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Discussion Starter · #1 ·
Working steady on my mr2 project since buying the car this winter and finding the engine was consuming a liter of oil every 100kms soooo, pulled the motor out of this 1988 NA after about three weeks of ownership, complete refresh, reseal of motor and found the main cause of the oil consumption (i hope). Sides of the cylinder wall were glazed and oil ring was stuck in the ring grooves... honed the cylinder walls with flex hone 220 grit 83 mm diameter and used the lisle ring groove cleaner and slapped everything back in. All four corners got a lot attention while in there... caliper rebuild, discs, rotors, all new prothane bushings, strut inserts, brake lines, ball joints, steering rack inner and outer tie rods and bushings... this thing going to drive so well and it was good already before...

so onto the problem....

no spark.

wiring harness has been completely gone over. tested for continuity on every line going from ecu and 22 pin connector to other end, some wires run directly just to test

distributor is getting G signals to the ECU and N Signals to the Igniter - both circuits ohm out at 165 ohms

No Ne signal to the ECU from the Igniter

So while sourcing a new igniter, my electronics buddy and I are replicating the igniter. Taking the N signals from distributor and sending a 5 volt N signal to the ECU.

Ecu reads this N signal and sends out only .6 volt signal out of the igT to the igniter and needs 5 volts. We successfully replicated this signal by plugging in a wall plug transformer 5 volts and could get spark all day... just not timed to the crank/cam shaft and was just for testing purposes to see if the igniter was doing its job...

Question: if we boost the N signal up, will we get a stronger 5 volt signal from the ECU igT to the igniter - which will then provides the power/signal need to get igniter to do its things - gets us the spark we're missing?

Said another way, does any one know what is the voltage of the N signal coming out of the igniter?

Another clue is that I'm getting no tach bounce when cranking to start... are these issues related?

A lot of work to replace a $200 igniter from rockauto or $500 from dealer! And part of the plan is hacking the system to aim for stand alone coil on plug system... phase one, get this mr2 on the road again. phase two make our own megasquirt / speeduino to run this car...

This car purchased in Jan 2021 as winter project (nothing else to do, hockey arenas closed, ski hills shut down, massage places not allowed to open... what to do? buy a mr2!) to mess around with this street legal go-kart. other cars include e46m3, 964, boxster, 335diesel, x3 daily...
 

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Ecu reads this N signal and sends out only .6 volt signal out of the igT to the igniter and needs 5 volts. We successfully replicated this signal by plugging in a wall plug transformer 5 volts and could get spark all day... just not timed to the crank/cam shaft and was just for testing purposes to see if the igniter was doing its job...

Question: if we boost the N signal up, will we get a stronger 5 volt signal from the ECU igT to the igniter - which will then provides the power/signal need to get igniter to do its things - gets us the spark we're missing?

Another clue is that I'm getting no tach bounce when cranking to start... are these issues related?
IGT does not function until the engine is running. I explained that in your other thread, and if you don't follow it, tell me what you don't understand. In short, you are wasting your time until you get a working igniter.

I don't know what the spec level for N is, but it is a logic signal. The ECU either sees it or doesn't, and if it sees it the amplitude does not matter.

The tach uses the N signal. No N out of the igniter, no tach.
 

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Discussion Starter · #3 ·
Thanks for advising the N signal is expected to be 'logical'. Would you know which type? TTL, CMOS, any idea what is maximum permissible voltage for that input?

I wanted to know the voltage of the N signal coming out of Igniter to the ECU. I've read some come out at 12volts and we've collected N+/- signal and changed it to a logical signal(TTL). Which now drives the ECU. As a result, we are getting igT however igT is not a logical wave form. And appears deformed as it's not a square pulse. It's triangular with max voltage of 0.6 volts.

Doing this exercise because wanting to learn more about the system as we are planning a coil on plug setup, maybe air flow meter replace with mass air flow / manifold absolute pressure.. and doing this to learn more about megasquirt and other standalone for my future s54 swap into 325 wagon bmw.. plus have a k24 lying around waiting for the right donor project... been eyeing a classic mini but i digress..
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My igniter definitely toast and have sourced a known working one... just haven't received yet. However igniter is not completely toast... we put a 5 volts signal into the igniter thru the igT and got spark all day... just not timed to distributor.

Really helpful to know the N signal needed for tach.

Thanks for help and will report back with N voltage with 'new' igniter
 

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Thanks for advising the N signal is expected to be 'logical'. Would you know which type? TTL, CMOS, any idea what is maximum permissible voltage for that input?

... As a result, we are getting igT however igT is not a logical wave form. And appears deformed as it's not a square pulse. It's triangular with max voltage of 0.6 volts.
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Really helpful to know the N signal needed for tach.
I would guess 12 volt pulse.

This is probably noise. IGT is not supposed to function until the engine is running.

Just hook up a signal generator and see what works. I think that I used 12 V to test tachs on the bench. The duty factor does matter.
 

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Discussion Starter · #5 ·
Okay got the igniter last night and have this aft to pop in.. will do some measurements and let's see what voltage comes out of there and more importantly... will i have spark???
 

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Discussion Starter · #6 ·
CORRECT ON THE 12VOLTS - we put the N signal on the O-scope and got 12 volts. have spark now with 'new' 30 yr old igniter. only getting back fire. have fuel at the rail and can hear the injectors pulsing.. checking timing and distributor install. have done this about 10 times now and think i have it correct... set top dead center and open the oil filler cap to confirm the mark on the cam, match up the distributor dimple marks and push the gear end into the hole... snug up 12mm bolts but not tighten, timing 95% correct no??
 

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Discussion Starter · #7 ·
rechecked distributor timing and don't even have backfire now.. spark at end of each of the four plugs and fuel at the rail... a little stumped...
 

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Discussion Starter · #8 ·
checking fuel injectors - all ohm out at 15.1 to 15.6 ohms. #10 has no signal #20 has signal on the ecu. suspect the ecu has issues and looking to swap in a known working one

also wave form off the harness shows cyl 1 and 4 working and cyl 2 and 3 no signal
 

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