could low vacuum cause no start?
07-06-2002, 11:50 PM
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could low vacuum cause no start?
i've replaced the fuel pressure reg. and the speed ref. sensor and numerous other parts, and checked all the ohm tests on everything in every manual i can get. spark plugs, cap/rotor, checked timing marks. i've held the air door open on the mass air flow while cranking. it will start for about 1-2 seconds and then flood out and stall. then after waiting about a day it will do the same (after it stalls it will only crank-i guess until the plugs dry out after a day). the tach moves fine when it starts. i've been given a lot of advice on numerous forums from some very helpful people but to no avail. could it be a lack of vacuum for the regulator, and if so what should i do to correct it? thanks guys-i sure appreciate all the help.--paul m.
07-07-2002, 12:02 AM
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no i haven't, and i also don't know where to find it. call me a rookie cuz i am. i have 2 good running bmw's (sorry to swear) and a lot of manuals on them, but with this non-running porsche i bought i feel totally ignorant. thanks in advance!(and in retrospect)-paul m.
07-07-2002, 12:20 AM
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go to the Porsche dealer and buy it - it is an updated 993 part and cost around $20. That is usually the FIRST thing to prevent these cars from functioning correctly. Best of luck,
07-07-2002, 12:33 AM
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when i got the car there was a box on the floor containing a dme relay that looks used but i don't know if the guy tried a new one or not. what i meant by "where to find it" was where on the car, but since then i looked by the fuses and found it. i'll try a new one and see if it helps. thanks again--paul
07-07-2002, 01:06 AM
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went out to check and the relay was replaced with the 993.615.227.00. so thats why the old one was still in the car i guess. any other suggestions would be very helpful!-paul
07-07-2002, 12:51 PM
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Try doing a compression check. Mine with 144K miles is 115-125 dry & 140 wet. It you do not have compression it will not run! Do you have spark when it is cranking? Check all four plugs, pull all the plugs out lay them on cardbord insulation so they do not spark. The one at a time ground the threaded part and crank the engine. You should see them sparking as the engine turns over. This will check the wires, cap, rotor, plugs etc. Assuming reasonable compression, spark and your engine is in fact flooding all thats left is the timing of the spark. Now you're back into the DME, sensors etc. I have not had any trouble in those areas 
so others can give better advice than I.
so others can give better advice than I.
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07-07-2002, 11:40 PM
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i'll borrow a compression gauge tomorrow and check that and the spark on each plug monday night after work. i've only pulled the front plug to check spark and thought that was enough but i guess i should check them all-that makes good sence. compression check should have been done already but i didn't have gauge.. how long should i crank each cylinder for reading?--thanks-paul m.
