1991 R32 GTR - No spark, ECU disconnects

[edzilla]

Hello Everyone,

Hoping to get some help with a 1991 R32 GT-R on a Link G4+ Plugin ECU. I did a search for these issues and tried all the suggestions I found but have not had any luck.

This is a brand new install. The car is a stock 1991 R32 GTR. 

First thing I noticed after installing the ECU was that it disconnects while cranking. Battery was low initially during cranking so I put a charger on it for the remainder of these tests. Even with the charger the ECU would disconnect. We decided to use a power probe to manually apply 12V power to pin 49, bypassing the ECCS relay for now. We did verify 45 had power at key-on. This finally allowed the ECU to stay online while cranking. We also tried dip switches in both positions, R34 and Other. Neither make a difference. The J1 jumper is removed. I reseated the ECU connector a few times, double checking to make sure the sides were not caught on anything or popping up, 10mm bolt is very tight/snug. I don't believe there to be an issue with the ECCS relay system. I've owned the car for the last 2 years and it's never given me a problem, so I'm still a bit confused as to why I need to manually feed it power to stay alive during cranking.

Second issue was now I was not getting any engine speed or spark while cranking. I am using the GTR basemap, I did not go through the Test ECCS Sync procedure. Widest slot was set to 24 per the basemap. I was never able to get spark while cranking so I wasn't able to run through the base timing setup either. I've tried trigger offset values of 0, -82, and -80 without any luck. I am able to use the ignition test function to trigger coil 1 and visually verify spark. While cranking, RPM stays at 0. I setup a new parameters window to watch Trig 1 and Trig 2 Signal, they always stay on 'NO'. I was only able to see this towards the end when we used the power probe to keep the ECU from disconnecting.

TPS calibrated fine. I am using the on-board map sensor.

The only thing I can think of is that the car came with an "Ultra" brand turbo timer. Its never seemed to work and I tried the above tests with the timer on and off. There are no sensors that have been wired in. I also tried unplugging both MAF sensors with no change.

After giving up, I swapped the PCB's and put he stock ECU back in place. The engine fired up on the first crank. 

It was difficult to keep the ECU online while doing these tests so unfortunately I don't have any logs to share. 

Any suggestions would be greatly appreciated.

Thanks,

 Ed

[Simon]

Try putting a temporary ground on to pin 16, This is the control pin for the ECCS relay and when at ground the relay should stay on.

Then make sure the voltage at  pins 49 and 59 stay at battery voltage at all times.

Also check you have power to the CAS during crank should match battery voltage

 

 

[edzilla]

Thanks Simon. Will give this a try and provide an update.

[speedotech]

Im having this exact issue right now on my  92 gtr engine trying to set up CAS.  Laptop is dissconecting when cranking like ecu is losing power . I will try what youve suggested tempory earth etc.

[Adamw]

The most common thing we see is low voltage on pin 49 or 59.  One of those is the main power supply (from ECCS relay) so should be near battery voltage.  Check these pins both with engine stationary and during cranking to confirm it is good.  It shouldnt drop much below 9.5V if battery and wiring is ok.  The ECU will switch off if it drops below about 7V.  The stock Nissan ECU seems to stay powered up to much lower voltage so often with the stock ECU you can have the low voltage problem without being aware.

Usually if it is low on these pins the contacts in the ECCS relay are tired, sometimes its deeper in the wiring supplying the relay.

[edzilla]

Hi Simon/Adam,

I was able to meet Jason (PSI) this past weekend and discussed my issue at an event, and we are thinking the issue could be tied to CAS wiring. Although the car did appear to be "bone stock" from Japan, it's a possibility that the CAS has been changed or wiring modified. I haven't been able to get to the car for the past 2 weeks but I will try this weekend. Power/ground/trig1/trig2 could all be flipped depending on if it's a R32 or R34 CAS. I'm waiting for a picture to be sent so I can see verify which CAS I'm dealing with. 

I'm hoping it will be as simple as re-pinning some wires at the CAS connector. Going to run a continuity test to see where things are wired as well.

speedotech - I'd suggest you verifying this aspect on your setup as well. 

Thanks,

Ed

[Simon]

The CAS wiring should not have any effect on the dropped connection but will impact the lack of RPM if incorrect.

[Kazu]

Me and My friends have not started the engine with the same phenomenon as Mr. edzilla.
I would like to watch Q & A.
I am using a translation, sorry

[edzilla]

Simon,

I was able to have my buddy send me photos of the CAS and wiring at the CAS connector. Everything is in the right position for an R32 GTR (Mitsu CAS). (120, 1, +12v, GND | Pins 1-4 respectively) The part number on the ECU is for an R32 GTR as well. It appears that the CAS is not the problem as you mentioned. I'm doubtful that wiring at the ECU connector has been changed, but I will check to make sure. 

I will try your temporary ground test when I get to the car this weekend and pull off the questionable turbo timer. 

Kazu - no problem. I hope this will be helpful to you.

Ed

[speedotech]

Hi , Simon was spot on . I am getting low or no voltage at pin 49 , 59 when cranking. ( was ok with factory ecu ) . Earthing out pin 16 solved  the link g4 from dissconecting when cranking. 

Should i wire in a new ecu relay or wire pin 16 to a relay ( earth when key on )?

 

[Adamw]

34 minutes ago, speedotech said:

Hi , Simon was spot on . I am getting low or no voltage at pin 49 , 59 when cranking. ( was ok with factory ecu ) . Earthing out pin 16 solved  the link g4 from dissconecting when cranking. 

Should i wire in a new ecu relay or wire pin 16 to a relay ( earth when key on )?

 

Lets go 1 step deeper to see if we can diagnose why Pin 16 is not grounding.  Pin 16 is controlled by the "ignition switch signal" on pin 45.  Can you check the voltage on pin 45 during cranking, it should be near battery voltage.  I dont know off the top of my head what the minimum voltage we need to see on this pin is but if pin 16 is not engaging I suspect you might have quite low voltage here.   Note pin 45 comes from the ignition switch but the same source also supplies power to the fuel pump, FPC module and 2 air valves so if voltage is low on this wire you really want to fix it rather than work around it.

[Grant Baker]

This is a REALLY common issue. Every single S15 plugin and 90% of GTR Plugins have this problem.

We get round it in one of 2 ways -

1) use the power from pin 45 to fire a relay which has battery power supplying pins 49/59

2) just use pin 45 to connect to pin 49/59.

Never a problem on OEM ECUs but is on plugins. I have reported this and it is being looked into by Dave@Link in the UK.

[ClintBHP]

The ECU drops out when the starter is engaged.

The only way to fix this properly is to use a Digital Input and set up the Hold Relay Circuit with a diode to stop backfeeding, this will stop the ECU dropping offline and also allow the car to start faster.

Cut the wire to pin 16 and Wire the Relay side of the wire to a spare Ignition output, set the Ignition output to ECU Hold Power.

Cut the wire to pin Pin 45 and connect the relay side of the wire to a Digital Input and ALSO connect this to the Cathode of an IN4007 Diode, The Anode side of the Diode connect to the wire on Pin 49, set the Digital Input to IGN Switch.

[Simon]

As much as the above suggestions will work there is still an issue in the wiring that should really be resolved as it effects more than just the ECU.

With the likes of the fuel pump being supplied from this feed you will also have a slow fuel pump and then in turn low flow.

There is every chance the factory is allowing the car to run and there is enough flow for a stock application. But start pushing things and there is every chance you will find other issues. 

My advice is diagnose and sort the issue properly rather than looking for a work around.

 

 

[edzilla]

Hi Simon/Adam,

I'm inclined to try the additional relay method suggested. I spent a few days this past weekend troubleshooting, and if I manually ground pin 16, the ECU does stay online while cranking. I was able to partially see that Trigger 2 was "ON" but I never saw Trigger 1 change status. Engine never started. I decided to put pin 16 back in the original location and the Link went back to the old behavior of disconnecting while cranking. 

I didn't have a chance to do a deep dive into the calibration when pin 16 was manually grounded this weekend... but I will try the relay method tonight. 

There are a few other things I want to mention....

1. At Key-On, the tach does a sweep that looks like a Defi gauge sweep. I don't think this should be happening? Is this an option in the ECU?

2. After re-loading the GT-R base map, I had 2 errors, AN Temp 3, and AN Volt 6. My concern is with AN Volt 6.. the original wiring for that is Oxygen Sensor. Could that be causing an issue with startup? 

3. At Key-On, if I depress the throttle, I hear a pump going. I'm guessing this is the ATESSA pump? With Jumper J1 on or off, it does this. Calibration file concern?

Is there any possible update from Dave@Link.... from what Grant mentioned?

Thanks,

Ed

 

[Leiden]

On my setup I wired the relay to switch off ignition, rather than controlled by the ecu.

The relay normally switches two constant 12v feeds, one for coils and the other for ecu, cas, maf, and possibly a couple other sensors. Its possible you have a wiring issue or back feeding.

With the Link all sensors, solenoids, injectors, coils etc should be on a switched 12v source, not a constant 12v feed.

[TechDave]

Voltage on pin 8/45 needs to stay above about 8.2V to keep the ECCS relay on. If it does drop then it will need to recover to about 8.7-9V for the ECCS relay to come back on and for the ECU to start up again. This can take a few seconds to happen. 

Try pulling your ignition barrel apart and cleaning the contacts, this seems to make the biggest difference to voltage during cranking.

[edzilla]

Hi Everyone,

I'd like to start out by saying that the car finally started tonight and ran very well for not having any wideband sensors installed. Those are next on the list to be wired in.

I want to thank Simon and Adam for their help. I spoke with Adam a few times tonight and he guided us in the right direction.

The fix that got it to fire was jumping battery 12v to pin 45. There does appear to be some voltage drop happening across that circuit. Could be corrosion on some of the junction points per Adam, or my thought was hardening of the harness creating additional resistance. My idea for now will be to repurpose the turbo timer harness and jump 12v straight to pin 45. I will trace the original wiring at some point to see if I can find anything else that might be causing this voltage drop. 

TechDave, you're pretty much spot on. I might look at the ign cylinder first. I did hear the ECCS relay clicking during troubleshooting. 

Grant/Baker - thanks for the suggestions as well. I started going down that path but it seems like the age of these vehicles is really starting to show.

Thanks everyone!!!

Ed

[rrob]

Pin 45(ign switch, black with a red trace) comes from the front fuse box. There's a connector you can test near the windscreen washer bottle(1 of the 2x 8 pin connectors). The wire is alot thicker there also. 

[Peet]

Hello i see i have simular problem as the ecu droping power and is dificult to start the car without jumppack when the car warm up is much easer to stert engine  if i connect power suply to 45 pin on ecu that will not discharge battery do i have to do any fuse or something like that ????