Hard to start when cold or warm

[Spieg16]

Hey everybody

Over the last couple of months my 75 280Z has gotten harder to start weather the engine is cold or warm. When it is cold it seems to be cranking for longer than usual and then sputters for a few seconds then begins to run normally, this will only happen when i hold the gas pedal down. If i dont give it any gas it will just sputter and die. Sometimes also when the car is warm, i will start it and it will idle at about 400 rpm and i have to rev it up for about 10 seconds and let off the gas and it will begin to idle normally. Ive ran injector cleaner through 2 or 3 times, it was recently tuned up, I pulled a plug and it looks to be running clean, and i put in a new fuel filter a few months ago. So i have no clue what's going on. If anyone has any suggestions they are greatly appreciated.

Thanks, Jason

[Montezuma]

Hey everybody

Over the last couple of months my 75 280Z has gotten harder to start weather the engine is cold or warm. When it is cold it seems to be cranking for longer than usual and then sputters for a few seconds then begins to run normally, this will only happen when i hold the gas pedal down. If i dont give it any gas it will just sputter and die. Sometimes also when the car is warm, i will start it and it will idle at about 400 rpm and i have to rev it up for about 10 seconds and let off the gas and it will begin to idle normally. Ive ran injector cleaner through 2 or 3 times, it was recently tuned up, I pulled a plug and it looks to be running clean, and i put in a new fuel filter a few months ago. So i have no clue what's going on. If anyone has any suggestions they are greatly appreciated.

Thanks, Jason

I thinking the "cold start valve" is the problem. It is an easy fix. The cold start valve is on top of the manifold and easy to change. If you have a shop manual it has a few troubleshooting methods for the valve. I had mine go out in my old 78Z, I simply picked up a used one in the local "Pocket Your Part" also known as Pick Your Part, I drop in the used valve and everything worked great and still does some 12 years later. How are things back in ol PA? I grew up in the Lehigh Valley.

[webdawg1]

For starters you'll probably want to download and printout the EFI Bible at the following url: http://www.72hours.net/~zcar/

Would also suggest you get a FSM (Factory Service Manual) if you don't have one, as the EFI Bible makes reference to certain sections/pages of the FSM. Troubleshooting cold/warm start issues starts on page 33 in the EFI Bible. Hope this gets you going in the right direction. EFI Bible is about 70+ something pages long.....

webdawg1

[Spieg16]

the thing that i found that's wierd in the morning is that once you start it, you could turn it off 30 secs later and walk away for a few minutes and when you come back and start it it starts fine, even though the engine is still cold

[zeiss150]

Just a thought... Does that year have a throttle positioning switch? If so check to make sure that is still working right. This could be a horrible suggestion but ... what the hell, right?

good luck, Matt-

[78 280zcar]

Another thing you might want to check is fuel pressure, its suppose to be 36psi! My two cents

[sblake01]

You might want to check the fuel pump check valve since you say the problem happens both cold and warm. A bad check valve would not hold the fuel pressure and each time you crank it, it has to fill up the fuel rail and build up the pressure before it will start.

[Spieg16]

One more thing is that if i drive it to school and it is warm and sunny all day, i could be in school for 8 hours and come out and it will start right up.

[sblake01]

It still sounds like the check valve to me. I had a similar problem on my 810, same fuel pump, and repacement solved it for me. The part number is 17014-N4225. Don't know if they are still available from the dealer but good ones are easy to find in the junkyard. Just check, by blowing through them, that they only let pressure pass through in one direction. I may even have a good one among my parts if your turns out to be bad.