Fuel Pump or Relay switch?

[justin23]

Hey everyone. I have a 1980 Datson 280ZX that wont start. It was running great untill one day I went out to start it and just fired up for about 3 or so seconds and then died.. If I let it sit for a few minutes and then try again, it will do the same thing--start for a few seconds then die.

So I am thinking two possble problems, either fuel pump or the relay switch. I would have just assumed the pump was the problem, but I have done some reseach and this relay switch keeps coming up in the search results, so I thought Id ask someone who knows.

Any other possible problems I am leaving out?

I have tested with a test light and verified that there is voltage (when the key is turned on) going to the wires plugging into the fuel pump, so its not electrical- but does that also rule out the relay? I currently have the electric fuel pump removed..anything I can inspect on it to help diagnose the problem?

Also, can these fuel pumps be rebuild for cheaper than buying a nwe one.

Where could I find one for the lowest price?

Thanks in advance for the help

Justin

[Zed Head]

The relay just directs electrical power to the pump so if you have power at the pump then the relay appears to be working correctly.

Are you sure that the engine dies because the fuel pump has stopped turning? You might have a plugged fuel line or filter or inlet screen.

You might also have a problem that is not fuel-related. If you could measure the fuel pressure while it was running, that would tell you if you actually had a fuel problem.

[justin23]

Thanks for the reply.

No im not sure its the fuel supply, although, I did turn the car over with the fuel line unplugged and it would not pump any fuel through the line. Any sort of weird vacume issues it could be or is the fact that fuel is not squirting out of the hose while engine is being turned over a give away that its a fuel delivery problem?

I want to be certain it is though before I spend the 120 on a new one.

Is there anyway to test the fuel pump since I already have it out? Such as hooking it up to voltage to see if it turns on ?

Also, do you know where the fuel filter and inlet screen is so I can check them?

Thanks again for the help.

[Zed Head]

You can run the pump on 12 volts from your battery with some spare wire to see if the motor turns freely. Some people run water through them to see if they pump. They will run backward so make sure you get the connections right. Watch out for sparks and gasoline.

Does gas pour out of the inlet hose to the fuel pump, the one from the tank? I assume that you have it clamped but that would give an indication of whether or not you have a plugged inlet screen. The screen is inside the tank. Take your clamp off and see how much gas comes out. It should flow freely. If not, the problem might be inside the tank.

I have used the pump to drain a gas tank, it doesn't gush out but you should get a steady flow. If gas comes out of the tank, and the pump pumps, then you can move up to the fuel filter in the engine bay to see if it flows. The fuel filter is that really big can in the engine bay that has a fuel line running in to the bottom and one out the top to the fuel rail.

Break the problem in to pieces and something will pop out, before you pay for parts. Most pumps for fuel-injection are over $100, although there are some junkyard pumps that work, but would be of unknown quality of course.

[justin23]

THanks again for the help. Those are all good ideas, I think since I havae the pump offf, I will start there and see if it pumps water hooked up to a 12 volt batt. I wont be able to test it till this weekend though.