Posts: 4 vapor lock??? HELP

--------------------------------------------------------------------------------

I just popped my 502 mag mpi in my 93 25 outlaw, so i replaced it with a brand new not rebuilt, new 502 gen6 roller. i upgraded to hardin headers, msd box, rc engenering flowed injectors, fuel pressure reg, and remaped the comp.

now when i idle for to long the fuel pressur goes from 40 psi to 10 psi and will barely run. I have a pressure release valve on the gauge. when i push, it spits air some fuel air air fuel air, you get the point the pressure drops and its empty. two seconds later push the button again air air fuel air????????????????????

please help

check the needle valve in the vst and check that you have the hose connections correct

I just put a new diaphram in because the vent tube to cyl # 8 was dumping fuel.

I would start looking there something isnt right, your problem is in the VST system double check connections and diaphram you sucking air somewhere there

I got in contact with Crockett Marine, Tyler helped me with the problem and we are going to dump the old fuel system and put there new system on. This includes a fuel cooler and external fuel pump. this will eliminate my problems and make the engine run better.
thanks for all your advise guys.

Vst was less than perfect even when it worked right,thats why merc went to cool fuel later on. You will be happier with a real pump,regulator and fuel cooler,I'm glad Crockett got you set-up,Smitty