I don't think you have a tune issue. I think you have a parts issue. If the tune worked it won't later just 'unwork'.

This sounds more like a fuel delivery issue prior to the injectors.

edited

Just seams strange that when i see the higher cranking pulse width it don't want to start. But of course i don't always have the computer hooked up. I checked fuel pressure several times over the summer. Key on engine off its always about 43 psi. One day it wouldn't start the cranking fuel pressure would drop 10 psi or so.

I am still a little confused. Where or in what table are you altering the BPW during the start (crank) cycle?

If this problem suddenly started (on the same tune) I have serious doubts it is a tune issue. Your altering of the bpw during start is merely a band aid or worse for a hardware issue. That is my suspicion.

What is your exact motor and hardware set up? We need more details.

I don't have a way to change the cranking injector pulse width. Some times it's around 7ms and other times it around 12ms. I wanted to know what makes it change. Every time i look at the ect it looks believable.

Its a 1994 502 mag mpi. 500 efi cam, TPIS throttle body, stock heads, Cut down and belled out lower intake Re programed MEFI 1, adjustable fuel pressure regulator. Ignigtion stock, emi exhaust. Stock fuel pumps mechanical and the one in the vst tank. Not a cool fuel.

You mentioned low fuel pressure during the no start at 10psi, check the yellowish line that runs from the vst to the mech fuel pump, if fuel is present in that line then there is a problem with the vst or mechanical pump.Always had a continuous problem with no start with vst pump,diaphragm, clogged screen.

Sorry i meant i would lose about 10 psi off of max pressure. I should have wrote down the exact #. I have checked the yellow line and the other line that dumps into the intake runner but never have seen any signs of gas.

Ok that helps a lot.

I take it you are able to monitor the data via Scanner Pro? If not, where are you getting your data from?

What camptappakeg69 said is spot on. Check that first. The mechanical fuel pump and the VST both have diaphragms that can go bad and fuel will travel through those yellow tygon lines into the manifold. This can cause starting issues.

I have the diacom software ( I had the mefi pro but this is way better ) I have checked the lines more than once and put my vacuum pump on all three ports and it held vacuum but as a hell Mary i did replace the vst diaphragm and put new float needle in. Annoying its so inconsistent.