A question for the EFI guys

[mazingerz1976]

Hi guys, two years ago when i purchased my ZX i replaced the fuel pump, and apparently it was overpressured so i rebuilt the old one and installed it back. The old one worked for a while but it’s broken again, and I had to fit the new one again and made a long road trip in this mountainous country, after two hours the smell of gas coming out from the pump area was too bad and the car started to failed until it shut down, I waited for a half hour and then the car started and it ran fine. This happened twice, I don´t know what to do, the fuel pump is 95 psi but the pressure on the fuel rail is 36 as it should be so the FPR is fine, maybe the fuel pump pushes too hard and get overheated? Don’t know!!!... the car wasn’t overheated, or did not running rich, had no electrical problems….if i change the fuel pump will the problem be fixed or should i check something else?

[sideshowbob]

Well, I would suggest checking the hoses carefully. It might be sucking in air through a leak before the pump and allowing vapor to escape the same way. This sounds like a dangerous situation due to the vapors, IMHO. Also: the pressure should be fine as long as it's 36 after the regulator, since the FPR is just allowing the excess to go straight back to the tank.

Edit: have you reconditioned the tank yet?

[mazingerz1976]

The tank is fine and washed... i will take your suggestion and check the hoses, but it seems like there is no leak,altough the hose between the tank and the pump is the original one, and it is time to replace it!.... thanks

[veritech-z]

95 psi? what kind of pump is that? My pump won't exceed 45 psi unregulated...

[sblake01]

Are you running the OEM fuel pump? You answered your own question when you stated the unregulated pressure. Max is correct that the stock pump won't reach pressures like that.

[mazingerz1976]

I haven't found the original pump, so I fitted an homologated one, that works on german cars, definitely I will make a search for a pump of maximum 45psi. Thank you guys for your answers….

[sblake01]

I think you'd be better off finding the OEM fuel pump.

[mazingerz1976]

Thank you Stephen, i will follow your advice.

Camilo

[sideshowbob]

It didn't strike me at the time, but I think even the hoses are only rated for 90psi?

[turbo 260]

Your pump should be around 90 psi. I run a 115 on my car. That pressure is only reached if the return line is cut off. If you run a 36 psi pump you will run lean at times. Do you still have 36 psi at the rail when the car dies? Does your tach jump around right before it dies?

Jim

[DatsunZsRule]

turbo 260 is correct,

The L Jetronic uses a Roller vane pump. The roller cell is driven by an electric motor at over 3,500 RPM. The factory pump used in these cars are capable of pressure in excess of 100 PSI which is far higher than any engine or F.I. system require. This is why this type of pump is located very close to or even inside the fuel tank because it does an excellent job at pushing the fuel. Like Jim said, That really high pressure is only reached if the return line is cut off. Plus you have a Fuel Pressure Regulator. It's there for an important reason.

[s14280zx]

This may sound stupid, but make sure if you changed any fuel lines, that you used FI hoses and clamps. Last Nov. when I bought my '78 280z, I changed all the fuel lines, even the 2" ones at the injectors, and I just went and picked up a package of fuel lines and regular clamps not thinking:stupid:,put them all on, took it for an hour ride, till it got warmed up, floored it on an on ramp, and it started to cut out, then shut off. Same symptoms as you had. I happened to read the package for the fuel line, and it said "for carb use only". :tapemouth . Turned out it was actually sucking the soft lines shut cutting off the fuel, and making bad fumes, like it was flooded. I replaced all the lines, and it ran good. I guess anything's possible.