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99 986 lost power then died. Nothing else seems to be wrong.


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I filled my car up in the rain the other day. Before this it had been running flawlessly. I made it maybe 50 feet and started to lose power. I pulled over and it idled roughly for a few minutes before it died. It seemed very similar to problems I had with a bad fuel pump ground on my ancient 911. Thinking I had just gotten a little water in the gas I turned it over again and it ran for a few more minutes then died. Now it cranks but doesn't catch. I had it towed home.

So far I've checked the gas and there's no indication of water. I checked that the fuel pump relay turns on the pump when the engine is cranked so that seems to be in order. I have checked the pump connection and the test connection on the fuel rails and there is pressure at both, so I believe the filter, regulator, and pump are all working for the most part. I have a durametrics cable and currently have no active faults on any modules. I have left the battery disconnected for several hours, and grounded the positive lead to discharge any capacitors in the car. I've looked at the top of the engine, the alarm module, DME, and tiptronic modules and other than the dust of 10 years there is nothing obviously wrong with any of them. Everything else in the car works; lights, windows, top, alarm, remote locks, etc.

It had it's 90K service done by me and the dealer, and a new water pump, about 8 months ago. I'm running out of things to check. This weekend I'm going to pull the throttle body and make sure I didn't suck up a bird or something, and replace the ignition switch just in case. Anyone else have any suggestions? There aren't any Porsche dealers in town anymore, and I haven't found a real porsche savvy independent guy yet.

Edited by ARModen
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I attempted to start the car with starter fluid (not the BBQ variety) injected into the throttle body. I also checked battery terminals and replaced the ignition switch. Still nothing! The first time I try to start the car it vrooms like it's going to work then immediately goes back to the whir of just the starter.

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I have the Durametrics cable. There are no active faults. There were a few stored faults; a MAF fault and an immobilizer fault. I don't remember the exact code numbers off the top of my head.

I was told a MAF fault could be checked by disconnecting the MAF to force the DME to use a different fuel map which would allow the car to "limp home." There was no change when the MAF was disconnected.

From what I read, the immobiliser signal to the DME is supposed to disable the fuel pump and injectors to prevent the car from being drivable if it's stolen. I checked the pump for flow and the injector signal with noid lights and both seem to be working properly and I have fuel pressure at the fuel rails. Also when I was fiddling with the ignition switch I'm pretty sure I tested the proper operation of every alarm in that car!

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Since the engine will run with the help of some start-pilot, the ignition looks O.K. Your problem seems like a faulty fuel pump or clogged fuel filter to me, to be sure you will have to (let) measure the fuel pressure and flow capacity.

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The problem came on very fast so a broken wire, bad switch or broken hose all seem likely. I don't think it's too serious because there was no bang, and no massive discharge of oil or smoke. It's something simple and I'm going to be kicking myself when I find it. Where would an air leak cause all of this?

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Had to take a week off from working on the car. I've replaced the fuel filter, no luck. I removed the throttle body and idle air valves and cleaned both. They seem to be working properly. I spent an hour or two playing with durametrics softwre and couldn't find anything wrong. It just cranks and doesn't catch.

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I tested the fuel pressure. I was getting 360kpa (55psig) while the fuel pump was running. It was bouncing +/- about 10 psig while I was cranking the car. After I bled the fuel lines a lot I managed to get the engine to catch for a few seconds (2-3) before it would die again.

I am really about out of patience with this car.

Edited by ARModen
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When you flushed the lines, did you flush it with gasoline from a source other than your fuel tank? If so, it's interesting that the engine ran for a moment on the fuel used to flush the lines but not when it started getting fuel from your tank. You said you tested for water, but maybe it's in some other way sub par.

Another thing...you describer your starter sound as a "whir." Is this a sort of free spinning electric motor whir, or a chug chug engine turning over but not firing whir? A weak battery can cause the starter to spin too slowly, meaning the bendix doesn't engage or releases the engine too soon. That free spinning whir might mean it's time for a jump and/or new battery.

Edited by secretagent214
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When you flushed the lines, did you flush it with gasoline from a source other than your fuel tank? If so, it's interesting that the engine ran for a moment on the fuel used to flush the lines but not when it started getting fuel from your tank. You said you tested for water, but maybe it's in some other way sub par.

Another thing...you describer your starter sound as a "whir." Is this a sort of free spinning electric motor whir, or a chug chug engine turning over but not firing whir? A weak battery can cause the starter to spin too slowly, meaning the bendix doesn't engage or releases the engine too soon. That free spinning whir might mean it's time for a jump and/or new battery.

No, I can definitely tell the difference between a loaded and unloaded start motor. I bled the lines through the pressure tester. So it is tank gas. And it might be bad gas of some sort. However I took a sample of the gas and allowed it to sit to check for oil/water separation. I also frozen the sample as water in the mixture should precipitate.

I did notice that my oil light is not going off when I'm attempting to start the engine. I hadn't really noticed it before as there are some lights that are on continuously until the engine starts. It should be out once oil pressure is sufficient from the pump. I know I use it when refilling the sump on the 911, but never really had to look at it on the 986. I know there is sufficient oil in the engine. Is it possible the oil pump is bad and that's effectively disabling the valves due to the hydraulic lifters?

My uncle shot this down as it should cause a noticable amount of noise fromt he lifters if they were air bound.

Edited by ARModen
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  • 1 month later...

Bad gas after all. Very odd, but dumping the tank and flushing the lines with fresh gas fixed it. Car started right up and idled right away. It's popped and idled rough a few times getting the rest of the crap out, but after a good drive down the highway everything seems to be working again.

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Any possibility it was Diesal, I filled up once with this gave similar symptoms.

I thought the same thing. I went back and checked the receipt to make sure too. Apparently not. I got charged for 14 gallons of 92 octane. I don't think the nozzles fit the same, but I'm not sure.

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If ethanol (alcohol) is added to the gas in your area, it is possible that they could have accidentally mis-mixed the gas with grossly too much ethanol. If E-85 "flex fuel" is sold in your area, then you might have gotten some of that by mistake. If you still have some of the "bad" gas, you can check for ethanol concentration fairly simply: find a small graduated cylinder and add a small quantity (5 ml) of your suspect fuel. Then add exactly the same quantity of water, cap the cylinder and shake it up. Let it settle, then look at how much "gas" you have on top (typically yellowish) vs how much "water" you have on the bottom. Any ethanol in your gasoline will be pulled out of suspension from the fuel and will be attracted to the water. For example: if you then show 4 ml of "gas" on top, and 6ml of "water" on the bottom, then your fuel was probably 20% ethanol. Your Boxster should run fine on 10% ethanol, but when the concentration goes a lot higher there will be problems.

Edited by Blue-S
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