Need to crank engine twice to start up.

[ssbowtie1]

I have a 408 with ported ls6 heads, headers, unknown camshaft, and fms redtop 30lb injectors..

When I start the car up, I get a few degrees of knock while its cranking and starting. Usually it won't start if I crank it over once.

If I crank it once for a second, then stop and crank it again, it will start right up.

Also when I turn the car off, it diesels for a few seconds before turning off.

I posted a log to show the KR during cranking. Ignore the rest of the tune as it was my first STFT log to tune the VE table.

Also attached is my current tune. The injectors are set to the correct parameters and the VE table is tuned in the idle and cruising range so far.

Once the car starts it idles and drives fairly well.

Thanks for any suggestions!

[WS6FirebirdTA00]

For the cranking issue, do you have fuel pressure in the lines during cranking?

[ssbowtie1]

For the cranking issue, do you have fuel pressure in the lines during cranking?

Thanks for the reply.

To find this out, should I hook up a fuel pressure gauge to the fuel rail and crank it while observing the fuel pressure? I would assume I would have fuel pressure in the rail as soon as I prime the pump.

What should pressure be while cranking?

[WS6FirebirdTA00]

It should be around 60 PSIG. You could have a bad check valve causing the rail to lose pressure. My car does this and I have to prime the pump several times once in a while.

[ssbowtie1]

It should be around 60 PSIG. You could have a bad check valve causing the rail to lose pressure. My car does this and I have to prime the pump several times once in a while.

Thanks, will test fuel pressure and update with results. So even during cranking, the fuel pressure should stay at 60psi? In regards to fuel pressure, what would be the signs that the check valve is bad?

Also, could this have anything to do with the dieseling on shut down?

[WS6FirebirdTA00]

If you have no pressure on it when off, then that would tell you.

[Sam88gta1]

If you have the stock file return the Cranking VE back to stock.
Its located under, Engine> AirFlow> General Airflow. Should fix your issue.