Rdodds033

iTrader: (9)

i was driving my FD and all of a sudden, cruising at 2k rpms under very little load. the car instantly died.

i thought it was out of fuel and it died 20 meters from a gas station, so fueled it up and it only took about a half tank of fuel.

i tried starting it (while some ******** were laughing at me) and i was going to check my pfc and the keys were lit up but the screen was blank. i took it out and it wasnt hot or anything. all the fuses looked fine.

i threw in my stock ECU and it still didnt fire up.

so i gave up and i called my dad and he towed my FD by the sway bar with a jeep 1 mile to my house.

i checked the circuit relay and the egi relay and they both clicked on and off without a problem, but for now i dont have a multi meter but i will have one tomorrow.

i pulled off the covers to the power FC and i saw no noticeable burn marks.

im gunna check to see if my coils work and my fuel pump works with my stock ECU

ill take some pics of the ecu harness which seems to be confusing. about 6-10 wires were cut and taped at the ends, i will get all the colors of the ones that were cut and see what they go to. some connectors are the same and im not 100% sure on which ones go where so maybe somebody does that can help

i just checked every fuse in my engine bay and every one of them was working, also the egi fuse had power on 2 terminals and grounds on 2 terminals

i found all the cut wires and what they go to

automatic warming solenoid
turbo pre control
double throttle
idle air control
charge relief solenoid
and EGR

it may not be getting a good enough ground so can i add another ground strap to the existing grounds that run into the engine bay?

i need some help and fast...
i want to try and get this working by monday or tuesday

Sgtblue

iTrader: (16)

Crank Angle Sensors?

wstrohm

If you jumper "TEN" to "GND" in the Diagnostic Connector and turn the ignition switch to ON, what does the CEL do? (This will only work with the OEM ECU, I think.)

Are you familiar with the On-Board Diagnostic codes?

Rdodds033

iTrader: (9)

i tried jumping those but my check engine light or my heat warnng light have never really worked.

would it work with the ecu off anyway, if it will then can i use a test light instead of the check engine light?

Rdodds033

iTrader: (9)

i tried the check engine light diagnostic thing with my stock ECU and it still didnt come on.

i checked the connections for my OMP and CAS and they seemed to be fine, havent been hit by the belt or anyhing.

wstrohm

With the stock ECU, does the CEL go on for 2-3 seconds and then off, when the jumper is in place and you turn the ignition to ON?? And if the jumper is NOT in, does the CEL go on and stay on while the ignition switch is in the ON position, with engine off? That is normal operation.

Rdodds033

iTrader: (9)

not once has the CEL ever came on, i was thinking that it should come on with the stock ECU but it doesnt. also, i tested to see if the HWL would come on with the PFC and it wouldnt either. is there any way to make a substitute CEL?

wstrohm

Not sure if this will work for you, but below describes a circuit built by the New Zealand Miata Club to add the fault display circuit to foreign Miatas. The RX-7 ECU fault storage design is very similar. Unfortunately I cannot show the picture referred to in the article, but it's just a light-emitting diode (LED) in series with a current limiting resistor. You can also buy an LED with the resistor built-in if the combo is rated for 5 volts.

The key is to connect the cathode of the diode to the "FEN" terminal and the anode (through the resistor if you are using one) to the "B+" terminal of the Diagnostic Connector. If your CEL bulb is out in your instrument panel but the ECU is storing codes, the LED should do the same thing as a normally-functioning CEL.

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So, what’s up with your engine? Is your engine playing up? Want to know what’s wrong with it? Well now you can find out what’s wrong with your engine, or, at least what the Engine Control Unit (ECU) thinks is wrong with it, which should lead you a good way down the path to correct diagnosis...
The MX-5’s ECU continuously monitors many of the parameters related to engine performance such as fuel, spark, air, RPM, etc. It uses this information to get the most performance and fuel economy possible from the engine. A nice side effect is that it can detect many problems your engine may be experiencing and it even has a way to tell you about them. You may have read in Miata Magazine about reading off the error codes on the check engine light on the dash-board, but our MX-5’s and Eunos Roadsters don’t have this light. Due to a bit of detective work by Glenn Stephens in England, we can now report to you how to make an indicator so you can read these error codes yourself, without having to bother your friendly local Mazda technician with his expensive special service tools.
You will need a Light Emitting Diode (LED) and a resistor. These can be purchased at Dick Smith Electronics, Jaycar or any other similar electronic hobbyist supplier for spare change - less than $2. You’ll also need a separate short length of wire. (An unpainted paper clip will do) If you buy a red coloured LED, you will need a 2000 Ohm resistor, or any other colour will need a 500 Ohm resistor. (If you happen to already have a selection of resistors, any value within about +/ - 25% of these will do). Simply solder one lead of the resistor to one lead of the LED. It doesn’t matter which side of the diode you put the resistor on, but it will pay to take note of which is the longer of the two leads on the diode, as this will determine how you plug it into the car.

The finished product is shown in the picture - it's that simple! Now, locate the Diagnostic Connector in the engine bay. It’s a small black box about the size of a packet of matches, near the top of the passenger’s side (Right hand drive MX5s) shock absorber, also near the engine air inlet snorkel (and it has Diagnostic stamped on it!). After you unlatch the cover, there should be a label inside explaining what the different terminals are called. With the ignition off, use the short piece of wire (or paperclip) to connect the TEN terminal to one of the several GND terminals. Now, connect the indicator between terminals B+ and FEN, with whichever side of the diode had the long lead towards B+ (If you get it the wrong way around, no damage will be done, you’ll just get no light out of it.)

Now turn on the ignition, but don’t start the engine. The LED will light up for about five seconds (assuming you got it the right way round) before it starts flashing out the error codes (if there are any). This will give you a chance to get around to where you can see the indicator. Count the number of flashes to indicate the malfunction code. If the code is a two-digit number, the tens digit will be displayed first with a long flash, then after a 1.6-second dark pause, the ones digit will be displayed with shorter flashes. If there are multiple codes, they will each be separated by a four-second pause and may include two-digit codes, so pay attention. (For example, one long flash followed by three short flashes would be a code of 13) The codes will repeat after four seconds so don’t worry if you miss them the first time. Take as long as you need to record the codes and then refer to the Fault Codes chart shown.
Keep in mind that the indicated device may not be faulty itself, but may have a bad electrical connection, or some other fault may be making it have an abnormal signal. The fault codes are stored by the ECU indefinitely, so after you’ve done something to cure the problem, you need to clear the codes by disconnecting the car battery for a minute or so. This will wipe the computer of its error codes. Now you can drive the car again for a while, and re-check to make sure the error code hasn’t come back. (If you didn’t clear the ECU’s memory, it will still have the old codes.) Hopefully, as several others and I have been able to, you’ll be able to use this information to find the cause of whatever’s wrong with your car. However, I do know one car that runs poorly, but has no fault codes, so its not a complete solution, but it should help the home mechanic (or any mechanic without Mazda’s diagnostic gear) get a better idea what any fault may or may-not be. I hope you’ll only need to use this info to satisfy your curiosity rather than from necessity.
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Rdodds033

iTrader: (9)

ok cool. do you think i can just use my test light to do this? or will it blow a fuse or something?

wstrohm

An incandescent lamp generally uses more current than an LED, so I don't know... I wrote above that the "combo" LED with built-in resistor needed to be a 5 volt type, but looking at the text again, they call out a 500 ohm resistor if you use just an LED and a separate resistor. So I may have been wrong... maybe the combo LED should be a 12 volt type. If so, a 12 volt test lamp might work, but I have not seen that called out anywhere, so the current might be too much for the ECU's driver circuit. Sorry to use so many words to say "I don't know!" I would buy an LED and 500 ohm resistor and go with that setup, just to be safe.

BillM

iTrader: (4)

got spark?
got fuel?

Rdodds033

iTrader: (9)

so far i dont have any spark, with or without the commander. i havent checked with the stock ECU though.

Rdodds033

iTrader: (9)

i pulled off my UIM and my wiring harness isnt in very good shape. would bad wiring cause the ECU to not turn on like that?

Rdodds033

iTrader: (9)

well, i just ordered a wiring harness from a guy on here so i should have that in soon. i guess we'll see what happens

i should be able to test my PFC in another FD to verify that it works

BillM

iTrader: (4)

If there is no spark (on all spark plugs), work your way back from the plugs - see if the common coil ground is good then see if the igniter is sending a signal to the coils. And then if not if the igniter is getting a signal from the ecu. The wiring manual is a big help. You can download it in the stickies...

Rdodds033

iTrader: (9)

theres no spark because the ECU was shut off and it cut spark.

i unplugged the OMP connector because i was getting ready to remove my engine harness. i went and turned on the key and i see "APEXi" light up on the PFC, and it started working again. i plugged the OMP connector back in and the screen went blank. i checked the resistance on the OMP wires and they were all good except one, the omp position sensor wire. i wiggled the harness around and the resistance changes alot so i think its just a short.

i got a good look at the harness and it was cut open by the main pully so now i just need to fix the broken wire and im good

Rdodds033

iTrader: (9)

i get it all put back together and the wire soldered and wrapped with heat wrap. the FD runs like a champ again