then with the fuel rail with pressure momentarily touch the piece of wire to a gnd point (ECU attach stud or such will do). Just a quick momentary touch of the wire to the gnd. Do not hold that wire to gnd for more than a moment. When you do that with the key ON to supply power to the injector.........the injector should pulse and fuel spit out the injector you selected. See if that happens. If it does spit...............I'd say that confirms the ECU injector drivers are shot.

It's NOT the AFM (not used in anyway during START). NOT the CAS because you have spark. NOT timing because it runs when starter fluid is sprayed. NOT ECU gnds cause it has spark and fires up under starter fluid.

Try pulsing one of the injectors like I mentioned in my last post above (fuel rail pressurized and key to ON (power for the injectors and ECU).

IF you had a spare CAS.........you could connect it to the harness. Then with key ON and fuel pump pressurizing the rails.........spin the bottom gear on the SPARE CAS with your fingers. When that is done with key ON.........you should hear the sparkplugs snap and the fuel injectors clickity click. Don't know what else to say right now. The movie Geko/Wallstreet isn't holding my attention right now. Might have wasted five bucks renting it on DirectV.

The ground wires on a series five car are at pins 3A, 3B, 3C and 3D.

3A and 3B are colored black/white.

3C is colored pure black.

3D is colored Brown/Black stripe.

You could pull the plug off the ECU. Put the meter on ohms.........Touch one of those wires one at a time and put the neg lead of the meter to a known gnd point (like that B/W wire near the ECU.

Meter should read less than an ohm. Like maybe .4 ohm or .1 ohm is normal.

I don't think it's a gnd problem buy you can double check the ECU gnds looking at each of those wires one at a time. Key OFF when doing the check.

Your looking at the wires in the elect plug, not inside the ECU when doing this (just in case).

It looks to me like the pure black wire and the brown/black wire are also connected together (spliced together) somewhere inside the harness. Just FYI. So they should read real similar.

The two black/white wires are also spliced together inside the harness. They terminate on top of the engine at one place only. Gnd point 8 according to the wiring diagram. These two black/white are the important gnds imho.

I tried grounding the Light Green wires at the ECU momentarily and it did indeed fire the injectors. And I also plugged up my N374 and when cranked it fired at least one of the injectors. I couldn't see if it fired both.

Just a thought.
do you have an aftermarket fuel pressure regulator on the car?
Have you tried cranking the Fuel pressure up to 40 to see if there is a difference?
..My thought is that the Fuel pressure needs to be sufficient enough to Let the Injectors pulse.If the pressure is not there, then the Injector will not "fire".
I dunno..it's just something I thought about..It wouldn't hurt to try if you had an adjustable FPR.

Do you have a spare CAS. Like out of the old engine?

IF you do. Then hang the primary rail up out of the engine and tie the injectors to the rail with zip ties etc. Pressurize the rails. Then with the spare CAS connected to the harness turn the key to just ON and spin the bottom gear of the spare CAS. The injectors should spit and you should see fuel come out of both primarys. You don't have to spin the CAS very fast to do this.

N374 ECU.........lots of bad talk about using those. More often than not they only half ass work. But you have another ECU you've been using. What is that one? N???

Since the N374 did cause one injector to spit..............it sounds like the problem lies in the ECU you've been using prior to doing that test with the N374. Shows the gnds and power are not the problem and you know the rail has pressure along with the one injector spitting fuel.

Well I think I've got it mostly figured out. I believe my Rtek chip is bad. Because I plugged my stock chip in and the injectors fire fine.
The only problem I'm having now is that it now sounds like my fuel pump is not getting full power. I looked at the FSM and looked at what it said. It said to check for continuity at a the pump connector terminal. And assuming I did it right, (continuity means using the voltage scale and touching one probe to each of the two terminals and checking for voltage, right?) Then yes I do have continuity.
The pump does work but it sounds like it's pumping slower and is not as high pitched as it should be at full power. What could cause this? Bad ground?

I finally got my new Rtek chip and put it in. He said the other one was completely dead. He couldn't read or write it. So that was why my primarys wouldn't fire. But I put the new Rtek chip in and I still can't get it started. I did what Hailers suggested with my spare CAS and spun it. And I can hear my injectors and my coils. I've checked and I'm getting spark. I'm getting fuel and my plugs were wet with fuel. I cleaned and dried them and turned the engine over with the fuel pump disconnected before I put them back in to dry it out. But even with the plugs cleaned it still won't start. Not even when I use starter fluid. And even when the Rtek was bad, I could usually get it to fire with starter fluid even though it wouldn't run. So I really am not sure what to check now. If you have some ideas please let me know. Thanks a lot, Ben

when youre carnking it, do you hear any noises that sound unusual? anything out of the ordinary at all that can help us determine what the problem can be? i have read this thread 2 times and cannot think of anything other than the ECU...