NZJDM

Hi there,

My Name is Marc i have a 1990 Fc 13b turbo its not my first Rx7 so i know a little but this particular issue has me stumped.

full story.
yesterday i was driving in traffic never got above 3-5k rpm for about an hour in total, i was about 3 quarters of the way through my trip when the car began idling lower (not miss firing) and when the car hit boost it choked and blew alot of black smoke..
i got home turned it off as usual then left it for a couple of hours (thinking its been over fueling) i tried to restart the car and it would not fire,
so figuring the plugs where fouled i pulled them out and put fresh ones in.
no luck! car still wouldnt fire,
so thinking that maybe i had not cleaned the chambers out properly i pulled the plugs out again. this time i noticed something i found odd. when the ignition was turned to full offthe t2 plug lead started firing randomly?? just T2 only.
Now im not sure if this is related but i figure it is and it sure seems odd to me ?

anyone had this before or know what the cause maybe?

thanks in advance to any input
Marc

misterstyx69

iTrader: (142)

Never heard of this one.
I can only guess a bad trigger in the Trailing coil.

satch

iTrader: (1)

Main relay must have been stuck closed. If you pulled the plug w/the Black/Yellow wires off and the wire had voltage w/key to off then this basically proves the relay is stuck closed as the B/Y wire should only receive voltage w/key to on. The B/Y wires power the coil.

NZJDM

hey guys thanks for your reponse's.

well....... what a day of head scratching so i found the cause of the trailing plug firing. a live wire was touching the the body intermittently i have fixed this but the car still wont start!!!.

i suspect i have fried something in the the fuses all seem fine(visual)

to add to this on my search through the wiring jungle to find the car is fitted with an mt-8 microtech that seems to piggy back the main ecu?

it has a green light that comes on with ignition on ? there are two other lights which stay off.

im sorry for the sporadic info but i have only just bought it and i was not made aware of the cars full
situation.

more than anything where should i start here? or do you think i should just take it to an auto elec?

please ask if you need any further info im trying my best to get you as much info as i can.

my goal is to just get it going so i can take it to be tuned.

thanks heaps guys

satch

iTrader: (1)

W/key to on the B/Y wire at either coil should have 12 volts and the B/W wire at the check connector near the lead coil should also have 12 volts w/key to on. If they don't then check the EGI fuse and the 15 amp Engine fuse. If you have voltage on both wires then you could disable the fuel pump and spray one to two seconds of starter spray into the air intake. If the car starts up briefly then you know you have spark and should focus on the fuel side of things.

NZJDM

Thank you satch, i will do exactly that..
im fairly sure i have fuel though as the plugs are wet. (after i did the full un flood procedure and re tried to start)

that being said i will report back with what i find

Marc

NZJDM

no spark..

i have power at the main fuse, both sides with the fuse in. i also have 12v at both terminals of the engine fuse without the fuse in? ie fuse removed touch the left stalk 12v, touch the right stalk 12v is that right? seems wrong to me?

i also have power at the both b/y wires and the main plug by the leading coil.

the trailing coil T1 output gives a small spark when the key is turned to on but none there after and the leading coil has nothing at all,

Marc

satch

iTrader: (1)

A stuck Main Relay can cause the Engine fuse to be backfed voltage. When I say Engine fuse I am referring to the 15 amp fuse in the interior fusebox. Are you talking about this fuse or the EGI fuse in the engine bay fusebox? The EGI fuse is powered by the battery so this fuse would always have constant power on either side of the fuse. Also, have you messed w/either the CAS or the AFM? And did you check for spark at the coil bore or the sparkplug end? It's best to pull the plug wire from the coil bore and rest the wire against the bore to check for spark. This eliminates both the plugs and plug wires as possible causes of your problem.

NZJDM

Thank you again Satch,

im very sorry it seems i miss read one of the posts you made earlier.

i was confusing the EGI fuse with the engine fuse so i will retest.

As for any other parts on the car ie CAS AFM etc none of these have been touched all that has happened is;

-car running one day
-car starts running rough not boosting
-car wont restart after use (i used new plugs and cleared the fuel)
-car still wont start wont even fire,
-i redo the unflood process as before and discover the trailing plug firing non stop with key in off
-discover a wire shorting on the body (fix)
-check fuses both in and out of the car. all seem fine.

thats all i have done so far also i did not test the spark from the coil, only from the lead but i did use two different sets of leads.

ill let you know how the re test goes.

Marc

NZJDM

ok more info that i hope can help.

-the rpm gauge does not bounce when car is turning over(read somewhere it should)
-the main RELAY Clicks when key turned to on.

as i mentioned earlier too the trailing t1 has a one spark when the key is turned to on (just one pulse)
this as caused the engine to do a random "fire" when i turn the key on a couple of times?

im trying my best to relay this information as best i can for you

Regards Marc

satch

iTrader: (1)

One thing you can do is test for the voltage on the Brown/White wire at the Boost Sensor w/key to on and it should register 5 volts or so (don't confuse the Br/W wire w/the Br/Black wire found in the same plug connector). W/o this voltage reading you will not get spark or fuel injection.

You also need to verify that the battery is properly charged and creating the proper cranking amperage. A car can start and run properly just from the lead coil so you should focus on that coil at this point in time.

And could you provide some more insight as to what wire specifically was bare and touching against the engine as previously noted? The wire color is of importance here. And can you trace where this wire either came from or runs to?

And in addition I am only really familiar w/the stock setup on these cars so that you have a Microtech component makes things a bit confusing to me.

NZJDM

Thank you I will test those things and see how I go

- the battery is fine plus I have a jump pack added to help out..

As for the wire.. it was for the Radio! a power cable running direct from the battery
it was touching the 10mm mount screw of the lead coil as it ran off the battery

(the wiring in this car has a lot to be desired) that being said its not uncommon to see this in old Mazda's here in Australia

Regards the aftermarket computer, I understand I really appreciate the fact that you have some helpful direction for me to follow..

it is just piggy backing the system, a common thing to do here to help keep the system less detectable

Marc

NZJDM

Ok Brown and white wire has no signal.

also there is an HKS ECV fitted to it so while the factory boost sensor is plugged (wired) in it is not hooked up to vacume.

Marc

satch

iTrader: (1)

Is this the unit you have?

http://microtechefi.com/download/MT_...2024%20WAY.pdf

You need to make sure that the unit is receiving 12 volts w/key to on. If you measured the Br/W wire at the TPS w/key to on and it had 5 volts then this should verify whether the MT-8 is powered up properly w/key to on.

NZJDM

Yeah that's the system.
There is power on the unit, All the lights come on as they should ill double check that it has the correct voltage though.

NZJDM

ok so i have 12v at the input for the microtech. i have 4.98v at the TPS ...

while testing the input to the microtech i left the key on for about 2 minutes the yellow and green lights on as usual but then the red light came on and was flashing, soooo thinking i was onto something i rang microtech they said this means a "sensor error" but i need the hand controller to figure out which sensor. (unless you have a way to figure it out) plus the MT-8 is now and old out of date computer.

The hand controller did not come with the car and costs 225+ some post which i guess is not bad.
but for 1000 i could have a power FC which has a controller and plugs direct into the system no crazy piggyback wiring. plus my tuner recommends them.

so maybe if you can help find the sensor that is faulty so i can save that 225 to put into a power FC?

maybe im getting ahead of myself so by all means if you have a better recommendation id be more than happy to follow your advice on this.

i just want my car to start haha

Regards Marc

Marc

satch

iTrader: (1)

You should have a check connector w/one single Orange wire located by the lead coil. Grounding this wire plus turning the key to on will spit out any error codes unless your car does not provide error codes. I know the JDM's do not but not sure if this is the kind of car you have. If it is then there is an alternate method for pulling codes which you can be provided with. The following link illustrates how to use the S4 version on an S5.


http://2ndgenrx7.freeservers.com/error%20codes.html

And there are only so many sensors connected to your Microtech as shown in the diagram I linked to. My best guess is it is the CAS or perhaps the AFM. You could possibly unplug the AFM w/the fuel check connector jumpered and see if you can regain spark. Do you happen to have a spare CAS on hand as this would help also?

NZJDM

I dont have a spare unfortunately. But ill try get hold of 1 ill also try the tests you have said above.

Thank you again for your very easy to follow help.

My car is Australia new. Im not sure what the spec differences maybe over JDM or USDM. But ill do some reading.

Does the fact that the rear coil has 1 spark when the key is turned on help the direction of testing etc ?

Again thanks for your help its really helping me understand the car better.

Cheers

Marc

satch

iTrader: (1)

Not really sure about just one spark on the trailing coil. As far as the lead coil is concerned it should have a plug w/two wires. One is B/Y and the other is Green/Yellow. The G/Y wire is the firing signal wire thus the voltage on this wire changes from 0 volts to 5 volts over and over when the main pulley is rotated w/key to on. You can rotate the alternator pulley which should turn the main pulley. As this pulley is rotated you should notice the voltage value briefly change to 5 volts and then quickly back to 0 volts in a repititious manner. If you don't see this change then something is going on in the CAS, AFM or ECU/MT-8. And both coils must be bolted firmly to the fender for grounding purposes or the igniters will not work.

And if you can get a spare CAS you unplug the installed one and plug in the spare and w/key to on you spin the CAS wheel and you should hear both the injectors and coils fire.

NZJDM

All i was able to check tonight was the green and yellow Firing signal wire ant the leading coil. i got 3.36v! constantly no change at all when rotating the engine in its correct direction.

as for the fuel check connector i could not find it? i saw your other posts and pictures but the all apply to usdm cars so far as i could tell?

then only plug similar and in that area has a male plug inserted with wires running into the loom.

Marc

satch

iTrader: (1)

The fuel check connetor is part of the Emission Harness which feeds the Boost Sensor so it lies between the passenger strut tower and the engine. Plug is Yellow encased in a Black rubber boot and has but two wires. You can also jumper the two wires on the bottom row f the Circuit Opening Relay found to the right of the steering column just under the dash and this relay is Yellow and Black. Focus on the CAS and AFM.

NZJDM

Ok will do. As for the fuel check connector. My car is RHD the boost sensor is also on the right (driver side) im just wondering if there will be a difference do you think? As I felt I was very thourough in checking that, I will look again though.
What I noticed yesterday was there where two relays becide the engine fuse box. I thought they were for the MT-8 and 1 is but 1 is for a direct feed to the fuel pump. If that is the case would they need to plug into the check connector?

satch

iTrader: (1)

I wouldn't think so. The only reason for jumpering the connector would be to make sure the fuel flows if you were to unplug the AFM which if done would normally interfere w/the fuel flow. If in doubt just jumper the two wires at the Circuit Relay.

NZJDM

Is the reason for the jump to allow the car to start with no afm?
Sorry if that maybe a stupid question. Im just trying to understand the process im going though as im finding it very interesting.

NZJDM

The above assumes the Afm to be at fault.