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.

What year car?

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.

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.

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

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.

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

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?

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.

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.

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.

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?

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

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.

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 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.

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

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.

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 :)

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.

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?

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

Yep, polarity makes no difference.

You may be barking up the wrong tree, the engine management computer gets its signal from the magnetic pulses from the Distributer(crank fire ) you may have the wrong Dist installed in your car,if so it will not run properly Is it a S4 or a S5 they are wired different even though they look the same ,or you may have a broken( magnetic pickup )wire inside the Dist (been there ),also to test the engine compression remove the lower air valve on the compression tester,then remove either both lead or trailing plugs remove the power wires from the coils, turn overthe engine and watch for compression readings If they are really 65lbs,each,and they do not go up,and you have tied to lube the seals,and remove the carbon by spraying the rotors with a Sea foam, .............or Varsol/ATF mix 50/ 50(been using for 30 years)into the spark plug holes.(let sit , up to three days after turning over(coils off ) It may be time for a rebuild.........Rotaries do not like to start with low compression(major flooding).....Good Luck

I'm not exactly clear on what the trouble is with OP's car. Did I miss the part about the symptoms OP is getting? OP?

OK, this problem has been going on since I bought this 7. It starts easily, within 2-3 seconds. Idles pretty good but it sounds like its running on one rotor and it misses enough to make the engine vibrate. It has no power, its hard to get it moving.

I've changed the CAS, TPS, fuel pump (Walbro), ECU (I'm on 3rd), wires, fuel filter. Timing is dead on, TPS is set to 1v, fuel pressure is OK, it runs on the primary coil alone as good as it does with both. I'm going to swap the wiring tomorrow, maybe.

Make sure the primary and secondary injector plugs are on right. Other than that it sounds like a bad rotor/seal. Hate to say that and probably shouldn't since I'm not there to see it. Has the traits.

IF the injector plugs are on right you might try swapping the injectors, putting the secondarys in the primary spots just to see if its an injector problem. assuming both primary and secondary are the same cc's.

Basis but has to be said: sparkplug wires on the right plugs? sorry 'bout that.

I'll try swapping the injectors, I have several sets.

The wiring harness arrived and so did the clips/connectors so I'm going to changed the injector clips and then swap out the wiring harness. I'll give everything a once over and fire it up. If it runs the same, I'll just prepare to remove the engine and tear it down to see what madness the PO did. He told me that it had 38000 actual miles on it and had recently been rebuilt with 3mm seals and had street ported. Maybe.... but if it doesn't run correctly I can just consider it all lies.

i would check to make sure your coils and injectors are in good working order before removing engine dude. check your compression too if you have a tester.

Well, the wiring harness arrived and I finally got it swapped over but now I don't have any spark. I checked and I have power from the main relay to the ECU.
That's as far as I've gotten. I'll look at the older posts and see if I can figure anything out.
Maybe I can get a word of wisdom from somebody way more intelligent then me.

I think I'm working backwards.

Go to the ECU and pull the plugs off.

Ohm out the coils inside the CAS from the ECU plug. Ohm out from 3G to 3H on the plug and then 3H to 3E.

Each should read approx 200 ohms or whatever the FSM Engine Electrical section says. I believe it's 200 to 220 ohms each from memory.

This will prove the wiring b/t the CAS and the ECU is correct.

EDIT: No it's supposed to be 110 to 210 ohms or anywhere inbetween those numbers will be fine.

OK, I did and they both check out. So I guess that verifies those two circuits and the CAS.
I was really careful making sure everything was hooked up. Maybe I was sold a defective harness.

Make sure the Black/Yellow wire(s) at the coils have power w/key to on. If not then check the EGI INJ fuse.

Thanks Satch, I'll check them in the morning.

Forgot that your car is an S5 so you have no "INJ" fuse found in an S4. Check for voltage on the B/Y wire w/key to on anyway and if that checks out okay then recheck the voltage on the G/Y wire at the coils for the cyclical 0 to 5 volt response as the engine is turned by hand w/key to on.

I checked the black/yellow wire and it does show 12 v. The G/Y wire shows continuity from the ECU to the CAS but I haven't checked to see if it is sending the fire signal yet. This is about where I was before I swapped the harness but before it ran, although it ran really bad. If I cant get the fire signal does that point to a bad ECU. I have another ECU but I would hate to fry that one also. I have about $625 in ECUs. It looks like some people are frying their ECU and just selling it to somebody else. NICE but maybe not.

to check out your Ecu open it up and remove the first board lay it over the edge and look at the second board are any of the resisters Burnt(blue now brown) if they are just take the resister code and replace it with a new one (cheap)or remove from scrap Ecu ,and solder in,I think you should check your wiring on your crank fire to see if they are connected,they control the spark,as well as fuel pulses.............................

Since the ECU is getting power like you said........and the CAS wiring ohm out from the ECU plug thru the CAS reluctors and back proving them good..........pull the elect plug off the boost/pressure sensor and with the key to ON see if there is five volts on the BROWN/WHITE wire or not. IF it's just 1-3vdc not good. That is ref voltage made BY the ECu and it it isn't there in full force of approx 5vdc the ECU is bad OR one of the other sensors that uses the ref voltage is pulling the voltage down. See what YOU have on the brown/white.

SUBSCRIBED:
i am having the same problem. all of the sensors and the ecu being backprobed checked out ok. it will fire up and run as long as my foot is on the pedal. if it stalls when i let off the pedal, it will not start again. it is getting spark on the trailing coil but not the leading. besides the ecu and cas.what controls spark on the coils? again, all the sensors and relays checked out fine.

I checked for reference voltage at the brown/white wire on the boost/pressure sensor and the meter shows less than 1 v. So, I removed that ECU and swapped in another one and it shows the same thing. Before I swapped out the em harness both of the ECUs worked and I had good spark. I just had no power and the motor sounded like it was running on one rotor, but now, I have no spark and evidently, 2 dead ECUs. The newer wiring harness looked to be in good condition. I changed a couple of injector clips but everything else looked good. It would be nice to figure out what happened to the ECUs before I swap in another one.
If anybody knows somebody wanting to sell a N374............ looks like I'm in the market.

ash

To get more attention to your post you should start your own thread.
Did your leading coil check out OK? Did you check for a firing signal from the ECU on the green/yellow wire at the leading coil? Did you have your injectors flow tested?

N374 have a bad history. Beware.

No voltage on the brown/white is bad news. Two ECU doing that is an oddity.

The brown/white feeds ref voltage to : afm, boost sensor, TPS, OMP on a series five, ATP sensor on series four only, variable resistor on early series four,

So what I'm getting at is this. Remove the connectors off all the above items. Then put the key ON and check for voltage once again at the brown/white of any of the sensors just mentioned. IF you now find approx 5vdc, that means one of those sensors is dragging down the ref voltage and you MIGHT be able to figure out which by plugging them in one by one and checking the ref voltage after you reattach each one.

No ref voltage means there's no way on gods green earth the coils/ignitors will fire because they are not going to get the zero to five vdc signal coming and going.

Several things you might try on that car but that is the one that is easyist and less time consuming.

Yep. Might try starting another thread but what I've said just about covers it. No sense looking at coils etc if there is no ref voltage present in the ECU.

The OMP "might" be the root of your problem.

The n370 I has the RTek 1.7 with the OMP eliminator chip. The OMP is not plugged in. I'm pretty sure the OMP killed the first ECU.
Unless the newest em harness has been miss wired someplace I can't imagine why both ECUs would now be dead unless they never worked properly to start with.

Thanks for the help , I appreciate it. My bf isn't really that mechanical but he can help trouble shoot if I know where to start.

I don't know how much money I should spend trying to get this 7 to run. I've got about $5000 in a 7 that doesn't even run. I'm way past trying to get my money back by parting it out, besides, I wouldn't even know where to start.

thanks again.......... ash

I'll pull the other sensors tomorrow.

I unplugged the sensors that use the 5 volt reference. Then I checked for the 5v at the ECU and the meter read 5v. So, then I started plugging the sensors back in. As I plugged the sensors back in I checked for the 5 volts and they all showed 5 v except the boost sensor. So, finally I found that at some point somebody miss wired the boost sensor.

At least the 5 v reference shows. Still won't start.

I did finally get the engine to fire up. The entire "no spark" issue was do to the previous owner of the wiring harness messing up the wiring of the boost sensor. Must have been grounding out the entire system.
Once I rewired the sensor and plugged the coil back in, it fired right up. I haven't been able to take it around the block but it sure runs better.
The original problem with the "bad miss" was fixed by replacing the wiring harness and the "no spark" issue was because of the boost sensor plug.

Thanks to everybody that chimed in........ especially to Hailers and Satch.

ashley