Slow start and Fuel pressure components

[schwar74]

Got another question guys, thanks in advance.

My 1990 NA 2+2 w/ 101,000 on it came with a slow starting issue. Soon after I got it I replaced the fuel pressure regulator. It seemed to improve things a little bit, but if the car sat for several days, it was slow starting again. Now the problem has worsened again. If it sits overnight it typically takes ~ 7-8 seconds of cranking before it gets fuel and then fires right up. My questions are:

1. How reliable are "generic" FPRs? I got mine at o'reilly, and I think I got the house brand. Might I have gotten a bad one?

2. Is it possibly the fuel pressure dampener? Will it cause the same issues if it fails?

3. I always hear the fuel pump engage for a second or two when I turn the key to the on position. After I crank it, it engages again for a few seconds. This seems normal to me. Is it?

4. I've been meaning to replace the fuel filter, as its most likely original. Could this be the culprit?

It runs GREAT after it starts. No problems with weakness, stumbling, roughness etc.

Thanks again.

Scott

[Ace2cool]

You may be barking up the wrong tree. Never a good idea to just "throw parts at the car." Have you actually hooked up a gauge and checked the pressure? BTW, never a bad idea to replace the fuel filter if you don't know how old it is.

[Shoey2]

when you change it, knock it on the ground with the ends plugged, then pour it out and see what comes with it. sometimes its crazy the amount of mud that comes out. good for making customers feel better about me spending their money once i show them.

[schwar74]

So I got my hands on a fuel pressure tester today and here's what I did and saw. Please bear with me as I don't have much experience with the fuel system I put the gauge in line just past a brand new fuel filter. When I turned the key to the on position, the fuel pump came on, the pressure shot up to about 45psi then dropped pretty quickly to less than 10psi. When I started it, the pressure shot back up and stayed in the 40-50 psi range at idle and while revving the motor. I think this tells me the pump is fine.

I also set my TPS today. It was reading 0.5 V but I got it reset to 0.45. It started slowly even after I did this.

Should the presure in the fuel lines stay at 45 all the time, even after its shut down? What tells the fuel pump to turn off, the ECU?

Where could the pressure be leaking off to? I'm assuming I don't have a leaky injector as it really seems to run well with no missing, hesitation etc.

Thanks again guys.

Scott

[Ace2cool]

http://www.300zx-twinturbo.com/cgi-bin/ ... &total=190

Dig through the EF&EC section of the FSM and see if you can find some more troubleshooting steps. And yes, the system should hold pressure while the car is off. It's supposed to be 43.4 psi.