Please help before I lose my mind! Fuel Problem.

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Hawkdriver

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I am about to lose my mind. Here's the story. I have an 02' Boxster S. I fill the tank, and it gets completely full... of course, only after manipulating the stupid pump handle to get the tank full as it shuts off every 2 to 3 gallons.... but I digress. I drive the car thereafter, and it runs perfect! Until.... just below 3/4 tank... should be approximately 4 gallons remaining. And then the car acts like it has freakin' water in the gas.... it quits, or stumbles, and shuts off for a moment, only to catch again... I though...ahhhh, I got water in my gas. So I put some fuel treatment into the tank that is the anti freeze/remove H2O from you tank stuff... I've used this in the past on various hoopties I've owned in the poorer days.... haha. I ran a couple tanks this way, being sure not to get below 3/4 tank.... and today was the day off to experiment by driving below 3/4 tank between to strategically located gas stations. Oh, I forgot to mention that when this crap happens... just a single gallon of gas, and the car runs like new again.... anyway... today, at just a tad under the 3/4 tank level... the car freakin' died, and absolutely would not restart until I put 2 gallons of gas into the tank... than like new again. I called someone that has worked on my car before... too far to drive at this point to be practical.... and he suggested maybe the fuel filter was clogged or the fuel pump was on the way out. I just finished searching every Boxster forum I could find, and the impending signs of fuel pump failure are nothing like this at all... But putting in a fuel additive does nothing! HELP!!!! I'm going to sit here and drink Sam Adams Cherry Wheat until someone replies! I'm going nutz! Thanks in advance.

Scott
Napa, CA
 
Stupid question for my own understanding:
You write that at 3/4 there should 4 gallons remaining
The Boxster has a 16 gallon tank....
 
Please read carefully....

ChrisZang said:
Stupid question for my own understanding:
You write that at 3/4 there should 4 gallons remaining
The Boxster has a 16 gallon tank....
Click to expand...

At 3/4 GONE, there should be approximately 4 gal. remaining. Let's please stick to the topic, and not argue semantics.... especially when I already admitted I am well into my 6 pack of Sammies. Thanks.
 
Quick question. If you remove and replace the gas cap does it then run?

The fact that you have trouble filling up may indicate a vent issue.
 
I replaced the gas cap shortly after purchasing the car as the o ring inside the gas cap was dry drotted... car runs perfect so long as I don't go below 3/4 of a tank of gas.... it was the dry rot on the gas cap that lead me to believe that there was likely water in the gas tank. .....
 
I just realized what you were asking... yes, today, when the engine quit, I unscrewed the gas cap, and screwed it back on... made no difference... would not start until I put in new gas...
 
Hmmmm.... maybe I need to supply more specific information.... gas in the tank. completely full. drive... until only 1/4 tank remains. than engine dies, until I add a minimum of 1 gallon of gas... than runs perfect.... like a stallion. changed the gas cap shortly after buying the car... this problem existed since I bought the car... so the problem was before AND after I changed the gas cap... just won't run at all when the gas level is below 1/4th tank.
 
Wow, pretty snippy for someone asking for help....:confused:
Getting the "semantics" straight, helps us help you:)

It may be a venting issue since you say you have issues getting gas into the car. I had a similar issue and had to have the flapper valve in my gas tank filler neck modified. There is a TSB about this issue.

Or you have a tank fuel pickup issue...sounds as if the pickup has been raised in the tank creating what would be similar to being out of gas. Perhaps it has come loose or was repositioned somehow incorrectly.
 
Sorry for the snipping... I AM losing my mind...haha... please tell me more about the pickup... could this come lose somehow and raise in the gas tank? How on earth can I fix that?
 
Not sure....you would need to take it to a shop....but it sure sounds like a pickup issue to me.
Would seem if it were a fuel pump going bad, it would happen intermittently at any fuel level.
 
I agree that it really doesn't have the 'bad fuel pump' feeling ... is it possible I could have that level of contamination in my fuel that it could cause this... or is the good money betting on the bad pickup? I currently have a full tank of gas... if it's contamination, could I siphon the top 4 gallons off to get the floating contamination out? Is that possible without doing damage? Just as an experiment? And if that doesn't fix this, then I can rule out that bad gas, and go for bad pickup... Ugh. I'm frustrated. Thanks for the input.
 
If it were contamination I would think it would be happening at any fuel level since the contaminants would be mixed up at any fuel level....doesnt sound ,Ike bad gas either...if you had that much contamination your fuel filter would be completely clogged along with a few injectors I would think.
 
OK - how many gallons do you put in when you fill it up? You really could have two separate problems.

1) I'm betting you've got a bad fuel gauge or sending unit and when you think you're at 1/4 tank you are actually running on empty. This would also explain why adding one gallon solves the problem.

2) Unable to fill the tank all the way. This has been a problem for others previously and it may not allow you to top off the tank. This would answer why you can only add 11 or 12 gallons to fill up.

Having two problems is an easier explanation (think Occam's Razor) than trying to figure out how your pickup got bent. See the attached PET capture.
 

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My SWAG would be your sending unit is faulty and the reason your getting so many diverse answers is its difficult to diagnose problems from an arm chair, so my advice is take it to a good mechanic. Since you're in Napa you might try Baldwins in Novato they're good and thorough.
 
Tom M said:
OK - how many gallons do you put in when you fill it up? You really could have two separate problems.

1) I'm betting you've got a bad fuel gauge or sending unit and when you think you're at 1/4 tank you are actually running on empty. This would also explain why adding one gallon solves the problem.
Click to expand...

Yup, that's my theory as well
That's why I asked about 3/4 full vs 1/4 empty
 
I have the same problem

I have the SAME EXACT problem you have, 1/4 gas left in tank and it runs like it is "out of gas". My fix is that I don't run the tank below 1/4;) I think it has something to do with the pick up of the fuel/bad fuel reading too, but I am not going to spend any money to solve the problem, just re-fuel more often - besides gives me a reason to have women come up to me at he gas station and ask me about my cool car!:cool:
 
There is an issue with some Boxster fuel gauges that has been discussed here and on other forums. My fuel gauge never read full even after topping off, which is not recommended, but my tank takes another two gallons of gas after clicking off. I replaced the sending/float unit and had the PS2 calibration done, which involves more than just hooking the computer up. The tank has to be drained and a set number of gallons of gas have to be put back in the tank then the computer calibrates. The whole process set me back around $700 and my gauge still goes not read full so go figure.:eek: I would think that calibrated or not your red low fuel warning light would come on, mine did before and after the calibration process.
 
As I read through these posts, my first impression was also a faulty gauge reporting 1/4 tank when you're actually empty, however, the one time I ran out of gas in the Boxster (momentary stupidity on my part), it scared the crap out of me. The engine started to studder horribly, then the CEL light started FLASHING. I thought I was experiencing the dreaded IMS failure. I pulled over and realized I was out of gas. I was able to walk home, grab the can and add enough gas to get me to the station. When your car quits, do you get any CEL on the dash?

I can't imagine running out of gas without the computer logging some nasty code(s).
 
Ok, here's the end of the story... Took the car to a local guy I know to have the fuel drained... either way, it needed to be done. It was either contaminant in the fuel, or some component associated with the fuel delivery system. He tapped into the fuel line, put a jumper in the fuel pump relay, and started pumping all of the fuel out of the fuel cell. It drained until it got to 1/4 tank remaining (where I had the problem), and would drain no more fuel at all. Curious. We popped out the battery, opened up the fuel cell, and took a look inside. Looked good. Nothing unusual. Fuel looked clean. Pump was still secured to the floor of the fuel cell where it was supposed to be... So, we pulled the pump out. Here's where it got interesting. The fuel reservoir, which should have been empty as the fuel stopped pumping at 1/4th tank remaining, was completely full of fuel. We popped open the reservoir, and pulled out the pump mechanism.... and looking down into the gas, there was some black plastic debris. We shined a flashlight into the opening at the bottom of the pump, and it was clear to see that the entire bottom row of impeller blades on the pump had broken off.... So the pump could only draw fuel down to the 1/4th remaining point, and would then be unable to drain the reservoir... I popped in a new fuel pump, and not adding a single drop of extra gas, it fired right up, and ran perfectly. So there you have it. I called every Porsche dealership service department in N. Cali., and was given the "hmmm, I've never heard of anything like that... I have no idea what the problem is...." I guess this isn't the typical symptoms for a failing fuel pump... so I thought I would share so that if this happens to anyone else, you'll know exactly what the problem is. Thanks for all the feedback everyone provided! Take care.

Scott
Napa, CA
 
I just went back and reread everyone's posts. Quick afterthought.

Blubox 03: You probably have the same problem I had. If it would be helpful, I can take digital photos and post so you can all examine the damage to the impellers in the bottom of the fuel pump.

Boxsterbob: Never once got a CEL out of this. Haha.

offshore: Thanks for the referral... I'll go see these guys next time. I HAVE been having trouble finding someone closer than Alden in San Jose.

Tom M: Thanks for the diagram. It helped when I took this mess apart.

And findally, the winner is....

Docdanracy: It was a pickup issue. Haha. For the reasons noted above.

Thanks everyone!

Scott
Napa, CA
 
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