Hey guys,

Here is a message I posted on another site (see below) about my pressure dropping off at WOT. I did a search here and I think I'm screwed....meaning I may need to go to a return style system----Please say it isn't so!

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Hey guy,

I'm going to revive this thread....as it contains a ton of great info!!!!! My truck is an '04 (Fuelsluts old ride) and I'm still experiencing the same fueling issue he was, but I have some new info. Hopefully, we can figure this out, provide some useful info for all of the '04 and up radix owners and finally see the potential of the mods he made to this truck. Here is a quick rundown:

04 Silverado SS
6.0 with a GT2-3 cam
Radix with 2.8 pulley (intercooled---sees 8-9 psi)
shorty headers, corsa catback
42lb lightning injectors
Volant cold air kit
Zippy tune
TB converter

When I got it, it had a failing fuel pump. I knew of the history (from these boards) so I knew it had multiple pumps put in it. I replaced the pump (Walbro from Magnacharger---thanks Brian!) and also found that I had a voltage drop in the factory harness as well as a dead Magnavolt booster. I removed the voltage booster and ended up making a new wiring harness. Voltage drop is gone. I have not sent the volt booster back to be repaired at this time.

I know that he had replaced the fuel sender basket (fuel regulator/filter/sender assembly) so I didn't mess with that. I did ck the o-rings though and blew through the fuel filter. It seemed fine and I ddn't find any signs of contamination/debris. I also did a visual inspection of the plastic and steel fuel lines from the tank to the rail and found no signs of damage. Truck has been running fine for the 6 months or so that I've owned it, but the tune is SUPER conservative (10-11^ of timing) and I want to turn it up and run some 12's!!!

Today, I put a mechanical gauge back on it at the rail and verified 62psi at idle. Under WOT at the top of 2nd, the pressure will drop all the way to 50psi. I had spoke to Zippy and this confirms the lean condition they were seeing on the dyno when they were trying to tune it (hence the conservative tune). Next I put the gauge in-line at the connection next to the tank and performed the same test. 62psi at idle but it only dropped to 53psi at the top of 2nd gear..........

Seems like I'm dropping too much pressure through these lines. Remember there was a foot or so of plastic line from the top of the tank to the connection where I teed in. Possibly the pressure drop might be even less if I teed in at the top of the sender. Unfortunately, that would mean dropping the tank to make the connection, etc... PIA would be an understatement....I'm not convinced that putting in a bigger line from the tank to the rail would fix this. I'm almost thinking that the issue is not enough pump for the given pressure/hp requirements.

Anybody have any additional info they want to share on this subject as it relates to the '04 on up systems???? I really don't want to convert over to a return style system and I don't want to spend an arm and a leg on this system to find out that it still isn't up to snuff.

Sorry for the novel, just wanted to provide all the details.....>>>>>

 

There is definitely a pressure drop from the tank to the rails on the returnless systems due to the reg being way back at the tank. But if you are already down to 53psi just outside the tank, I would say you are likely out of pump.

 

I don't think I would get all that concerned with the pressure drop without seeing what the truck is actually doing with a wide band. I drop to under 50 psi on my gauge with the same injectors and still have 11.3 afrat WOT at the top of second and all through long 3rd pulls. Remember those injectors are rated at 45 psi of fuel pressure. I worked alot on that truck and I think you can get what you want with a wide band dyno tune.

 

I have a return style system, with a guage at the rails as well as a dash guage/display. I had my system altered as I was afraid the returnless wud have trouble keeping stable. Only drawback is during cold starts I have to 'prime the system' by turning the key and getting the pump working for a 5 count before activating the starter.
I'm pretty stable just either side of 60 (bottoms out around 56-57ish)....prob the only thing that works right! I have the Walbro in tank but a KenneBell BAP and purposely went that route as it had decent reliability according to others.

 

My truck must be wierd. Cause with the 255 walbro in tank and nothing else I was seeing 68 PSI at idle and WOT it only dropped mabey 5#. That was with the maggie, LT's, and dual 3" exhaust.

 

There are different intank pumps for different years and models. The best pump buckets to use are the Flex-Fuel. The Flex-Fuel pumps and the TrailBlazer SS pumps seem to be the stronger pumps for this style system. When matched with a MagnaVolt these pumps really shine.

I had a post on here about a custom fuel line I built for the TrailBlazer SS that split the line to (2) -6 lines. This way both rails are fed individually.

https://www.performancetrucks.net/fo...system&page=19