Have resolved some issues, but still won't take much throttle

[81 ZXT]

I have a 1981 280ZX Turbo. When I bought the car the PO had clamped the return fuel line and said the car "screamed" aka ran very well. I replaced the fuel pressure regulator and also had to replace rack, ball joints, & bushings under the front end. When I started the car, it missed and I could'nt give it much gas. I have corrected the miss and the car starts but idles a little rough. I can't get her to rev very well and this is compounded if put under load (like driving in gear). My fuel pump makes a heck of a racket and I get lurching and backfiring if I try to push the throttle past about 1/4. Do fuel pumps make more noise as they weaken? Or do I have some problem with sensors letting air in. The car seems to run a little better after it warms up but if it does at all it is hard to tell. I was planning for my next step to be putting a fuel pressure gauge on it to see if pump is putting out 36-38 psi?

Does anyone know anything about this?

[zbane]

The pump does indeed get louder as it nears the end of usefulness, or so I have found.

It may also just be a symptom of an overly stressed pump. I would imagine that you have read the importance of having a clean tank...

It may be that your efi system is in fine order, but isn't getting enough gas due to a clogged pump. Then again, you might have bad connections at a variety of sensors (clean, inspect, and replace pigtails/sensors as needed)

Could be as simple as the timing being off...

[81 ZXT]

Thanks, zbane. If the pump gets louder as it nears the end then mine is drawing it's last breath. I will check the screen in the pump for gunk and then check the timing. Oh wait, I think I will check the timing first. The tank and fuel filter were clean when I got it home (replaced filter, looked for gunk in old filter), but the gas was about 3 years old. I siphoned the old out but after adding 5 gallons from a can I drove to the station and it only held 6 more. I have a 21 gallon tank so that means there is still 10 gallons of old still in there. The old gas was clean but did not smell like gas. It did'nt smell like anything.

Could that be my problem?

[zbane]

The old gas was clean but did not smell like gas. It did'nt smell like anything.

Could that be my problem?

That would be a great place to start! Run a line from your gas can to the pump, see if that changes anything.

Regardless of that, you really should check all the electrical connections-not just a quick "that looks ok" sort of thing...rather do a good job cleaning the male and female connectors and know that that is not the problem.

Same with vacuum lines (which I forgot to mention in my previous response)

[81 ZXT]

Should I check the ECU? Is it just a bunch of pins with wires connected to it. Could some of the wires/connectors have corrosion on them?

[sblake01]

You should always check the electrical connections on these 25-35 year old cars. Doubtful that there would be any problems with the ECU connector since it's not exposed to the elements like the one's under the hood.