20psi Fuel Pressure??

[PaganEgyptian]

I have been getting Lean codes for both banks and decided to measure my rail pressure. I get 20psi at "on" , I start it, and get 20psi at idle. I give it throttle and its drops to 15psi. I am guessing a fuel pump problem.. or stock FPR problem.

In spring I installed a Walbro 255 in the tank, I double checked all connections and hoses and they are nice and tight. I installed 36# injectors last year, and just installed a new Fuel Filter.

I am baffled, doesn't a FPR usually fail in the open position, where you get too much pressure? If thats the case, the Walbro should be sending very high pressures to the rail, like in 60-80psi?

[landj]

Re: 20psi Fuel Pressure??

The best way to check the FPR is to monitor the fuel pressure while slowly pinching the return line (if it's rubber, if metal or plastic, you'll break the lines, so don't pinch them) when the engine is running. (alternatively, if line is not rubber, you have to temporarily install a valve or rubber hose inline with the fuel return line). If the pressure increases, you know it's the FPR. You must be careful not to pinch the line too quickly as the fuel pressure will go dangerously high if the regulator is the problem.

If the pressure does not increase when pinching the return line, then it's most likely a bum pump or possibly a pinched fuel line or bad filter.

All this said, it's probably easier to just replace the FPR with a new one, and if that doesn't work, take another look at the pump, filter and fuel lines.

I don't have enough experience to be able to say whether it's more likely to fail high or low...

[ssms5411]

Re: 20psi Fuel Pressure??

Sounds like there is def. something wrong with the pump, I know my Walbro 255 and 36lb injectors my idle is 44-48 PSI and at WOT it is 52-54 PSI. Since you checked the hoses at the pump and filter , then I would check the FPR and lines like said above ^.

[PaganEgyptian]

Re: 20psi Fuel Pressure??

I tried clamping the fuel return hose with no increase in pressure.. I am guessing it sounds like a bad pump. I will be ordering an Aeromotive AEI-11109 pump this morning. Its rated continuously at 325lb/hr (190lph) @45 psi with peak demand being higher, according to Aeromotive. Since I am running E85, I needed a pump I knew would handle alcohol so I picked this one. I just spoke with a representative and am sending the Walbro back to Summit for a credit.
Maybe I should get an adjustable FPR also, but I dont know how to bypass the stock one.

[ssms5411]

Re: 20psi Fuel Pressure??

Viper has a write up in FI section on doing a adj. FPR , might want to look at that.

[PaganEgyptian]

Re: 20psi Fuel Pressure??

I checked, but no mention of by-passing the stock 43psi FPR.

[ssms5411]

Re: 20psi Fuel Pressure??

http://forum.camarov6.com/showthread.php?t=16617


It has pics. and tells you what you need and what to do.