If I have about 7 gal. of old fuel in my tank and plan on changing my filter,can I just unhook the line at the filter turn the ignition key on and let the fuel pump run that way?Or will the pump not run that way,or is that not safe.If I just unscrew the line without running the motor with the fuel pump fuse out,other than fuel spraying out,won't hurt anything would it?Your opinion counts!

 

u dont have to drain the tank to change the fuel filter, just unhook the line with the key off and no fuel will spray out of the line

 

For the IROC - there's a schraeder valve on the pass side fuel rail - where you can test fuel pressure at. Put a rag over the valve, press valve stem with phillips screwdriver and release pressure, then change filter.

If the other two cars don't have the schraeder valve, undo gas cap to release pressure.

Regardless, fuel will leak out when you change filter, but not gallons worth - maybe 1/2 cup at most (although it will seem like alot).

 

only fuel past the regulator is kept under pressure, pre regulator pressure is lost soon as the pump is off.

 

Don't test that theory on a LT1 car! Plenty of pressure on the fuel rail, even after the car has sat overnight! I assumed TPI was the same.

 

I want to get all the old gas out before I change the fuel filter.It was messing with my injectors and stinking like paintthiner or somthing when the car was running.I put injector cleaner and seafoam in it,with 5 gallons of gas.But I think I need to empty the tank compleatly of all the old fuel.Put new fuel and seafoam without the injector cleaner.changing the fuel filter was just part of it.

 

the fuel rail is after the regulator, so of course its still plumb full of PSI.
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OP
Once the fuel line is off the filter, the fuel will self siphone out of the tank FAST, drain all you want. It will go till empty.

 

Gumby, the FPR is on the OUT side of the fuel rail, so the rail will hold pressure when the pump is off.

OP, no, if you want to completely drain the fuel tank, you'll have to drop it. I tried draining mine with the fuel pump and there's still about a gallon or so left in the bottom after the pump started sucking air and getting nothing out of the end of the fuel line in the engine compartment. I haven't finished draining mine yet...

 

thats what I was afraid of.Think I'll just do a flush job.Drain all I can,add more gas and drain it again.Maybe 2 or 3 times.then let the seafoam go to work on the rest and see what that dose for it.I droped the tank on the 86 and put a new fuel pump in,just last week.I learned alot.If I do a flush on the 89 I think it will work.If not I will do one of thoughs inside seal jobs. By the was,I got injector cleaner and seafoam both in the gas now.

 

Why not just siphon out all you can (via the gas cap) and then top up with new fuel? Seems to be some over thinking here...

 

Thats what I said, twice, everything past the FPR will have PSI still in it, like the fuel rail, Am I speaking chineese???

 

You've got it backwards... Everything BEFORE the FPR (NOT past) will retain fuel pressure... The ONLY thing PAST the FPR is the drain in the fuel tank, and there will be ZERO pressure in the line unless there is a blockage or restriction.

Fuel tank>Fuel Pump>Fuel Filter>Fuel Rail with injectors>Fuel Pressure Regulator>Fuel Tank. Not hard... "Past" implies "After".

 

These things are not all that easy to siphon out.I've taken out my 86 tank and changed the pump on it.Have you ever taken a tank out and sean how there made? You cant even dump 5 gallons out the filler neck!It's true,if ya want all the fuel out ya gota drop the tank and go in through the sending unit hole and mop it out with a rag.You can get most of the fuel out siphoning through the pump hole.

 

So what's the best method here? Just siphon from the tank? Isn't there a ball valve or something in there to prevent you from siphoning?

 

You can pull off the feed fuel line, unhook the fuel pump relay on firewall and jump it together with a wire to start the pump without having car on. You'll use your own fuel pump to extract the contents of the tank. Works best if you have rubber or steel braided lines so you can direct it right into a gas can.