cold start relay or fuel pump relay?
 

I have a 1980 280zx (non-turbo) that starts a little rough. It has to turn over a bit before it wants to really get going. I am thinking that it is either the cold start relay or maybe one of the fuel pump relays. Is there an easy way to tell which one it might be?
(or if there might be another reason for it to act this way that I'm missing)

I have noticed that on my other two 1979 zx cars that when I first turn my key you can hear the fuel pump turn on and start working. My 1980 does not. should it?

On the topic of fuel pump relays.....I see in the wiring diagrams (electrical chapter in the shop manual) that there are two different relays with different connectors to test. However when I look into purchasing fuel pump relay there is only one option???

Thanks for any help!

Looking at 1980 FSM under the Engine Fuel chapter on page 21 you'll see the schematic of the fuel injection system. You can see that when you turn the key to Start that B on your ignition switch is tied to the +12V on the battery and power is shorted to Ignition and Start outputs on that switch. Power then goes through the starter relay from the Ignition side through the coil on the "L" side of the alternator to ground (when the engine isn't running). (It also goes through the Start portion of the relay circuit and activates the other Fuel Pump relay). That coil pulls in the relay for the circuit that goes through the oil presure switch (when the engine isn't running) to ground. That pulls in the second set of contacts that activates the other Fuel Pump relay and sends a signal to the ECU.

It looks like the secondary relay is to cut fuel if the oil presure switch opens which it shouldn't do when the engine is running. Safety switch if you loose oil pressure.

So to make a short story long it looks like the fuel pump should run forever if you have the key in the start position whereas other S130s have a fuel pump controler that just runs the pump for a few seconds in the start position.

https://www.zdriver.com/forums/attac...1&d=1322859329

Thanks for the response....I've read the chapter over again I think that I get it.

If I'm understanding it....it can't be either of the relays because fuel pump relay 2 activates fuel pump relay 1 to start the fuel pump. Since my car (therefore the fuel pump) runs once started then....they are both working. duh.

I was just thrown off because I can hear my fuel pump start running on my 79 [I]before[I] I 'start' the car when I have the key in the 'on' position. (but that is not to say that it is correct. I know that I have charging issues with that car and shouldn't use it as a base comparision :/ )

The 1980 should be the same though - when you turn the car to "ON" before starting that's the same as Ignition and the fuel pump should come on AND keep running as long as it's in the ON position. My 1983 had a device that just lets the fuel pump run for a few seconds then shuts it off before you start it.

It's possible the fuel pump on the '79 is really loud compared to the '80 because the '80 is obviously working since the car runs....

oh yea and for the cold start relay there is actually a cold start valve that the ECU controls based on temperature. These frequently fail so that's worth checking out...

Go ahead and check that, but I just had a similar problem and fixed it by cleaning off the CHTS connection. That thing will drive you crazy chasing things down and all you have to do is clean that connection and plug it back in.

Thanks, I'm thinking that I do need to clean some connections. I can hear the fuel pump start sometimes seconds before the engine starts to turn over and sometimes if I jiggle the key between 'start' and 'on' I can hear it kick on but it's not consistent. Its obviously getting power, but perhaps not 100%. How ever it runs fine after it does start.

And I do know of the quirks for sure...went to see why my 79 was having charging issues this weekend and 'poof' they were gone. charges fine......but for some reason my windshield wipers and turn signals have both stopped, lol.....it's not fuses so looks like I've got some hunting to do.....

I have the same exact issue on mine and its also a 1980. I wished that they would have finished this thread but it cut off short.