I saw the thread about starting issues.. in particular the symtom diagnosis chart was interestinga nd I have printe dthat for future ref.

Coupla Q's:

1) the chart shows multiple symptoms and a stated cause.. would, for instance, a sensor plate sticking be causing all of the stated symptoms could it be just one of them...

I am having starting issues that are seemingly random and no pattern..

hard starts.. turn the key and engines turns fine.. might start to fire then dies immediatley..then another turn of the key and engine turns over and not firing.. 3 or 4 more cranks with 30 seconds in between it will fire and run..when it does fire (after this hard start) it is real slow coming up to idle..it might be at 300 RPM for a second or two before winding up to 1500..

it can hard start cold or it can hard start after going to the mall for 30 minutes..or sitting for 3 hours after a run up 210 degrees.. other times it just fires right up and no idle issues at all..

Million dollar question: what do you guys think it is?

Rob
Project '78 911 SC Targa

 

Rob
Sounds to me like fuel delivery for starters. You might be the guy but we were discussing a very similar problem earlier and suggested starting with fuel presures. This is your starting point. I have a 78SC Targa also by the way.
You might want to read the thread on the WUR. ( warm up regulator ) and get in touch with that guy, sounds like he has similar issues. It is tough to find the " magic bullet" as there are few symptoms but relatively hndereds more causes. Start with some solid daignostic techniques, buy a Bently and have fun. If you can get a fuel pressure tester compare with the W.U.R Thread.

Good luck.

 

CIS expert can take several hours to diagnos and fix permantly. I had an 83 and it was a hot start issue that brought me to the shop. The tech assigned to it worked on it (can't remember how many hundreds of dollars), and when I picked it up next day, didnt start. It tool him all day to fix under warranty.

Ran great that night.

I would take her in. BTW I may have even thrown in part(s) w/o success. That was several years ago/

Good luck!

Bernard Reyes

 

Just read this out of my Bently that sounds like your problem , and it does sound like the sensor plate .. it reads ..
Note _ If the engine starts only during cranking , check the airflow contact (contact stuck closed )
This may help, also check fuse 16 contact#87 on fuel pump relay. This takes over the fuel pump power after starting, I woild definitely try a fuel pump relay , worth having a spare regardless.

Keep us updated.

 

I am currently having the same problems and recently replaced the regulator/accumulator and did a tune-up, but would like to figure this out before I get stranded.

 

That seams to be the one thing we need to get better at as a group. reporting back on fixes. I guess there is not much we can do about t he guys who sign up to get his one problem fixed then bolts... oh well..

 

I suspect I will just start with a new fuel pump relay and hope someone else has some ideas if that is not the case.

 

nixtfy: If you're not inclined to do any diagnostics, then start cheap and go up the expense ladder for CIS system parts. Unfortunately, parts get expensive pretty fast. Easiest would be checking for vacuum leaks and replacing vacuum lines. How's your mixture adjustment? There's lots of reading all over the forums on the CIS system. It's advisable to begin a systematic diagnostic process ruling out each component of the CIS system as the problem. Good luck.

Brett

 

MY mixture was recently just set and passed emissions easily. The one thing I do have on my to do list is that I have paltinum tipped bosch plugs which need to be switched out as my mechanic says create problems. Any chance high temps of 95 and above could cause this problem? I am new to Porshe's and mine is a 78 sc. Lastly, the car runs great idle's and accelerates as it should.

 

Nixtfy: Is your starting problem a hot starting problem. Typically, this is caused by a failing fuel accumulator. It's a part that maintains fuel pressure when the car is turned off, specifically for hot starting. The part is located right next to the fuel filter.

You're well advised to buy a Bentley SC manual. Very much worth it.

Brett

 

I did replace the accumulator and I am not sure if it is hot starting related or if it is possible it's just temperature related outside being over 90 degrees this time of year.

 

you might take a look at the check valve at the front of the fuel pump. Its a very common problem with cis cars. Usually it shows on hot start problems

 

get rid of the bosch platnums your mechanic is dead right !

 

Hey thanks for th responses. First of all the temperature has dropped below 90 degrees the last few days so I don't know if that was causing the condition. I did lower my idle speed a little and i think it might have alleviated the problem some, but I will be changing the spark plugs in the mean time. I also realize I did fill up from a different gas station on the last tank before this problem became so persistent. Some variables I hope that got rid of my problem.

I will respond back to the forum either way though.

 

Any chance this would cause the fuel pump to sound differently or just not as loud? I have noticed the fuel pump being quieter in recent weeks.