air in fuel line

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horsepower

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90 Firebird 3.1 starts up and runs great. On warm days after four or five errands and car is warm it will act like vapor locking and won't start until car cools down or it hesitates at first and clears up. Have tossed a lot of parts at car. Finally when acting up I did a fuel pressure check on schrader valve and it was letting all kinds of air out schrader valve. After checking the valve, the car started right up and was good until it got hot again. Fuel line is not by anything hot. Wrapped fuel rail with heat tape that runs under plentum. Still nothing. How is air getting in? Put new fuel pump, gas cap ,fuel filter, fuel reg,another set of injectors, and have no fuel leaks anywhere. Unpluged purge valve on the canister and still nothing. Car will still act like it's vapor locking when warm.
 
Have you checked the fuel pickup in the tank?
 
I did replace the fuel pump and new screen on pump ,i know its fuel related and when it gets hot just driveing me crazy.
 
if you google "3.1 hard start warm" you get hits with other suggestions than fuel related, such as coil pack overheating. Try some of the other possibilities.
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I thought the same thing intell i released air from the schrader each time it acts up know and it runs good tell left alone when hot.
 
are you sure it's air and not fuel vapor caused by hot gasoline? I would start looking at the ignition or the IAC.
 
I did replace iac before i found air in scrader valve.funny thing is every time the car will not start i release air out scrader valve and it will start up every time .funny thing is i cant figure out how air is getting in thinking i have narrowed it down to the car likes fuel instead of air .but driveing me up a wall only acts up on hot days.have a couple other ideas but but what part will stop air comeing in
 
I replaced ign module ,pick up coil .cap rotor,and i had a old coil sitting around tryed it out and same thing, what about a fuel relay ,there are 3 on firewall that are the same and switcht them around same thing what are the chance the relays are bad when they get hot.
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all 3 doubful, what is the hot fuel pressure and how long does the fuel pressure hold?
 
The pressure will hold for about 30 to 40 min slowly bleeding off.when car acts up it will run poor for a sec or will not start at all untill it sits for about 30 min or you can bleed of the scrader valve and it will start up like a charm .wondering if its running to rich when the car is warm .what would cause this .replaced o2,map,iac,fuel reg,maybe the computer.
 
No sign of gasoline in the vacuum line going to the pressure requlator?
 
Anybody got thougts on bad computer.
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no gasoline in line going to reg.have never seen anything like this before bogels my mind why the schrader valve needs depresseurized by hand then runs great. kinda dangerous doing this.maybe the fuel is not going back to tank, should i take compressed air on the return line to tank with out hurting the fuel pump not shure it would work anyway.
 
with the pump running everything is positive pressure so air cannt get in, only way is if the pump is sucking air. I know it's a pain but you may want to take a look at the pump and lines attached to it.
 
The car runs great most the time. the only time it acts up is on a hot days when car is shut down for a min after warmed up.have no fuel leaks on lines anywhere .ill take another look in tank what about rubber seal on top of tank would that suck in air in line after shut down.the fuel rail is under plentium which gets really hot the only place the fuel may get hot or like some else said i may have hot fuel vapor ,i put heat tape on the rail how else can i keep this area cool.
 
Have you actually checked the pressure with a gauge. What it the pressure with the key on, engine off?
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I tested the fuel pressure key on is 24 ,and engine on 29,and the pressure held for for at least 10 ten so i took gauge off.I took of the check valve off the gas line in back for venting and blocked off egr and some lines from charcoil canister .going to drive around and see what happens.if it acts up again going to lower my thermostat to a lower deg sitting at 195 now ,the plentium has water going through it maybe it needs a little cooler water going through would not think so but running out of ideas.plentium sits above fuel rail only place i maybe getting hot fuel vapors.
 
i would check the specs for your car, those pressures sound low. I believe you should have mid 40's.
 
Ok the car gets up to 240 then drops down to 200,just orderd a part fan hyperteck cooling fan switch that will kick on fan at 200 and turn off at 180 so cant wait for part to come in will let you know in about a week.seems to me that car is way to hot at 240.cooking fuel when car is off hopeing.:eek::eek:
 
sounds like you have a bad temperature sensor and low fuel pressure
 
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