well i got my third set of fuel pumps in last tue. and i got the pumps switched out last night. This time i installed the gss 307 high pressure pumps. First off these did not fit like the other 255s i had from JLP. the inlet is very large and caused some issues with mounting into the factory holder/bracket. any way got everything switched and back in the tank. then i hook up my fuel pressure gauge and turn the truck on. guess what same issues that i had before. the pressure gauge shows 30psi and would not go past 40psi. I am at a lose now. i have replaced the pumps (x2 now), filter, relay, resistor, fuel lines in the tank, tunes, etc.. I am going to unhook the factory fuel lines from the tank, filter, and rails and blow them out just to make sure nothing got into the lines. Any other ideas?

 

Regulator?

 

no i have switched the regulators also.

 

did you check voltage to the pumps?

 

Check the gauge

 

two diff gauges also. the a/f went over 16 on the dyno so the truck is not getting fuel.

 

Must be a voltage issue. Even with a partially blocked fuel line you should be able to register 40psi with the key on and even possible at idle. If you do try to blow the lines out be sure to blow from the engine back. Check you voltage at the pump and also watch to see if you get a drop with the pumps running. Those big pumps draw a lot of juice and may need heavier gage wire to function properly. Also check you pump relay. Normally relay work or not however I have seen some that kind of work but have way too much resistance.

 

So when you bypass the fuel resistor you DO get full pressure right? If that's the case it's down to electricity or the PCM controlling the pump voltage/fuel tables/etc. Is there any chance you can "borrow" a PCM from someone and see if maybe you have a wonky computer?

Also, how is your electrical system? Good battery, alternator putting out good voltage/amperage? Good chassis grounds??

Hope you get it licked bro!

 

I agree with the above, check the voltage at the pumps to start with, is the second pump running or set to run constant duty, does it turn on? The fuel filter is a Motorcraft correct? I remember guys running Frams having clogging issues even on newer filters, is the new pressure regulator adjustable? Now reaching a bit, how about the MAF, would a bad unit cause an inaccurate read and make the truck run fat, how about clean job on the current unit, what about oxygen sensors, are they reading properly? Again I'm reaching. Good luck, Todd

 

corrected spelling of thread title

 

lol thanks

brand new sct 2400 maf

will be checking elec. system tonight

thanks everyone

 

Can you dead head the pumps?try and block the return line and see what happens if the psi stillwon't get above 40 then you know it is in pumps or you have a leak somewhere.Also to ck voltage you need to have a load[pumps working] otherwise you will read bat voltage with a digital volt meter.Stan

 

sorry to hear you still fighting that