RB25 Starting Issues, Possible The CAS

[tylink720]

Hey,

I'm having some starting issues with my rb25det neo. Its in a pretty much stock R34 GTT with an Elite 2000. It will just crank and not start, but sometimes will fire right up. I'm wondering if its my CAS that is the issue, but once it does start, it seems to run great.

It started this year after the Haltech install. Never had an issue before, and it worked perfectly for a week after installing the haltech too. The first time it happened, I could smell unburnt fuel, so I pulled the fuel pump fuse and it started up, so I thought it was just flooded. Now that doesn't work. 

I put the timing light on it again, and the crank timing marks were nowhere to be found. Took the cas off thinking the key snapped, but it was fine. Put it back on and it started, and I checked the timing again and it was lined back up. Its almost like the ecu was seeing the timing 180 degrees out somehow. This has happened multiple times now, including this morning.

Some things I've tried:

• I've taken out each coilpack and I get spark from all of them while turning my cas, and I hear the injectors clicking too.
• I've synched my timing with the ecu each time.
• I've cleaned the cas with sensor cleaner.
• I've logged the ecu while cranking and it's getting signal from the cas.
• I've looked over some wiring and can't see frays or anything. 
• Double checked my trigger settings, and they are the same as the original base map

I'm nervous to drive around now as it seems to be random when it wants to start. And it seems strange that once it actually starts, it runs great. Any ideas? I don't know anyone with a confirmed working cas otherwise I'd try swapping to see it it helped. 
 

[robbo_rb180]

What is the condition of your battery as voltage may be dropping below arming/trigger setting. Adjust them if need be.

Check that and if not the problem invest in a NZwiring trigger kit. Super easy to install and setup too.
https://www.nzwiring.com/index.php/product/trigger-kit/

[tylink720]

Hey thanks for the reply. Yep I've been looking at some trigger kits so I might just have to take the plunge and buy one.

The battery seems to be good, and I've also tried starting while being jumped by another running car, with no luck. I will see if I can find the those voltage settings in the ECU and give it a go.

[tylink720]

Update on this:

I got the car sketchily started and made it home now. I had to add 40 degrees to the TDC Angle setting in the Haltech and then it barely started but idled like crap. Put the timing light on it and sure enough the timing was out by about the 40 degrees. I put the same number I had before back in, 115, and its back to proper timing and idled fine.  

Somethings off when its cranking it seems. I'm planning on just buying the trigger kit now

[joshuaho96]

On 6/21/2022 at 9:09 AM, tylink720 said:

Update on this:

I got the car sketchily started and made it home now. I had to add 40 degrees to the TDC Angle setting in the Haltech and then it barely started but idled like crap. Put the timing light on it and sure enough the timing was out by about the 40 degrees. I put the same number I had before back in, 115, and its back to proper timing and idled fine.  

Somethings off when its cranking it seems. I'm planning on just buying the trigger kit now

Scope the signal the ECU sees during cranking. This sounds like it could be a signal integrity issue.

[tylink720]

On 6/21/2022 at 4:44 PM, joshuaho96 said:

Scope the signal the ECU sees during cranking. This sounds like it could be a signal integrity issue.

I will try this as well thanks. I've ordered up the NZ Wiring kit so hopefully that will be here soon too

[tylink720]

Another update for this. I put the NZ Wiring trigger kit on and it was doing the same thing. Scoped the signals and was getting perfect readings off of it. 

Ended up going through all of my fuses again and found one had blown, one of these ENG CONT fuses.

Replaced it and the last 3 starts have been flawless. I'm hoping that this is finally the fix for it!

Side note, what do these 2 fuses actually do? I'm wondering how the car was even able to run if it was blown?

 

[GTSBoy]

The wiring diagram tells all. "Eng Cont" means Engine Control. These kinda run all the things that matter in the engine/ECU world.

[Duncan]

Yes, but the weird thing is, a standard 33 gtst runs fine with that fuse blown, while at least some aftermarket ECUs need it (it was actually absent from factory in S2 which is even weirder.) I've never traced the wiring for it though

[tylink720]

The starting issue seems to be fixed due to replacing that fuse. I also emailed NZ Wiring and he gave me some tips and I have the car working very well now. Had to lower my trigger arming voltages a lot compared to the numbers in the install instructions. Thanks for the help!

I do get a trigger error once every couple of drives. It seems to happen when I press in the clutch during a lower rpm decel, or when letting out the clutch at a low rpms. It will happen once, then wont come up again for the rest of the drive or even multiple drives after. Strange

Edited July 21, 2022 by tylink720