Fuel pressure!

[78 280zcar]

Hello ya all, long time. I have a question about fuel pressure. When the car is idle it has 40 psi, is it suppose to sustain this level when the car is off or is it suppose to go back down to 0 psi. Thanks

[sblake01]

It should sustain it.

[78 280zcar]

Even after the car is off! I have an aftermarket fuel regulator I was thinking about changing it back to the stock regulator because of that, but wasnt sure. Before when I would get gas alot of air would come out when I took the gas cap off, but now it doesnt even do that. Thanks

[sblake01]

Sure, that's why you are cautioned in the FSM to release the fuel pressure before you remove a fuel line. You might want to look at the check valve on your fuel pump. When they go bad they can cause the fuel pressure to go away when you turn the car off. One indication of the would be difficulty starting after a quick stop such as to run in to a convenience store or geting gas.

[78 280zcar]

I have the new aftermarket fuel pump the one they sell you now instead of the stock one that comes with the car. How do I look at the check valve on these type. Thanks for the help

[78 280zcar]

Here is a picture of the regulator if it helps with what I am talking about.

[sblake01]

I'm not familiar with the aftermarket fuel pump but I would think that the check valve would be in the same place, in the oultlet.

[78 280zcar]

Here is the one that they sell in its place,

http://www.partsamerica.com/ProductDetail.aspx?mfrcode=MST&mfrpartnumber=E8312&parttype=52&ptset=A

[sblake01]

Did you notice the fuel pressure problem after installing this fuel pump? The operating pressure you mention (40psi) is actually a little high. The FSM says 37psi with the stock pump. I have no personal experience with the Master E8312 fuel pump but I remember reading on another board about it. It was quite a while back, maybe three years ago, but one of the members suggested to stay clear of those. It's about the 7th post (by Socket2Me). This is another area where I would recommend OEM. http://www.zcar.com/forums/read.php?f=1&i=325026&t=324986

[78 280zcar]

I just got done doing a rebuild on the engine, the fuel delivery was pretty much the same before the rebuild, It could be the fuel pump but I havent the money for a stock bosch fuel pump at 195.00. The regulator is adjustable, I just figured that 40 psi was easier to set it at.

[78 280zcar]

I changed the fuel pressure regulator back to the stock one, now it holds pressure when the car is off, but when the car is running it only reads 30 psi. What would cause this. If I unhook the vacuum line going to it it will read 38 psi, could it be a vacuum leak maybe in the intake manifold. Thanks

[78 280zcar]

It seems that it doesnt hold pressure a leaking injector or cold start valve, it takes a long time for it to go down, (about a half an hour). Is there a way to check which injector is leaking with the injectors still in the car:rolleyes: .