Stalling not just in High, Hot, & Heavy
- Thread starter Pskhaat
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1. Swap the metal fuel return pipe that's bolted to the back of the engine for a soft fuel line affixed up on the firewall, insulate it.
2. Add adhesive heatshield to fuel tank where it is nearest to the exhaust, especially on front and rear corners of the tank where the factory insulation does not cover.
3. Add additional heat shielding to the cats where they come close to the fuel lines on the driver's chassis rail. Do the other side where the rear AC lines run while you're at it.
4. Bypass the fuel pump resistor, or put a cooling fan on it, or put it in your airbox for more airflow.
5. Don't run the tank below 1/4 full especially on long road trips where you will be driving for hours.
Interesting… I get #2-4, but what does changing out the fuel return pipe do? I assuming you mean the pipe that takes excess fuel, beyond what is needed by the fuel pressure regulator, back to the fuel tank.
The return pipe is steel and bolted to the back of the engine. So basically it gets as hot as the hottest part of the engine bay and it's steel so it will transfer that heat into the fuel very effectively. It's a good 14 inches or so.
we’ve tried everything, and yet the simplest thing and cheapest thing to do first is bypass the fuel pump resistor by just soldering the 2 wires together, most 100series don’t come with the extra resistor anyway.
and we’ve been colorado wheeling for 2 years no issues after soldering the resistor on top of imogene
OK, I assumed that. So is the working theory that one of the causes is that return fuel heated by the engine gradually heats up the fuel in the tank, along with heat from the exhaust? That definitely makes sense for one of my stalls (at less than 1/4 tank), but two other instances happened with over 3/4 tank.
It just comes down to heat. The thing about the 100 is that there are multiple places where heat can get into the fuel. Limiting the heat or trying to remove it is the best way to solve this problem.
Looked back at your post and you said it has happened when it was 104F both times. I think that pretty much seals it as a heat related issue.
I have a theory that the fuel can start to boil in the fuel rails themselves which will lead to stalling. I think I've experienced that in stop and go traffic in the mountains where I was climbing up a hill at 5 MPH just barely above idle through road construction. After maybe 45 minutes of that my truck lost nearly all power and would barely accelerate. I luckily made it to the top and then as soon as I started building speed and coasting down the other side I got all my power back and never had any other issues. Coolant temp, AFR, etc was all in spec. I was less than 200F water temperature.
That's what lead me to start thinking about the fuel pump running in slow mode and fast mode. If it's in slow mode during that type of driving that will not only cause the fuel to sit around and absorbing heat but also will reduce the pressure in the fuel rail. So then you have fuel sitting longer and getting hotter in the rails and even inside the injectors which can vaporize if given the opportunity. Add in a weak pump itself from running hot and suddenly the truck stalls out.
That's the thing about a heat related issue like this, it's not going to happen every time it ticks from 103 to 104F, it requires a combination of factors all coming together in just the right way. So if you can stop or slow down some of those factors early then you can pretty much solve it.
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Resurrecting this thread... I want to tackle this problem on my LC 100 now. I have some time on my hands but my access to a garage space to work ends soon (April 18).
An observation that may shed some light: On that same trip to AZ where I had the stalling, we needed to return to the Bay Area. So I had to make the run from Kingman AZ, to Barstow CA through the desert. In both cases, the stalling happened in low airflow conditions: When slowing down to a stop from interstate speed, or climbing a small hill at around 30 mph.
So I drove the entire distance from Kingman to Barstow (206 mi) without stopping, and avoided slowing down below 60 mph. At one point the outside temp gage in the LC read 118ºF! I kept a close eye on coolant (got up to about 205ºF, but would lower if I reduced AC ) and transmission temps and set the AC to as high a temp as I could stand. But we made it without stalling. Thankfully some clouds moved in from the West and cooled things off past Barstow.
So I think we can conclude that lack of airflow is an issue. I suppose that the constant airflow under the LC would carry away air that was hotter than ambient.
I'm not sold on the idea that the fuel pump resistor getting hot is a cause. But it would be relatively easy to relocate the resistor. I wanted to do a test with a temp chamber but I never had time and now I'm no longer working there (company wide layoffs). Can anyone confirm that the resistor really does increase Ohms when heated?
I'd also be very interested in hearing from anyone that insulated their fuel lines. What type of insulation did you use, where did you apply it, etc.
Some of the jobs I am applying to are in Austin, and it if I relocate it will be in June. So I may yet have more desert crossings to do in the Land Cruiser!
Thanks in advance for your help!
2001LC
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Radiator fins need cleaning! Alert Alert Alert
I've a 06LC w/192K I just bought. In reading history I found PO complained of engine temp raising when both front and rear AC on. Toyota Dealership diagnosed with clogged radiator fins. Recommended new OEM radiator, $600 for the US spec Radaitor plus coolant and labor. They should have added...
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fj40alex
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Had this same problem with my 2006. The advice here was helpful. I did 2 of the items - plus replaced my fuel pump. Here is the insulation I used for the tank and lines. Seems to be working.
Thanks for posting! I'm planning to do the fuel pump replacement and do as much of the fuel line insulation as I can next week. I ordered the DEI insulation for the lines. The metal lines are Dia. 8mm, and the rubber fuel line from the fuel filter to the fuel rail is Dia. 12mm.
The questions I keep thinking about:
- Is the reduction fuel pressure when the fuel pump resistor is placed in the circuit, combined with the hot fuel in the fuel line allowing the fuel to boil?
- Where is the place in the fuel line that the most heat is transferred to the fuel?
- Is the metal return line at the rear of the engine a place of particularly high heat transfer to the fuel (suggested by another member here)?
- Would it be more effective to insulate as much of the fuel line as possible, even in the engine compartment?
- Should the fuel filter canister be insulated?
Oh, and why did the Toyota engineers not discover this problem during hot weather testing of the new engine?
I know that as a general rule, cooler fuel results in more power generation from the engine because the fuel reduces the charge intake temperature when it is injected and evaporates. This is one reason why ethanol increases power for turbocharged cars, especially direct injection, as it absorbs more heat from the charge air than gasoline does.
