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Followup To
Question -
I have a 1984 Porsche 944 that I just purchased off a friend. It would not start. I diagnosed that it was not getting spark. I replaced the DME,wires,coil,plugs,cap,and rotor. The parts are all stock replacements. I re-soldered the DME relay according to directions from a Porsche repair issue stated on their web-site. I changed the fluids. I added dry-gas/octane booster to see if it was a fuel quality problem, but once it starts it idles and runs fine. The car will not start without a "whiff" of starting fluid. Once it starts, it runs like a champ. Idle, fuel,oil,electrical all show signs with spec. It drives fine once it is running. It will not restart once it is shut off, whether cold or hot without a minute shot of starting fluid.. I also by-passed the temperture/fan relay to see if the sensor was a problem. It did not make a difference. This problem is keeping me from enjoying a nice daily driver. Any help would be great. Thanks,
Scott
Answer -
Scott,
Just to remind you, my expertise lies in the older 356 models. Luckily, many early designs/concepts have lasted since the early 50's and appear in revised forms on 911's, 914's 944's, Boxsters, etc. Where this happens I'll promise to try to give you the best answer I can.
You've done a great job getting your new baby to this point. I know how it feels to be so close to 'just right', but one little nagging problem keeps popping up. Have you thought of running a tube from the driver's seat to the engine so you can squirt starter fluid and get going without having the hood open? Sorry, bad joke. I've been trying to devise such a system for a truck I have that uses huge quantities of oil...anyway, more on that later.
You've got an air/fuel mixture problem. When the engine is running it generally requires much less fuel to air than when starting. Starting requires a 'richer' mixture. Hence, the positive result when you richen the mixture with starter fluid.
These engines are just complex enough to have multiple possible causes for this situation. I'd bet it's the throttle switch, but it could also be the air flow sensor. I'd be surprised if it was the fuel injectors themselves, but another culprit could be the fuel pressure regulator (fuel is arriving but not under enough pressure for starts).
Here's what I'd suggest. Go to your local auto parts store and find the Porsche 944 Automotive Repair Manual, published by Haynes. It's their product number 9U4-1027. I highly recommend this for someone like you. You'll quickly find it helps to resolve problems like you have now, and will quickly give you a deeper understanding of how the car is put together. Not that you'd want to, but with this manual, you could tinker with your toy all day long. It's well worth it. If you don't like the price at the parts place, I'll bet you could find the manual less expensively from booksellers on the net.
In the meantime, if you'd like to tackle the throttle switch first, let me know; it's a bit involved, but if you just can't wait for your manual to arrive I'll walk you though it. Use the followup question feature on Allexperts.
Good lick with your new toy. It sounds like you're well on your way getting full enjoyment from it.
Dave
Dave,
Thanks for your prompt reply and suggestions...alas, still the same problem. I purchased the book and followed the trouble-shooting guide for electrical and fuel. I've done the following in order ..:
Removed the TB and tested the throttle sensor/switch- ok. Eletrical measurement passed according to spec. Tested the air sensor...and cleaaned out the throttle body..Passed to spec. I then tested the engine temp sensor..passed. I tested the fuel regulator and when pinching off the return according to the book it went above 58lbs with a fuel pressure tester. Aha! bad regulator. Great. Purchased a new one , installed..no start. It's "hooked" on the starter juice. I also tested the fuel flow rate,pressure, and volume,.All met spec according to the book. Fuel injectors passed the electrical ohm test. Ohms were right on on each one. Same symptom, once it's running...like a top!. Two questions:
Could it still be the injectors even though they test ok? I'm stumped.
It does sound like air/fuel when cold/hot. I'm still chomping on the bit. Any other suggestions would be a great help!
Thank you for your time,
Scott
PS: The hook-up from the driver's seat is getting too close to happening....NAH!
AnswerScott, I was expecting you to say EUREKA!...I found it. This follow-up was supposed to to let me know all is well with the world. I'm thinking that if you buy starter fluid in bulk quantities, you'll have enough in case there's another oil shortage.
You have been an extremely busy and thorough boy.
At some point we do still have to consider the injectors themselves. I just checked Performance Products catalog and they have them for $100 each. But the seals are about $6 each. Given that the car runs fine after being squirted, I'd still assume the injectors are OK, except that the seals may not be. If there's a leaky one, it would contribute to your woes. Unfortunately, replacing the seals is one of those..."well I'm so deep into this now I might as well replace the injectors while I'm here"...kind of projects. But you shouldn't have to. You've definitely got the patience to change the seals and try the engine again with the original injectors. I'd do it.
I may be wrong but I seem to recall that some shops will test and/or clean injectors while they're out. You might check into this. One last idea I noticed while thumbing through the catalog...virtually EVERY other model in the Porsche line has a 'cold start valve'. Yet the catalog doesn't list the 944. The Haynes manual doesn't refer to it, but what if you have the one 944 with a valve installed...perhaps by mistake. First, it would be like finding a Lincoln penny with old Abe smiling...that 944 would be worth a mint. Oh yeah...with all this time you've put into her there's no way she'd be sold now.
Anyway, keep an eye out for a cold start valve, there's a picture of one here:
http://www.performanceproducts.com/ProductPage.aspx?productname=Cold+Start+Valve
OK, so now I've resorted to having you check for faulty parts that weren't installed on your car in the first place. I think you've stumped me. Am I on Candid Camera?
One last idea. Porsche owners are quite good about sharing common experiences. You may find a web-based forum at your local Porsche Club of America or 944 Club, or a 944 Registry. Let's bet you're not the first guy to be exasperated with this problem. Best of Luck
Dave
