Losing power at a half tank

[RunnerJeff]

Okay so this has happened about 3 times in the past month. This issue ONLY happens when I hit the half tank mark and I mean when it literally covers the whole dash mark on the fuel gauge.

Driving a 2005 Toyota 4Runner SE

Basically what happens is right when I hit that half tank mark I start losing power. Engine is still running and I will have power to run the electronics, but when I accelerate I go no where. The engine starts down shifting and it is very, very shaky. Of the three times it always happens when I am on the highway going between 60-75. I try to pedal the accelerator and nothing happens. I have to pull over..come to a slow roll and SLOWLY accelerate and I can get to a gas station. If I hit 55-60 after the roll I can tell it wants to start happening again so I let off. But when I get to a stop light (when going to the gas station) I can rev the engine up as high as I want and then accelerate as hard as I want and it is perfectly fine. This all happens and no codes are thrown at all (very odd). Does anyone have a solution to this? I did replace all O2 sensors last year because I had this problem BUT I got P0174 as my codes and I thought I fixed it.

Any help would be great!!

 

[crashman]

This may be a long shot but have you checked if you have a air leak on your intake after your mass air sensor?
This doesn't explain why it does it at half tank though

 

[Matt fe2o3]

Well that is pretty close to exactly what happens when a submerged flexible fuel line in a gas tank splits.

Is there a submersible line from the in tank filter to the feed?

If so there is possibly your culprit. It sounds a lot like what a bunch of guys I know have been through and I'm waiting for my turn (non-toyota).

So it looks like there are two flexi hoses from the pump to the baseplate / feed. They look exactly like the crap lines Aprilia puts in their tanks. Exactly. I'm not sure what it takes to drop a 4R tank, however you can rule this out before pulling the tank with a pump siphon and a few big gas cans. Drain your tank to less than 1/4. If it dies then fill it back up and see where you don't have an issue.

If it is a split hose you should be able to hear it gurgle.

Submersible hose is a bit hard to find, Gates submersible fuel line hose is about the best.

 

[earthrealm]

weird.......bkmrkkked

 

[gm350reratliff]

Well that is pretty close to exactly what happens when a submerged flexible fuel line in a gas tank splits.

Is there a submersible line from the in tank filter to the feed?

If so there is possibly your culprit. It sounds a lot like what a bunch of guys I know have been through and I'm waiting for my turn (non-toyota).

So it looks like there are two flexi hoses from the pump to the baseplate / feed. They look exactly like the crap lines Aprilia puts in their tanks. Exactly. I'm not sure what it takes to drop a 4R tank, however you can rule this out before pulling the tank with a pump siphon and a few big gas cans. Drain your tank to less than 1/4. If it dies then fill it back up and see where you don't have an issue.

If it is a split hose you should be able to hear it gurgle.

Submersible hose is a bit hard to find, Gates submersible fuel line hose is about the best.

I'd check into this^^^

Could also be that the bottom strainer is plugged. Once the fuel level drops below the top of the fuel pump bowl, it can't pull enough fuel through the bottom strainer alone.

Sounds like you will have to drop the tank to find out what is going on.

 

[RunnerJeff]

Well that is pretty close to exactly what happens when a submerged flexible fuel line in a gas tank splits.

Is there a submersible line from the in tank filter to the feed?

If so there is possibly your culprit. It sounds a lot like what a bunch of guys I know have been through and I'm waiting for my turn (non-toyota).

So it looks like there are two flexi hoses from the pump to the baseplate / feed. They look exactly like the crap lines Aprilia puts in their tanks. Exactly. I'm not sure what it takes to drop a 4R tank, however you can rule this out before pulling the tank with a pump siphon and a few big gas cans. Drain your tank to less than 1/4. If it dies then fill it back up and see where you don't have an issue.

If it is a split hose you should be able to hear it gurgle.

Submersible hose is a bit hard to find, Gates submersible fuel line hose is about the best.

Shit...
I might be able to try this. I am at a half tank right now and have been driving around this afternoon and nothing as happened, it's been running great. If the hoses were split do you think they would do it now? I've only been going 30-50mph, nothing faster.

 

[NJshadow93]

Shit...
I might be able to try this. I am at a half tank right now and have been driving around this afternoon and nothing as happened, it's been running great. If the hoses were split do you think they would do it now? I've only been going 30-50mph, nothing faster.

If you were going slow, it might have allowed enough fuel in to allow for this. If it only happens when you go faster (where the engine needs more fuel) this could still explain the theories above. Dropping the gas tank shouldn't be big deal. Remove the skid plate, disconnect the hoses, the gas tank probably has 2-3 metal braces holding it up, unbolt those and it should drop. This is obviously easier with as little gas in the tank as possible so it will be lighter.

 

[Matt fe2o3]

Before you pull the tank you should check it out and it should only takes 15 or 20 minutes. Borrow a few gas cans from your buddies or neighbors that have quads or off road stuff if you need to.

Like I said grab a siphon and a few gas cans and drain your tank to as low as you can, add back in a couple gallons or so. Now how I siphon is not how anyone else should. You should only use a device rated and designed for siphoning fuel. I however grab a hose of suitable diameter (1/2' or so), feed it to the tank bottom, wrap a rag tightly around the filler cap and hose and blow long and hard into the hose. This slightly pressurizes the tank and forces fuel out the hose, keep the hose end below the bottom of the tank the second you stop blowing and gravity will do the rest for you (err, I mean me). Do not get smart and use an air compressor to pressurize the tank. You will probably burst your tank.

Pull out as much fuel as you can and add back a couple gallons. See if the symptoms are the same. or if it stops running. As the pump works a little harder the hose if split may lift up / flex and that might be why you can run around at slow but not at higher consumption.

If it stops running then you have a pretty good idea what the issue is, and can nail it if the vehicle runs fine when adding up to a certain level of gas.

That flex hose is not like fuel line, it is thin wall corrugated plastic junk that I think ethanol is not so kind to.

This of course is just a guess, however I have seen the exact same thing a dozen times (literally) over the past year with Aprilia stuff.

 

[RunnerJeff]

Before you pull the tank you should check it out and it should only takes 15 or 20 minutes. Borrow a few gas cans from your buddies or neighbors that have quads or off road stuff if you need to.

Like I said grab a siphon and a few gas cans and drain your tank to as low as you can, add back in a couple gallons or so. Now how I siphon is not how anyone else should. You should only use a device rated and designed for siphoning fuel. I however grab a hose of suitable diameter (1/2' or so), feed it to the tank bottom, wrap a rag tightly around the filler cap and hose and blow long and hard into the hose. This slightly pressurizes the tank and forces fuel out the hose, keep the hose end below the bottom of the tank the second you stop blowing and gravity will do the rest for you (err, I mean me). Do not get smart and use an air compressor to pressurize the tank. You will probably burst your tank.

Pull out as much fuel as you can and add back a couple gallons. See if the symptoms are the same. or if it stops running. As the pump works a little harder the hose if split may lift up / flex and that might be why you can run around at slow but not at higher consumption.

If it stops running then you have a pretty good idea what the issue is, and can nail it if the vehicle runs fine when adding up to a certain level of gas.

That flex hose is not like fuel line, it is thin wall corrugated plastic junk that I think ethanol is not so kind to.

This of course is just a guess, however I have seen the exact same thing a dozen times (literally) over the past year with Aprilia stuff.

I was definitely going to siphon it out before dropping the tank. I am pretty sure my friend has a electric siphon because I think we have used it before. If the issue is that flex house line, is there something I can switch to (like a hardline) where this won't happen again? Or do I have to just order the flex line from an OEM distributor and deal with it?

 

[Matt fe2o3]

Jeff, this is what I see on line for 2005 circa fuel pump assembly (this is on fleabay for a v6), not sure what the v8 assemblies look like.

You can see the hoses. I suspect you can order a couple feet of gates submersible hose, grab some fuel injection type screw clamps and be done with it for not too much cost (maybe 50 bucks) - IF that is the problem.

Not sure if Toyota just sells the line but that type of line is SHIT. Once you determine if that is the issue, then pull the tank and gauge the hose. It's all over the web for sale, Napa might even have it, for sure municipal aircraft supply stores will stock it. Probably 20 bucks a foot.

Be careful taking things apart, the plastic can be brittle.

Jeff, if you do find this to be the issue please take a photo of the split fuel line and post it. If it is not then please post the final solution.

 

[RunnerJeff]

Jeff, this is what I see on line for 2005 circa fuel pump assembly (this is on fleabay for a v6), not sure what the v8 assemblies look like.

You can see the hoses. I suspect you can order a couple feet of gates submersible hose, grab some fuel injection type screw clamps and be done with it for not too much cost (maybe 50 bucks) - IF that is the problem.

Not sure if Toyota just sells the line but that type of line is SHIT. Once you determine if that is the issue, then pull the tank and gauge the hose. It's all over the web for sale, Napa might even have it, for sure municipal aircraft supply stores will stock it. Probably 20 bucks a foot.

Be careful taking things apart, the plastic can be brittle.

Jeff, if you do find this to be the issue please take a photo of the split fuel line and post it. If it is not then please post the final solution.

Thank you so much for supplying that picture. I am working on getting a schematics of the tank assembly. I was under there this weekend looking for that pump, but I assume its on the top of the tank (I had my tires off for rotation). I was thinking about just replacing the entire fuel pump. Do you think that would be ideal? I will definitely post a writeup/solution once I get around to this problem. Waiting for some decent weather and time to get this project started.

 

[Matt fe2o3]

Jeff, I'm not an expert, the symptoms you describe are exactly like what I have seen before. The Toyota pump assembly is Like 7-800 bucks. Major cost for not much. A used pump is less but no better perhaps than what you have.

The pump assembly is fully contained in the fuel tank. It sits vertical so you can imagine in that orientation that a split hose will screw you when you get to a certain level of fuel.

If you do your testing and find that to be the issue you drop the tank, replace the flex lines with gates and while you are at it replace the fuel pump itself. (Not the assembly just the pump). Napa will have a pump that fits inside the assembly for little coin. The problem is the plastic housings of the assembly become brittle so be real carefull pulling the assembly apart.

First do the volume test.

 

[RunnerJeff]

Jeff, I'm not an expert, the symptoms you describe are exactly like what I have seen before. The Toyota pump assembly is Like 7-800 bucks. Major cost for not much. A used pump is less but no better perhaps than what you have.

The pump assembly is fully contained in the fuel tank. It sits vertical so you can imagine in that orientation that a split hose will screw you when you get to a certain level of fuel.

If you do your testing and find that to be the issue you drop the tank, replace the flex lines with gates and while you are at it replace the fuel pump itself. (Not the assembly just the pump). Napa will have a pump that fits inside the assembly for little coin. The problem is the plastic housings of the assembly become brittle so be real carefull pulling the assembly apart.

First do the volume test.

I will definitely test first before I go to all this trouble. I was going to replace the pump with this one from Underdog Racing Development Or do you think I should just get the hoses from Gates and the pump from Napa and call it good? I kind of like the one from URD because it will put the filter outside of the tank instead of inside.

 

[Matt fe2o3]

I will definitely test first before I go to all this trouble. I was going to replace the pump with this one from Underdog Racing Development Or do you think I should just get the hoses from Gates and the pump from Napa and call it good? I kind of like the one from URD because it will put the filter outside of the tank instead of inside.

1). We assume the possibility one or more of the in-tank hoses are cracked.

2). I guess another possibility is the OEM filter is clogged (..?) and the gravity of full to half a tank of fuel is enough to feed the system but the pump can't handle it without the gravity pressure of a few gallons. Fuel is 8# per gallon so the fuel weight w/gravity assists the pump pull the head for sure, but it should not have to, ever, eh?

Based on #1 above if true, I personally would simply replace the hoses with Gates, and swap out a rated fuel pump that would fit in the assembly from Napa, button it up and call it a day for probably south of 60 bucks. The only reason I would replace the pump is they are cheap as chips and your are already in there. But that's me.

Based on #2 above If the filter is suspect / clogged then I guess I would look at running an out of tank pump and filter. Certainly cheaper than an OEM assembly however you have to keep your assembly and tank float functioning so pay attention to the assembly wiring.

Either way you replace the fuel pump for good measure. If you go #1, take your old pump in hand down to Napa and they will match it up with something suitable. Or order one from Summit Racing or some such once you know the dimensions. If you go #2, then whatever pump/filter you want. I think there are a bunch of threads here on that particular mod.

The risk I see here is the assembly in the tank. If it is brittle and it breaks taking it apart to replace the contained pump or lines you are back at #2. I would probably set the pump assembly in a cardboard box in the sun for a few hours (God please don't grab the wagner heat gun..:flame to try to get it a little more pliable. I have never done this to a 4Runner but have busted plenty of plastic components in my day and with Colder brand plastic fittings used for fuel they break real easy.

Edit: if you get to the point of dropping the tank and assembly, check all the electrical connections and pins very closely.