according to my chiltons manual the spec for idle is at least 30 psi to run properly at idle. a few psi lower and you'll have running problems. if only a few psi total then it wont start. if the pumps dont prime to at least 30psi then you'll have to see which pumps arent working properly. you have a low pressure intank pump and a high pressure inline pump on the frame rail right?

All i did to check for pressure was push the valve in. What is an average pressure reading.

ok then your not getting enough gas into the engine. what was the pressure at the rail? or did you just check and see if there was pressure there? if thats the case then you need to actually check the pressure with a gauge.

It is fuel injected and im using a small bottle with gas in it and dumping it into the throttle body intake.

what do you mean prime intake? giving it some throttle? is it carburated or fuel injected? if fuel injected then just crack the throttle open a little bit, if it starts then it sounds like the iac is sticking. if you have to push it to the floor to start it then it means that there are leaking injectors.

I have a 1987 inline 6 that wont start unless i prime intake, checked both fuel pumps and are working fine, changed my fuel filter and checked pressure valve at fuel rail. There is gas at the fuel rail and at the fuel regulator. If a new regulator does not correct the problem what else could it be?