Engine start issues

I did not check the psi on the fuel yet. Assuming since the engine works perfect once it’s one. I do not have a fuel pressure issue. I do have an electric pump in line but I never turn it on. The fuel manifold has the return line caped off. Someone suggested I uncap it and connect that line to one of my vents in the fuel tank. 
The engine is on an Interplane Skyboy. 

"Turn on the mags and start. That’s all. Won’t start no matter what. Only way it starts is if I turn the fuel valve off and then once it starts I put the fuel valve back on."

I doubt that my engine would cold start ,with your technique.

Mine is:

# Fuel On

# Boost pump On,  until fuel pressure stabilised (normally 5 psi/34 kpa)

# Boost pump off

# Choke on full

# Ignition 1&2 On

# Starter engaged

# Engine starts within three revolutions

# Immediate 1/2 choke

# RPM stabilises 2500 rpm

# Choke completely off

# Adjust throttle to maintain between 2300 & 2500 rpm, for warm up

This may not solve your problem, which sounds to be a carburettor assembly error.

Ofek, I suggest you have a close look at the carbis, particularly part no. 30 and the position of the little dent-type of marking. Should this point towards the prop engine start becomes almost impossible. As shown on the tech drawing the marking must point to the rear of the carbs. Just a thought.

Hi. Thanks for the reply. The dot is in the correct position. Thanks. 

Sean Griffin wrote:

"Turn on the mags and start. That’s all. Won’t start no matter what. Only way it starts is if I turn the fuel valve off and then once it starts I put the fuel valve back on."

I doubt that my engine would cold start ,with your technique.

Mine is:

# Fuel On

# Boost pump On,  until fuel pressure stabilised (normally 5 psi/34 kpa)

# Boost pump off

# Choke on full

# Ignition 1&2 On

# Starter engaged

# Engine starts within three revolutions

# Immediate 1/2 choke

# RPM stabilises 2500 rpm

# Choke completely off

# Adjust throttle to maintain between 2300 & 2500 rpm, for warm up

This may not solve your problem, which sounds to be a carburettor assembly error.

I'm sure that somewhere before "starter engaged" you will also have "throttle fully closed".

Mine won't start if you miss that out!