engine stalling / running rough on startup

[RB30DEVL]

I've got a question about my VL, as some people may know it runs an RB25 head ,pistons & ECU (from a 95 model R33 Skyline) and RB30 block , rods & crank , I've also got the external fuel pump running off a swirl pot.

It has only been in the last few months ,and it seems to coincide with when the petrol stations have been putting ethanol into their fuel , well it started doing it on Shell V-power , sometimes it will start then stall when cold or just run rough for a few seconds then clears up.

These are things which I have checked :-

- Fuel pressure (o.k.)

- internal fuel system leakage , fuel pressure regulator seemed to leak back to tank within a few seconds , fitted an aftermarket adjustable fuel pressure reg which fixed that problem but the starting problem still exists , some hose ends were leaking so I tightened the hose clamps up , didn't fix the problem.

- fuel pump non return valve tested o.k. (had this problem before and that's what caused the problem)

- checked fault codes - flashes code 55 (o.k.)

- spark plugs are new & running clean

- checked for air leaks , was leaking air in from around PVC grommet but the fault still exists.

- oil filler cap was leaking & oil was being forced out past the cap , replaced that but the problem still exists.


- airflow meter & all connectors were cleaned with contact cleaner , problem still exists (I run a K & N air filter).

- Checked ignition timing (o.k.)

- Checked TPS output voltage (ranges from 0.5 @ idle to 4.5 volts @ WOT)

- Checked fuel pump volume (low & high pressure ,o.k.)

- On a trip up to the north coast I felt the engine miss once under load.


I had this problem on a single cam VL engine and it was caused by , but not all at once by :-

- leaky injectors

- faulty airflow meter

- loose fuel hose clamps

- faulty fuel pressure regulator

- maladjusted TPS

Once the engine is started , it starts fine there on after , even when cold.


The last thing I want to check is the in tank fuel pump strainer despite the volume being o.k. because I also let the tank run low on a couple of occasions, I'm also thinking at worst , blocked injectors but the engine doesn't hesitate when warm & runs smooth.

[Tensop]

25 inlet still have an aux air valve coming off the idle motor piping? pull both ends off and check if the disc inside opens/closes with application of cold air(freezer) and hot hair(toaster)

Usually the cause of stalling on rb20's and rb30's as the idle motor makes the front bank of cylinders run very rich due to no airflow(idle motor is righ up the other end)