Fuel Pump Overheating / Tank Cavitation - Post LS Swap

[jstouder]

Update:

Fuel pump was replaced as the potential culprit. Thinking was, with the closed, non-vented system in place for months, the fuel pump was damaged. The evap/recirc system is in full working order (tested and validated), with the recirc pulling fumes appropriately and the venting working as designed.

After forty-five minutes of driving in the mid-day heat, the fuel pump began it's all-too-familiar ramp to Wailing Banshee loud. No change in the issue.

I'm now absolutely convinced it's temperature related. Something is cooking the fuel tank. I confirmed as much by taking readings all around the fuel tank, with it hitting 185 degrees at its closest point to the exhaust. Additionally, the evap hose routes very close to the exhaust and was 162 degrees at its warmest reading.

Next steps:
- Wrap the muffler with a kit from Design Engineering
- Wrap the 4" exhaust pipe coming into the muffler, back past the cross-member (approx 8-10" of muffler pipe)
- Wrap the evap hose that runs close to heat sources
- Replace the Walbro fuel pump with a Quantum unit which is quieter and more efficient

We are not going to touch the fuel supply line as it didn't get more than 128 degrees (at the elbows) and was around 115 at the filter/regulator.

 

[cruisermatt]

What pump did you install this time? The one I recommended?
I don’t think tank heat is your problem, think about the fuel rails that are bolted directly to your engine, and under 50-60lb of pressure, and a much smaller volume. The fuel doesn’t boil out of those

 

[jstouder]

What pump did you install this time? The one I recommended?

@cruisermatt Grateful for your continued support. I'm two years in and losing my fn mind on this.

We swapped out the old pump with the same unit believing the original to be faulty due to extreme tank pressure when the tank was sealed.
We used the TIA/Walbro GSS343GS.

Doing so made no difference at all.

I'm grateful for your suggestion regarding the 2UZ 4Runner pumps (950-0226). In the past two years, I've put six different pumps through the system and all have succumbed to this issue (slowly winding up to a wailing banshee scream). Haven't tried that one though so will keep it in mind.

Regarding heat, a gas tank shouldn't be 185 degrees. Also, minimizing heat cannot hurt the effort to solve this problem and it's not that expensive so that's the next step. If it persists from here, I'm snagging the pump you suggested.

 

[WCBlueSky]

I occasionally have similar fuel boiling issues with my stock 1FZ-FE. The issue is also very common for the 100 series, many threads here on MUD. For example this thread has 51 pages! Gas tank building excessive pressure & fuel smell. Dangerous for sure! Why does this happen? - https://forum.ih8mud.com/threads/gas-tank-building-excessive-pressure-fuel-smell-dangerous-for-sure-why-does-this-happen.1214321/. Here is an 80 series thread: Excessive fuel tank pressure - https://forum.ih8mud.com/threads/excessive-fuel-tank-pressure.292965/page-21. My charcoal canister vents like crazy sometimes, and I sometimes hear boiling in the gas tank long after I shut off the engine, especially when I'm at high altitudes. My fuel pump doesn't make any noise though. Many people said a new canister helped, but I changed the charcoal in the canister without any improvement. If the gas tank is 185 deg F and boiling, it is going to quickly overwhelm any evap system because this is well beyond the normal vapors. As soon as I add cooler fuel from a gas station then all problems stop.

From what I've read, the first thing to check is that the engine is not overheating, or even running hotter than normal. Other than that, I'm still searching for answers.

The boiling point of a fluid is dependent on pressure, so the issue is worse at higher elevation due to the lower boiling point of gasoline. Gasoline also has different blends for winter and summer, which affects the boiling point, as does ethanol vs non-ethanol. I've had better luck with non-ethanol when I can find it and care enough to pay more for it.

The fuel goes through the rail and pulls in heat from the engine, which is around 200 deg F. If you run for long enough, eventually the gas tank is going to heat up due to hot fuel in the return line circulating from the engine to the tank. There is also convective heat from the fan pushing hot air away from engine, radiant heat from the exhaust that can be transferred to the tank and fuel lines, heat from the ground on a hot day, and heat from the fuel pump itself in the tank. I don't know which of these is most significant. Maybe they all contribute. I've had fuel boiling when it was cold outside but I was on a high overlook. Another anecdotal point is I had a leak in the fuel pump pickup hose, so my fuel pressure/flow was lower than normal, and it didn't seem to have any venting/pressure issues on that hot day, but they immediately came back after I fixed the leak. Others have said insulating the tank/lines seemed to help them.

I have an IR camera and plan to image the underside to see what is hottest, but other than that I'm at a loss for how to fix the issue.

Also I personally think that opening the fuel cap and allowing the fuel to boil out doesn't help much and could be dangerous, i.e. start a fire. This is assuming the evap system is not plugged and bleeding off at least a little vapor. It will boil until it cools down, which can be several minutes, and wastes fuel. It's not like opening the cap will let out the pressure in a few seconds; the pressure is continually produced because it is hot and boiling. Better to shut off the engine and let it cool down without opening the cap if necessary.

 

[Dougal]

To heat a tank of fuel that much would require more heat energy than a pump should be able to produce. I think the pump is the victim here.

But you've got this exhaust system right beside it shedding hundreds of kw of heat constantly. Shield or wrap the exhaust and muffler and see what happens. It's cheaper than anything else.

 

[jstouder]

@WCBlueSky and @Dougal appreciate the response and feedback.

An update:

- Wrapped the muffler with the 10529 kit from Design Engineering
- Wrapped the 3" exhaust pipe coming into the muffler, back past the cross-member (approx 8-10" of muffler pipe)
- Wrapped the 4" exhaust pipe leaving the muffler
- Shielded the evap hose that runs close to heat sources
- Replaced the Walbro fuel pump with a Quantum 255LPH HFP-341

So far the difference has been immediate. First, the Quantum noticeably quieter on startup and during normal operation. It's a different design and it comes with a shroud around it to insulate it and keep it cool. I'm a fan thus far.

Drove for 3h yesterday in moderately warm conditions that, previously, would of caused the issue to occur. Haven't off-roaded or gone higher than 7,500' so time will tell. Heading to higher elevations in the coming weeks and will reply with good news, hopefully.