RB20 Ignition/Start Problems

Post by **DSMs_Suck** » Mon Jul 12, 2004 5:40 am

Ok, so just to give a quick update as to where I am coming from:

95 240sx se with a rb20det... basically done with the swap and just waiting on the shop to do a bunch of piping on the car at this point...

In any case I go to fire the car up, just to see if I could get the thing to even attempt to studder... and all I got was cranking.

So I start checking stuff... The ECU will flash 55 at first then once I try to start it it flashes 21 (ignition circuit problem). So I checked each plug for firing, and 1-5 all spark when turning over, but #6 will not. So I switched the coil harness (wiring) from cylinder 5 to 6 and vise versa... then 1,2,3,4,6 all fired and 5 didnt meaning there is some wiring issue with #6, NOT a coil issue with #6.

Any ideas? If anyone has a wiring schematic on how the ECU fires the coils I would love to see it. I take it each coil looks to be provided with power, ground and signal... any idea which wire is which?

Anyone have an rb20 ignitior I could try?

Murray

Post by **DSMs_Suck** » Mon Jul 12, 2004 5:40 am

Ok so I found a nice diagram in the r32 GTR FSM.

That plus a little research on automotive ignition coils, plus a little background in electronics and I'm pretty sure I have a handle on how the system works. I'll keep everyone updated as to what I find and if I still need to source a test ignitor/power transistor

Murray

Post by **Wulfgang** » Mon Jul 12, 2004 5:40 am

Sounds like a blown transistor in the ignitor.

Post by **DSMs_Suck** » Mon Jul 12, 2004 5:40 am

Wow got lucky... #6 pin on the ecu wasn't getting a very good connection, to the ecu. Getting that debugged was difficult cause continuity ran through everything the pin just was pushed back a bit.

Anyways in case anyone is reading this in the future. This is how the r32, rb20 or rb26 controls the spark. I would also assume this is the same for the 25. The ECU has 6 seperate ignition wires which "talk" to the ignitor/power transistor. The power TR then essentially charges the coil (actually while ECU gives it a "high" signal), then once the ECU drops the signal "low" the power transistor stops charging the coil, fields break down, blah blah blah and the spark plug fires. So basically if you are checking wires, check from the ECU plug to the "in" (6 pin connector) on the power transistor, then check from the power transistor "out" (7 pin connector) to each individual coil "-" wire. Thats basically how the system works, if you need more help feel free to email me.

Ok now with that figured out, I have a new question.. Here is where I stand:- I have everything connected except for vac lines (namely the AAC stuff), and the MAF.- I get a signal from the ECU to injectors. AND I have pressure at the rail. READ I HAVE FUEL- I have spark on all 6 cylinders verified with my own eyes.- Compression seems good, gives the starter a decent work out.- Car will turn but doesn't seem like it wants to fire, not even a studder.

I know the ECU should be mad about the MAS not being there, but shouldn't it try to run?

MurrayBTW ecu now flashes 55 before trying to start and 55 afterwards. Its as happy as a rb20ecu can get

, esspecially now that it has control over cylinder 6.

Post by **JonPowell** » Mon Jul 12, 2004 5:40 am

reverse the fuel lines, the one from the filter should go to the line that runs to the BACK of the fuel rail...the return line comes off the regulator...I messed this up also when trying to start my car the first time.

Post by **DSMs_Suck** » Mon Jul 12, 2004 5:40 am

JonPowell wrote:reverse the fuel lines, the one from the filter should go to the line that runs to the BACK of the fuel rail...the return line comes off the regulator...I messed this up also when trying to start my car the first time.

Pretty sure this is how I have it run, but definately worth checking into. Thanks for the idea, I will definately have to check that out.

Post by **Yellow4g63** » Mon Jul 12, 2004 5:40 am

IT should try to run even without the MAF hooked up like a DSM would.

Post by **RBpower** » Mon Jul 12, 2004 5:40 am

If it has compression, fuel and spark it will start. The motor has probably been sitting for a long time. I dont know how fast your starter is turning the motor over but with mine I had to get some more rpm's. I connected a tow bar to my rodeo.Then I let my friend pull the 240 and I poped it off in second gear. Worked like a charm. Just a thought.:eh:

Post by **DSMs_Suck** » Mon Jul 12, 2004 5:40 am

Yellow4g63 wrote:IT should try to run even without the MAF hooked up like a DSM would.

Thats what I was wondering.. I was told DSMs were strange creatures in that reguard because I was told they were one of only a few cars that could physically run without a MAF hooked up...

Guess I better start lookin at more stuff

Murray

Post by **JonPowell** » Mon Jul 12, 2004 5:40 am

The RB should run with out it, but it will idle at like 2000 RPM and kiss like crazy...if you can get it started.

Post by **DSMs_Suck** » Mon Jul 12, 2004 5:40 am

Ok all. Figured I would keep everyone updated.

Well, (wow I feel stupid for this one). Exactly as Jon Powell said I had the fuel lines reversed. I honestly have NO IDEA why i ran the filter line to the FPR. But I noticed that, got really excited, switched the lines and then tryed to start it.

No joke I think it cranked like 2-3 times and BOOM fired right up. Had no MAF, no turbo, and a few vac lines off... go figure... apparently it wanted to live.

Murray

Post by **JonPowell** » Mon Jul 12, 2004 5:40 am

Dont feel bad, I did the same thing....it happens to the best of us.

RB20 Ignition/Start Problems

RB20 Ignition/Start Problems

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