LRA pump fill speed

[kcjaz]

I’ve had my 24 gal LRA aux tank for a couple years now. I upgraded the pump at the very beginning and I’ve had no issues. My fuel transfer protocol is to let the main tank gauge get down to less than 1/4 tank and then push the button to transfer fuel and let the pump run for 12 minutes. This is always transferred about half the fuel (12 gallons) to the main tank. The pump I bought should do about one GPM and my general use seems to show that that’s what I get.

This passed week in Ouray, I noticed that it was taking longer to move the fuel. On the way home down I70 it was more like 20 minutes to move half a tank. The only reason I can think of for this would be reduce voltage or something at the pump terminals. Maybe some corrosion or gunk or something. I’ll check that when I get a chance, but wondering if anyone else has any ideas as to why my pump would suddenly be flowing at a slower rate than before.

 

[BadReligion]

I’ve had my 24 gal LRA aux tank for a couple years now. I upgraded the pump at the very beginning and I’ve had no issues. My fuel transfer protocol is to let the main tank gauge get down to less than 1/4 tank and then push the button to transfer fuel and let the pump run for 12 minutes. This is always transferred about half the fuel (12 gallons) to the main tank. The pump I bought should do about one GPM and my general use seems to show that that’s what I get.

This passed week in Ouray, I noticed that it was taking longer to move the fuel. On the way home down I70 it was more like 20 minutes to move half a tank. The only reason I can think of for this would be reduce voltage or something at the pump terminals. Maybe some corrosion or gunk or something. I’ll check that when I get a chance, but wondering if anyone else has any ideas as to why my pump would suddenly be flowing at a slower rate than before.

Higher vapor pressure in both tanks. Mine does this too in high temps, high altitudes, and towing.

 

[kcjaz]

I’ve had my 24 gal LRA aux tank for a couple years now. I upgraded the pump at the very beginning and I’ve had no issues. My fuel transfer protocol is to let the main tank gauge get down to less than 1/4 tank and then push the button to transfer fuel and let the pump run for 12 minutes. This is always transferred about half the fuel (12 gallons) to the main tank. The pump I bought should do about one GPM and my general use seems to show that that’s what I get.

This passed week in Ouray, I noticed that it was taking longer to move the fuel. On the way home down I70 it was more like 20 minutes to move half a tank. The only reason I can think of for this would be reduce voltage or something at the pump terminals. Maybe some corrosion or gunk or something. I’ll check that when I get a chance, but wondering if anyone else has any ideas as to why my pump would suddenly be flowing at a slower rate than before.

I thought about the pressure in the tanks being higher with heat build up and possibly boiling, which I've only experienced once before in Breckenridge, but the pressure in the tanks would be theoretically as they are vented to each other so I didn't think that would reduce the flow. What I didn't think about was vapor pressure being higher with heat and altitude. The way the pump suction tube is configured requires the pump to prime itself by "sucking" up gas from the aux tank. With high vapor pressure, the pump likely cavitates and the flow would drop. Now that I'm back down at 925', I'll see if I'm back at 1 gpm. Bet I will be. Thanks.

I love the LRA. Drove from Ouray to Colby KS in 8 1/2 hours (~525 miles) without stopping. I could have gone another 130 miles with the 10 gallons I had left but 8 1/2 hours was the bladder limit.

 

[prharper]

I have LRA 24, installed by Slee with upgraded fuel pump.

I drove from Ouray to Dillon on Thursday. Stopped to fill up and there was a lot of pressure built up while slowly removing the fuel cap.

In MO or OH, I transferred 1/2 a tank from the aux to the main tank. That took 20 mins and does seem longer than previous transfers....

 

[Fisher23]

Mine takes 12 to 15 minutes to go from 1/4 to 3/4.

 

[WCDAVE]

Recent experience: when driving through Grand Junction on Friday with the temp at a solid 102° I stopped at Loves to fill up both tanks. By the time we got to the canyon heading up to Glenwood Springs the check engine light came on and the biggest PIA, the cruise stopped working. I contacted our great friend at Ed Martin - Mr. Sarjeant - to see if we could get in for service on the way home which he kindly arranged. The CEL went out in KC as the boiled fuel that had temporarily clogged the cannister was cleared. We confirmed that the CEL was for the fuel system emissions/cannister. Protocol for elevation in the heat is no more than 2/3 full going forward to avoid overwhelming the cannister.

Apologies as this was unrelated to OP, so let me offer that my best guess is 1 gal/min., as previously stated, with the pump that I have. Vapor pressure may be an issue in transferring, but I would think that the systems being vented together through the filler neck would make this not an issue. I have had my connection on the wires to the pump get fouled with dust/dirt and had to manipulate the boot on the contacts to "clear" it. That was an all or nothing thing, not a slowing of the flow though.

 

[kcjaz]

Protocol for elevation in the heat is no more than 2/3 full going forward to avoid overwhelming the cannister.

So both tanks at 2/3 full?

Other than CEL and cruise going out were there other symptoms? Did you get the evap system codes? I’ve never had and evap issues but this last LCDC is the first trip at elevation and it really wasn’t too hot ambient wise. I’m reading the related threads on this trying to learn more so I’m prepared if it happens. Seems like it’s likely it will. Can it cause a the truck to go into limp mode or prevent 4lo?

 

[WCDAVE]

So both tanks at 2/3 full?

Other than CEL and cruise going out were there other symptoms? Did you get the evap system codes? I’ve never had and evap issues but this last LCDC is the first trip at elevation and it really wasn’t too hot ambient wise. I’m reading the related threads on this trying to learn more so I’m prepared if it happens. Seems like it’s likely it will. Can it cause a the truck to go into limp mode or prevent 4lo?

Yes, what I was told is the the cannister has to handle the combined vapor from both tanks - so 2/3 both tanks. I am not familiar with how the evap system is plumbed, but those were the directions i received which works for me if it avoids the CEL issue. The codes the CEL threw were for the evap. Never tried 4lo under the CEL condition, but my guess would be no effect, but I would not bet on it. Does not induce a limp mode. Only other "symptom" is the smell of gas in the car. The main indicator that something is up is the fuel pump shutting off below 1/2 on the main tank. I don't have an order on fill ups - sometimes I fill the LRA first, sometimes the main - not sure if that impacts or not.

As an aside, the tech did say they were considering coming up with a pre-evap filter to avoid the evap getting overwhelmed, but nothing at this point is done.