Rb25 Swap Complete! (PIC) Issue keeping the car running

[opponheimer]

i finally got my car together, manifold/turbo/full exhaust is on the car... the car still starts up, then shuts off.. Its getting fuel pressure i believe... had no issues with pump 3 weeks ago when it had a ka24de.after a while of sitting this is what happens:
1. turn key, car starts, tach goes to like 3k (uncalibrated) and shuts off after 2 seconds.
2. try to start again, car starts and shuts off right away (0.5 sec)
3. car is unresponsive to hitting throttle.
4. i've looked everywhere for vacuum leaks and everything is fine, no leaks.

its almost like if i shut it off and leave it a while the car will run a second longer... I don't know if the cylinders are getting flooded or anything..




This has a lovefab manifold, stock mafs (for now) q45 TPS/Q45 TB, freddy intake manifold, gt3582r, fmic, exhaust..

o2 is installed as well.

http://www.bizlocker.com/cars/rb/mini-P1000294.JPG





Stock ECU (S2 AUto) , Stock mafs
Clamping fuel line does nothing, CAS is about half way. Is there such thing as a fuel pump Relay? Could that have gone bad or be losing 12v signal? What about the AAC/Boost Valve/VTC Control what if that is wired wrong?
Unplugging mafs or TPS does nothing, no change. And like i said the car doesnt respond to any throttle. I do have a q45 TPS, but i believe its wired correctly.



I am so so stumped and tired of this s***! How do you check codes on an ecu w/o an LED? Who thinks its something electrical?

[RaVeNouS14]

congrats on the install. now make it a fire breathing monster.

[opponheimer]

yeah... when it starts running..

[projectRDM]

Fuel pump relay is called the EGI pump relay on an S13. Try hardwiring the fuel pump temporarily to see what happens when it's powered all the time to rule out furl problems.
With the key on, measure voltage/resistance on all the required sensors, TPS, MAF, CTS, etc. If it's not fuel something isn't acting right or not connected.

[opponheimer]

Fuel pump relay is called the EGI pump relay on an S13. Try hardwiring the fuel pump temporarily to see what happens when it's powered all the time to rule out furl problems.
With the key on, measure voltage/resistance on all the required sensors, TPS, MAF, CTS, etc. If it's not fuel something isn't acting right or not connected.


I have S14... The fuel pump relay is in the cabin by the fuse box/kick panel i believe. (according to the FSM - plug M4 on page EL-218 of t his FSM: http://www.nicoclub.com/FSM/240sx/1996/el.pdf )

What is the CTS by the way? I tried starting car with and wihtout mafs and tps plugged in and i had the same crap.

The element in my fuel filter is loose and rattles around (up and down) inside of my new fram fuel filter.... i plan on replacing that, but don't know if that coudl be it...

[clark]

I have S14... The fuel pump relay is in the cabin by the fuse box/kick panel i believe. (according to the FSM - plug M4 on page EL-218 of t his FSM: http://www.nicoclub.com/FSM/240sx/1996/el.pdf )

What is the CTS by the way? I tried starting car with and wihtout mafs and tps plugged in and i had the same crap.

The element in my fuel filter is loose and rattles around (up and down) inside of my new fram fuel filter.... i plan on replacing that, but don't know if that coudl be it...

is it the original crusty old fuel pump from your KA24 engine? or is it an upgraded one. if not, you have to upgrade that, i really doubt you'd have that large a turbo and that large an engine without upgrading your fuel pump because you seem to know what you're doing.

get yourself a Z32 fuel filter.

CTS = coolant temperature sensor.

Russ is definitely spot on with his suggestions.

i personally think your issue is timing.

i think before you do the fuel testing, pull your fuel pump fuse completely and make sure ALL your plugs are sparking.

where did you get your engine harness? is it haggared at all or does it appear to be in good condition?

what do you mean cas is half way? is that an RB thing...?

i had a similar problem with my front clip (sr20) and my O2 sensor wiring was frayed and all worn possibly from engine movement or it was grounding out or some BS, either way i eliminated that and ran great.

make sure your fuel source and return lines aren't mixed up either you fool! jk jealous of your engine!

[opponheimer]

is it the original crusty old fuel pump from your KA24 engine? or is it an upgraded one. if not, you have to upgrade that, i really doubt you'd have that large a turbo and that large an engine without upgrading your fuel pump because you seem to know what you're doing.

get yourself a Z32 fuel filter.

CTS = coolant temperature sensor.

Russ is definitely spot on with his suggestions.

i personally think your issue is timing.

i think before you do the fuel testing, pull your fuel pump fuse completely and make sure ALL your plugs are sparking.

where did you get your engine harness? is it haggared at all or does it appear to be in good condition?

what do you mean cas is half way? is that an RB thing...?

i had a similar problem with my front clip (sr20) and my O2 sensor wiring was frayed and all worn possibly from engine movement or it was grounding out or some BS, either way i eliminated that and ran great.

make sure your fuel source and return lines aren't mixed up either you fool! jk jealous of your engine!


brand new walboro that was confirmed working before i pulled the ka
i plan on getting a new z32 ff (i already have a new z32 but its rattling)
i was just trying to say the cas isnt all the way retarded or advanced..
dont think its the o2 sensor wiring
my harness is weird as hell.. it looked like it was from an auto to manual converted skyline. i'm trying to get a new one from the person i got my engine from.
my fuel lines are not swapped.. thats the first thing i checked..
i really need to check voltage to fuel pump see if it goes out... and or supply constant power to it like russ said. and see what happens.

the fact that the engine sounded alright when the car did start up for 2 seconds then shut off makes me think timing is fine... although u cant be sure.

[MeanS14]

I had the same problem happen to me twice on my rb. Once it was the fuel pump turning on then shutting off right away becasue the relay was crapping out. The other time it was my coilpacks. Check all your wiring and measure all the readings on your sensors. Multimeters become your best friends when you have an rb.

Just a little side note. On my rb the cas all the way advanced is only 16 degrees. When I have it in the middle it runs like poo

[ANVIL]

do you have the large vacuum hose from the IAC still connected to your new cold pipe? is ur maf hooked up?

[opponheimer]

All the way advanced means all the way to the right correct? Mine is more like closer to the right than to the left, if that makes sense.

I really need to check fuel pump relay... It kinda confuses me the car was rnning fine like a week ago. Coudl there be a short and the relay is unswitching/protecting the circuit?

What do you mean it was your coilpacks.... all of them or just a few?? I still dont know what values other than resistances and voltage from sensors I need. Or even why a sensor could cause the car just to die right away..

[opponheimer]

do you have the large vacuum hose from the IAC still connected to your new cold pipe? wheres ur maf at?


I took the mafs off in that pic, but it was at the intake of the compressor. I do have my IACV plumbed to a 0.5" diameter nipple on the cold pipe.

[ANVIL]

whats your fuel pressure at? do u have an adjustable regulator?

[Chernobyl]

Sounds like your pump is priming but is not staying on when you turn the car on. Follow Russ' suggestions and test it.

Putting a fuel gauge in the line would really help you diagnose this also.

CAS in the middle is fine. Mine's somewhere there and it runs fine (RB20). I hear they are very sensitive to timing though.

Engine temp sender (the bigger sensor for the ECU) may also cause these symptoms you are describing. Find an FSM and check the resistance across the terminals to make sure it's in good shape.

Good luck.

[ANVIL]

the cas in any position will run... but you still have to time it with a light to make it run better

[opponheimer]

Sounds like your pump is priming but is not staying on when you turn the car on. Follow Russ' suggestions and test it.

Putting a fuel gauge in the line would really help you diagnose this also.

CAS in the middle is fine. Mine's somewhere there and it runs fine (RB20). I hear they are very sensitive to timing though.

Engine temp sender (the bigger sensor for the ECU) may also cause these symptoms you are describing. Find an FSM and check the resistance across the terminals to make sure it's in good shape.

Good luck.


Guys: i used the coolant temp sensor from a running motor (s14 ka, so it will work with cluster) but the coolant temp sensor plug on the harness was smashed, so i used another random plug, that barely went on..

Would this problem be caused if the plug wasn't connected properly causing infinite resistance? (its being held on by zip tie now...)

[Chernobyl]

Guys: i used the coolant temp sensor from a running motor (s14 ka, so it will work with cluster) but the coolant temp sensor plug on the harness was smashed, so i used another random plug, that barely went on..

Would this problem be caused if the plug wasn't connected properly causing infinite resistance? (its being held on by zip tie now...)

Hmm i think you need the sensor from an RB. Is your ECU throwing codes? Oh wait, it's a S2 so that'd be hard to tell...

Another idea... and this may make you feel stupid, but it's very common with these swaps: did you hook the fuel lines up correctly? The line from the fuel filter goes to the "open" end of the fuel rail and the return line hooks up to the fuel pressure regulator... Don't be mad if I'm patronising you... but people swap these by accident all the time.

[MeanS14]

You keep saying "mafs" like you have more than one...why?

And rotating the cas counter clockwise advances the timing

The problem with my coilpack was that they would fire for a couple seconds when I turned the car on but the 4 wire relay behind the passenger side kick pannel by the ecu would lose voltage so my coilpacks would lose power after a second or two. Someone correct me if I'm wrong but I think it's called the ECCS relay

[Chernobyl]

You keep saying "mafs" like you have more than one...why?

Mass Air Flow Sensor.....

[s13gebala]

replace that fuel filter..

there like 10 bucks.

[opponheimer]

You keep saying "mafs" like you have more than one...why?

And rotating the cas counter clockwise advances the timing

The problem with my coilpack was that they would fire for a couple seconds when I turned the car on but the 4 wire relay behind the passenger side kick pannel by the ecu would lose voltage so my coilpacks would lose power after a second or two. Someone correct me if I'm wrong but I think it's called the ECCS relay


Ok and what did you have to do to correct the problem... change the relay or the wiring?

[Chernobyl]

Ok and what did you have to do to correct the problem... change the relay or the wiring?

Power for your ECCS relay should come from the 1 pin on the F3 plug. It's a switched 12V.

[projectRDM]

Guys: i used the coolant temp sensor from a running motor (s14 ka, so it will work with cluster) but the coolant temp sensor plug on the harness was smashed, so i used another random plug, that barely went on..

Would this problem be caused if the plug wasn't connected properly causing infinite resistance? (its being held on by zip tie now...)

The CTS runs the ECU signal, it's the two prong sender, the single prong sender just does the cluster, it's not need to run. Typically a CTS won't cause non starts, it just won't switch to a hot fuel map when the engine warms up and run rich as hell. TPS alignment would cause a non start since it's seeing an incorrect signal, but it's highly unlikely you adjusted it out much if at all. Check it and see, it's probably similar to the KA/SR and should see about .45V-.5V when closed.
A bad MAF would allow for start but poor idle, limited revs.
Start with fuel, that seems to be the issue. Then check the plugs one at a time for spark. Eliminate the common and easy symptoms first.

[opponheimer]

The CTS runs the ECU signal, it's the two prong sender, the single prong sender just does the cluster, it's not need to run. Typically a CTS won't cause non starts, it just won't switch to a hot fuel map when the engine warms up and run rich as hell. TPS alignment would cause a non start since it's seeing an incorrect signal, but it's highly unlikely you adjusted it out much if at all. Check it and see, it's probably similar to the KA/SR and should see about .45V-.5V when closed.
A bad MAF would allow for start but poor idle, limited revs.
Start with fuel, that seems to be the issue. Then check the plugs one at a time for spark. Eliminate the common and easy symptoms first.


crap i think i put the ecu's 2 prong temp sensor from the KA into my RB... i dont know if that would do anything do you?

[flip3d]

When I first swapped in my SR, it would rev to 4k and throttle would be unresponsive.

I vote for IACV.

Then again, my gas tank was rusty. Change the fuel filter too :P

[Chernobyl]

Another idea... and this may make you feel stupid, but it's very common with these swaps: did you hook the fuel lines up correctly? The line from the fuel filter goes to the "open" end of the fuel rail and the return line hooks up to the fuel pressure regulator... Don't be mad if I'm patronising you... but people swap these by accident all the time.

Did you check this yet?

[opponheimer]

Did you check this yet?


yeah i thought i said i checked it already.... its not iacv guys,.

[MeanS14]

Mass Air Flow Sensor.....

I was thinking that but whenever i talk about it with people I just call it a MAF. I never heard anyone abbreviate mass air flow sensor as "MAFS", we just say MAF

[Chernobyl]

I was thinking that but whenever i talk about it with people I just call it a MAF. I never heard anyone abbreviate mass air flow sensor as "MAFS", we just say MAF

Do you call the CAS the "CA"? The TPS = "TP"?

Do you call the ATM the "AT" too? "Hey let me stop by the AT... I gotta get some cash..."

[opponheimer]

Chernobyl: shutup lol

Well i replaced the fuel filter, fuel line, hardwired the fuel pump power to constant 12V... clamped return line... nothing...

Tried runing with and without mafs/tps/temp sensor plugged in

What do i do??

[Xracer]

what size injectors are you running?

[MeanS14]

Do you call the CAS the "CA"? The TPS = "TP"?

Do you call the ATM the "AT" too? "Hey let me stop by the AT... I gotta get some cash..."

Hey fag boy try using "MAFS" in a sentence

My mafs on my sr is bad.....doesnt that just sound retarted!!

Now trying talking about 2 different mass air flow sensors. What do you say? MAFS'S?? The correct punctation would be MAFS' but thats not the point

Chernobyl: Hey what kind of mafs's are those?
Me: Sorry what did you say? You studdered and I couldnt understand you :madfawk::keke:

[projectRDM]

Chernobyl: shutup lol

Well i replaced the fuel filter, fuel line, hardwired the fuel pump power to constant 12V... clamped return line... nothing...



Well there it is, no fuel. Fix it.

[Chernobyl]

Chernobyl: shutup lol

Wow. And to think, I was trying to be helpful earlier in this thread.. Oh please forgive me for having a little fun.

Hey fag boy try using "MAFS" in a sentence

Blind insults will get you far in this world...

And I'm still right about your MAF/MAFS logic. What you said makes no fucking sense.

[Forge_55b]

are the plug wires in the right firing order?

[opponheimer]

Well there it is, no fuel. Fix it.


This is ridiculous... i had the fuel pump on constant prime... and the car will not keep firing... i think the prime feature on the ecu is burnt... i think the ecu i have is fucked totally, but i'm not putting my AEM EMS on this thing if the wiring is bad...


Car started on brake parts cleaner.... and ran... dammit anyone in the VA area with an rb25 ecu?

[Forge_55b]

if you can figure out the wiring, id bet it is wrong. at least i would check it out if you had a wiring diagram before changing out ecu's

[opponheimer]

Just to post solution, the ECU was fried, the priming mode was gone.

Also the harness I had was for an rb20det, my vendor sent me the wrong harness