The problem is I think it would probably take it a while before it runs bad. Heck it took an hour of highway driving before i noticed the problem. But I guess its worth it over dropping the tank and finding out that isnt the problem. Im glad I bought that fuel pressure guage. But if the fuel pressure starts to drop when its running bad that would indicate somethings wrong with the fuel pump?

 

""""*Weird Side Note:
I noticed yesterday (with 1/4 tank) that the fuel pump was a lot louder than usual. I got some gas and it quieted down to normal. After I got the car home from the track (with about 1/2 tank) the Pump is extreamly loud again. Any ideas on whats wrong with that, and if it might be the cause of the other problem."""

I think you in the right area, if you here the pump start changing pitch theres something tearing up inside. It can't take much of that.......

 

I just dont understand what could have happened. The only thing I can think that could have gone wrong is the positve and negative are arcing off eachother. Unless somehow the intank filter came off and the pump fell out of place. The pump doesnt have maybe 100-120 miles on it.

 

From my experience Walbro pumps like to die if run low on fuel, they overheat and freak out. That would definitely cause your issues. We fight that alot on the RX7s and in the Grand Prix GTPs.

 

Uh...if you had electrical arcing inside your gas tank you'd know about it already.

 

agreed..
what you need to do now is figure out whats happening when it goes bad.. check the fuel pressure, check voltage, ect... if you can find a friend with HPtuners to log it, that would be great too...



how so? no oxygen....

 

Have you checked to see if the tank is venting properly? Try to simulate your failure again. If it starts acting up, take the gas cap off and see if the problem goes away.

 

Ya know I think you may be right now that I think of it. Whenever I take off the gas cap a lot of air is released. And now that I think of it again, I just put a little rubber cap over the vent line. It was running fine so I was assuming that the air was still escaping the vent line, but maybe its not. I know your supposed to hook it up to a purge solenoid or something like that? But I dont know how to do that, anyone know how to hook up a purge solenoid to the vent line? If that was the problem and there is no other damage, that would make my day.

 

This almost sounds like those hot start issues... When someones car stalls and it wont start up again... Was the solution found to be the crank sensor? Just a bit of info thrown out there for ya.

-Matt

 

I have a very limited knowledge of modern emissions systems but I believe that in most new cars the tank vent is run to the Charcoal canister with a solenoid in between them. The cannister's main job is to prevent unwanted fuel vapor from escaping in the atmosphere. The solenoid only opens under certain conditions and is controlled by the computer. The old school way is to run a vent line to the atmosphere (not in to the trunk!!) and put a tiny air filter and/or a PCV valve to prevent spills in case of a rollover.

 

Well the vent line is already ran into the engine compartment. Can I just rig up a fuel filter and be done with it? I dont think there is any easy way to have the LS1 computer control it. I can deal with the smell of gas as long as my car runs!

LS1 chevelle: Are you saying people with similar symptoms had issues with the crank sensor?

 

The LS1 should have it built in. It may be called CCP or Carbon Cannister Purge (that is what it is called on LT1's) Regardless, yes you could should be able to put a filter on it and be done. You shouldn't smell to many fuel vapors if at all.

 

Hmm that sounds like an easier solution than figuring out how to make the computer run a solenoid. Now would a gas tank not being vented make a car run that bad...is it not able to pick up the fuel or something?

 

In one word absolutely. As fuel is pulled from the fuel tank in to the engine, the displaced volume of fuel is replaced with air from the outside of the tank via the venting system. If no vent is available the tank goes in to a vacume state making it harder to pump the fuel out of the tank and in to the engine. If you want to see it for your own eyes there is a simple experiment you can do with a 5 gallon fuel tank you would use to transfer fuel to a lawn mower. You know that little vent cap opposite the filler neck. Leave it plugged and pour it for a set amount of time into another container. Now undo the vent cap and try it again. The results will make it obvious.

 

Yea I know what your saying, without the venting pouring gas (or any liquid) of a container is greatly restricted. But why would it be worse the longer the car runs? Shouldnt it be constantly running bad? Or is it bulding up pressure over time making it worse? And when I turn the car off the pressure slowly goes down making it run ok until it builds back up? Makes sense to me.

 

the oppisate.

it would be pulling a vacuum.

let it sit, air seeps in, and eventually equalizes it..


but it only starts becoming a problem when you drive for a extended peroid of time...

the fuel is pumped out, but theres no air to take its place in the tank.

 

Ah ic...so when I loosen the gas cap, the sound Im hearing is Air rushing into the tank, not rushing out? Makes sense. Now I just hope that I dont have any damage to the fuel pump.

 

Help me understand your earlier assertion that says there's no oxygen present in the tank...

If there's arcing above the fuel level inside the tank, you'd have all three requirements for an explosion: fuel (gasoline vapors), oxidizer (ambient air), and ignition (arcing).

 

yes, technically theres O2 there... but its not in a concentration that can spark...

and thats good, because your fuel pump DOES have a little spark in it when it starts, and a warn fuel level sender can make small sparks... but they wont ignite anything with a explosive force.


you couldnt light a match in there if you tried.

 

true...my friends tried to put a fire cracker in a garden gnome with gas in iton 4th of july, and the Gas put out the wick in the fire cracker. Must not have been enough oxygen in the gnome to cause a combustion. Now a better question is why they were putting a firecracker in a gnome filled with gas...that I cant answer.