I've been having increasing difficulty starting my '84 US lately. For the last couple of years it has sometimes taken an extra couple seconds of cranking the ignition to start when cold (after sitting for 6+ hours), though it has always started quickly and without need of extra cranking when the engine was warm (sitting for just a few minutes since running).

In the last few weeks I have been starting to get some new symptoms though. For starters (no pun intended), when I start the car I notice that the exhaust is noticeably gray for the first mile or so of driving if the car has been sitting awhile, and I'm pretty sure that wasn't happening before. The car also idles high when started cold (sometimes as high as 1000 rpm) , but then goes back down to normal after a mile or two of driving.

Secondly (and more troubling for me) the last couple of times I have started the car the car starts to cut out while I am turning the ignition on. The first time it happened it cranked like normal, and then it seemed like everything (cranking, electrical, etc) just cut for a split second before the car fired up. Then this morning as I was about to take the car for a drive, and when I turned the key everything just died. I had to turn the key on about three times before the car started. I ran it for a few seconds, and then I shut it off. I waited about 10 seconds and tried to turn it on again and it fired right up with no problems.

The car has never had problems once it's up and running, it just seems to have trouble starting.

The first problem sounds like a Fuel Pressure Regulator or Fuel Dampener problem to me. If the diaphragm is leaking and gas is getting sucked into the engine, that could cause a delay in starting due to a lack of fuel pressure, and it would also account for the grey smoke in the exhaust (burning off excess gas). BTW, I have sniffed the vacuum lines leading to the dampener at the front of the engine and the vacuum lines that lead to the two FPRs at the rear of the engine and I can smell fuel in all of them. The two vacuum lines to the FPRs are joined at a three way connector so they aren't both necessarily leaking, but I figure that I'll replace both of them as well as the dampener anyways. If I'm wrong with my hypothesis please let me know, as I fully admit I'm a noob at this stuff.

What I would like to know is, could this also explain the second problem I'm having with everything cutting out during start up? Do you think this could be caused by one of the FPR's or dampener leaking for a while causing the first set of symptoms, and then another one of them started leaking more recently, creating even less fuel pressure on startup bringing about the recent troubles in starting my car?

I'm going to be replacing the FPRs and dampeners for sure, but I want to make reasonably sure that this will address the most recent start issues that I've been having. If according to your expert opinions the cutting out during startup problems can't have anything to do with the FPR, I want to know where to look so that I can order the right parts and get her back into great running shape.

Sorry for the long post, but I just wanted to explain my situation as best I could. As always, thanks in advance for your input!

 

My first guess on the newer cutting-out problem is the ignition switch, or the link between the lock part and the switch part.

A leaking regulator or damper usually causes hard starting for thirty minutes after shutting down a hot engine - not as likely to cause problems on a cold engine.

Try pulling the vacuum lines at each of the fuel units and checking for fuel at the unit vacuum connectors and in the lines there.

 

Thanks Wally! I've never dug into the ignition switch before, so I'll do a little research on that and see if I can narrow down the problem.

 

I too was going to suggest ignition switch.....it is a very common failure item, and can cause all sorts of mayhem...

 

Update on the starting issues...

I was able to swap out the ignition switch on my car with one from my parts car, and everything seemed to work great for a few days. It would fire right up for the most part. Sometimes it would take an extra couple seconds of cranking to fire up but that's what was happening before, so as long as it was doing that I wasn't going to complain.

After driving the car around all weekend on some long drives without any incident, it started to have the same "cutting out while cold starting" problem. I attached a video showing what it does. What you are seeing is me turning the ignition once and it dying. I then turned it again and it fired right up. Sometimes it requires me turning the ignition three or four times (with it cutting out each time) before it actually fires up. It only does this when the car hasn't been started for 6+ hours...when the car is warm it starts right up.

Another symptom that might or might not be related is that the coolant light came on over the previous weekend (this only happened after the symptoms originally manifested themselves). The actual coolant level was fine and the temp wasn't rising even after long drives, so I ended up finding out where the sensor was on the water bridge and jiggling it and the warning light stopped coming on. If that sensor is faulty, could that be affecting my cold starts? Maybe it isn't telling my computer brain that the engine is cold and is screwing stuff up? Or maybe something as simple as the fuel pump check valve? Could it be an ignition wiring problem, where I jiggled the wires the right way when replacing the ignition switch and that made it work for awhile?

I know that I'm throwing a bunch of stuff out there and I apologize for that...I'm just trying to narrow stuff down as best as I can before I throw money into a bunch of parts that I might or might not need.

P.S. A fellow Rennlister checked my FPRs and dampeners and they were fine, so it looks like I can rule those out.

 

That hesitation seems like the starter or battery power. I would loosen the starter and check/loosen, the engagement between starter and flywheel. It can also be low CCA's on the battery. I've also cleaned the ground for the battery and magically there is more voltage for everything.

 

On 84 replace bat ground strap and temp/time switch.
Polish the grounds located on passenger cam cover, these are where engine electronics ground.
There are two sets, one above O in word Porsche is completely hidden by an emissions valve.
Best to remove that valve completely to clean the ground, then replace.
Easier than it looks.

The temp/time switch controls the cold start injector. My understanding is that when it fails it doesn't turn the injector off, causing a flood condition. Common. Just replace it. Located near water bridge, its a sensor that is mounted axially, not vertical like Temp II.

I think you have multiple small issues overlapping. Which makes troubleshooting a PITA. Best is to go through the car and replace all sensors /clean all electrical joints possible.

 

Thanks for the tips! I'll start looking into those fixes and let you all know what happens.

 

I was just looking back at some of my old posts and I noticed that I never followed up on how this issue was resolved, so I figured I'd close the book on this in case someone else had the same problems.

First off, the white smoke while driving soon after startup was caused by a leaking head gasket (the white smoke was of course coolant being burnt off in my exhaust), which necessitated an engine removal and rebuild. While I had the engine out, I figured I'd get the starter examined at a local shop, and sure enough the starter was wonky and not fully engaging all of the time, so that was the cause of my cutting out during cold starts.

Both were actually easy to check for if I was smart and knew what I was doing, but everything I know about cars I learned on my 928, so this has been yet another learning experience for me. Hopefully this might point someone else in the right direction someday!

 

Just to add info on a thread if anyone is looking for hard start on an '84 US. Temp Time switch was out on the one I've been working on, combined with a bad harness. With those replaced all is well in the world on this car.