How fast will a fuel pump fry when running dry?
10-16-2007, 09:50 PM
#1
Burning Brakes
Thread Starter
How fast will a fuel pump fry when running dry?
So, as per my earlier post my fuel pump appears incapable of keeping pace with my carb, which is surprising given it's an 85 TPI pump and I only need 4-6 pounds of fuel pressure. Thinking back I realize that while checking the connections to the fuel pump we accidentally ran it about 10-15 minutes with a basically empty tank (empty enough that we didn't get any fuel at the regulator). We thought there was gas in the tank and it was an electrical problem keeping us from getting any fuel, but it turned out the pump ran just fine and the tank had evaporated/leaked whatever fuel had been in there over the last year. Is it possible we killed this pump? It still pumps fuel, but I can't keep the carb full and I've checked all the connections. Will a fried pump still work, but with very little flow/pressure or will it stop working all together? Is there any way I can check the pump besides replacing it and seeing if the new one works?
10-16-2007, 09:52 PM
#2
Team Owner
Yeah its possible but i'd check to see if it turns on. When you turn the key to on, you should hear it making noise for a second or two. If thats all good then check the fuel pressure and if thats all good then so is your pump.
10-17-2007, 06:29 AM
#5
Burning Brakes
Thread Starter
Sounds like that's my problem then. It ran for atleast 10 minutes when the tank was dry enough that nothing was coming out at the regulator. *sigh* I get fuel now, and pressure when the engine is not running, but as soon as the engine starts the pressure drops to zero and it runs the bowls dry. Guess I'll look for a new pump.
10-17-2007, 08:59 AM
#7
Race Director
Member Since: Jan 2003
Location: Summerland B.C. Canada
Posts: 19,667
Likes: 0
Received 36 Likes
on
32 Posts
10-23-2007, 08:16 AM
#10
Burning Brakes
Thread Starter
OK, I had to take a little hiatus from workin on the vette. Last night I finally got my buddy over and we decided to mess with the fuel pump. Took the line off at the regulator and ran the pump and a ton of gas came out. Flow was great at effectively 0 psi. Now, taking my fingers I pinched the rubber hose partially closed. When we restarted the pump the flow was down to almost nothing. It kinda gurgled and trickled. Releasing the hose and the flow comes back, pinch it and the flow is practically nothing again. I'm pretty sure the pump is bad. Is that what it sounds like? I've got nothing to compare it to, but it seems like the flow should stay pretty high even when increasing the pressure (restriction).
10-23-2007, 10:02 AM
#12
Burning Brakes
Thread Starter
Come again??? You mean you think there's a split in the rubber hose that connects the pump to the steel line of the sending unit?
Anyone else had this happen with similar symptoms?
Anyone else had this happen with similar symptoms?
10-23-2007, 10:11 AM
#13
Race Director
Member Since: Jan 2003
Location: Summerland B.C. Canada
Posts: 19,667
Likes: 0
Received 36 Likes
on
32 Posts
I believe Redrose is talking about the pulse damper that is between pump and steel line. That part caused my fuel pressure to drop to zero within seconds of shutdown. Removed it and replaced with a piece of fuel injection hose and 2 clamps, all good now. 
10-23-2007, 10:24 AM
#14
Melting Slicks
Member Since: Feb 2006
Location: backwoods upstate ny
Posts: 2,753
Likes: 0
Received 12 Likes
on
10 Posts
NOT to recommend that you try this as gasoline vapor is prolly the most dangerous explosion hazard encountered, but my ''test'' rig is a plastic gallon milk jug with a big hole cut in the side, under an inverted glass fish tank, plastic drain pan to a ''catch can''... set up outdoors abt 50 feet from the nearest thing of any value...milk jug abt 1/2 full of gas to immerse the pump/pickup.
Last edited by redrose; 10-23-2007 at 10:39 AM.
10-23-2007, 11:20 AM
#15
Race Director
Member Since: Sep 2000
Location: The Top of Utah
Posts: 17,298
Likes: 0
Received 23 Likes
on
22 Posts
Originally Posted by JLeatherman
Come again??? You mean you think there's a split in the rubber hose that connects the pump to the steel line of the sending unit?
Anyone else had this happen with similar symptoms?
Anyone else had this happen with similar symptoms?
RACE ON!!!
10-23-2007, 09:15 PM
#16
Burning Brakes
Thread Starter
Ok, checked the rubber piece and it seemed ok but I replaced it anyway. I ran the pump and checked the pressure. With the engine off I could build 15 pounds of pressure. With the pump off, it would hold that pressure for over a full minute. No leak down. BUT, when Is tarted the car the pressure gradually headed to 0 again and the car starved for fuel. It's gotta be the pump now, right?
10-23-2007, 09:42 PM
#18
Burning Brakes
Thread Starter
I suppose it could be electrical connections. I'll check the resistance on them.
As for the regulator, there's no throttle body anymore (carb) and it's an external regulator. Plus, even if I pinch off the return line after the regulator, so all the fuel has to be going to the carb, I can't build any pressure once the engine is running. It's really weird.
As for the regulator, there's no throttle body anymore (carb) and it's an external regulator. Plus, even if I pinch off the return line after the regulator, so all the fuel has to be going to the carb, I can't build any pressure once the engine is running. It's really weird.
10-24-2007, 08:34 AM
#20
Race Director
Member Since: Jan 2003
Location: Summerland B.C. Canada
Posts: 19,667
Likes: 0
Received 36 Likes
on
32 Posts
Took the line off at the regulator and ran the pump and a ton of gas came out. Flow was great at effectively 0 psi. Now, taking my fingers I pinched the rubber hose partially closed. When we restarted the pump the flow was down to almost nothing. It kinda gurgled and trickled. Releasing the hose and the flow comes back, pinch it and the flow is practically nothing again. I'm pretty sure the pump is bad.
Did you set up the fuel bowl level(s) ??