Fuel Pump Overheating / Tank Cavitation - Post LS Swap

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jstouder

jstouder

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For the past two years, since I swapped to an LS3, I've been working through a persistent fuel tank cavitation issue.

Problem: After >1h of driving, exacerbated when going to elevation (11,000+), the in-tank fuel pump starts to whine, building to a wailing banshee scream. This began since the swap and persists through a tremendous amount of work and expense including swapping fuel pumps four times, a custom Chevy evap/recirc installation, a rerouting of fuel supply lines away from heat sources, using vented and non-vented gas caps, pulling the entire system and rebuilding it, and more. When using a vented gas cap, pressure builds such that fuel will pour out of the gas cap even when only 1/2 full. I've tried non-ethanol fuel to decrease pressure with no change in behavior.

Additionally, my father-in-laws truck was swapped at the same time, side-by-side. He has a vented gas cap and very basic evap setup and has no problems. Something is obviously wrong I'm looking for ideas on what to do to resolve this issue. At this point nothing is off the table so take your best shot.
 
jstouder said:
For the past two years, since I swapped to an LS3, I've been working through a persistent fuel tank cavitation issue.

Problem: After >1h of driving, exacerbated when going to elevation (11,000+), the in-tank fuel pump starts to whine, building to a wailing banshee scream. This began since the swap and persists through a tremendous amount of work and expense including swapping fuel pumps four times, a custom Chevy evap/recirc installation, a rerouting of fuel supply lines away from heat sources, using vented and non-vented gas caps, pulling the entire system and rebuilding it, and more. When using a vented gas cap, pressure builds such that fuel will pour out of the gas cap even when only 1/2 full. I've tried non-ethanol fuel to decrease pressure with no change in behavior.

Additionally, my father-in-laws truck was swapped at the same time, side-by-side. He has a vented gas cap and very basic evap setup and has no problems. Something is obviously wrong I'm looking for ideas on what to do to resolve this issue. At this point nothing is off the table so take your best shot.
Click to expand...
@jstouder :

A fuel pump whining then building to a scream tells me it is pushing deadhead against full pressure, not "starving" which would be a cavitation.

I'm weak on the LS fuel systems, but I'll give it a shot from what I know and what direction I see from a troubleshooting perspective:
What would cause a fuel pump to overpressure?
The injector rail not using fuel as fast as it is being pumped in.
Does the whine decrease under WOT?
* You installed a return line to the tank.
Is this line large enough?
Does the return fuel have a place to go?
Since there will be a negative pressure on the tank because the engine is using fuel and the return to the tank is replacing volume, the tank needs to allow air to come in.
* Is the check valve on the charcoal canister evap system stuck / missing / replaced? (Does it exist?)
* What is the LS stock fuel system setup?
* Is the tank becoming pressurized? If so, it could be due to heat, increased elevation (reducing vapor pressure) and E10.
* Is the return line to the tank large enough? If after an hour it builds pressure to cause whine, that tells me the pump is building pressure over time in the line.
Is there a fuel pressure regulator on the LS fuel rail? Has that been changed?
Is your fuel tank blowing up like a balloon from being over pressured?
Is it sucking in and collapsing due to sucking a vacuum?
Have you measured you actual fuel pressure at the injector rail?
Is your fuel pump too large for the application? (240LPH-340LPH appears normal) High flow? (above 340 LPH)

It may come down to making sure that ALL the components of your engine fuel system are in spec with YOUR SPECIFIC YEAR AND MODEL of LS swap and computer it uses. Another friend of mine has been fighting many issues on his C10 LS swap because of having to identify an exact year (VIN#) of the swap to resolve issues.

There is a ton of info on "LS Swaps" on the interwebs, but you must know what generation, what version of everything that engine started life and carry it all the way through. There are a lot of things that don't cross over between Gen IV and Gen V.

LS Fuel Pump / Regulator info
1722356305493.webp
 
Lots of basic info missing from your post.

What part number fuel pump are you using?
What are you using for a fuel pressure regulator?
Do you know what your base fuel pressure is?
How about monitoring fuel pressure in real time while it is doing this?
 
@cruisermatt agreed, more info below
@BILT4ME thank you, hopefully the below helps answer most of your questions

Engine: GM LS3 430HP V8 Non-E-ROD - Performance part number 19432414
Transmission: 6L80E 4WD
ECU: E67 with the 19354328 controller kit
Fuel pump: GSS343G3 (link)
Fuel filter/regulator: GF822 (link)
Fuel pressure: 58 to 60 PSI at the rail at all times, regardless of fuel pump whine or pressure in tank

Regardless of gas cap (vented, or OEM non-vented), the gas tank builds up tremendous pressure. Exacerbated during the warmer months and at altitude (9,000' and higher). Outside of the obvious fuel pump whine, this is evidenced by pulling the non-vented gas cap and the tank then venting voluminously for five minutes or more. With the vented gas cap and around 1/2 tank or more fuel, pressure builds to the point of fuel pouring out of the vented cap.

The check valve was replaced and installed correctly including being tested outside of the tank for proper operation. The purge solenoid was then wired up to the ECU and enabled in the tune by professional aftermarket / 4WD tuners. Regardless, it doesn't appear to be actually opening the valve to allow gas to vent.

The question that is being asked now: is their any material difference in ECU's between E-ROD and Non E-ROD LS packages? Meaning, can the installed non-E-ROD ECU, regardless of being wired up and set correctly in the tune, actually engage the purge solenoid?

103_0984.JPG
 
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If you really have that fuel pressure at the rail at all times then I would say the pump noise and tank pressure are not related. I would recommend a Denso-made pump. We use 2UZ 4Runner pumps (950-0226) very successfully.
As for your tank pressure - that really should not be related to your swap unless something was done wrong.
Plenty of 80's running around at those elevations without these problems. If it were in my shop I would be putting it side by side with a stock 80 and seeing what about the EVAP system was modified exactly and why
 
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Update:

The purge valve settings were set correctly in the ECU. While the solenoid was wired with a new home run from the ECU, it wasn't making contact in the ECU harness. That has been resolved, and the solenoid has been tested. It's operating as designed. Additionally, cfm was tested coming out of the vent line of the tank to the evap canister and it's venting as designed. No kinks or blockages.

I took her for a drive in the summer heat and after about an hour of driving the pump was screaming again and, at idle, the psi at the fuel rail was hovering around 70psi. We are now pursuing a replacement fuel pump as it could be damaged from multiple occasions of it heating up.
 
jstouder said:
Update:

The purge valve settings were set correctly in the ECU. While the solenoid was wired with a new home run from the ECU, it wasn't making contact in the ECU harness. That has been resolved, and the solenoid has been tested. It's operating as designed. Additionally, cfm was tested coming out of the vent line of the tank to the evap canister and it's venting as designed. No kinks or blockages.

I took her for a drive in the summer heat and after about an hour of driving the pump was screaming again and, at idle, the psi at the fuel rail was hovering around 70psi. We are now pursuing a replacement fuel pump as it could be damaged from multiple occasions of it heating up.
Click to expand...
Was going to say why have all the evap stuff if it's turned off on the ecm but I see here you fixed that. If your gonna throw parts at it might as well put a new filter/regulator while you doing the pump.
 
landtank said:
Check the path from the fuel pressure regulator back to the tank and any heat source near it that would influence the temperature of the returning fuel.
Click to expand...
This happened to me on one of my work vehicles, when it would start acting up all I had to do was fill it up and it would stop. Talked to one of our techs and he suggested touching fuel tank before filling up, dang thing was so hot I'm surprised it didn't catch fire. Moved return line that was hitting exhaust and problem was solved permanently. Hope this helps...
 
Any pictures of exhaust routing mainly catalytic converter placement. Oem fuel lines? The oem fuel lines run down the driver side.
 
Great input and things to cross off the list. Further info:

After the swap, the fuel line was the prime suspect as it was run very close to the DS header in the engine bay before routing DS to the reg/filter. As part of the complete rebuild of the fuel supply / evap / recirc, the line was re-run with heat and longevity in mind. Pics attached.

This is a non-E-ROD install so no catalytic converter or O2 sensors.

The muffler is adjacent to the gas tank and I've toyed with the idea of wrapping it with insulation as a potential culprit.

IMG_4005.webp


IMG_4007.webp


IMG_4008.webp


IMG_4009.webp


IMG_4010.webp
 
I build heat shields next to the fuel lines on 80 swaps. Have not had the issues you are having to date.
 
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