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hesitation, stalling, fuel pump quiting


280Zen

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My 83 280zx NA is having a few strange problems, This car was sitting for well over a year or more before given to me. The fuel pump and fuel relay were bad so I replaced them. After that the car ran fine for a week but with a bit of hesitation which I was chalking up to clogged injectors. But today while driving home it started bogging down when I stepped on the gas then stalled out on me, after pushing it home I started testing a few things.

 

I disconnectd the fuel line from the fuel filter to the engine and got very little gas out when the ignition was turned to the on position, I got much more fuel out the line before the fuel filter! Possable bad fuel filter

 

I then tested the voltage to the pump while the ignition was in the on position and got aprox 12 volts but suddenly the pump quit and the voltage dropped to 0. Not sure why

 

I then hotwired the fuel pump to the battery and the car started and ran fine for about 15 minutes then stalled out at idle, when i checked the pump was not pumping and no voltage.

 

any clues would be helpful, right now I have 3 dead cars in my driveway :(

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I then tested the voltage to the pump while the ignition was in the on position and got aprox 12 volts but suddenly the pump quit and the voltage dropped to 0. Not sure why

 

Just thought of something, When you turn your key to the on position the fuel pump does kick on for a minute then stops unless you crank the car. :bonk: You gotta love it when you answer your own questions! :D

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I had this very same problem with my 79 ZX. Mine sat in a garage for 3 years before I purchased it. My solution was to remove the fuel pickup/float from the fuel tank. The fuel pickup line was completely plugged with varnish from old fuel. The pump could not draw enough fuel through the greatly restricted fuel pickup line in the tank. I cleaned all of the varnish from the line and reinstalled. Voila! no more starvation. I hope this helps.

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The fuel filter was totally clogged up so I replaced that, The spark plugs were pretty fouled so I replaced those as well as the plug wires. The car ran great for a day or so then did the same thing. So now I will drop the fuel tank and clean both it and the fuel pickup/float line and clean it all out.

 

So, How big a job is dropping the tank?

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Ok Folks, removed and cleaned the whole sending unit, fuel screen was totally clogged, the fuel line/return line was also gummed up real bad. After replacing the unit I let the car idle for about 1/2 hour then took her up and down the block about a dozen times, She ran great. After turning the engine off and restarting her she started hesitating and idling ruff again. :(

 

I took a look down into the tank while the sending unit was removed and could see what looked like rust/junk sitting on the bottom of the tank so I assume some of that gunk is being sucked into the fuel screen and clogging up the works again. So Saturday is drop and clean the tank day! Does anyone have any tips to make this job any easier? How about good ideas on cleaning the tank out. I was planning on using a air compressor to blow all the junk out.

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What are we talking about here cost wise for a shop to clean and coat??

 

I also have a 83 2x2 donor car that was running before I took the valve cover off, I was also thinking about dropping that tank and taking a look at it as a possable replacment for the current one.

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Pulled the gas tank off the donor car, both it and the sending unit were super clean inside. Drained 90% of the gas and pulled the tank off the coupe, after the gas sloshed around in the tank a bit it was a milky brown nasty color, real bad! anyway, after putting the donor tank on and putting clean gas in the car runs great! no hesitation, backfire. Now I just need to figure out what happened to the clutch.

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