My VG30DETT swapped z31 cranks but won't start.

[ZettoSanIchi]

I bought a VG30DETT swapped 1985 z31 as a project and I can't get it to run. The guy said it was faulty injectors keeping it from starting. I replaced the injectors with bigger 880cc injectors and cleaned the fuel lines and tank, checked the fuel pump, filled it with premium, cranked it... And cranked it... And cranked it. And no dice. I replaced the PTU, spark plugs, and coil packs and it still won't start. Any ideas?

[Zinprogress]

Have you tried running codes on the ecu? Also is the ecu tuned for 880cc injectors? Without any adjustment for larger injectors, theres a theoretical 138% more fuel than whats needed being sprayed every time the injectors pulse. Did you try spinning the cas by hand and checking for spark/ injector pulsing? These motors really don't need much as far as sensors to start on a basic level.

Also please post some pictures, i have owned about 8 z31's and years ago wanted to do this swap.

[ZettoSanIchi]

The guy before me was an electrical engineer and wired the motor to a stock 85 turbo ecu. I'll post some pictures tomorrow. The motor fits waaay better than the original.

[Zinprogress]

Well there is a big problem right there. The 85 ecu and the vg30dett are quite different animals. Im not saying its not possible to run a vg30dett with a vg30et ecu but im going to go ahead and guess that your problem lies in the union of 90's technology married to late 70's early 80's computing.

The z31 ecu still has a self diagnostics, run it and see what codes you get and also check for spark/ injector pulsing. The z31 uses a cas and runs a distributor and its quite different from the z32 cas, but if this guy got it to work then it should in theory still work the same.

Also going to throw in that having the title of electrical engineer doesnt mean that he knows what hes doing. Ive met wyotech graduates that i wouldnt let change my air filter and ive also met electrical engineers who i wouldnt let change my gfci.

[ZettoSanIchi]

Lol you're right! I'll check for codes and see what it's throwing at me, I'm also going to test the cas (or buy a new one just in case) the plugs and coils are brand new, like replaced-yesterday new, but I'll also check the clips for power/ground. Thanks for the help man. I'll get back to you on that.

[Zinprogress]

also another thing to note, i believe the vg30dett injectors are high impedance and the 85 z31 turbo ecu utilizes low impedance injectors. This also makes things even worse if a stock 85t z31 ecu is in fact firing the injectors because that would mean that with your 880cc injectors installed that at all times there is about 238% more fuel being sprayed than whats needed.

[Zinprogress]

I wouldnt just buy a new cas, the test is simple. Use some white out to mark its orientation so you can reinstall it exactly the way it came off, then unbolt it. turn the ignition on and spin it by hand. You should hear the injectors firing and if you pull your coils and put spark plugs in them and ground them to the plenum they should all fire in sequence as you rotate the cas.

also pics

[ZettoSanIchi]

I don't know how to upload pics

[ZettoSanIchi]

So I did a test on the cas. I think I found the problem! No clicks, and no spark. I tested the clip for continuity and it was all good to go. It seems the cas is the issue. Time to pony up some dough for a new one. Thanks! I'll post again when I get the new one installed.

[zxFarside]

"The guy before me was an electrical engineer and wired the motor to a stock 85 turbo ecu"

What a mad man.

[ZettoSanIchi]

"The guy before me was an electrical engineer and wired the motor to a stock 85 turbo ecu"

What a mad man.

Yeah. I was surprised as well. If someone can tell me how to upload pics I'd love to show you guys.

[NolimitZ32]

I would suggest that you rip out whatever ridiculousness the "Electrical Engineer" compiled and run the proper EFI harness and ECU, you'll have to trace and supply power and grounds to the harness but you will be so much happier running the right ECU for the engine.

[Zinprogress]

I would suggest that you rip out whatever ridiculousness the "Electrical Engineer" compiled and run the proper EFI harness and ECU, you'll have to trace and supply power and grounds to the harness but you will be so much happier running the right ECU for the engine.

This 100%. I foresee an ongoing battle with electrical gremlins. Not to mention getting this to work is the equivalent of getting a super nintendo to boot a nintendo 64 game. Even if you made it work, it would be limited and a lot more work than just running the dett harness and computer. I even have pretty much everything you could possibly need except id strongly recommend a new harness and id gladly part with all of it. I like the idea of this swap and almost took it on myself once upon a time.

[ZettoSanIchi]

So I got my CAS in the mail took it outside, put it in the car... and she didn't do anything different.. She still didn't fire and just kept cranking. I can't afford a new harness and ECU right now so I'm stuck essentially. Any Ideas on if it might be something else, a specific part that I might need that could be the problem?

[ZettoSanIchi]

Alrighty Gents. So... I was cleaning out my car and I found a harness connector completely chopped off, it was for the Z32 ECU. It turns out the ECU that's currently in the car, is not from an 85 turbo. It's stamped with a number 22. Which, if you're familiar with the skylines, is from a RB20DET! How strange! An 85 300zx with a 94 300zx motor running a 92 RB20DET ECU. I'm out of words for this one guys. I was going to pull the trigger and buy a z32 ECU. Luckily I didn't. Now I have to scour the internet for the pinouts on the ECU of an RB.. Wish me luck boys.

[itsa300zx]

Isn't a RB20Det a four cylinder? Anyways, good luck with your progress, too many unknowns for my liking.

I also agree with A new Z32 harness and TT ECU; will yield much better results.

[Zinprogress]

No, the rb20det is a 6cyl and is actually an original engine to the z31. It was the 200zr in japan, pretty neat car actually. So knowing that, the god forsaken combination seems a little less difficult knowing that the z32 cas is a common swap to that motor.

So once again, back to one of my original questions: Have you tried to pull codes or check to see if the ecu even powers up? Also im really willing to help you trudge through trying to diagnose this thing but if you dont figure out how to post pictures of this thing i will definitely lose interest!

[itsa300zx]

No, the rb20det is a 6cyl and is actually an original engine to the z31. It was the 200zr in japan, pretty neat car actually. So knowing that, the god forsaken combination seems a little less difficult knowing that the z32 cas is a common swap to that motor.

So once again, back to one of my original questions: Have you tried to pull codes or check to see if the ecu even powers up? Also im really willing to help you trudge through trying to diagnose this thing but if you dont figure out how to post pictures of this thing i will definitely lose interest!

DOH, Yes you are right, for some reason I was thinking SR20DET; LOL

[Zinprogress]

I figured lol, you dont hear too much about the 2.0 inline six these days but that sr is everywhere!

[ZettoSanIchi]

No, the rb20det is a 6cyl and is actually an original engine to the z31. It was the 200zr in japan, pretty neat car actually. So knowing that, the god forsaken combination seems a little less difficult knowing that the z32 cas is a common swap to that motor.

So once again, back to one of my original questions: Have you tried to pull codes or check to see if the ecu even powers up? Also im really willing to help you trudge through trying to diagnose this thing but if you dont figure out how to post pictures of this thing i will definitely lose interest!

Progress, give me you email do I can shoot you some pictures, I'm operating off my phone. I know you're knowledgeable enough to shed some light on the situation.

[ZettoSanIchi]

I figured lol, you dont hear too much about the 2.0 inline six these days but that sr is everywhere!

Honestly. I've seen some gnarly(in a good way) SR's in my area, they're easy to build and parts are way more common to come by than VG parts. But I'm a Z guy so I'll stick to my V6's.

[Zinprogress]

PM sent.

SR20's are definitely good motors. Parts are cheap and they are simple to put together. Had a local guy buy an sr20 and "built" it and it kept spinning bearings within days of putting it together. Tore into it and found that the crank had been machined and ordered some oversized bearings and put it back together and he has been beating the hell out of it for a little over two years now with no major problems. Pretty impressive to put up with that kind of abuse and keep trolling around.

[Zinprogress]

[Zinprogress]

Ok, I have a few concerns from the pictures:

1. That fuel filter is for a carbureted setup and will explode under the pressures required to run fuel injection, also that orange hose looks like silicone vac line? If its not braided fuel injection hose, it will also rupture and it will spray fuel everywhere when it bursts.

2. The rust on that ecu concerns me. It looks like its either had water dripping on it for a while or its just sat in water. Id be a little worried about its bill of health if the insides have been exposed to water.

3. That "custom" wiring is atrocious. If that ecu does turn on, i bet its full of codes.

[itsa300zx]

Looking at that third picture; Is the fuel line(orange line) with the filter the inlet side; ie from the pump?

I ask because the inlet side to the engine should be on the other line. On my Z they are reversed.

Also that harness in the second last pic doesn't look like a Z32 ECU harness connector.

[NolimitZ32]

This thing is ridiculous, I would love to put my hands all over it!

[ZettoSanIchi]

I'm so dumb. My ECU wasn't dead I just had to turn the little screw all the way clockwise, wait 2 seconds, and then turn it all the way counter-clockwise. I got a code 34 which is knock sensor, so I just bought a knock sensor relocation kit. I checked both VG30DETT and RB20DET codes and Code 34 is the same for both motors.

[NolimitZ32]

Well that's a relief, did you get it running?

[everpresentnoob]

Is no one going to even mention the skateboard used as a hood prop rod??

Seriously, I would definately look at that fuel line, as stated the way its plumbed the filter is AFTER the injectors and everything.

What do you mean your ECU wasnt dead, you just had to turn the screw clockwise.... so it will go into diagnostic mode, but wont let the car start?

[ZettoSanIchi]

Well that's a relief, did you get it running?

Nope. Also I don't think the knock sensor is going to keep it from running. But I'm sure the ECU will throw another code when it's fixed.