Engine shutting off during long trips.
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Which one is the FPΩ?
What you are saying is true of some electric motors (lower voltage = higher current draw). But if the LC 100 fuel pump was that type, why would Toyota have added the resistor? It must be an unregulated motor that runs slower at lower voltage. Otherwise there is no point to the resistor.
I still have not been able to find anything to confirm that the resistor getting hot could be the cause of the stalling, but there seems to be consensus that it could be a contributing factor. But exactly how?
Relocating the resistor to the airbox makes no sense to me. The condition where the resistor gets hot is low RPM closed throttle in high ambient temperatures. That is the condition where you will have the least airflow into the airbox (closed throttle).
The only relocation position that makes sense to me is behind the plastic grille ahead of the radiator and AC condenser, off to the side. There will be airflow there even with the vehicle stopped due to the mechanical cooling fan. It will also be easy to hit with a cooling spray (50:50 water and ethanol).
Summer is around the corner and I plan to complete this "stall-proofing" project this year. It SUCKS to be by the side of the road in 104ºF waiting for the thing to cool down!
The last time this happened to me, I had two stalls, both in 104º+ temps, both on slow-down. This was on the original fuel pump at 18 years and 180k miles.
On the return leg of the trip I drove from Kingman, AZ to Barstow, CA non-stop through the Mojave never dropping below 60 MPH and watching the ScanGage II like a hawk while the outside temps neared 120ºF. But in continuous motion the Landcruiser did not stall.
I have already changed the fuel pump and filter and have done some partial heat shielding on the fuel line between the filter and the fuel rail.
I'm wondering if anyone has made any progress on this issue in the last few years? Any new info or insights?
Calvinswartz, idea to move the fuel pump resistor, into the air box. Was so, fresh air flow would cool resistor. He came up with the idea. After I pointed out, His aftermarket component. Which were bolted on, within an inch of FP resistors' heat sink. Was trapping heat. His trapped heat could be felt, just touch fender/hood, near/above FP resistor. Will cooling FP resistor, help with known fuel pump issues of the 06-07. Not likely! The FP resistor run very hot, ergo the heat sink.
When I see the classic lean fuel mix engine stall condition, in 06-07. i.e. After driving in higher RPM (fuel pump high speed), typically on hot sunny day. Like when ascending a mountain pass. As we start descend, letting of gas pedal, dropping RPM. Engine stalls/dies. A BK1 & BK2 lean DTC, is seen if scans run.
I replace fuel pump. Works ever time, to correct issue.
First one I knew of, having this fuel pump stall issue. Now has 150K miles and over 10 years, on its new fuel pump. Second one, has 7 year on its new fuel pump. I've replaced many, 06-07 fuel pump over the years. Non have had stall issue since.
Bottom line. The factory fuel pump in the 06-07. Which was the first change in fuel pump (smaller), in the 100 series. Many were defective. Not all 06-07, but about 50% have a bad fuel pump.
Many confuse this, with fuel boiling stall or rough running. From cogged charcoal canister.
When I see the classic lean fuel mix engine stall condition, in 06-07. i.e. After driving in higher RPM (fuel pump high speed), typically on hot sunny day. Like when ascending a mountain pass. As we start descend, letting of gas pedal, dropping RPM. Engine stalls/dies. A BK1 & BK2 lean DTC, is seen if scans run.
I replace fuel pump. Works ever time, to correct issue.
First one I knew of, having this fuel pump stall issue. Now has 150K miles and over 10 years, on its new fuel pump. Second one, has 7 year on its new fuel pump. I've replaced many, 06-07 fuel pump over the years. Non have had stall issue since.
Bottom line. The factory fuel pump in the 06-07. Which was the first change in fuel pump (smaller), in the 100 series. Many were defective. Not all 06-07, but about 50% have a bad fuel pump.
Many confuse this, with fuel boiling stall or rough running. From cogged charcoal canister.
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Thank you for the reply @2001LC When this issue first appeared for me in 2019, you had suggested replacing the fuel pump back then. I ordered the pump in 2021 and probably got the last of the DENSO pumps (I've read they are not making them anymore).
The problem never came in many tens of thousands of miles driven, including a coast-to-coast drive. But conditions were all mild or cold weather.
It was not until I had to cross the Mojave in July 2024 that the stalling came back. I finally got around to doing the fuel pump job in 2025
I feel more confident after what you have said above, that I won't be risking another hot shutdown.
I now work in vehicle engineering, and having seen how much testing we do, I had a hard time understanding how Toyota could have missed this issue. Some fuel pumps having a defect makes sense as a root cause, because it is possible that the pumps that were used for hot weather validation testing happened to not have the fault.
In view of the above, do you think there is no value in insulating the fuel lines? I did place a little insulation between the fuel filter and the fuel rail.
Likewise, is there any value in relocating the fuel pump resistor to a place where it gets more cool air flow?
ALSO: Could it be that the defective pump slowed down so much when it got hot, along with the resistor getting hot, that the fuel pressure was too low to prevent fuel boiling in the lines?
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I've never insulated any fuel lines. So I've not done any testing with insulated.
NO. I don't see much value in cooling fuel pump resistor. In pure stock 100 series. Although running cooler, reduce resistance. The fuel pump resistor, should handle heat. With very minimum voltage & AMP drop, since that is what it is designed for.
YES. If heat is trapped, by aftermarket components. If the heat sink, can't shed heat as designed. If, they then keep reaching higher internal heat than designed for. Likely then, some value in added cooling. Excessive heat, over long term. Resistor will likely, become less effective. Which could drop Voltage & AMP, that it delivers down stream a little. I suppose they could even fail in time, if heat to high. But I've yet to see one fail.
I ran a fuel pump resistor heat test, one summer. I saw resistor heat sink, between 129F & 198F w/OAT of 79F to 97F. As read w/IR temp gun. In summer sun, on the 2003-2007 100 series fuel pump resistor. Which one w/165K miles 07LX had new Fuel pump, to correct stall. One 145k miles 07LX had factory fuel pump, no stall issues ever reported in history. A 320K miles 03LX and last one 198K mile 06LX, with no reported stall, unknown if FP replaced.
Old wires and or reduce ground at contact points, from oxidation/corrosion. Would likely drop voltage & AMPs, more than hot resistor.
Risk, placing fuel pump resistor inside air box.
Where it should reduce heat of resistor, while engine running. There's risk, perhaps more so in the 06-07, which has special filter for fuel vapor, in the air box lid. In cases where EVAP not working as it should. This may result in, excessive fuel vapor saturation of this EVAP filter. The extra heat, may result in spontaneous combustion. After engine OFF, since air follow stops and heat would climb even higher for awhile.
That fact, replacing fuel pump. Has solved the issue, in all I've done to date. Indicates the primary cause, is the fuel pump. Likely motors wire winding insulation defect.
Possibly, a defect in fuel pump motor. Is supported, in first case I read about. It was a new car owner, report stall (service history stated vapor lock) from the very beginning of his ownership, of a 2006 LC. He report, while driving on I-70 to/at Eisenhower tunnel, it would stall. For those that don't know. This Tunnel passes through the continental divide at about ~11K feet above sea level (ASL). Which we must ascent to the mouth of tunnel, for serval miles. Which we're in higher RPM doing the climb, which runs fuel pump at full speed during the climb. A Toyota Dealership, tried solving this "vapor lock" for years over its first 100k miles. The service notes, even stated: Shop foreman, Tech and service mrg. All dove up together, into mountains on I-70 with Tech Stream hooked up. They couldn't figure it out. Then some years later. A few days after a T-belt service. It came back in again, with report of "vapor lock". Only this time Dealership shop, replace the fuel pump. 10 yr & 150K miles later, still repeat of stall issues.
It was study the above 2006LC service history. That clued me, when it happens to me for the first time. While I was driving back and 07LX I just purchase. From west of Vail & Eisenhower passes on I70. First stall was on Vail pass, a second stall at Eisenhower tunnel. A third stall, after a subsequent climb, then throttle back. Fuel pump replaced, all good since. As has been the case with many I've remotely and hands-on diagnosed and R&R fuel pump.
It not a high altitude issue. As there have been many cases, in flat lands like Las Vegas. Where driver was passing/accelerating resulting in high RPM, then stall as RPM drop back to cruise. It is almost always in summer heat. When roads or hot. Heat increase resistance, in resistor, wires and fuel pump as does running fuel pump at high speed.
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great post 2001. I should add that if i’m not mistaken the fuel system state going from open loop to closed loop when pulling up at a stop light or releasing the gas pedal, was the main causation, this along with an old fuel pump pulling increased amperage will not provide enough fuel pressure. the open loop runs current straight to the pump and uses the fuel pressure regulator to return all unused/extra fuel back to the tank. below a certain fuel demand the circuit is changed to closed loop putting the fuel pump resistor in line thus decreasing the pump speed reducing the amount of fuel returned to the tank resulting in effectively a “closed loop” fuel system.
wanted to check in and make sure you got the problem rectified. i know how frustrating this can be especially with the summer heat coming nationwide. in hindsight i realize how stupid the airbox relocation is, and i thank 2001lc for his patience with my stupid ideas years ago when working through this issue, not that it is an excuse but i was 17 when i had this issue. I attribute troubleshooting milestones like this to my fight through my current Mechanical engineering/ aerospace degree. last night i heard about how running these fuel systems in a closed loop can lead to significant effeciency gains, with my current solution of bypassing the resistor i would be interested to hear what you ended up doing.
i read 2001lc's lost above and would like to add that that i did a test aswell where i heated the resistor with a heatgun, verified temprature with a thermocouple, and recoded internal resistance. I saw no real change. as noted above by 2001, the main culprit is more than likely the fuel pump. although it begs to ask the question, what is the correlation to the closed loop fuel pump circuit? aging/defective fuel pump? ageing resistor? the resaon i have a hard time believing that it is as simple as pointing your finger at one of these parts is haw easily I saw the problem fixed with ethanol free gasoline.
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I'm certain at this point I am the exception to this solid case. But I replaced my 06 fuel pump with OE and this issue did not resolve for me. Likely there is more to at least my scenario/story, but I feel I should raise the hand and say this didn't work 100%.
I also stall at altitude randomly (with no obvious load/light cycling) which is what I contribute to more an EVAP situation. My 06 is well-maintained.
The 06-07 fuel pump issue symptoms are in some cases, mistaken for EVAP issues. Some have both!I'm certain at this point I am the exception to this solid case. But I replaced my 06 fuel pump with OE and this issue did not resolve for me. Likely there is more to at least my scenario/story, but I feel I should raise the hand and say this didn't work 100%.
I also stall at altitude randomly (with no obvious load/light cycling) which is what I contribute to more an EVAP situation. My 06 is well-maintained.
06-07 fuel pump symptoms:
- After driving engine in high RPM, for extended period, on hoy day. Which high engine RPM, runs fuel pump (pressure/flow) in high speed.
- Then as we let off gas pedal, dropping engine RPMs. Which also reduces, fuel pump speed.
- Fuel trim go lean, BK1 & BK2. Due to fuel starvation. Cause, fuel pump speed reduce to much, due to increase resistance. Resistance is due to heat of day, and heat created in wiring and fuel pump, while it ran at high speed.
- Engine stalls, just after the RPM drop back from high. Often wrongly, referred to: as vapor lock.
The above symptoms are always the same. Key points are after a high engine RPM extended run. Stall, after engine RPMs drop back.
If a scan run, through OBDII port. Before IG key turn off, after engine stall. BK1 & BK2 to lean condition DTC often found pending. If watching fuel trims closely, we see LTFT high (lean condition correction), just as engine RPM drop back.
EVAP issue tend to be slight different. Most times engine just runs very rough, during event. But if combined with weak fuel flow, engine will stall. Most EVAP issue is associated with, extended low RPM driving, more so on hot days. This is due to different engine RPM, EVAP opens to engine vacuum.