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-   -   Signal from ECU to leading coil (https://www.rx7club.com/2nd-generation-specific-1986-1992-17/signal-ecu-leading-coil-953064/)

alritzer 05-05-11 04:02 PM

Signal from ECU to leading coil
 
OK guys. I have it pinned down but I don't know why its happening. I went back over several of the ideas that have been offered.
I was checking the leading coil and found that the ECU is not sending the signal for the coil to fire. There is supposed to be a 0 - 5 v signal coming from the ECU to the coil but my ECU is not sending the signal.
I don't think its a faulty ECU because I have 2 ECUs and they both don't send the signal and I checked the continuity of the signal wire and its OK.

So, does anybody have any ideas? Is it part of limp mode? This has to be the problem because it runs exactly the same with or without the leading coil plugged in.

HAILERS2 05-05-11 04:34 PM

What year car?

HAILERS2 05-05-11 05:28 PM

IF it's a series four then check out the CAS wire that is green and ohm it out from the CAS's plug to the ECU's plug at 1N.

Unplug both plugs doing that. Ohm from one end to the other. No long leads? Then get a piece of wire and put one end into 1N (the plug wire, NOT the ECU itself) and ground that new wire. Then check for ohms at the green wire of the CAS with that plug disconnected. One meter lead into the green wires socket and the other meter lead to a known gnd point. Meter on ohms.

Then you might just undo your gnd at 1N and make sure the meter reads open.

Lead depends on the G signal which is from the Green wire of the CAS's plug.

Trail coil(s) depend on the Ne signal on *other* CAS wires.

Is this a swap of some sort? Series five somewhat different.

HAILERS2 05-05-11 06:35 PM

1 Attachment(s)
If sereis five some of the above does not apply.

See attached jpg.

The G signal is on pin 3G. It's a White wire at the CAS going to 3G on the ECU.

So ohm that wire out with the plug off the CAS and the ECU.

Also make sure the Red and the Green wire at the CAS plug are both going to 3H at the ECU plug. See attachment.

alritzer 05-05-11 07:52 PM

I'm sorry, I've posted so many times on here about this 7 that I forgot that people would not know what car I was speaking of.

1990 GXL auto/T2 5 speed swap. The swap motor was a 1990 also.

Rtek 1.7
720 cc secondaries
walbro 255
3" straight thru exhaust
no emissions except BAC
TPS set by 1 v and leds
timing is dead on

starts right up but sounds and feels like it is running on 1 rotor
Runs no different if leading coil is unplugged

arghx 05-05-11 08:50 PM

I question your grounding.

alritzer 05-05-11 09:45 PM


Originally Posted by arghx (Post 10606926)
I question your grounding.

The grounding should not be a problem. I just recently re-did all of grounds. I added a 10 ga ground from the battery to the base of the ECU and a 4 ga cable from the middle iron to the firewall and another 10 ga from the battery to the middle rotor.

alritzer 05-08-11 07:51 AM

I checked all of the wires from the CAS to the ECU and they all have continuity. The CAS resistance value all check out OK also. I checked for continuity from the green/yellow wire from the coil to the ECU and its also OK.

Would any thing else cause the leading coil not to recieve the firing signal from the ECU. I have 2 ECUs and neither sends the firing signal.
I check for the signal at the ECU and it is not there.

thanks guys

HAILERS2 05-08-11 09:49 AM

Nope. Don't know of anything else. Try another CAS. Their bullet proof unless someone sticks a screwdriver down in 'em, but if you have another try it.

Both the Lead and Trail coil assys must be bolted to the frame with at least one fastener for them to work. The ignitors internal circuit depends on a gnd from the coil assy's body to the car frame. So you have four studs holding the thing in and you don't want any paint b/t the coil assy and the car body/studs.

satch 05-08-11 10:08 AM


Originally Posted by HAILERS2 (Post 10610489)
Nope. Don't know of anything else. Try another CAS. Their bullet proof unless someone sticks a screwdriver down in 'em, but if you have another try it.

Both the Lead and Trail coil assys must be bolted to the frame with at least one fastener for them to work. The ignitors internal circuit depends on a gnd from the coil assy's body to the car frame. So you have four studs holding the thing in and you don't want any paint b/t the coil assy and the car body/studs.

Just a thought, but what if he by chance rotated the engine in the wrong direction. Would doing so prevent the signal on the Green/Yellow wire from being present?

K-Tune 05-08-11 10:53 AM

Are you absolutely sure that your injectors are plugged in properly? n/a versus turbo harness do NOT plug into the fuel injectors the same way. If you have both your primary plugs on one rotor then you will only fuel one rotor.

The signal that comes from the ecu to the coil may be hard to see on a volt meter since it's very brief and only happens while the engine is rotating.

HAILERS2 05-08-11 11:58 AM

I just now did this on one of my cars. I used a really cheap but good meter called CEN-TECH from Harbour Freight.

I stuck the neg lead probe into the neg termina of the battery.

Pulled the small white two wire plug apart at the Lead coil assy.

I cut a half foot of small gauge wire and cut the insulation off each end. I wrapped one end of that new wire around the positive meter termial. The other end of the new wire I stuffed into the white connector where the G/Y wire is.

Key On. No voltage showing. Turned the front pulley by putting my hand over the front of the pulley and turning it clockwise. Duh. After two complete turns no change in voltage. errrr ahhhh had the meter on amps.

Put the meter on the lowest scale on this meter which is 0-20 vdc. No voltage showing. Slowly turned the front pulley with my hand over its face. Voltage turned to 4.99vdc before a full turn of the pulley. Turned it maybe a quarter turn more and it went back to zero.

You don't have to turn the front pulley fast at all. I was turning at less than one turn a minute.

I turned it counterclockwise to see it it would produce running backwards and still works. Shows zero thru most of the one turn then turns to 4.99 vdc and that goes away after (guessing) a quarter turn or less.

Hoped that answered any questions from above. Normally I use the A/C belt and pull on that belt towards me to do this. The car I was using had no a/c belt so instead of getting a ratchet/socket out I used my had over the face of the pulley and turned clockwise (although counter clockwise will work just fine).

So even a cheap in cost digital meter from Harbour Freight will work fine. It's just their meter leads have those probes on 'em that are hard to work with sometimes. Like i say, I stripped some 26ga wire and wrapped it around the pos probe and stuffed the other end into the G/Y socket on the small white plug.

Make sure you meter probe is touching the terminal inside the white plug. It might be too large a dia and not getting far enough into the socket to touch the termainal inside.

alritzer 05-08-11 03:33 PM

I really appreciate you guys staying with me on this one. I'm going to try to get a reading from the ECU again and even I don't get the reading I'll pull the UIM again to double check the wiring to the injectors but I used the wiring schematic the last time.
I don't think both ECUs are bad.

I bought another na emissions harness. If I we haven't figured it out by the time it comes, I'll swap that out.

Would be nice if I knew somebody local that would let me try my ECU in their T2.

alritzer 05-09-11 02:34 PM

Well it must not be the firing signal from the ecu because it runs just as good without the trailing coil as it does with. I let the engine warm up and then I unplugged the trailing coil harness, nothing changed - rpm stayed the same and it still sounded the same. So the primary coil has to getting a signal to fire.

I went back and checked for compression again. I could only get bounces in the 65 psi range but all faces were even and when I checked without holding in the release valve on the compression gauge both rotors were 90+ psi. I don't know what to make of the 65 psi reading but there was definitely 3 bounces per rotor.

Any ideas how to proceed?

HAILERS2 05-09-11 03:13 PM

Idles???? how. Kinda ok at ??? 700-900 rpm or so?

You can check to see if the primary injectors are plugged in by just going to the ECU's small plug and back probing the Light Green wire and then the Light Green/Black wires on the small plug of the ECU. All plugs connected up and the key to On and engine OFF.

If you see batt voltage on those two wires then the plugs are on the primary injectors.

Its possible to have mixed up the primary and secondary injector plugs . About the only way to prove if you have those right is to pull the intake manifold and check either the wire colors on the injectors or key ON......backprobe a primary injector.......see batt voltage on it......pull plug off primary injector........voltage disappears on the meter proving you have the primary injector plug on the primary injector.

Primary injector plug on the secondary injectors would make the engine run kinda funky. Three even pulses on each rotor should eliminate a broken apex seal even if you just put a finger over the sparkplug hole and feeling for pulses.

alritzer 05-09-11 10:28 PM


Originally Posted by HAILERS2 (Post 10612453)
Idles???? how. Kinda ok at ??? 700-900 rpm or so?

You can check to see if the primary injectors are plugged in by just going to the ECU's small plug and back probing the Light Green wire and then the Light Green/Black wires on the small plug of the ECU. All plugs connected up and the key to On and engine OFF.

If you see batt voltage on those two wires then the plugs are on the primary injectors.

Its possible to have mixed up the primary and secondary injector plugs . About the only way to prove if you have those right is to pull the intake manifold and check either the wire colors on the injectors or key ON......backprobe a primary injector.......see batt voltage on it......pull plug off primary injector........voltage disappears on the meter proving you have the primary injector plug on the primary injector.

Primary injector plug on the secondary injectors would make the engine run kinda funky. Three even pulses on each rotor should eliminate a broken apex seal even if you just put a finger over the sparkplug hole and feeling for pulses.

I checked for voltage at the light green and light green/blk wires and neither showed any voltage.
Shouldn't the engine be running? Shouldn't voltage be present only if the injector is firing?

I'll check at what rpm it idles at. Maybe I can get a video.

thanks

HAILERS2 05-09-11 10:47 PM

1 Attachment(s)
Ah shucks. I forgot this is a series FIVE car.

Still, the colors of the primary wires are whats shown in the attached jpg for a series five. View is looking into the Wire side of the ECU plug.

Power is there anytime the key is ON. What makes a injector work is the ECU pulsing a ground on those wires.

So you should see batt voltage on the light green wire and the light green/black wires and even the other two secondary injector wires any time the key is ON.

Doing this your allowed to remove the plug from the ECU and then put the meter on the wires in the plug. Key to ON should show batt voltage if the injector plugs are on the injectors.

Injectors have two wires going to them on series five. One wire on all those injectors is black/yellow and it feeds power to the injectors. Power passes thru the injectors coils and comes out the Other wire on the injectors and that wire goes directly to the ECU plug. So you can see how those injector wires should have power on them anytime the key is ON.

No the engine does not need to be running at all.

Make sure your meters neg lead is on a good ground when doing this.

Still no power on the light green or light green/black wires? Then some problem exists with the plugs on the injectors themselves. Check the secondary wire in that plug for power also. I mean if this car has been running, at leas two of those wires has to have power on 'em.

alritzer 05-10-11 03:53 PM

OK, I re-checked for voltage using a better meter (Fluke). All four injector wires showed 1.7 V. I used the ground that goes to the bottom of the ECU. I checked each of injector wires that goes to the ECU and they have continuity. There must be an intermittent open on the blk/yellow wire. I see that it goes to both coils also. Should I expect to have continuity from the blk/y wire at the injector to the blk/y wire at the coil?
It shouldn't even run with that voltage unless the wire is broken but close enough for the electric arc to jump it....... right?

any thoughts?

HAILERS2 05-10-11 07:24 PM

The car won't run with the injectors seeing the low voltage your mentioning. Your doing something wrong. I know not what. Your doing something wrong with the meter your using.

You put the key to ON. You pull the plug off the ECU. You checck each of the injector wires one at a time. They all should have batt voltage on them.

satch 05-10-11 08:21 PM


Originally Posted by alritzer (Post 10614263)
OK, I re-checked for voltage using a better meter (Fluke). All four injector wires showed 1.7 V. I used the ground that goes to the bottom of the ECU. I checked each of injector wires that goes to the ECU and they have continuity. There must be an intermittent open on the blk/yellow wire. I see that it goes to both coils also. Should I expect to have continuity from the blk/y wire at the injector to the blk/y wire at the coil?
It shouldn't even run with that voltage unless the wire is broken but close enough for the electric arc to jump it....... right?

any thoughts?

The ECU has 4 mounting bolts. Use one as the ground source for the multimeter.

e_deher 05-11-11 07:04 AM

my ecu sends a signal to my coil even when its not bolted down... i am building a kit car and wired up the coils myself and they seem to spark but the spark seems weak to me. the coils are bolted down because none of the wires coming from the coils are grounds. they are grounded by bolting them to the chassis.

alritzer 05-11-11 08:41 AM

Thanks for the input guys. I'm most ascertained that I'm checking for voltage in the correct manner. I took a class last year on electronics and we used the Fluke often. I took the UIM off, maybe something is unplugged.

What a PIA. No matter, I purchased another NA harness and it will be here today. I'm not even going to try to trouble shoot it now. I'm going to swap out this harness.

If I still get the low voltage readings then I must have forgotten how to use the meter or maybe just blame it on me being blonde :).

I'm not sure if this is related: Until recently my oil pressure gauge worked, now it doesn't move at all.

I think the moral of the story is: Don't ever buy a gxl/t2 swap that was done by a 19 year old and his friends.

thanks guys........... to be continued!

ash :)

HAILERS2 05-11-11 11:30 AM

1 Attachment(s)
Thread owners coils are working but I thought I'd add this jpg showing why a coil/ignitor assy needs to be bolted to clean metal of the chassis for the coil to work.

alritzer 05-13-11 03:51 PM

My replacement wiring harness should be here tomorrow.

I was looking over the wiring on my present harness and I noticed that one of the primary injector's wires are not connected in the correct order. At some point the previous owner installed new clips/pigtails on the primary injectors but one injector is wired opposite of the other. One injector has the red wire going to blk/yellow and the other injector has the black wire going to the blk/yellow.
Since its a DC circuit I guess that they would both need connected in the same manner.

Comments?

papiogxl 05-13-11 04:31 PM

Injectors are non polar, it doesn't matter which wire goes to which side.


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