I dont know of any way to test it. I would swap it out for sure before I dropped the tank. Would only take a few minutes and I think they are under $50.

 

1Slow, I just edited my post right before your last reply, And again thanks for the help
Mark

 

An adjustable one would be better, I think. I will most likely go to that as well. I am waiting to see how my Air Fuel ratio (AFR) looks on the wideband during my dyno tune. Then I will decide. You can get a stock one just like normal and it should work, the radix reuses the stock FPR. I don't know where it is located on the 2004. Hopefully someone who does will chime in or wait til Monday and call Magnuson for advice. Hope you get it figured out, and when you do post up the answer. It also could be as simple as the fuel filter. 1 tank of really crappy (stuff floating in it) gas could clog up the filter enough.

 

1slow,
It really sucks that in 2004 they went to an intank fuel filter. What kinda $hit is that. Like you said 1 bad tank of gas and it could get clogged. What do they expect you to do, drop the tank every time that happens? Also how do you adjust the adjustable FPR?
Mark

 

The 04 and newer have a returnless fuel system while the 99 to 03 have a return type fuel system with a vac/boost referenced FPR. The 04 and newer have the fuel filter and FPR in the tank with the fuel pump. The 04 does not have the accessable vac/boost operated FPR that the previous trucks have it is all in the tank. The return portion of the fuel system for the 04 is in the fuel tank. If you are having a problem with your fuel pressure then I think it must be in the tank.

 

Your 04 does not have an external FPR, it is in the tank as part of the fuel pump module assembly.
Mort beat me to it

 

This seems to be more of a limitation of the returnless fuel system. The pump itself is probably OK. Unless we all got bad pumps. Maintaining adequate fuel pressure is even more important under boost because injector flow drops as intake pressure rises. Actually, it is preferable for fuel pressure to rise equally as intake pressure rises to maintain a constant injector flow rate. With a non boost referenced system the PCM has to increase the injector duty cycle to compensate for the decreasing flow rate. Hence these systems will max out the injectors sooner. Even with the replacement Walbro GSS341 in the tank my injectors are maxed by 5000 RPM and the AFR starts to lean out quickly. Also with the Walbro you lose an important feature of the tank module to supply fuel during hard acceleration or cornering under low fuel conditions so you should never let your tank level drop too low.

There is currently no good plug n play solution to this problem. Anything I have seen so far makes compromises.

I am converting my system to a return style($$) with a larger supply line, parallel feed to the rails, adjustable boost referenced regulator after the rails, inline filter, and possibly an inline check valve to replace the one in the pump outlet orifice. I will use the factory feed as the new return line. This should greatly enhance the capacity/reliability of the system and allow the pump to perform at it's potential. I will have the ability to add an inline pump also if necessary. I have stripped the in tank module so that only the pump remains in it. It has also been modified to restore the venturi fill feature that is lost with the Walbro pump. I am investigating what can be done to increase the reserve capacity of the module's bucket as well.

 

2004Denali: Looks like you're dropping the tank

DrX: That sounds like a lot of work. I'm sure it will work when you are done but it seems as if there should be an easier solution

 

yes, it makes a difference. You might need a Boost a pump. Which brings up another question, is your fuel pump getting full voltage?

 

Sure is and I wish there was. A voltage booster might help but it doesn't address all of the issues with this setup. Might even be better to use one with the stock pump/module. I can cut some corners to save a few hundred $ but I am not designing something based on a price point. I don't want the fuel system to be a limiting factor and as long as I have everything apart I might as well do it right.

A less costly approach could include: retaining the in tank filter and blocking off its FPR orifice- but I want my filter easily accessible. You could also get a factory regulator from an earlier model truck and the corresponding Radix fuel manifold(the aluminum block pictured above) and keep the single feed to the rails. This would save a lot of fittings and 6 ft of hose. Cheaper non teflon hose would also trim costs.