So, yesterday, I installed a Quadzilla Commander Fuel Pressure module on my '99 24V. The instructions were for the later common rail trucks so I wasn't exactly sure where to connect the banjo bolt and fuel pressure sending unit. So, I threaded it in at the VP-44 inlet side--the line coming straight from the fuel filter housing to the VP-44.

Anyway, yesterday, I get a reading of a whopping 8-9 psi at idle that dropped to 6-7 at WOT cruising down the road. Today, I fire her up and watch in horror as, all day, I never see a reading above 6 PSI. In fact, most of the time it hovered around 4-5 psi and dropped as low as 1 psi at WOT.

So, I'm freaking out and I go to my buddy's shop where they have their tech hook it up to a fuel pressure tester--on the fuel pump inlet side of the filter housing. It reads 13 psi at idle and drops to 10 at WOT, sitting stationary. He needed to get back to the paying customer's vehicle so I couldn't get him to hook it up to the fuel filter housing's outlet side but I figured, "if the pressure's good BEFORE the filter, maybe it's just a clogged filter."

A quick stop to NAPA on the way home and I figure I'm in business. Half an hour later I've got a brand new fuel filter installed, fire the truck up and I"m still only getting 4-5 psi at idle Edited By Moderator?!?!

Now, my question is: for this particular model sending unit, did I select the proper location to plumb it inline? I wanted to get a reading post-filter so that I'd know if I needed to look at it first before blaming a lift pump. Could there be any other explanation I've overlooked why my fuel pressure is complete crap post-filter? Possibly a bad sending unit? I'm already planning on ordering a Vulcan lift-pump relocation kit. Should I plumb the sending unit inline before the filter, say right at the relocated lift pump? Quad, if you're reading this, will I even be able to do that with this particular sending unit seeing as how the Vulcan kit eliminates banjo bolts?

Thanks for all your help, guys!

 

I was really considering a Q-zilla with FP module until I did a search here and found several people who said the Quadzilla FP module never performed properly. So I decided not to go this route at least until they figure out how to get it to work reliably. I guess the implementation of the FP module is problematic in this unit.
Well, at least now you've got a new filter in, that's a plus.
As far as the location, it is just a pressure transducer, it shouldn't matter where it goes to. Except that if it is not a real good one, pulsation could affect it, but the fuel will pulsate everywhere. The only way to reduce that would be to put it after a small orifice (a needle valve) or onto a tee with rubber fuel hose, I think.
-P

 

my fuel psi sender works find. call quad and get another if you doubt it.
i also have the vulcan big line kit, one of the 90's that goes into the vp inlet is threaded for the sender unit.