tiguy99

How's the car driving Kevin?

kevin3344

Great! Man this car is a tank. Ever since I replaced the fuel pump haven't had an issue. I am coming up on my second TB/WP change at 220,000 miles (currently at 219,479) but I consider that normal maintenance. Hope to take it in later this summer to have that done.

Paul1307

Ho Boy...

Does this sound familiar. I've had a similar experience three times over the past six to eight years. First thing is, you can't count on the error codes to be accurate when the car can't get fuel and there is no indication that you're running on the "emergency fuel" in the tank. This I got from a Lexus mechanic.

The first time it happened we were in the middle of nowhere in Texas. With over 1/4 tank indicated on the gauge, the car began to stumble, then just stopped running altogether. I pulled to the side of the road. I tried restarting the car, but no dice. We finally called the insurance company for a tow and eventually a truck came out and picked us up. Eventually we got to Lubbock, TX where the Lexus dealer had the car for about two days and could not find a single thing wrong with it. They tried everything, but the car just wouldn't quit. We finished our trip to AZ, and the problem seemed to disappear.

Until it happened again. This time we were in Florida, and driving home from the grocery, it just quit. Being not far from the house, we walked home and got a neighbor to take a gallon of gas to the car. I poured it in, and the car started just fine. The gauge showed 1/4 tank.

Driving from FL to AZ, this time the car stumbled and died in almost the same place on the interstate as it had the first time. This time I recognized the problem and fortunately there was an exit right there, so I pulled up the ramp and stopped short of the crossroad. I got out, visited a nearby bush, came back to the car, and loosened the gas cap. It hissed a bit. I tightened it back up, got in the car, and it started immediately. Narry a problem the rest of the way to AZ. After the first two times we never let the tank get below 1/4 tank, and this time it had at least 3/8 of a tank showing.

And then last weekend, coming back from Monterey, CA, after years of no problems, the car died 59 miles outside of Phoenix. I pulled off I10, called the highway patrol, then Geico, and had them send a truck with two gallons of gas. An hour later, the gas arrived, he put it in the tank and the car immediately started right up. We drove about seven miles to the first gas station, and filled the tank. It only took about 12 gallons to totally top it off indicating we had at least six gallons of gas in the tank.

Damn these "saddlebag" fuel tanks.

In Florida, the Sarasota dealer pulled the back seat and checked inside the tank. He explained that the tank was a "saddlebag" type that surrounded the drive shart and that a siphon hose pulled gas from one side to the side with the fuel pump, and that maybe the siphon hose had slipped off somehow. That seemed plausible.

So here's the bad news and my best guesses, and please feel free to comment.

1) I doubt that your fuel pump was actually the problem since I've experienced a similar problem four times now, over a period of probably 80,000 miles, and surely if the pump was going to just up and quit it would have done so by now.

2) According to Lexus mechanics, a sudden cessation of fuel flow without the low/empty light being on can generate a number of false error codes since the cutoff of fuel is an unexpected and un-programmed-for error condition. The error codes are secondary and can/should be ignored.

3) I can't help but wonder if there isn't something in that loosening of the gas cap and the inflow of air indicating that the tank is being evacuated as fuel is being drawn, and eventually the vacuum in the tank makes the syphon ineffectual. That actually makes sense since the fuel pump is capable of crushing a fuel tank if in sucking the gas out it's also creating a vacuum in the tank, but that lame syphone is only going to draw until the vacuum reaches a certain point. If only I had tried loosening the gas cap last weekend (my wife noted that "she thought of that but just didn't mention it") I'd have had a pretty definitive answer.

4) It is possible that something in the syphon system is malfunctioning, but it's a dirt-simple system, and seeing how little the tank shares gas between both sides leads me to believe that the syphon must be working or I'd be running out of gas at about 1/2 tank or so regularly, which, I don't.

5) Three times out of four, the car had been driven for about 10 hours and we were on a very slight uphill grade. This last time, had I thought of it, I would have slammed on the brakes to move the gas, and maybe swerved back and forth (little traffic I10 that night) to maybe have sloshed some gas over to the pump side, and made it to the gas station. (Ah, woulda, coulda, shoulda)

Any other ideas would be greatly appreciated. in the meantime I'm going to try to do a controlled test where I "run out of gas" in my driveway, if I can control the scenario (with a can of gas at the ready, of course) just to see if I can force the situation, then see what corrects it, like loosening the gas cap, or rocking the car.

kevin3344

All is well, I haven't had an issue since I've got the car back in May. Dealer did a fuel pressure test and diagnosed a faulty fuel pump and that seemed to fix the issue. Just passed 221,000 miles!

tiguy99

I absolutely LOVE this thread bc this is exactly what happened to my wife and I the day we drove our GS400 home from Minneapolis back to IL....see below for our story
https://www.clublexus.com/forums/gs-...help-asap.html

Was about to get the pump replaced along with a few other items in the coming weeks.
From what I'm seeing below, can it possibly be not only the gas siphon hose in the tank but a potential problem with these old gas caps?
Would it be work replacing that as well?

I plan to replace:

1. fuel pump & filter
2. both left and right fuel sending units
3. siphon hose in tank

What else would you recommend replacing?
I'm at 201K miles

FrankT

1998 GS400 285,000 miles
Let me be another to join the, "out of gas at above 1/4 tank".

On my return from New Mexico I drove nonstop after a fill up and ran out of gas 9 miles from a station with about 5 gallons in the tank. I was monitoring my scangauge and I knew I could make it to the next town to fill up.
I was hoping it wasn't a dead fuel pump. I heard the pump in the tank then I spilled a small splash of camp fuel on the air filter and the motor ran for about 5 seconds. Then an angel in a pickup truck came with a couple gallons of gas...I drove off like nothing happened.
My fill up was about 12 gallons.

since then I have driven below 1/4 tank in normal use near home and work without issue.

I will be replacing the pump and filter, I see no reason to replace the sending units.

Here is a good dialogue between a JustAnswer.com mechanic and a GS owner about the fuel tank issue.
http://www.justanswer.com/lexus/869t...html#re.v/173/

Paul1307

Because this has been so sporadic, and usually, it happens after the car has been running all day, certainly since the last fill-up. Like the other folks, there was plenty of gas in the tank. And I'm not trying to disagree with anyone who is a "real" mechanic since my wrench-turning days are long done. What I'm hoping is to diagnose this issue at the least cost possible for everyone (which includes me!).

I just went out and turned the gas cap, and even though the car hasn't been driven in a few days, there was a small in-rush of air. I also noticed that the cap says something like "don't use a cheapo cap or it may trigger an engine trouble light." This would indicate to me that a small amount of vacuum in the tank is "normal" in that it demonstrates that gas fumes are not leaking from the tank, presumably, through the gas cap. So far, so good.

Here I'm going to turn to the web for answers, and a possible explanation that reinforces my earlier suspicion. I'm still not sure, but I'm certainly leaning in the direction of something blocked, preventing air from getting back into the gas tank. Remember, the venturi on the siphon will only work if the negative pressure at the venturi is lower than the pressure in the fuel tank; the venturi only works because of air pressure.

Quoting from: http://www.aa1car.com/library/evap_system.htm

"HOW THE EVAPORATIVE EMISSION CONTROL SYSTEM WORKS

"Sealing the fuel tank is not as simple as it sounds. For one thing, a fuel tank must have some type of venting so air can enter to replace fuel as the fuel is sucked up the fuel pump and sent to the engine. [Italics mine] If the tank were sealed tight, the fuel pump would soon create enough negative suction pressure inside the tank to collapse the tank. On older EVAP systems, the tank is vented by a spring-loaded valve inside the gas cap. On newer vehicles, it is vented through the EVAP canister."

"EVAP SYSTEM COMPONENTS

"The major components of the evaporative emission control system include:

• Fuel tank, which has some expansion space at the top so fuel can expand on a hot day without overflowing or forcing the EVAP system to leak.
• Gas cap, which usually contains some type of pressure/vacuum relief valve for venting on older vehicles (pre-OBD II), but is sealed completely (no vents) on newer vehicles (1996 & newer). NOTE: If you are replacing a gas cap, it MUST be the same type as the original (vented or nonvented).
• Liquid-Vapor Separator, located on top of the fuel tank or part of the expansion overflow tank. This device prevents liquid gasoline from entering the vent line to the EVAP canister. You do not want liquid gasoline going directly to the EVAP canister because it would quickly overload the canister's ability to store fuel vapors. The liquid-vapor separator is relatively trouble-free. The only problems that can develop are if the liquid return becomes plugged with debris such as rust or scale from inside the fuel tank; if the main vent line becomes blocked or crimped; or if a vent line develops an external leak due to rust, corrosion, or metal fatigue from vibration.
  
  "Some liquid-vapor separators use a slightly different approach to keeping liquid fuel out of the canister vent line. A float and needle assembly is mounted inside the separator. If liquid enters the unit, the float rises and seats the needle valve to close the tank vent.
  
  "Another approach sometimes used is a foam-filled dome in the top of the fuel tank. Vapor will pass through the foam but liquid will cling to the foam and drip.
  
  "If a blockage occurs in the liquid-vapor separator or in the vent line between it and the EVAP canister, the fuel tank will not be able to breathe properly. Symptoms include fuel starvation or a collapsed fuel tank [italics mine] on vehicles with solid-type gas caps. If you notice a whoosh of pressure in or out of the tank when the gas gap is removed, suspect poor venting. [Italics mine] You can check tank venting by removing the gas cap and then disconnecting the gas tank vent line from the EVAP canister. If the system is free and clear, you should be able to blow through the vent line into the fuel tank. Blowing with compressed air can sometimes free a blockage. If not, you will have to inspect the vent line and possibly remove the fuel tank to diagnose the problem."

Note especially the symptoms and test in that last paragraph that I have highlighted with italics. I just loosened my gas cap after not having driven the car for a few days and got the whoosh of inrushing air, and as soon as I can locate the cannister and the vent line I'll be testing this. This makes more logical sense to me than a component failure that mysteriously only occurs on long trips and can be immediately fixed by adding a gallon or two of gas to the tank. Note that taking off the gas cap to add the gas probably does more than adding the gas itself does. If only I had loosened the cap on my last trip I'd have known for sure. I will be testing the vent line as per the article to see what I find.

At least we have something we can try, and if this prevents another club member from having to replace expensive components that may or may not have been necessary it will be well worth the time I spent researching this for me and anyone who has a similar problem. Now, if anyone knows where that darned canister and vent line are located I'll get right on it, LOL.

Paul1307

Let me add one further comment. I'm an engineer, not a mechanic, and when confronted with a problem like this I tend to come at it from the perspective of "If I designed this, how would I do it?" Likewise I try to look "backwards" from the symptoms to see what I would suspect if something wasn't working properly. This is my analysis:

1) The gas cap creates an air-tight seal. As gas is burned, by design, a vent is supposed to allow air into the tank to equilibrate the air pressure in the tank. If the vent is blocked, as gas is burned, the limited amount of air in the tank has to fill more space and its pressure goes down until eventually the venturi cannot draw gasoline from the "other side" of the tank and the resulting fuel starvation shuts down the engine.

2) The vent serves two purposes. On a hot day it allows the expanding air in the gas tank to vent to the activated-carbon filled canister where the gasoline is separated and stored, then sent back to the gas tank as the temperature falls. Secondarily, as gasoline is burned and leaves the gas tank, if the vent isn't working properly, the air in the gas tank progressively develops a lower and lower air pressure. As the article points out, a "whoosh" when opening the gas cap is one sign that the vent isn't working properly. A whoosh when opening the gas cap is not normal seems to be the implication. I need to research this more since my memory is that every car I've ever owned "whooshed" when the gas cap was removed.

3) If a partially-evacuated gas tank is not normal I would then suspect that testing fuel pressure from the gas pump could possibly contain a built-in bias when the tank is down to 1/4 or so. If a blocked vent is capable of creating fuel starvation I would expect low fuel pressure which should, in theory, go up if the gas cap is opened to let the air pressure in the tank equilibrate with the ambient air pressure. Further, I would expect that everything fuel-related would not be working optimally until after the gas cap was removed, then screwed back in place. This could easily result in the "necessity" of replacing a lot of expensive components when the real culprit might simply be a plugged fuel vent. I would ask my mechanic (or I would myself) check fuel pressure without loosening the gas cap, then again after having loosened it to see if there are any differences. Any difference in results would raise a red flag leading to checking the vent operation.

4) The venturi siphon system doesn't use suction to draw gas, it uses the difference between the pressure at the lower-pressure venturi and the higher-pressure air in the gas tank to push gasoline up the siphon tube. The siphon works as long as the air pressure is higher that the pressure at the venturi, but should the air pressure in the gas tank drop to equal the pressure at the venturi, the siphon will stop working. Should the air pressure fall even lower - as it would with a plugged vent, and as more gasoline is burned - the siphon will begin to work in reverse, pulling gasoline from the side of the gas tank with the pick-up tube and dumping in into the side of the tank without it. Looking at a picture of the gas tank I'd have to guess that each "saddlebag" holds between five and six gallons of gas which is how much two of had in our tanks when we stalled out. I suspect that simply loosening our gas caps would not have "fixed" the problem because the possible total lack of gas on the pick-up side would mean that no gas was being pumped up to the engine and being returned to the tank where that returning gas is used in conjunction with the venturi to siphon the gas from the "other" side of the tank. It would actually require the addition of some gasoline to put the pick-up "underwater" for it to actually pump the gasoline that would be needed to make the siphon work. So much for testing this theory by simply opening the gas cap.

5) On the other hand, even with a plugged vent line one simple solution to prevent this problem from ever recurring is to stop every quarter tank or so, take the gas cap off, then screw it back on to get air into the gas tank. Crude, but effective. Ultimately, clearing the vent is the "correct" solution, but at least it's good to know why this problem is occurring in the first place and what to do to mitigate it short of replacing fuel system components unnecessarily, and at great expense.

6) I want to thoroughly investigate the specifics of the vent system on the Lexus GS-400 so that I can develop a clear idea of exactly how all of this is supposed to work. What if the vent has a spring-controlled check valve? Blowing compressed air through it could possibly ruin components in the gas tank. What if my vent line IS clear; what then? I'll post more as I discover it, my goal being to save members money on unnecessary repairs. In my case, this isn't a bad fuel pump that goes bad only on long trips 30,000 miles apart that magically fixes itself by adding a gallon or two of gas to the tank. And I would respectfully recommend to FrankT that he hold off on any expensive repairs until he has tested his fuel system as I recommended in paragraph 3, and further, to wait until I can do a little more research on how specifically the Lexus system is supposed to work.

Now, if anyone has any diagrams and detailed instructions on how this whole EPA vent system is supposed to work on a 98-2005 GS-400 I would be greatly obliged to you for any help. I'll also search the web for information, and once I have some solid information - very soon, I hope - I'll be testing this on my beast extensively to see what I can find, and reporting back in this thread. I want to believe that even complex problems can sometimes have simple solutions if you dig deeply enough, something all too common in my own engineering experience.

tiguy99

THIS is exactly why this forums needs a thanks button.
wow...just read it all and will also try the open & close gas cap
every 1/4 mile to see if it helps

recently i came across this check engine light codep0446 for EVAP and another for P0136 O2 sensor
Now it makes sense

Could the EVAP canister be the cause of our fuel gremlins?!When my car stopped, no check engine light came on.
Wasn't until about a week or so later.

What could that mean?

Paul1307

If, and it's a big "if" the car is gas-starved any code you get is likely to be bogus. As I said, a Lexus mechanic told me that.

I've spent the last two days looking at diagrams of the emissions control system and searching the web for any information on the operation of this system with very little luck even though I have found some pretty detailed service manuals. Not one has mentioned the "running out of gas with five gallons in the tank" issue. I also found out that the cannister with all the gizmos on it are located above the rear axle in an area you can't get at without putting the car on a lift, so I won't be doing any testing.

From what I've been able to find, canisters rarely go bad though it is common for Lexus to replace them when the problem is actually the VSV (Vacuum Switching Valve), which is replaceable. Canister = about $900!

Nobody seems to get the CEL though. There are error codes associated with different canister problems: P0440 (leak in the fuel tank or open gas cap), P0441 (Vapor Purge Flow), P0442 (small leak in gas tank), or P0446 (Canister Leak Detection or Three-Way VSV failure). But, no CEL then no error code.

I'm sticking by my theory until something better comes along, but (LOL) I think I'll loosen my cap up every 1/4 tank or so... if you know what I mean...

On the other hand I did find some stuff on programming keys without going to the dealer which I'll post maybe tomorrow - very cool if it works!!!

Mcon

iTrader: (1)

[QUOTE=tiguy99;9598255]THIS is exactly why this forums needs a thanks button.


tiguy99,

I was the first member that said, where is the like button Or was you . I'm 100% agree with you friend.

Paul, Excellent Theory

tiguy99

[QUOTE=Mcon;9598678]
Thanks Mcon!
Yes I think it was one of us lol
Yes we REALLY need that button. Can't say it enough.
Paul''s theory seems spot on.

This thread should be a sticky.
As for me, I'm strating to gather parts for my next service appt. Will definitely grab a vsv valve and see if the siphon hose can be replaced.

I'd rather replace the entire pump assembly with fuel filters for peace of mind but before I do that I will try the gas cap whoosh test and see how that goes.

Thanks guys

Paul1307

One more small thing: In some threads there is some concern about letting a tank go below a half-tank out of concern that the fuel pump won't be properly submerged and thus being cooled by immersion in the gasoline. The pump sits up pretty high in the tank, so there is some legitimate concern there, but from what I've seen of Lexus vehicles, if the designers put the pump that high then I'll accept that they know what they're doing, and why. My suspicion is that they count on the cooling effect of the continual and constant flow of gasoline through the pump for cooling rather than the immersion of the pump. I don't think I'd worry too much about running a tank below half-way other than the possibility that fuel starvation might occur.

On that note I'd like to point out that three out of the four times this has happened to me I had been driving for quite a few hours without stopping, on an interstate, and that equates to basically in a straight line for hours on end, never encountering curves tight enough, and certainly not corners, to cause the gas to slosh around in the gas tank as would be more normal in city driving. I'm still going to loosen the gas cap at the half-tank point regardless.

Tiguy99: if while you're doing all of that you get a chance to check out the cannister there is one thing you can do. Pull off the vent line and see if, with the gas cap off, you can force or blow some air through it. I've tried to attach a jpeg of the vent line - we'll see - and here are the instructions for taking it off:

"Push connector on vent line hose toward charcoal canister and pinch both sides of retainer on connector, and then disconnect vent line hose with connector from charcoal canister." It should not take much air pressure to blow air through the gas tank and out of the opening where the gas cap would normally be screwed it; be sure gas cap is removed before doing this. According to the second diagram (the EVAP system) there is supposed to be a check-valve in the tank on the vent line as well as another check-valve labeled "vacuum check valve." What I can't see or find is any mechanism for relieving the vacuum in the gas tank and letting its air pressure approach ambient air pressure, which seems to me to be what causes the problem since that check valve pictured in the gas tank would seem to prevent air from getting into the tank as fuel is burned off. All a bit confusing, and I think I'll have to write to Lexus America to see if I can get any more information. The other possibility might be that the gas cap is supposed to "breathe" a bit when the vacuum in the tank reaches some certain point, but my cap is a Lexus part and doesn't seem to have any mechanism for that either.

Mcon

iTrader: (1)

Paul,

I do the gas cap whoosh test and I did not hear that whoosh sound. This issue start already for several week ago and I did not hear that whoosh sound when I try to fill the tank. I'm having occasionally idle problems. I go to the dealer and buy a new gas cap and nothing change. Maybe is one of the valve on my gas tank that is bad. BTW, filter for the pump are less of one year and not CEL light come one. Also, I double check with my tester.

eicca

Subscribed. I haven't personally experienced this but I'd like to be armed with the information.

Also, I noticed one or more members mentioned that their problem occurred after lots of highway driving. My 1999 Land Cruiser will develop evap issues after lots of highway driving as well, but it's only a terrible smell and thankfully not a problem that leaves us stranded. But the parallels are there: The evap system stops working after lots of highway driving. I'd wager a good bet that the systems are extremely similar as they use sibling engines, share a lot of common design features and are the same overall generation of vehicle.