boiling fuel and chevy spider injection

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john hennessy
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boiling fuel and chevy spider injection

Post by john hennessy » Mon Jul 21, 2014 1:34 pm

as the title says, does this bunch of geniuses, or should that be genei, know anything about fuel vapor locking in chevy spider style fuel injection,


chevy astro,

the simptons,

ambient temp is above 100 degrees,
the fuel tank temp as taken with an infra red gun is 126 degrees,
the intake air filter is 156 degrees because its directly over the radiator,
engine coolant temp is at about 180 degrees,
after a drive of 150 miles or there abouts within 20 miles, the vehicle will cut out while driving and refuse to start unless the hood is opened,
when trying to start the vehicle, a groaning noise can be heard from the gas tank even after the ignition is turned off,
if allowed to cool for maybe ten minutes but only with the hood open, it will start but the groaning noise can still be heard from the gas tank,
the vehicle has had 3 new fuel pumps installed and the groaning noise does not sound like a noisy fuel pump which i have heard many times,

my only guess is that incomming air is being heated inside the air cleaner before it enters the manifold and is sufficiently hot that it raises the temp inside the intake manifold causing the fuel to boil in the spider injection unit.

if it were a problem in the tank with the fuel pump, how would opening the hood for a few minutes allow the vehicle to start. if you don't open the hood, it won't start for about half an hour.

i have also replaced the ignition module which is located on the outside of the intake manifold just in case this was failing.

any thoughts would be appreciated.

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Re: boiling fuel and chevy spider injection

Post by Greenlight » Thu Jul 24, 2014 2:29 am

I'll venture a guess at your problem and make a few other comments.

1) On a fuel injected engine, the fuel boils (at 45 or so psi) at a much higher temperature than fuel in a carbureted engine (atm. pressure in fuel bowl). So I seriously doubt the fuel is getting to a high enough temperature to boil (vapor lock, etc.).

2) I suspect the groaning noise that you hear is an equalization of pressure (caused by a slight vacuum in the fuel tank), caused by a malfunctioning fuel vapor recovery system.

3) The vacuum in the tank is not allowing the fuel pump to pump an adequate fuel pressure to the injectors, thus contributing to a lean driving condition and the hard start condition.

4) Once the tank vacuum is brought to atmospheric pressure, the fuel pump can operate normally and the car will run until the fuel tank vacuum causes the fuel pump to fail to pump adequate fuel pressure.

This is just a guess, but it is worth investigating.

Try removing the gas cap next time it won't start and/or install a fuel pressure gauge on the fuel rail.
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Re: boiling fuel and chevy spider injection

Post by buck » Tue Jul 29, 2014 3:35 am

I agree with the statement above. I've never seen that issue with any GM central port fuel injection. Tank vacuum will cause this problem.
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Re: boiling fuel and chevy spider injection

Post by jake197000 » Mon Aug 25, 2014 8:43 am

maybe you have a bad coil.try spraying some carb cleaner in the intake when it happens that will tell you if its lack of fuel.

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