mudbog42

Well, I just got my 86 K-5 up and running last weekend. I put in a 2003 5.3l (flex fuel engine). I have been getting check engine codes for the MAF and bank 1 & 2 running lean.

Also when I hook my pressure gauge up turn the key the pressure will rise and quickly fall. So I have to turn the key on and off about 4 times to build enough pressure to start the truck. Once started, it seems to run great. The pressure reads a steady 40 PSI at idle. Not sure if this is too low or not. I read somewhere that the flex fuel motors run at a lower PSI but not sure how much lower. Also if I pinch the return line the fuel pressure will stay, so I thought for sure it would be the regulator. I also took a reading before the regulator and the pump held a strong 75 PSI with the key on engine off.

I have replaced the regulator twice already and it still does the same thing, cleaned the MAF, no difference. Also the o2 sensors are brand new on it. I am not sure what the problem could be.

Any help would be greatly appreciated

Thanks

Old Geezer

iTrader: (3)

Way low on FP... Should be 58.
Running at 40psi could shoot a lean code.
W/ 75psi before the reg, the only way for it to drop is either the reg is letting it go, or the injectors are leaking..
How do you have it plumbed?

mudbog42

I just have a pressure line running through a filter and to the rail and a return line coming off the rails running back to the tank. I plumbed another conversion this same way and never had an issue.

mudbog42

Is there a way to test the injectors? If it were the injectors though, why do I get an instant increase in pressure as soon as I pinch the return line?

Jhankinson

iTrader: (1)

You said pressure line to the rail and then return back to tank. Where is the Fuel Pressure Regulator? And what type of FPR is it (stand alone, corvette filter??)

mudbog42

The FPR is on the fuel rails and is the OEM type. Its the return style intake and rails.

mudbog42

Ok well I pulled up the injectors to check for any leaks and all of them were dry as can be. All the fuel is leaving out through the return line. If I pinch the return line the pressure goes where it should be. Could it another bad regulator?

mudbog42

Well third times a charm I guess. Just swapped out yet another regulator and pressures are within limits and holding strong. Hard to believe I got so many bad ones, but its working good now with the new one. Now hopefully the check engine light will stay off too.

Thanks for all the help and replies