Runs Nice for a Few Min. Then Rough, Then Kills...

[siteunseen]

You won't have to remove the fuel pump all together. The hose from the tank to the pump can be removed at the pump to reveal a small cone shaped filter, about the size of a sewing thimble; maybe smaller. Mine was really fragile and I had to use tweezers to get it out. You should put in a clear filter between the tank and the pump also. They're about $4 at Walmart, Z Car Tech Tips Fram G3 Filter Installation.

Great looking car too!

Edited October 3, 2013 by siteunseen

[OldSkoolFool]

Here is a weekend update:

-Checked the hoses from tank to filter: all good

-Checked the fuel filter in the front: fuel that came out was excellent, no evidence of rust

-There was an aftermarket new fuel pump in the car. No screen to check on the input side of it. Absolutely no evidence there of rusty fuel. Not sure if it was a bad fuel pump or not. Does not look like a 100% stock replacement item.

-Tried running the car briefly without the fuel filter (no PSI difference), without the part right after the fuel pump that evens out the flow (no PSI difference), and tried playing with the fuel pressure regulator (no difference).

-It still would run for a few minutes when cold at about 20-30 PSI then would settle down to about 10 PSI. Not sure what we did, but it would hold pretty consistent for awhile from 15 PSI to 22 PSI.

-Absolutely nothing we took apart/did suggested there was a rust issue in the tank.

I did have the stock Nissan pump. I check to make sure it worked before putting it in, and it did spin. We put it in and the car would not start at all, no pressure at all. Not sure if too much air got in the line or what. Is it possible that too much air in the line could cause it not to work? Put test leads at the stock pump and it apparently was not getting power. Messed with the leads and added another longer wire to the positive and that let it get power. It still would not spin/turn on when cranking the car and was getting 11 volts + at the pump. So, not sure what is going on there. I did pull out the thimble filter and it was super clean.

I have on order a stock replacement fuel pump and a stock replacement pressure regulator that should be in tomorrow. It was suggested that if the pressure is that low that the aftermarket fuel pump might actually be bad/not producing the necessary PSI.

Thoughts? Is there anything from the computer that would cause it to make the fuel pump run intermittently? Not sure how it is supposed to be on the 280Z but the fuel pump does not run constantly when the ignition is turned to the on position.

[OldSkoolFool]

Oh, and when I put the new fuel pump on, I will be putting one of those clear fuel filters on before it.

[SteveJ]

The fuel pump relay operation is dependent upon what year Z you have. 75-78 used the flap in the AFM to indicate the car was running. I cannot remember off the top of my head what provided the signal for the 78, but I'm sure one of the people better versed in that year will say something.

[Wade Nelson]

Did you try running it with the gas cap off yet?

[superlen]

Shane,

Looks like you had a busy weekend & were covering all the bases pretty thoroughly. Are there any numbers on the aftermarket fuel pump? If so, you could look up the flow rate and we could determine if it was undersized. Obviously the stock one you have on order will take care of it if that was the problem.

As for fuel pump control, the ECU for your car doesn't control the fuel pump at all. The fuel pump relay can be energized be either a) the key turned to the 'start' position or the vane in the AFM being sucked in by the engine running(or your finger if you want to test that). Note: Even though the ECU doesn't control it, there is a wire that runs from the fuel pump relay to the ECU. My assumption is that Bosch Engineers were planning on taking control of the fuel pump via the ecu from the beginning, but didn't get around to it until 78. I'm with Steve, I don't remember if the 78 took over or it was 79. I *think* it was 78. I have the FSMs at my office and can look it up to confirm if needed.

Lenny

[SteveJ]

The fuel pump relay operation is dependent upon what year Z you have. 75-78 used the flap in the AFM to indicate the car was running.

This is a typo. It should have been 75-77. As Lenny stated, in 78, the ECU took over.

[Captain Obvious]

Still a typo.

75-77 used the AFM switch.

78 used alternator output AND oil pressure switch.

Then in 79, the ECU took over.

[superlen]

Thanks Captain,

I remembered something different about 1978 (other than my Stretch Armstrong was eaten by the dog), but didn't recall what it was. I also wondered if the stock unit just used the wire running to it to sense if the pump *should* be running & then did something with that info such as... pump isn't running -> stop firing injectors. I'll know more about this in a few weeks & I'll report back.

Regardless Shane, you can skip the ECU if trying to diagnose the fuel pressure issues.

Len

[SteveJ]

Still a typo.

75-77 used the AFM switch.

78 used alternator output AND oil pressure switch.

Then in 79, the ECU took over.

Shows my memory isn't what it used to be.

[Captain Obvious]

Haha. Memory? Naaa... I looked at the wiring diagram. I didn't spend a lot of time on it, but I'm going with that read unless someone convinces me otherwise.

[FastWoman]

I did have the stock Nissan pump. I check to make sure it worked before putting it in, and it did spin. We put it in and the car would not start at all, no pressure at all. Not sure if too much air got in the line or what. Is it possible that too much air in the line could cause it not to work? Put test leads at the stock pump and it apparently was not getting power. Messed with the leads and added another longer wire to the positive and that let it get power. It still would not spin/turn on when cranking the car and was getting 11 volts + at the pump. So, not sure what is going on there. I did pull out the thimble filter and it was super clean.

So back to your Nissan pump: It runs when you test it, but not when you install it? You eliminated the issue of it not getting +12, but is the ground good? I don't recall where it grounds, but it's NOT through the case. That second wire feeds through a rubber grommet somewhere in the tool compartment area and then.... ???

I had a problem with fading pressure and volume from my old pump. It would be good for about 30 min, and then would fade to the point the engine would be starved for fuel and die. The pump quickly got weaker after that, during driveway diagnostics, and would only run for maybe 30 sec before the pressure would fade and die. A new (Nissan) pump fixed it.