Sevex

Running into a lean issue when the truck runs above 5500ish rpm. watching the fuel pressure gauge as I make a pull shows good pressure as the second pump come on but will all of a sudden drop and the needle will bounce and fluctuate like crazy. If you let off and get back on it will do the same exact thing as soon as RPM comes up.

Voltage is good, stays are 13.5-13.3 v the whole pull. both pumps have 10ga wiring right from the battery (battery is in the back, short run from the battery to pumps). both pumps are on relays with the second pump on a hobbs switch. second pump is coming on according to the LED I wired in on the dash.

Both pumps are inside the stock bucket with the stock feed returning to inside the bucket. the bucket is not cut in anyway. I gutted the bucket and stuffed the pumps in. the tank is from an 05 with the larger bucket, I THINK they came with the venturi setup? but I gutted all that and don't have other holes in the bucket.

long story short I have a feeling I'm sucking the bucket dry with both pumps running for a few seconds. I just filled the truck up before this test so the tank is plumb full. Anyone run into this? I ran out of time this morning to test pump I was going to disable the second pump and try it. the truck is on low boost and I shouldn't max one pump at my current level. if that fixes it I'm going to try to move the feed of the second pump to outside the bucket.

fuel system is setup as follows
Dual 450's in a gutted 05 bucket
-8an feed and return, with return going to stock feed port on the hat
aeromotive 13129 regulator, referenced to manifold
Deka 80's, running about 55% DC when problems happen
I feed one rail, crossover, return off the second rail.

skolman91

iTrader: (28)

Regulator is placed after the rails correct? Does it happen when the second pump kicks on or only upper rpms after second pump has been on?

Sevex

yep regulator after the rails. it happens after the second pump has been on for a few seconds.

skolman91

iTrader: (28)

With the tank full i have a hard time believing its sucking it dry. But anythings possible i guess, wouldnt hurt to try just one pump to see the results. Just have a yblock in the tank connecting pumps, no check valves or anything anywhere?

Sevex

no check valves, pumps just Y'd in the tank. going to run through the wiring as well just to see, I will disable the second pump tonight and test.

LongBlue

Try reconfiguring your pump wiring to make the second pump your primary and your primary pump your secondary. Just because the LED light turns on for the 2nd pump, doesnt mean the pump is actually working or working at designed capacity. By making the second pump your primary, you should be able to see that it is good to go.

I swap my 2 pumps around via my wiring every couple months to give both pumps an equal amount of run time. Think about how often the second pump on the Hobbs switch gets used for time wise.

And yes, agreed with above. If your tank is full, there should be no way to suck it dry if the level is constantly over the top of the bucket.

Atomic

iTrader: (42)

If the tank is full it is not sucking anything dry, it is literally submerged in gas. Does it break up at that rpm even under light load? Use the gear shifter to get you there.

Sevex

doesn't break up or run funny all, just goes lean on the wideband. its always 5500-6k it will lean out to mid 12's low 13's. truck has a black box and is manually shifted, I will try to run it up in first and see.

GMCtrk

iTrader: (27)

I'm with atomic. Negative. I had 2 450s in 2000 tank. Always ran above 1/2 tank though to avoid cavitation

Sevex

So i did some messing with it today, changing up my pump wiring, battery wiring, and added a 4ga charging cable to the alt instead of the fusible link. going out to make some pulls in just a minute.

also checked my fuel filter, summit brand -8 filter (pn number 23116-b) and while the element had some trash in it i dont think it was enough to cause an issue. what i did how ever notice is that the filter is only rated for 180GPH. converting that into LPH you come up with 680LPH. with both pumps running i should be surpassing the flow limit on the filter. I am wondering if its causing issues when both pumps are full tilt.