Anyone running dual pumps??

[EMX5636]

I took the Galant on its first real highway road trip. I have dual 255's in tank. When I was getting down to the 3/8 tank area, I noticed something weird. After a prolonged 65+mph (3200 rpm) drive, I physically watched the fuel gauge drop as I was driving. It went down from 1/4 tank to empty and the fuel light on within like 4-5 mins of driving. I got off to look for a gas station, and as soon as I got off and let it idle for a min at a traffic light, and the gauge rose back up to about a 1/4 tank.... WTF

So my assumption is that the dual pumps are sucking the baffled section of the pump dry at prolonged high RPM drives. Does that sound right? Anyone else ever notice this?

Justin W

 

At 65-70 mph you should still be in closed-loop, 14.7:1, so I would *assume* that you aren't burning that much gas, right? The fuel system is a closed-loop, so every drop the pumps are pushing out goes right back into the tank, except for the small anmount being burned. What fuel are you running? Why the dual pumps? Are you sure that you just haven't disturbed/relocated the tank level sensor? Was the car heavily loaded in the back or anything that would fool the sensor?

 

[EMX5636]

Well that's kind of what I was thinking, the fuel was being pumped out faster than it could return back into the tank and fill the baffled section up again. Seriously, like 2 mins after I got off the freeway and back to sub 40mph variable speeds, the gauge went back up to where it was. It seems to be getting around 200ish miles around town, so its not really sucking a ton of gas or anything.

I am running gas, and have 2 pumps because I was going to build the car for 5-600hp, but then wanted to be able to DD so I downsized a couple things like injectors, turbo, etc but the pumps were already in the car.

Only thing in the car was a sub box, so nothing heavy. When I did the twin pumps, I was very careful to mount them to clear the sending unit. I did have to bend it away from the pump a bit, but I bent it back just after the pumps and compared it to another stock one. It was in the exact same position at empty, and doesn't hit through it's entire sweep.

 

[gtluke]

the float is probably just not accurate or hanging up with the twin pumps taking up it's normal sweep.

 

[EMX5636]

I would agree with that if I ran out of gas at a 1/4 tank or whatever. Around town the gauge seems normal, only on the highway for more than say 10-15 miles does it rapidly go down. I only noticed it below 3/8s of a tank, and as soon as i got off the freeway into a town again, it went back up to what it started at.

This is why I don't think it's a float problem...