First start after engine install problems

[wacko]

I have just reinstalled my engine after replacing broken head studs. When trying to start it almost starts but then backfires and dies. I assume it is my timing giving me problems.

I have checked and distributor is lined up with plug number one at the Z1 mark

Will it fire at all if I have distributor set 360 degrees off?

It is a 1978 911SC 3.0

Any suggestions appreciated

Thanks

[pors1968]

check timing but first check pop up valve if you have one if it open.

[wacko]

Pop up valve ok

[pete3799]

Plug wires going in a CCW direction?

[wacko]

Plug wires good

[pors1968]

Power brake hose tight on air box.

[wacko]

Power brake hose tight on air box.

Where is power brake hose?

[pors1968]

On left side airbox .

[Brown747]

Timing too advanced...?? Try retarding distributor till it runs then put a light on it to bring it into specs

[wacko]

I tried adjusting the timing both ways with no luck.

I think I have a leaking injector on cylinder 2 which is not allowing residual pressure to build up. Would this cause the backfiring and prevent it from starting?

[T77911S]

is the dist 180 degrees out? you usually get a loud backfire when it is 180 out.
check the plug wires again. i have a bad habit of getting 4 and 5 mixed up

i just replied to your other post.

pull an injector, remove the plug on the back of the AFM, turn on the key and adjust the mixture CW until it starts to spray, then back CCW until it stops. or, try raising the sensor plate with your hand to richen the mixture while cranking.
make sure you have fuel getting to the fuel dist.

unplug the power to the WUR. thsi keeps the fuel pressure from going up. BTW waht is your cold CP?

[pors1968]

Did you have problem before head studs repair.

[VFR750]

It is very easy to have the distributor out 180. Z1 is #1 and #4 at TDC. One has the valves open. Pull one of the upper valve covers and find which side is trying to open the valves. That's the "wrong" one.

I did it too when installing a new distributor.

[T77911S]

VFR 750- thats an old one.

[wacko]

Did you have problem before head studs repair.

No problem before dropping engine

[wacko]

It is very easy to have the distributor out 180. Z1 is #1 and #4 at TDC. One has the valves open. Pull one of the upper valve covers and find which side is trying to open the valves. That's the "wrong" one.



I did it too when installing a new distributor.

I pulled the theft side valve cover and confirmed cylinder number 1 valve is loose at z1 and when the rotor is pointing to number one wire

[VFR750]

If you think you have a leaky injector, that would be a problem. The engine would run poorly at best.

Only way to confirm is pull them out. If you put each one into a jar, you'd be able to see if one leaked more than the other. You will need to lift up the metering plate to get the pump to run (with the ignition in the run position)

Obviously this is a little dangerous, as you are pumping fuel over your engine. The safer alternative is to remove them entirely, and blow compressed air through them. I have an old fuel line connected to the injector, that I use to get a bit of fuel through the injector during this bench test. At 30-40 psi nothing should flow out. At roughly 50-55 psi the injector should spray a nice fan pattern.


If you don't have a compressor, you are stuck using the fuel pump to pressurize them.

[wacko]

If you think you have a leaky injector, that would be a problem. The engine would run poorly at best.



Only way to confirm is pull them out. If you put each one into a jar, you'd be able to see if one leaked more than the other. You will need to lift up the metering plate to get the pump to run (with the ignition in the run position)



Obviously this is a little dangerous, as you are pumping fuel over your engine. The safer alternative is to remove them entirely, and blow compressed air through them. I have an old fuel line connected to the injector, that I use to get a bit of fuel through the injector during this bench test. At 30-40 psi nothing should flow out. At roughly 50-55 psi the injector should spray a nice fan pattern.





If you don't have a compressor, you are stuck using the fuel pump to pressurize them.

I did this by lifting the metering plate. They all spray when I lift up and stop when I let it down.

If I were to unplug the AFM and turn key on should the injectors spray or just hold pressure?

Thanks

[theiceman]

I find baby food jars are very usefull for this exercise .. just label them for each cylinder , then line them up on a bench and compare ..
the peas arent to bad either with a beer

[theiceman]

this however sounds like a timing issue not a fuel issue ..

I hate to even bring this up but are you sure you timed your cams right ?