PSK

I just checked the fuel pressure on my ls1 and at idle speeds it is quite erratic. The guage needle is jumping around about 3psi above and below the normal pump pressure of 58psi. When I give it some throttle the pressure comes back steady at 58. Pretty much all through the rev range it is steady except for idle. Is this normal??? Any ideas what it could be?

Thanks

zmonsterjb

iTrader: (16)

goood question

TheBlurLS1

iTrader: (8)

Fuel surging in the line would probably be to blame for that. The pressure gage is fluctuating because the engines fuel consumption is fluctuating, undetectable under higher RPM where it becomes more of a steady state.

It's also worth mentioning that the regulator is about 1/2 mile away from the rails.

zmonsterjb

iTrader: (16)

I will buy that blur ( fuel surging in the lines.). So how do you correct it?

TheBlurLS1

iTrader: (8)

You can correct it by not worrying about it lol. It isn't really hurting anything, 'cept for maybe the gage itself if it's a Bourdon type gage. I noticed when I had the stock system, my gage bounced around a lot. One day I looked under the hood and the gage was on zero. After re-doing my fuel system, I took that gage apart and found the problem. There is a tiny tube curled into a circle inside the gage. As the pressure inside the tube increases, it tries to straighten out. This in turn moves a little set of gears, which turns the needle. All the bouncing caused my little brass gears to strip out.

Here's what it looks like on the inside....



My gage is rock solid now FWIW, but I have a custom fuel system with a true return and the regulator after the rails.

zmonsterjb

iTrader: (16)

I have a electrical gauge and it bounces from 60-100psi when crusing. When this happens the afr jumps from a constant 14.7afr @ 60psi to a lean 15-17.xx afr. When I am giving it part throttle the gauge settles back on the 60psi and the afr works its way back to commanded. ANy idea?

Drake

iTrader: (1)

Have you done any data logging? What are you using to get this data?

Are you sure you're not just seeing the system operating in closed-loop during cruise?

zmonsterjb

iTrader: (16)

Well I would normally be useing HP tuners, but I am waiting on my laptops power cable to come in. I have a in car aem afr digtal guage and fuel pressure guage so I can see whats goning on.
What do you have in mind or what are you thinking?