Fuel system

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Fuel system

Postby anedarado on Mar Wed 31, 2010 4:34 pm

So my Porsche is acting up, its never seen a winter, always been garaged and only at 61k miles. it ran like a dream for a while, i put a little over 500 miles on it and no problems. I put some jb injector cleaner in the gas tank (not sure if its related). About 2 days later i drove about 5 miles, parked it, then when i tried to drive home it just had no power. Now the thing idles fine but as soon as ya give it any gas it just doesn't do a thing, except for a sort of loping thing but no power. I figured the fuel filter was clogged because of the injector cleaner so i changed that but it still does the same. if i let it sit for a bit i can get the rps up for about 20sec then it gives out again, but it still idles fine. :banghead: it has a in tank fuel pump and one just outside the tank, maybe one is failing? injectors clogged? i checked the plugs brushed em and checked em w/ a timing light. Any suggestions???
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Re: Fuel system

Postby Roadhog on Mar Wed 31, 2010 5:42 pm

fuel pump screen?
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Re: Fuel system

Postby Mikewire on Mar Wed 31, 2010 7:27 pm

Do you have a valve on the end of your fuel rail (kinda like a schrader valve on a tire)? If so turn on the ignition and open the door and with a rag at the valve and if you get a bunch of fuel your pump is providing pressure.

That's how I would test a pump on an Audi or VW, I have no idea on a Porsche so I could just be talkin'.

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Re: Fuel system

Postby ValveFloat on Apr Thu 01, 2010 8:23 am

I don't recall for sure if the 944 has a flapper style air flow meter, but if it does you could check to make sure its not stuck, or sticking.
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Re: Fuel system

Postby Darkside on Apr Thu 01, 2010 10:52 am

Intake leak or CIS problem??
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Re: Fuel system

Postby anedarado on Apr Fri 02, 2010 3:24 pm

I just borrowed a working fuel pump from a mechanic friend, hooked it up and it ran the same way. Now i know the problem isnt the pump. I also made sure gas ran freely from the tank to the pump to make sure the pump wasnt being starved but that too was fine. I checked the intake, plugs, wires, and the throttle controll, all fine. I find it slightly odd that the fuel line runs straight from the bottom of the tank, to the pump, then to the filter. Im assuming there must be some kind of sock or filter in the tank to protect the pump. From what i can see there isnt another pump in the tank, looking at diagrams and such.. Could it be my injectors? im stumped :retard:
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Re: Fuel system

Postby Mikewire on Apr Sat 03, 2010 12:23 am

You know, what you described sounds a lot like a vac or pressure leak somewhere - have you gone through and inspected all the hoses and vac lines? And like ValveFloat said, maybe check the air flapper?

Almost sounds like it's starving for air, since you know that the pump is good and it is getting gas.

Mouse nest in your intake :unibrow:

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Re: Fuel system

Postby Rennwagen1 on Apr Sat 03, 2010 11:25 am

I agree. You need 3 things for combustion, Fuel, Air, Spark. If you have two, you need the third. I would check air intake system/vac system also
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Re: Fuel system

Postby kompressorgolf on Apr Sat 03, 2010 4:49 pm

may have got a bad batch of gas too, it can happen!. i would check fuel pressure, first and foremost. sudden problems in my experience have been fuel pumps, happened to my truck a month ago.
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Re: Fuel system

Postby anedarado on Apr Wed 07, 2010 10:05 pm

Thanks for your help guys. Finally found the weak link! It was my throttle position sensor. Jeez that took some thinking. The best idea we can figure out is I got it wet when i washed it and then it froze that night. gotta love montana weather. :laughing:
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