78 SC starting issues

[rpo420]

I have a 1978 SC. the car was running well for a while, and then it would die and not run.. then run again, and on and off. I first replaced the fuel filter.. and the old one was clogged, you couldnt even blow air through it.. changed that and she ran great for a few weeks.. So i say to myself, you need Air, you need fuel and you need spark.

On Fuel. I bought the bosch book on CIS. Tested all my pressures. Control 74psi. Cold System 14 psi. Plunger moves freely. Blew out return line to the Tank. WUR has power to it when the car is turning over, but I didnt check the WUR and time it to change system pressure, but i pulled all the injectors and when you lift the arm the fuel pump runs and and the injectors have a nice spray pattern and each bottom had the same amount of fuel.. i was amazed how much fuel comes out in like 20 seconds.. So i say to myself you have to have enough fuel to start the car.. but still no start. Also before this all happened it was running really nice. it would cut out and come back sometimes while still rolling..

Ignition. So i think I have no spark.. I have a permatune CD box, put it in many years ago after stock CDI went bad. I have ready many call it permadoom. I called Lonnie and who is the guy in Long island who is the company guy who i actually bought it from but his voice mail box has not been set up and he didnt answer my e mails on how to actually test the Permatue.. Coil is american made permatune too. So today i took off the coil and bought a multimeter. I am not genius with electronics to note. When i looked inside the big hole of the coil i saw some blue type residue in there, cleaned it out with a dremil, cleaned all contacts to the connecting wire to the distributor as well. Distributer is immaculate inside as well. Tested the coil, outside 2 poles pos and neg i get .6 ohm.. i read thats what its supposed to be. When i test the ground and the inside circle i get 10ohms.. tech article said 600ohms.. tried to start it and she started for maybe 7 seconds. my excitement lasted so short! uggghhh....would have been too easy that just to clean a wire could have done this.. so i want to ask someone who knows 2 things.
1) i still have a spark if i take the wire coming off the coil and put it by a ground.
So can you still have a spark off the coil if the Permatue CDI box went bad?

2) Is the coil not producing a hot enough spark?

3) does anyone know if the permatune can be tested and if so how do i do it?

I need some wisdom here, and i will methodically go through anything that you think i should and will post shots and be quick about it.

any help would be greatly appreciated.

[casor]

Rpo - First let me say that I am not an expert on elec ignition here but I can offer advice on the peripheral stuff to hopefully eliminate what is not wrong. I don't think you have a fuel or CIS issue and besides, the elec's are the weak link, so check this first.

First, make sure your grounds are good. I have a 78 SC also that I completely redid - as part of this I replaced the coil and the flat, braided ground strap under the car near the transmission. I have had experience with these on my old Ducatis which used the same thing and they easily corrode between the exposed strands and ultimately stop grounding. Get rid of it before you do anything else and replace it with a multistrand strand, floppy vinyl covered copper cable with copper lugs. I got my from Motoelectric. Also run a ground from the coil mount on the fan housing to an unused lug on the alum intake runner. Bad grounds will fry an elec ignition system.

Next, replace the coil with a Bosch unit - reasonably cheap if you search. If the ignition cables are original, I would consider replacing them also. I replaced mine with silicon covered cables with no issues vs the braided cables that are original.

Clean all, and I mean all the connections and check the fuse terminals for corrosion and dirt. Check the fuel pump relay pin base - mine went bad even though I never touched it during the resto and prevented the car from starting - they short out.

Make sure you have a good battery and that its connections are perfect. After all this is done and you still have the issue, you might have eliminated all the variables down to the elec ign unit. At this point, I would start getting in touch with either the tech people here or good shops. Do searches on your unit to see if they can be tested. IF it were up to me, I would simply replace and take the chance.
Rob

[Porscher]

Sounds like my 78sc, we hade some bad fuel in it and had to change filter, accumulator and renovate the WUR. Runs like a champ now.

[zelrik911]

Do the easy (& cheap) things first, as noted above erratic running MIGHT be bad earths. There is an earth bundle/bolt near the CDI unit.
I always distrust my red fuel pump relay & I have a ziptie holding it in as they fall out of their socket. Buy a new one to be sure its good.

For testing my coil I found a friend with an older Euro car (Bosch) & plugged in my coil. It worked in his car for a minute or so & I knew then my coil was OK. I suggest you also test the green ignition wire to the distributor as its another known falure area.

My problem was my original CDI unit going bad. I found it very frustrating trying to test engine stuff when I had to use the key to turn over the motor for testing. I got a remote starter so I could sit at the motor & try stuff. I put a plug lead on a spare sparkplug so then I knew the ignition was kaput. My solution was to get an MSD Streetfire unit for about $150. Its a great solution for an SC. Plenty of help on this forum for detailed installation advice.
The forum member who does wiring looms (Tippy??) can sell you the right plug so you can connect the MSD unit wiring to a Porsche plug. Everything worked as expected - even the Tacho. Your Permatune is non original so you have no concerns about originality. I set everything up with temporary wiring and got the motor running - when I was happy with it, I cut the wires & installed the plug. It will be a great replacement for a dead Permatune..

Good luck with your troubleshooting.

[T77911S]

the coil just went bad on my 930.
don't remember the exact numbers but I think it was about the same as yours.
car would act like it would start but it would not.

stick to the coil first.
you got some suggestions that may be sending you off on a tangent.
you have bad reading on your coil, stick to that first THEN if needed look at some of the fuel issues. after all, you are getting good fuel out of all injectors and the other good thing is the volume is equal. good test.

CCP seems low, but don't know the outside temp for sure.
you do have the vacuum controlled WUR which when cold CAN drop the CCP down to .8 to 1bar depending on temps. you should also have a thermo time valve (TTV) that within about 15seconds of starting will raise the CP about 1bar.
this is something to look at later.
tony wont like me saying this but if it starts good at 1bar CCP and idles good, I would not mess with it. tony wont like this either, I don't worry about the warm up time of the WUR unless there is an issue.

74psi I assume you mean system pressure.
you might as well check warm pressure. check with and without vacuum to verify that circuit works. should be around 3.6bar and 2.8 bar.

[rpo420]

UPDATE. first off i want to say i am sorry that i duplicate posted this. After i figured its not fuel, i tested my coil, the test on with the outside two posts got me 7 ohms. sounded right. Tested the inside and only got 10k ohms. i read it should be north of 40k. So i sent it the coil (a permatune) and the CD permatune box and sure enough Lonnie got back that the Coil had no oil in it. The coil is maybe 10k miles old. Also what i am suspect about, is that i work on the car alot and clean stuff etc and there is not one drip of oil or any discolored anything on the fan shroud where i woudl assume the oil would fall. Unless it evaporates i dont buy it. Because the coil failed, Lonnie from permatune said the CD box is cooked as well. So its on to something new.. I have ordered an MSD and new coil and will put it back together mid week and will report back. Thanks for all of the Advice, CASOR i am going to redo the ground straps as well when i do it, and yes i have ducati's too, seems we have the same affliction, and i have seen this happen there too.. had a bad ground actually cook the tank hold down strap on a 900ss. saw it just melt! With that said i do appreciate all the responses and i will report back as soon as i am done.. fingers crossed!