LSXJeep

Here goes. I have a vin "Z" 03 5.3 engine which is a flex fuel vehicle. Vin "T" is a regular fuel engine. I have changed my flex fuel regulator (AC Delco #217-1582) in the fuel rail 3 times because most say it should be 55 or more psi at the rail but all the fuel regulators I have installed produce about 44 psi. I now have a regular fuel regulator ( AC Delco #217-3073). What would happen if I boost the pressure 10 or more psi to the rails? As I see it the flex injectors are higher output or larger. Would the pcm compensate or relearn according to the O2 sensors and mass air flow plus the other inputs?

LSXJeep

Any ideas???

G Atsma

LS engine fuel pressure should be 58psi. That does not vary for flex fuel.

LSXJeep

I beg to defer. Since I posted the previous statement I tried to install the "T" fuel pressure regulator in my "Z" flex fuel engine and it leaked and after comparing them not even close. The O rings and virtual dimensions are way different. All 3 NEW flex fuel regulators I have tried are approx. 44 psi with out disconnecting the vac line. Please check the dimensions. THEY ARE DIFFERENT. If you are right G Atsma please give me the proper part numbers.

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Read #18

LSXJeep

Non flex AC Delco # 217-3073 fuel regulator
Flex fuel AC Delco # 217-1582 fuel regulator

JoeNova

Is the regulator port larger in the flex fuel rails as well?
This is surprisingly good news. It opens up the possibility of using very large fuel pumps on stock truck rails/regulators without pressure control problems.

LSXJeep

Here is a picture of the fuel regulators. The left is the non flex "T" code regulator and on the right is the flex fuel "Z" code. The fuel rails must be different. 3/8 supply and 5/16 return to tank on the flex 2003 and 2004 GM & Chevrolet trucks as far as I know.

big hammer

LSXJeep

OK Big Hammer but the physical size and port differences are definitely easy to see in the pictures. My 2013 highlander says no E85 on the gas cap. This 03 Tahoe engine resides in a 1993 Jeep YJ and is quite the beast. I also use only regular with 10% ethanol. I do not use E85 at all. Oh and the injectors are different in flex vehicles. I read they flow more also.

big hammer

LSXJeep

OK Big but I can only focus on what I have if that is OK. Specific years and engines not with standing. With that said mine works well. I should clarify this is 03-04 flex truck engines and may apply to others. I have never used E-85 in anything so far.