Help With Rb20Det Nistune

[HG20DET]

Can someone help me, I have an RB20det from an R32 GTS-t, I installed a nistune board in the ECU and had it tuned and it was running fine. Since then I have replaced the afm with a Z32, and put in 550cc Sard injectors. After changing the afm and resizing injectors on the computer it ran very rich (blowing heaps of black smoke at idle and could smell fuel) however it always started fine and idled. I have only run it like this for a few minutes. So the other day I installed a wide band afr gauge and O2 sensor in the exhaust, since then it won't start at all.

I didn't think I would have touched anything that would effect the car starting while installing the guage, all I did was pick up power and a ground for the new gauge and welded a new bung in the exhaust. The factory O2 sensor has been left untouched apart from cutting off the wire that I had joined to the signal wire to run a crappy narrow band gauge.

I started it up just before putting the gauge in and it ran, then as soon as i tried after nothing.... It just cranks over, I can smell fuel, and if I keep cranking maybe every 15 seconds or so it sort of half fires for a second or two...

I have checked the wiring of the AFM it all seems fine.

If anyone can help me, or point me in the right direction of where to start looking it would be greatly appreciated.

Thanks, Pat.

[GTSBoy]

Perhaps you cooked something whilst welding? That could be in the ECU. Or, given the description of the non-starting behaviour, maybe the CAS is at fault.

Best (quick and dirty) check would be to see if the ECU will allow another engine to start.

[HG20DET]

I will give it a go, I do have another RB20 in another car in the shed, just have to hook up a fuel pump for it. Cheers.

[RRob]

Fouled spark plugs.

[HG20DET]

Fouled spark plugs.

I was thinking about that, but would it go from idleing fine, not missing or anything to not starting at all? I would have thought it would run a bit rough for a while first? Might pull the plugs and check them...

[GTSBoy]

If you've got a spare engine, try the CAS from that on the non-starting engine first, as it will be the easiest swaptronics..

[Rolls]

I was thinking about that, but would it go from idleing fine, not missing or anything to not starting at all? I would have thought it would run a bit rough for a while first? Might pull the plugs and check them...

My mates with rotaries would fould plugs trying to start and flooding it, then it wouldn't even splutter just turned over with nothing. It is easy enough to pull one and see if its black with soot, usually a bit of steel wool on them to brush them clean is all they need.

[HG20DET]

Cheers for the advice guys, I tried changing over the CAS but still the same problem... I pulled a plug and it was pretty black, it was sparking but very weak spark, so i cleaned it up and the spark was a lot stronger. So I'll clean the rest of them in the morning and see how it goes.

[SiR_RB]

try leaning the hot start out. i had a very similar problem

[MrStabby]

Did you perform a sensor check in Nistune?

Also WRT the richness, did you adjust the injector latency? If the Sards are faster acting than the stockers this could be the problem. The latency adjustment is in a different location to the injector resize function (which doesn't seem like a good idea to me).

[GTSBoy]

That latency idea ^^ is a good one. Could easliy stop it from injecting any fuel at all at cranking.

[DVS JEZ]

Injector resize isnt perfect u still need to log a low load run and tweak the k constant with 02 feedback off an get close to 14.5 then if idle is rich adjust the latency. Then turn the 02 back on when finished

[HG20DET]

Cheers guys, got it started again, turned out to be the spark plugs. Now just have to get the afr's right...