Porsche Repair: 1981 911sc fuel injection, inline fuse, fuse block

Question
My car is a 1981 porsche 911.  In the AM or anytime it has sat a while it is VERY hard to start, and doesnt want to run.  I assume this is some kind of fuel injection issue but dont know where to start.  I just got it running again after a tow home, it was the fuse to the fuel pump, actually the conection on the fuse block was too coroded to use so I wired it with an inline fuse and at least it runs again.  BUT, my problem is the crappy running at start up.  Any suggestions are very welcome. Thanks, Tim

Answer
Gosh Tim,

This is like asking why your wife unhappy with you?  Let me count the ways!

For an '81, there are many possibilities, ranging from simple ongoing maintenance issues like fuel filters, air filters, etc....to a tired fuel pump or tired injectors...and finally to the inner workings of the computer that controls all this black magic.

When you indicated there are some corrosion issues around that fuse block it made me think immediately of the first topic...basic maintenence.  Sure, a dirty fuel filter, for example, wouldn't by itself cause your hard starting, but that in combination with another small problem certainly could.  Same thing with a tired fuel pump.  It could be supplying enough pressure to keeping the car running once running, but starting it could be dicey.  And do you know how many volts are getting to the starter when you hit the key.  12.8 volts?  10.9?  9.3?  

I'd suggest the following to start:

1.  Remove the OEM fuel filter temporarily (if its old, throw it away.  Replace that section of tubing with a hard line and some clamps.  Find a suitable location in the engine compartment and cut into the fuel line flexible tubing/hose and add TWO fuel filters.You can buy two very inxepensive but perfectly good FRAM fuel filters at your local parts supply store.  Buy the universal style that are plastic and clear so you can look at them and see or not see crap in your fuel lines.  You can buy them in 1/4" or 3/8" inlet/outlet sizes to suit your needs.  Obviously, when the hard starting problem is fixed, you can remove these perectly good and easy to see fiolters and replace that very expensive 911 OEM filter when you'd like.

1a.  While the line is open, install a fuel pressure gauge permanently, its kinda cool looking...or at least temporarily, and measure the fuel pressure right there close to the intake.

2.  Change the air filter.

3.  Do a tune-up.  Change the plugs and their wires and the cap and rotor and anything else you feel comfortable renewing...so you know what's NOT a possible issue.

4.  Measure the battery voltage after the car sits for a typical "while".  If it's not 12.8 or pretty close at rest, (14.6 running), that car will never start.  Carefully and with a close friend figure out how to put your voltage tester on the battery terminal of the starter and measure the voltage at rest and when it's cranking.  At rest the voiltage should be exactly the same as the battery voltage.  While cranking, it should also be exactly the same as the battery voltage measured at the battery when the starter is cranking.  If there's any discrepancies, I'd renew the wiring... or at a minimum, undo the wiring and clean the terminal ends very, very well.

Please write back with any questions from the above before you do something... in case I've not been clear.  Otherwise, write back after you've completed some steps and let me know your progress.

Dave