Jump to content
SAU Community

Recommended Posts

A bit of history before we start.

Car is originally an RB20E auto Cefiro.

2 years ago the engine and gearbox was swapped with a manual RB20DET from an R32 skyline. We used the loom and ECU from the skyline so all engine parts etc are skyline parts (not cefiro/laurel bits).

Besides the occasional leaking cooler pipe and dodgy coil pack it hasn't missed a beat for the last 2 years.

Recently I got a Z32 ECU that had been socketed and remapped (to suit a VG30) and I bought a nistune kit for the Z32 ECU.

I put the nistune gear in the Z32 ECU and loaded in factory RB20 maps.

After comparing the pinouts for the Z32 and the R32 ECUs, the only wires that needed to be swapped was injector 2 and 5, so I did that at the ECU connector.

So the RB20 was running fine on the Z32 ECU for a few weeks until one morning it started running on 5 cylinders. Thinking it was probably the spark plugs I bought a set of 6 NGK coppers and did that and an oil change. Still running on 5 cylinders (cylinder no 5 is not firing).

So then I pulled out the nistune, swapped injector 2 and 5 again (back to normal) and put the standard R32 skyline ECU back in. Still missing on 5.

Pulled the coilpack and swapped with cylinder 2, no change. So I borrowed from my mates working R32 his coilpack loom and ignitor still no luck.

I borrowed a tester and checked that cylinder 140psi, a bit low but still within specs according the the R32 engine manual.

I got a couple of spare RB20 injectors (but they haven't been confirmed as working) I pulled the rail out, removed injector 5, replaced it with the injector from cylinder 1 (known working) and put one of the unknown spare injectors into cylinder 1. Still missing on cylinder 5, cylinder 1 was working with the untested injector.

The RB20 injectors are batch fired (1, 3 and 5 injectors fire at the same time, their respective ECU pins are joined inside the ECU). So I swapped the wires at the ECU for injector 1 and injector 5 (pin 101 and 110).

Now cylinder 5 is working, but cylinder 1 is not.

So having thought that the problem was identified to the ECU I returned the wires for injectors 1 and 5, but cylinder 5 continued to run and cylinder 1 continues to not fire.

Tried wiggling the wires at the ECU connector and it is definitely bolted down straight and correctly.

So now I was trying to identify why cylinder 1 won't fire, I've swapped coilpacks, coilpack looms, ignitors, sparkplugs, I plugged an LED into the injector loom plug to see that there is a signal getting there from the ECU.

TLDR - Cylinder 5 wasn't working, checked coilpacks, coilpack loom, ignitor, sparkplugs, swapped injectors, no luck. Swapped wires for injector 1 and 5, cylinder 5 works but cylinder 1 stops. Returned wires, cylinder 5 continues to work but cylinder 1 now not working. Can't find the cause of the problem.

So now I've run out of ideas.

Going to try a spare standard R32 ECU tomorrow.

Link to comment
https://www.sau.com.au/forums/topic/307437-rb20-runs-on-5-cylinders/
Share on other sites

you have well and truly established the problem is wiring. make sure youve pinned it right again, try swapping them again ETC. then check for continuity to earth, there might be a cut in the harness somewhere.. find it.. kill it.. kill it with fire (read solder and tape)

dont stress, you have done well so far and are close to the fix.

Anyone familiar with a noid light? You plug it into the injector loom plug and it lights up with every injector pulse.

I did plug an LED into the injector plug corresponding with the missing cylinder and it was lighting up....

But I read somewhere that you could get false results using a high impedance device (like a volt meter or an LED).

Just had a thought though, I have spare injectors in the garage, I could just plug that into the loom and I'd be able to feel/hear it clicking straight away.

UPDATE!

This arvo I unplugged all the injectors and put my LED into the plug for injector 2, lights up okay.

Plugged it into the connector for injector 1, lights up okay.

Then, because I was worried about the high impedance of the LED giving a false indication, I got another spare injector and plugged it into the loom for injector 2 and held it in my hand. Turned the CAS by hand and the injector was clicking. Did the same for the loom connector on injector 1, same clicking noise.

So, that proved loom was okay.

Plugged injector 2 and 3 back into the loom and the plug for injector 1 plugged into the spare injector in my hand. Again it was clicking.

This proved that with the ECU was able to drive the 3 injectors without problem (remember they are batch fired).

So then I unplugged all the injectors and reconnected the loom to only injector 1 in the rail. Again, it is clicking.

This proved that the injector is firing.

Next I removed the sparkplugs and coilpacks for cylinders 1 and 2 and checked the spark across the plug while turning the CAS by hand.

There was no difference in the appearance of the spark between the two. Swapped spark plugs and tested again, no difference. Swapped coilpacks, tested again, no difference.

So, now I'm confident that the spark plugs are firing okay.

Put it all back together and still not firing.

Things I hadn't proved.

Compression in this cylinder.

Fuel rail pressure.

Is the injector flowing or clogged.

Cylinder 1 was working fine until.... I installed the untested injector.

And Cylinder 5 (the one that was originally missing) started working as soon as I put in a known working injector.

So the next logical step was to put a known working injector on cylinder 1.

Lifted the rail again, removed the questionable injector from cylinder 1, shifted the know working injector from cylinder 2 to cylinder 1. Installed another spare (untested) injector onto cylinder 2.

Started it and now running on 6 cylinders ! Though after all this I still have doubts about the condition of the untested injector I put in cylinder 2.

Also, I think there is a leak on the inlet piping because it has alot of hesitation and stutter when driving under normal conditions. So I'm going to make up a cap to go in the turbo inlet and pressurize the piping using an air compressor, should be able to find leaks without the engine running then.

Hooked the air compressor up to the inlet this evening and found quite a few leaks.

4 leaks where I had plugged unused vacuum lines with bolts, was able to seal them off by tightening the bolt further into the vacuum line.

Had a leak where the hose clamp wasn't tight enough on a pipe join.

One of the intercooler pipes has a leak where a hole has been welded up.

And there is a leak on the throttle body butterfly shaft seal (air is coming out from behind the throttle position sensor).

That was at a test pressure of 0.5 Bar, keen to see what happens at 1 Bar.

Good to see shes running on all 6 now mate! that goes to show that even tho an injector is clicking away it could still be blocked internally.

Props to you for working it out and adding an excellent thread for future reference. :blink:

Welded up the leaks on the intercooler pipes but the throttle is leaking quite badly.

Incase anyone wants to know the RB25 throttles don't fit on the RB20 plenum. Can't remember whether it was series 1 or 2, but one has a TPS that is incompatible with the RB20 (unless you were to modify the wiring). I didn't try fitting it. The other one has a TPS with the same style plugs for the TPS and throttle switch but it was physically larger.

Also, any sort of software that interfaces with the ECU via the consult port makes it really easy to adjust your TPS (can see TPS voltage and throttle switch position).

Edited by daisu

Fitted a replacement RB20 throttle this arvo, pressure test came up good. It was still loosing a little pressure but very slowly and I couldn't hear it.

Idle is very smooth now. Took it for a drive, still hesitating and bucking a bit but I'm hoping that it's just have to adjust the timing.

  • 5 years later...

Hi i no this is a old az post but im having problems with my no 1 cylender running a wasted spark set up all leads are getting spark but its only running on 5 cylenders if i take no1 plug off nothing changes i pulled plug out it was wet with gas all other cylenders are dry any 1 no wat it could b

Hi i no this is a old az post but im having problems with my no 1 cylender running a wasted spark set up all leads are getting spark but its only running on 5 cylenders if i take no1 plug off nothing changes i pulled plug out it was wet with gas all other cylenders are dry any 1 no wat it could b

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • 2 does "sort of" applies, maybe......but looking at what parts would be needed for the swap to get engineered, registered, and insured, and basically that's everything under the car, the modifications the make it legal would be problematic and horrendously expensive, all for a street car that just cruises around and hits a few twisty roads on the weekends Also, from looking at the NSW rules and Regs, with all modifications that is required just to make the car safe and not twist itself to pieces, and then actually get registered for street use, may still be impossible nowadays As for 1, when you add in a fresh engine, fresh transmission, rear cradle and diff, tailshaft, suspension, brakes, cooling, and all the other fabrication required, your probably looking at up to $100k to do it right, all for a 20 year old MX5 that is over engineered and you would never be able to actually use the power it has on the street, much like your beastie, which I love, but you actually track that thing and can use all of its powers in anger, in a safe environment  Hell, the old Bogan Cruise Ship had more power than I could use on the street, and in hindsight, I went a bit silly on that thing, it didn't really need the 500hp it had for what I actually used the car for, it was fun, but basically unusable on the street if you value your licence  As for cams, yeah, I'll probably book it in for them to get installed and tuned soonish, like next month after MX5 Mania are back at work....... and yes, I've already sent a email to bin the turbo quote and quote instead to install cams and a new Fluidampr balancer that will suit the 2.5 better than the OEM 2.0 balancer that is swapped over for the 2.5 install, as the balancer needs to get pulled to time the cams it's a while your in there sort of thing I did think a bit about flex fuel for a laugh, but being na, and no where really around locally anymore to get E85, I've binned that idea, so no sweet sweet corn smells are set for the car I wish E85 was more of a standard fuel, it's better for the environment, better for tuning, plus that sweet sweet smell we all love As for fitting in the family, that's not needed, as everyone in the family already owns a car that can seat 5 humans comfortably enough, the MX5 is "my toy" As for buying a car that is already built, nah, I would rather pick and choose my parts, I enjoy the process, and in the big picture, the additional cost is well worth the enjoyment, and the occasional frustration, I get out of doing it, albeit with other people spinning the spanners, and me, just paying the invoice 🤣
    • Excuse me, but 2) does apply 1) Would also apply if you consider how much is spent in the alternatives. Also there's the option of 3), buy one pre-built that you can put your family in (it's me, it's my car)   That said, I went on a ~500km drive the other day. I didn't use anything more adventurous than 3rd/4th gear at about ~3000RPM and 50% throttle and I was going as fast as anyone has any sense doing on a public road, with enough grip to the point where I didn't want to go any faster. I was obviously under the limit of the current car etc etc. MX5 with 2.5 N/A to achieve the same speed would be more fun for any road scenario. Maybe consider cams. I wouldn't boost it. The use case is just not there and it won't actually make the car more enjoyable unless you really do plan on wringing gears from 1st to 3rd (at least) at 100% WOT on a public road to 150+kmh.
    • Great if: 1. You had all of the money for everything else that is required  2. Lived in a country where you could actually do this and drive it legally on the road Sadly, neither applies to me As for the turbo, I am having second thoughts, mainly for engineering/registration legality reasons and insurance  Not saying I've finished doing stupid things that I probably should do to the MX5, but boost, and V8 engine swaps isn't on the cards Strange, but true 
    • I like this page, better than that silly turbo kit   https://v8roadsters.com/product-category/engine-conversions/engine-conversion-lsx/engine-conversion-lsx-nc/  
    • That would be my Shoei helmet
×
×
  • Create New...