R32 GTST RB20DET Crank no start - Tomei ECU?

[joshuaho96]

The MAF isn't even used to get the engine to crank over. It's only looking at RPM and coolant temperature if I recall the Nistune documentation correctly.

[Tim32]

OK got the new ECU today, hooked it up, and still crank and no spark.

So managed to get a different (second hand) ignitor module.. still no spark. However, I tested the new ignitor module using this guy's youtube video as a guide and I couldn't detect any resistance from any of the pins so it could be a dud also?? I couldnt get any resistance readings from any of the pins on the old one also... Maybe Im doing it wrong? 

Ugh.

[GTSBoy]

41 minutes ago, Tim32 said:

I couldn't detect any resistance from any of the pins so it could be a dud also?

Well, that would depend on which part of the test you're talking about. He's basically doing a rough transistor test there, which will reveal some possible problems and maybe not others. You have to know how a transistor works in order to appreciate what and how to test them.

The base is the switching input. That is is the signal from the ECU. It is obviously either there, or it is not, depending on whether or not the ECU wants to fire the coil. When it is ON, a current will flow from the base to the emitter, which is earth (and the emitter is a common earth for all 6 transistors in the package).

The collectors are the 6x lines coming from the coils. These have 12V on them all the time. When the base is not fed by the ECU, there is no (ie very little) conductivity from the collector to the emitter, so no coil current flows. When the base is fed from the ECU, its little current flow to emitter allows the collector to also flow current to the emitter - ie, the resistance between C & E drops low, where it was previously high.

From what I can see of that video, he didn't measure any C-E resistances. If he did, with the test gear he had, he'd only expect to see high resistances (maybe even open line) on C to E. He'd need to wire up a 12V circuit to feed the B-E and C-E properly and be switchable on the B-E side to be able to discriminate whether the transistors are switching properly or or not. The test he did really only shows whether the collector is properly isolated from the base, which only indicates one possible failure mode.

[Tim32]

@GTSBoy Thank you so much for that detailed explanation, that is really helpful!!! Makes me realise how much more I don't know  

Here's the last frame of the video which shows his test results (attached)... I don't get any readings doing what he did. 

The only resistance reading I get is when I bridge two pins on B > E... ie. B (Pin 1 + Pin 2) > E...

I have an auto electrician coming on the weekend again, so i'll get him to run some tests on it, I am very much out of my comfort zone.

Really appreciate your time to explain it clearly.

[morboost]

i didn't think it was the ecu, finding a good auto elec is difficult seems more common to turn up look busy run the tab up then when they have made enough for the "job" point to something and use words like could be, maybe, probably.

The coil pack harness is plugged in right?

this is a ptu harness that's used when bypassing the ptu for r35 coils use the pic as a colour guide

even check your spares box if it came with this car to see if you own one of these

[Tim32]

OK so we've kicked the can down the road a little bit more this weekend. Turns out there is no injector pulse either, the tacho doesn't move when cranking. One of the green relays was a bit sus near the ECU so Im going to replace that this week. We tried a couple different ignitors, we're getting 12v at the coil plugs, but no spark.

So thinking maybe CAS??? There is power to the CAS.

EDIT: I ran a fault code check using the jumper wire and engine light flash method, and it came back with 55... which is No Malfunction??

Edited April 7, 2024 by Tim32

[Duncan]

If you remove the CAS and spin it with the ignition on, can you hear the injectors click?

[Dose Pipe Sutututu]

Are you getting +12V at the injectors?

If not, check the ECCs relays, then trace it back from there.

[Tim32]

OK, some positive news, I pulled the CAS and turned it by hand and the injectors pulsed. When I put it back in and cranked, it tried to start, so now its spluttering trying to start, but still no start.... Previously its just been cranking and no spluttering.

Could it be the timing is out or the sensor is stuffed?

 

[Duncan]

It really sounds like a bad CAS or CAS wiring issue if messing with it had it go from not working to "sort of working"

[morboost]

On 29/03/2024 at 1:38 PM, morboost said:

heres a china one like i said they are close, i think you will be good to go when you get the stock ecu and crank it over I personally would have a timing light on it when you go to start it unless you have pulled the timing cover already and all the marks line up, if it has adjustable cam gears they are tight and the cas is sitting were it should be.

did you read this? 

[Tim32]

Thanks guys, yeah @morboost  we pulled the cover and checked the timing, looked OK? see pics attached.

The wires going to the CAS have been spliced open, guessing someone was checking with multimeters at some point, also the connector doesn't feel great when pushing it in, no click and looks a bit shabby.

Is there a proper way to remove and reinstall the CAS, does it need to be TDC or something? or just as long as the spline matches up its all good???

It actually fired up and ran for about 5 seconds (terribly) then stopped. Now nothing again, just cranking.

 

[morboost]

nice, think of your cas like a distributor needs to be set correctly or your timing will be off. Have you had your maf off and cleaned it? I noticed you had a headlight duct so worth checking its clean. Yeah wiring problems over the internet are impossible so your on your own on that one. You said it had a vacuum leak, if this car did have a map based ecu in it there will be a vacuum hose run from engine to the ecu area so delete that if still there.

[Dose Pipe Sutututu]

27 minutes ago, Tim32 said:

spline matches up its all good???

just this and roughly in the centre, once the car is running you can adjust the CAS to hit the required base timing (if you're ever using an aftermarket ECU, do not do this as you can offset in the ECU and/or the factory procedure will not work).

[morboost]

wonder if something like the mod has been done to the cas

https://frenchysperformancegarage.com/products/nissan-rb-crank-angle-sensor-modification-24-1

If it was me doing this I would have removed the cold intercooler piping, set the maf as close to the throttle body, move the cas around while cranking till it almost starts and spray start ya bastard into a wide open throttle through the maf.

What injectors are in it ?  need to be oem size with your oem ecu.

[Tim32]

OK, update time. We finally got it fired up and running!!!!!! We think it was a combination of things but having 4 unhealthy spark plugs was definitely not helping. 😆 Yes, probably should have started there.

Once we fired it up, it's having the same issue as what the guy said it was having, where if its idling its OK, and revving is OK but once you rev it and then let it idle again, it stalls.... I did a bit of digging here and came across some robust discussions about after market BOVs with stock ECUs being trouble... which this has, so probably thats where I'm going to start.

Really just wanted to say thank you to everyone who posted here suggesting things and helping me out, really appreciate it and its great to be always thinking when I run into trouble there's a place we can come to get some great insights, so thanks everyone.

[Murray_Calavera]

54 minutes ago, Tim32 said:

after market BOVs with stock ECUs being trouble... which this has

You can have an aftermarket BOV that 100% recirculates (the same way the factory one works)

Does your BOV vent to atmosphere? 

[Tim32]

Yeah vents to atmosphere... So the issue I think is that the stock ECU isn't accounting for the loss of air and effectively it's a vacuum leak, so it will run rich and foul plugs etc?? is that right?

[Murray_Calavera]

8 minutes ago, Tim32 said:

Yeah vents to atmosphere... So the issue I think is that the stock ECU isn't accounting for the loss of air and effectively it's a vacuum leak, so it will run rich and foul plugs etc?? is that right?

Basically, yep.

However I can't see you fouling plugs from that alone though (not enough time spent in the rich condition to do anything meaningful to the plugs). 

If I cast my mind back 15 or so years ago to the I last time I saw this actually happen in person, it just made the car really grumpy for a few seconds and nearly stall and only really had any effect at low speeds/low engine speeds. 

For sure this is the perfect excuse to get an ecu, delete the maf sensor and keep the bov lol. 

 

[Tim32]

So with an aftermarket ECU it gets tuned to handle the BOV? and why doesn't an aftermarket ECU use the MAF sensor? Do they all not use the MAF? Do they just have everything programmed into the ECU?