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RB25DE 240Z Wiring/electronic help!


EMWHYR0HEN

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I just finished swapping out my L28 with a RB25DE into my 1971 240Z. Got all of the mechanical parts hooked up, and took care of all my fluids. I have the lower engine harness hooked up to the chassis and everything seems to be working fine (engine cranks, however not 100% sure about the alt. because I havent started the engine yet, but I did bypass the volt. reg. w/diode) Anyway, my problem is that the engine isnt starting. Im not getting any spark @ my ign. coils/spark plugs. So, I checked my ign. relay and im getting power, which means im also getting power to to all six ign. coils ( I checked all six ign. coil harness for power and is good. Then, I checked the ground for the six ign. coils on the coil harness, and they were all being grounded properly. So then I went to the power transistor, and checked to make sure that it was being grounded as well, which checked out ok. i also noticed that the power transistor was warm after trying to crank the engine for a while, so i assume it was working? I also made sure that my ECCS relay was getting power, which cheked out ok. I also have the rb25de fsm, and have gone through the steps in checking the ignitions system. so im thinking it comes down to this:

 

1. faulty power transistor

2. I have the wrong or faulty ECU

 

if it is my transistor, does anyone know if that part can be found on any U.S. spec nissan/infiniti? and just to make sure that i have the correct ecu, can anyone please give me a part #.

 

anyhelp would be greatly appreciated as I am stuck in a hole right now and cant seem to figure out this problem.

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I'm far from an expert here, but If all the wiring is correct I would check 2 more things;

1) Is the Ign Relay sending power to the coils? (not the same as getting power)

2) Is the Power Tans getting signal from the ECU? (I don't think that it should be getting warm)

 

If 1&2 are good I would swap out the Transistor.

 

But I would PM someone like Q(240Z Master) or JT.

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Thanks for the reply Ed260Z. I'm not an expert myself, but i know enough to understand how certain things work.

 

1) Is the Ign Relay sending power to the coils? (not the same as getting power)

 

check. the ignition realy is getting power, and is sending power to all of the six ignitor harnesses . all six ignitor harnesses are also getting proper ground.

 

2) Is the Power Trans getting signal from the ECU? (I don't think that it should be getting warm)

 

This I dont know of this yet, im in the process of checking that right now. However,since the harness on the ignitor, going to the ECU has 7 prongs, and one of the prongs is a ground, doesnt that mean the computer gives the ignitor chip (transistor) a positive (+) signal? thats my assumtion, someone please tell me if im wrong.

 

as far as the ignitor getting warm, I have no clue if that a bad thing or good thing. although, the transistor has a large heat sink on it, so i assume that its sopost to generate some heat. anyone know anything about that? also, if the transistor is getting warm, does this mean its working? i wish i could anser this myself, but dont have any speacial tools to test the transistor neither does my mechanic friend.

 

PLEASE HELP, ANYONE!

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2) Is the Power Trans getting signal from the ECU? (I don't think that it should be getting warm)

 

This I dont know of this yet' date=' im in the process of checking that right now. However,since the harness on the ignitor, going to the ECU has 7 prongs, and one of the prongs is a ground, doesnt that mean the computer gives the ignitor chip (transistor) a positive (+) signal? thats my assumtion, someone please tell me if im wrong.

 

PLEASE HELP, ANYONE![/quote']

 

when the engine is cranking you should be getting a reading of .2 to .3 volts at the connecter prongs, while you are gounding to the ground on the connector.

Ed

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I talked to someone about the whoel ignitor getting warm thing, and he says its abnormal. he says that it shouldnt generate any heat from just being in ignition and not actually firing the coils. just to make sure, could someone with an RB with ignitor please check and see if there ignitor gets warm from just being in ignition for about 3-4 mins.

if it doesnt get warm, then i know for sure that something is getting power when its not sopost to, or shorting somewhere.

 

anyfurther help/sugestions would be GOLD.

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240Zmaster. Yeah, im good with the fuel, I have the pump running on a switch. also, i gave 12v. to the grey wire that powers all six injectors (AF81, or somting like that) and i checked to see that i am getting power at each injector. then, I checked that the ECU is sending out a ground to all of the injectors, and i do have a pulsing ground going to all six. So fuel is already eliminated from my problem.

 

I have:

 

1. fuel delivery

2. engine cranks.

3. ECU power

4. IGN. power

 

but still, no spark at the coils or plugs......

 

 

someone HELP!

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Check for a pulse at the power transistor input wire. It's usually the smallest wire but I'm not sure on your setup. It will be a faster pulse but an analog voltage meter would work if you use the DC setting at about 20V. A digital multimeter with analog display would be even better.

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Thanks 2slo4u.

 

i'll give that a try. Does anybody know how to test an ignitor chip (transistor). i have the fsm. but im not auto technitian, i dont understand how to test it. can anyone explain?

 

Im getting another ECU next week from the guy i bought the engine set from. alot of other people and I think that the ecu is faulty, even though it has no physical damage. kinda weird.... is that even possible?

 

Also, I thought maybe that it was my Crank Angle Sensor, but then again, im getting a pulsed signal to the injectors which gets a signal from the CAS. Anyone know if the CAS gives seperate signals (one for fuel and one for Ignition) to the ECU?

 

I HATE ELECTRONIC PROBLEMS!

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Get a new Transistor from him while your there. I think you'll find the the transistor is faulty, based on your problems so far.

 

When I can't figure out exactly what's wrong with a car I'll start swapping out parts until it works. I start with the most likely suspect and work my way down the line.

 

The Transistors have a history of going bad, and it's one of the easiest components to swap out. If it stilldoesn't work you anly wasted a few minutes of your time.

 

Let us know what it finally was.

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Hey all.

 

OK I think the problem I have is redeced to a few things now. But still stuck in a very deep hole........

 

Today I headed over to a friends shop and tried my Ignitor on his R32 GTR. It started right up. So, it's definately not my Ignitor.

 

I removed my engine harness and showed him my harness to confirm with him (he's really experienced with Nissan swaps) that my wirings are correct, which totally are!

 

He let me borrow a RB25DET ECU to try to eliminate the possibility of my RB25DE ecu being bad. He wasnt sure if it would run properly, but for sure that I would get Ignition while cranking.

 

Heres the thing....... I'm still not getting ignition. So, I checked:

1. CAS. I made sure that there was continuity between the 2 wires from ECU to CAS.

2. Power and Ground @ CAS.

3. Removed CAS. With harness still connected and Ign. ON, I rotated the CAS shaft and I could hear all six injectors working.

 

So, I have Ign. power, ECCS power, injectors power when cranking, Ignitor is fine, but still no ignition.

 

Here are my concerns:

1. Ignitor gets warm, (up to 85 degrees F) Ok fine its gets hot.From what all the knowledgeble poeple say, its not sopost to. also had a friend w/rb25det leave his car in ign for several mins and observed transistor temp, and was nuetral temp.

 

so i took apart my coil harness to make sure there were no short circuits, and was ok.

I checked all my coils according to FSM and all check out ok.

 

what in the world could there be left to check?!

 

PLEASE HELP!

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Thanks Ed,

 

well I checked all of the coils and made sure that they had the proper resistance according to the R33 FSM. yeah, the engine cranks over. just no spark. I took the coils out of the hole, and i can physically see if there is spark or not. timing should be ok, theres only one way for the CAS to go in, and i marked the position of the CAS before i took it off. It still even had the Nissan sticker over the CAS bolt, so i was the first to actually take it off, or move it.

 

I took apart my entire harness. I mean its to the bare bone of wires, and everything is where its sopost be to be. No shorts, no burnt wires. I still have no clue what this could be. Help anyone?

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Thanks Ed' date='

 

well I checked all of the coils and made sure that they had the proper resistance according to the R33 FSM. yeah, the engine cranks over. just no spark. I took the coils out of the hole, and i can physically see if there is spark or not. timing should be ok, theres only one way for the CAS to go in, and i marked the position of the CAS before i took it off. It still even had the Nissan sticker over the CAS bolt, so i was the first to actually take it off, or move it.

 

I took apart my entire harness. I mean its to the bare bone of wires, and everything is where its sopost be to be. No shorts, no burnt wires. I still have no clue what this could be. Help anyone?[/quote']

 

Myron, I would say retrace the wires and see where they're going.

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Are you sure your start signal is going through? The engine will not start without it being connected. Also, if you have connected ignition to the accessories connection, you will loose your ign signal when cranking. What error codes are showing up on the computer? Put the computer into diagnostics mode and check.

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well, I feel ive tried everything possible. I did the most dishonerable thing.... I'm paying someone to get my ignition working. The problem was driving me nuts, +school. It just wasnt worth the headache. $75.00 bucks and hour to fix my car. ouch!

 

i'll post pix when everything is running, and let everyone know what my problem was.

 

oh also Thanks, to everyone who gave me some input

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