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Old 12-18-2009, 07:37 PM   #1
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Waterlogged 99 Boxster

Ok, I've been driving the boxster to work this week because the Jeep needed a new plug and I hadn't had a chance to replace it yet. It's been a torrential downpour since last weekend. The cars been running like a top all week regardless. It's been putting the jeep to shame really. I got the low fuel light on the way back from lunch thursday. On the way home, I stopped and filled it up. It was on for maybe 10 miles. I stopped and put almost 14 gallons of premium in it. I made it maybe 50 feet before I started losing power. I pulled back into the station. It idles rough for a few minutes then stopped. I started it again, it idled again for a few minutes, then nothing. Now it turns over but doesn't pick up.

So far I've verified no blown fuses. I don't have a CEL and didn't have any warning lights when it was still running. There haven't been any problems or any recent maintenance. I tried to sample the tank but can't get a siphon line in far enough yet.

I assume it's bad gas and either I have enough water to prevent it from running, or I've sucked something in and clogged the filter. It's also so full that I can't get a significant amount of alcohol in to dry the gas out. My plan tomorrow is to get it up in the air, change the filter, and in the process drain the lines and the bottom part of the tank. I figure it's not an electrical issue because there were plenty of oppurtunities for that to occur earlier in the week. Does anyone have any other suggestions?

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Old 12-19-2009, 07:19 AM   #2
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Call the station

you got it filled at and ask in a non-confrontational manner if they have had any reports from others. See if you can pin-point the cause before you start trouble shooting.


Also plan on where you'll dump 14+ gallons that could blow up a sewer if dumped there.
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Old 12-19-2009, 12:50 PM   #3
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I asked and they hadn't received any complaints, but the woman behind the counter was pretty clueless as to whether or not anyone have gotten premium gas in the last few hours.

I hooked up the durametrics and it said there was a p0102 (porsche code 115) error. Anyone know if this sounds like a root cause, or just a symptom of me trying to get it to start?
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Old 12-19-2009, 05:18 PM   #4
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Someone smarter than I can chime in - but Google says those are MAF codes. My understanding is that you can disconnect the MAF and try starting it to see if the situation improves - if so, maybe just a bad MAF.
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Old 12-20-2009, 04:32 PM   #5
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Remove the battery.

Remove the tray under the battery.

Remove the hose on the fuel pump outlet.

Attach a spare hose to the outlet and siphon out enough gas to check for water.
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Old 12-21-2009, 08:21 AM   #6
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waterlogged

Just for fun.. if it's been raining that much, check under the drivers seat and see if it's wet?? lost my control mod due to water. It controls a ton of stuff. If it's wet water will enter the box from the back side lower plug and ground things out. It can be causing the alarm to kill the spark. Engine will still turn over but will not crank.
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Old 12-30-2009, 02:39 PM   #7
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It is probably bad gas. I had the same problem about 2 months ago.

Car has been running fine. On the way to work I stopped at the gas station (Shell - always go there) and filled it up with premium. Aproximately 2 miles down the road my car started backfiring, shaking, and wanted to quit running. Made it to my dealership where they put it on their tester. All cylinders were misfiring and errors all over the place. They kept the car for several days and compared with readings of another Boxster. Finally put in a can of Octane Booster and observed it for awhile longer.

Bottom line - bad gas. Cost me $400.
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Old 01-23-2010, 02:41 PM   #8
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Just geting back to weorking on this. I disconnected the MAF and had no change in operation. Engine still rolls, but doesn't catch/no combustion.

Last edited by ARModen; 01-23-2010 at 02:43 PM.
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Old 01-23-2010, 03:33 PM   #9
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Ok, so further investigation leads me to believe the fuel pump is bad or plugged up. I disconnected the line on top of the tank and attached my siphon line. I then hooked up the battery and turned the car on expecting to use the fuel pump to pump down the tank. Nothing came out. I tried with my siphon hose attached to each line and same result, no flow. Not particularly the safest operation, but if it was bad gas, using the fuel pump to pump the tank down would be the fastest fix.

I checked the fuel pump fuse (C4) fuse wasn't blown and that there is 12V there. There doesn't seem to be 12v across the plug on top of the tank though.

So either it is the fuel pump and I'm not reading the plug right, or maybe theres some relay in the circuit to control the fuel pump that I'm missing. My ancient 911 fuel pump pumps till the fuel rails are full then stops by itself.

So if there is anyone thats familiar with the fuel system I have a few questions:
1. What would prevent gas from pumping out of one of the three pips on top of the fuel tank?
2. Is there a relay somewhere between the fuse box and the pump?
3. What should I be seeing across the pins of the plug on top of the fuel tank.
4. Mostly importantly, how on earth do you get that ring off there to get the pump and level sender out?

Last edited by ARModen; 01-23-2010 at 05:12 PM.
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Old 01-24-2010, 12:21 PM   #10
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Apparently there is a relay. Now I need to find it, and see if it's bad or if it's indeed the computer or alarm system thats disabled the pump.
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Old 01-24-2010, 12:55 PM   #11
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As always use at your own risk:

I would apply 12v to the fuel pump (plug unhooked) to the terminal that is fed by the gn/wt wire and ground the terminal fed by the br wire.

There are 2 relays involved:

fuel pump relay in position 13 on the relay panel in the left foot well.

the MFI/DI relay in position 1 on the relay board on the left side of the firewall in the rear trunk.

the pump is fed by a 25 amp fuse in c4.
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Old 01-24-2010, 01:01 PM   #12
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VW special tool 3217 is used to remove the fuel pump. Spec is 52 ftlb so it is tight.

The fuel pump relay can be jumped by connecting posts 30 and 87 (3 and 5).
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Last edited by Paul; 01-24-2010 at 01:18 PM.
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Old 01-24-2010, 01:19 PM   #13
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Thanks Paul. I did some more checking, I checked the fuel pump relay and it was good, but when I jumpered it out and turned the car on I can now hear the fuel pump running. I'm charging the battery on the charger now and I'll see if it starts up. The fuel pump runs continuously right now even when the ignition is off so this can't be a permanent fix.

So now the question is where does the control signal for that relay come from?

D Williams said:
"Just for fun.. if it's been raining that much, check under the drivers seat and see if it's wet?? lost my control mod due to water. It controls a ton of stuff. If it's wet water will enter the box from the back side lower plug and ground things out. It can be causing the alarm to kill the spark. Engine will still turn over but will not crank."

So next place I'm going to check is under the seat. I don't see any water or water marks behind the drivers side, but maybe I go some in around the doors considering the weather that week. I believe that's the alarm control module. The durametrics thing didn't report any errors in any control modules so maybe it's just a bad wire.
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Old 01-24-2010, 01:23 PM   #14
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http://www.samstagsales.com/vwaudi2.htm#fuel
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Old 01-24-2010, 01:28 PM   #15
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Haha, that's a $300 factory tool! Only Porsche...

Luckily I shouldn't have to get into the tank now as long as I don't burn up the pump with my current set up. Battery is almost charged then I'm going to start back tracking the control signal for the relay.

Any tips?

Last edited by ARModen; 01-24-2010 at 01:31 PM.
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Old 01-24-2010, 01:32 PM   #16
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The DME through relays 1 and 2 in the rear and relay 13 in the front are all needed for the car to start.

FP relay control is pin 63 on the DME
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Last edited by Paul; 01-24-2010 at 01:39 PM.
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Old 01-24-2010, 01:43 PM   #17
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Quote:
Originally Posted by Paul
The DME through relays 1 and 2 in the rear and relay 13 in the front are all needed for the car to start.
But will 1 or 2 in the rear turn off the fuel pump? I'm going to start it in a sec here when the battery charger is done, but I assume the ignition system is working and I'm getting a spark because it was running poorly after the problem arose. So I think it was firing but becoming fuel starved.
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Old 01-24-2010, 01:44 PM   #18
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Quote:
Originally Posted by ARModen
Haha, that's a $300 factory tool! Only Porsche...

Luckily I shouldn't have to get into the tank now as long as I don't burn up the pump with my current set up. Battery is almost charged then I'm going to start back tracking the control signal for the relay.

Any tips?
right above the real one is a $134.50 alternative.

Note that this is a VW tool, oh wait VW owns Porsche....
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2001 Boxster bought new. Installed used motor at 89k.
1987 924S . 2002 996TT. PST2
Owned and repaired Porsches since 1974. Have driven them all the way the Dr intended...

Last edited by Paul; 01-24-2010 at 01:47 PM.
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Old 01-24-2010, 01:50 PM   #19
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Have you checked the alarm computer under the seat to see if it got wet?
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Old 01-24-2010, 01:58 PM   #20
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The fact that they'd make a $300 tool for this instead of just just putting a flanged cover with a few bolts on it is pretty amusing. The 911's has a gasket and 4 screws.

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