My fuel pump works but doesn't

[zeeboost]

Cliffnotes - I can spin the shaft of the fuel pump with my power drill and it works fine. I hook it up to a battery, motor kicks like it's got plenty of juice and sounds healthy, but doesn't suck in any fuel.

 

 

More detailed version:

 

Okay, in my '83 280zxt that got left out in a field, the gas cap was also off, so I've been trying to clean out all the sediments that accumulated in there. I read that the inlet to the fuel pump has a little screen in it that can get clogged up, so I took the four screws off the cap to check it out and make sure everything is clean. When I put it back together, I haven't been able to get the pump to work at all (worked fine before removal). I'll spare you the details of all the testing that I've done, but here's where I'm at now:

 

I took the outer casing off and hooked the shaft of the motor to my power drill. The top portion was assembled together, just the casing was off. I put a hose on the pump inlet, stuck it in a bottle of water, spun the drill watched it suck the water in just like it was designed to. So I put the casing back on, wired the motor up to the battery (still with the hose in the water) and I got nothing but air bubbles. When I had tried this before, I never saw air bubbles or any other type of movement - this just started happening after I spun it with the drill. So then I reversed the polarity (makes sense, because it looks like it's pushing air, right?) and though the motor made a terrible noise, it sucked water in. The motor would keep dying on me if I left it connected for longer than a couple of seconds with the polarity reversed. After a few seconds it reached the point where it wouldn't suck in any more water. By the way, when I hooked up the pump normally, it would kick to the left, so I'm guessing it spins counter clockwise. I'm pretty sure I was spinning the drill clockwise when I got it to work.

 

This whole time nothing came out of the outlet. So I removed the outlet, wired the pump normally and I had a little bit of water dribbling out, but nothing was being sucked from the bottle. I decided to reverse the polarity again to see what would happen, but this time it sparked pretty bad so I didn't bother with hooking it up backwards again. When examining the outlet, it looks like there's a little check valve in there because I can't see through it. If I blow through it the same direction that the gasoline would flow, no air comes out, so I'm guessing that pressure is required to move the valve up to allow passage for the fuel. If I used a pin to hold the valve up, I can blow through it. Again, this is all assuming there's supposed to be a check valve in there, I really couldn't see what it was, but that's how it acted.

 

 

I'm on day 2 of messing with this stupid pump and I'm getting nowhere. Can't find any reliable pumps around the area, and don't want to buy some crap from autozone. Plus, I this pump looks and acts like it should work fine, so it's really frustrating me that I can't get it to. If anyone could tell me WHAT THE CRAP IS GOING ON!!!! I would be ever so thankful.

[zeeboost]

Too wordy? Confusing? I think I'll be picking up an n/a pump tomorrow just for a temp fix to get this car rolling again, but it would be nice to figure out what's wrong with my turbo pump. Anyone?

[Pyro]

msd-2225 efi pump will work.

 

so will a z NA efi pump.

 

I would bench test the pump with a 5 gallon gas tank. pull gas from the tank with the pump and pump it back in.

 

I bet the tank is rusted up.

 

 

http://www.summitracing.com/parts/MSD-2225/

Edited March 17, 2011 by Pyro

[zeeboost]

Yes, I've been bench testing the pump with a clear liter bottle of fluid, so I can see everything that's going on. The only way I can get it to move fluid normally is by removing the casing off the pump and spinning the shaft with my power drill. If I hook up the electric motor straight to the battery it just spins but doesn't suck anything in, but does slightly when the polarity is reversed.