Fuel issue no start NEED HELP

[cengland]

I have a 1975 280z 2+2 and am trying to get it started. I have a problem with my fuel system and need some help troubleshooting. Fuel pump, filter, and lines are all good and I have adequate fuel pressure. When I turn the key to try to start it I can hear the EFI relays click. Ive checked to fuel injectors themselves for power with a test light to the harness but I am not exactly sure I can rely on that kind of test to know they are good. However, I did the same thing to the cold start valve connector at the harness and the test light did not light up. I was able to start it by overriding the fuel system with brake clean and the brake booster vacuum hose. So I know I have a fuel problem. What other tests should I do? Any help is greatly appreciated!

[cengland]

I am also wondering if there is any other way I can test injector pulse other than the bulbs you would typically use

[Zed Head]

Have you checked for power at the injector connections? You should have 12 volts on each pin in the connector. That's the first thing you should do. No power, no injector open.

[rossiz]

the injectors get power in a rather odd way (my non-electrical engineer assessment) - it has to do w/transistors that ground them for each pulse. that said, there is a way to test them to ensure you are getting power pulses. iirc, both pins are +12v, and one grounds for each pulse. so you should be able to use a christmas light bulb and get it to light between each pin and the ground (engine) and if you put the light to both pins and crank the engine it will pulse with each revolution.

check for posts by fastwoman - she explains it better...

i had an issue w/the efi relay "clicking" but not necessarily sending power - it was related to the fact that i had relocated it and there was some strain on the wires which flexed the pin and pulled the relay gap out of tolerance. but the important thing to note is that just because you hear a "click" doesn't mean all is well - you need to check for power pulses at the injectors.

also, there are quite a few grounds and plug connections in the efi circuit - take all of them apart and clean them, scrape to shiny metal, use deoxit and re-assemble. this makes a big difference.

[siteunseen]

Z Tech Tips EFI & Fuel (AtlanticZ.ca) || |* |** |*** |***** |******* |********* |

http://atlanticz.ca/zclub/techtips/electricalconnections/index.html

Edited May 25, 2014 by siteunseen

[240260280z]

With the key in the ON position, you should be able to hear the fuel pump by simply lifting the flap in the AFM.

On 75's to 77 the AFM has a fuel pump cut-off switch that kills the pump when no air is flowing through the AFM. Lifting the flap simulates air.

To hear the fuel pump you may need a friend to listen at the rear passenger area or you may also hear fuel flowing through the fuel rail.

[FastWoman]

First dumb question: Fresh gasoline?

Second dumb question: Have you confirmed you have fuel pressure (36 psi while cranking)?

If you check the factory service manual, which you can download for free from xenons30.com, you will find a procedure for testing your individual injectors in the Engine Fuel (EF) section. You can actually ground them individually and, if all goes well, hear them click as you ground them. I imagine if they click, and if there's any fuel pressure behind them, they'll spray fuel. However, I suppose there's also a remote possibility they are all clogged up. (Was the car running recently, or has it been sitting for years?) Here's a test you can do: Fire up the fuel pump to pressurize the system, and then shut it off. Hopefully the fuel rail will hold pressure for you. Then short an injector to ground. When you do this, you should see the fuel pressure bleed off. That is a confirmation that the injector is actually spraying fuel.

BTW, the cold start injector is only actuated when the engine temp is below 50F (which it's not been these days, at least in Virginia), and even then, it's not actuated for very long.