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Rb25 Neo Wont Start, R32 Swap.

amnash

By amnash,
in Engines & Forced Induction

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amnash Enthusiast

amnash

Posted
Posted

OK, so I have been trying to get this rb25 neo running for a couple of weeks now. I've done all the wiring myself and I'm about 98% sure its all done properly.

i have fuel pressure, pump is wired to 12v constant through relay.(actually spikes way up to about 100psi)

new tomei fuel pressure regulator.

listened to the injectors with long screwdriver while turning the CAS and they're all clicking.

pulled the coil-packs out, and with the spark plugs in them i turned the CAS. there's spark.

I re-checked the cam timing, and its bang on.

ive tried to start with maf unplugged. nothing.

tried to start with ICV unplugged. nothing.

installed fresh spark plugs after them getting fouled

so im running out of ideas.. the engine cranks from the starter turning, but it doesnt even try to start. any ideas from anyone of what i could try next??

the rb25 is from a r34 GTT.

One thing i noticed was the TPS has 6 wires going to it. in two sets of 3, one set is black red and white which is connected. and the other set of 3 is brown yellow and green which isn't connected to anything and aprears to blacked of from the factory.(looks like and oem blanking plug)

2012-08-17203407.jpg

2012-08-17203423.jpg

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amnash Enthusiast

amnash

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how would i go about doing that? just by adjusting the FPR? what if i didnt have an adjustable one? when the tomei FPR was on my rb20 i have is adjusted for 35psi and havnt adjusted it since. why would it be higher now?

The Dan Grand Master

The Dan

Posted
Posted

A given flow through a restrictive orifice will increase if the flow is increased but the orifice is not.

The reg doesn't know how much fuel you want. It only knows how much resistance to create. If you increase the flow of fuel by increasing the size of the pump or replacing the pump, the pressure will increase because the reg still creates the same resistance

blind_elk Grand Master

blind_elk

Posted
Posted

It's a stupid question, but hey, you wouldn't be the first - is the fuel connected to the rail correctly? Stick a pressure gauge in the inlet side of the rail.

Are the coils and injectors firing in the correct order?

Do you have compression?

What ECU are you using?

Have you got a good battery to start the engine with?

amnash Enthusiast

amnash

Posted
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Posted

Elite, that makes sense. ill dial down the pressure then to compensate for the extra flow from now running 12v constant at the pump. good thing i have the adjustable FPR then or i wouldn't be able to do that. ill go with 35 psi.

Elk, the fuel lines are hooked up correctly. i have a pressure gauge installed in the feed line constantly and another fuel pressure gauge inside cabin. i have pressure. i have great compression, did a dry compression test while i tested for spark and it was 160~170 on all 6 cylinders. i believe im using a r34 GTT ecu part number # 23710-AA500. and my battery has 12v. i keep it on a trickle charge at night.

how would i check to see if the coils and injectors are firing in the correct order? and if its wrong, how would i fix it? the CAS can only be installed the one way..so it couldn't be that.

GTSBoy Grand Master

GTSBoy

Posted
Posted

A given flow through a restrictive orifice will increase if the flow is increased but the orifice is not.

The reg doesn't know how much fuel you want. It only knows how much resistance to create. If you increase the flow of fuel by increasing the size of the pump or replacing the pump, the pressure will increase because the reg still creates the same resistance

Actually, the definition of a pressure regulator is that it is actually set to a given pressure, not a set restriction size. That is how they actually work as a regulator. if it was a fixed orifice, then upstream pressure would yo-yo as the demand went up and down.

On that basis, if you were to take a pressure reg from an RB20 with a small fuel pump and put it on an RB25 with a big fuel pump, then provided the reg was actually big enough* to flow the required amount of fuel back to the tank, it should run at exactly the same pressure as it did before.

*and being an aftermarket adjustable reg intended for use on arbitrary engine/pump combos, you would expect it to be big enough.

Nevertheless, if the pressure is set too high, then follow Dan's advice and wind it back down to something sensible.

blind_elk Grand Master

blind_elk

Posted
Posted

how would i check to see if the coils and injectors are firing in the correct order? and if its wrong, how would i fix it?

Your OP suggested that it is a custom wiring job. You will need to have the injectors and coils removed from their fittings when you spin the CAS. They should activate in the firing order 1-5-3-6-2-4. If they don't fire in that order, re-wire the loom. (Stick the injectors in a bucket or similar to catch the petrol. You could also try and observe the spray pattern of each injector.)

If, on the other hand, you have used a factory loom, then it should all connect up correctly.

the CAS can only be installed the one way..so it couldn't be that.

If the locating tab in the end of the exhaust cam is broken, then it is possible to put the CAS in in about 10 different ways.

amnash Enthusiast

amnash

Posted
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ya elk, its a factory loom. the only parts i messed about with was connecting the loom to the chassis plugs.

does anyone here have an r34 GTT? just to check how many relays are on the engine loom near the ecu. because on mine there is only one 6 pin brown relay. maybe i am missing a start relay or something (although there are no wires that aren't connected)

amnash Enthusiast

amnash

Posted
  • Author
Posted

Kiwi, its not the mitsubishi one, it has a plastic cover. looks like the r34 one. pretty sure its not r33. and its making the injectors click, and spark plugs spark. so should be fine i think

DVS, i thought that could be the issue as well, but when i took the CAS off to check, the slot it actually off centered. so it can only go on the one way.

GTS, if its just the one brown ECCS relay then im good. it clicks when i plug it in with ignition set to ON.

what would i be looking for with the timing light while cranking the engine?

amnash Enthusiast

amnash

Posted
  • Author
Posted (edited)

sooo there is definitely something fishy going on with the fueling system.

- i turned the FPR max each way and it didnt even change the pressure at all.

- i removed the fuel pump fuze and cranked the engine to see if the pressure would drop and it doesn't even budge.( injectors arent spitting?)

- and with a hunch i removed the return line going to the FPR and its bone dry!... there much be a blockage inside the rail somewhere? probably before the injectors.

http://www.youtube.com/watch?v=gABQmtQiDPk&feature=youtu.be

what should i do from here? does this mean i have to remove my intake mani and access the fuel rail?? :( I've done it before, but what a pain in the ***

Edited by amnash
The Dan Grand Master

The Dan

Posted
Posted

Are you absolutely sure you have the lines around the correct way? The R34 fuel rails have pressure dampeners on both sides of the rail as well as the factory pressure regulator. If you feed fuel in reverse, it will show pressure on that gauge because you have it on the feed side but the reg won't work in reverse. Just try swapping the fuel lines around mate. It sounds exactly like it by your description

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