356 C Cab won't start when cold, what's going on??

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Ron LaDow
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Re: 356 C Cab won't start when cold, what's going on??

#16 Post by Ron LaDow »

Dave,
Cs are about as fool-proof as any 616 engine the factory ever built, so let's start with the basics:
What has been modified from stock?
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Dave Finburgh
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Re: 356 C Cab won't start when cold, what's going on??

#17 Post by Dave Finburgh »

Ron, nothing modified from stock...except the addition of the electric fuel pump. Still original 6 volt system. I restored the car from end to end about eight years ago. About four years ago, my mechanic was told by another 356 expert that he felt there was evidence of piston slap. We then rebuilt the engine again, replacing the faulty pistons. Ever since then, the car has driven pretty well. Only in the last few months has this hard start problem showed up. The first time, I couldn't start the car, so after having it towed to my mechanic, the carbs were cleaned and all the jets were cleaned. The next time it wouldn't start, after having sat for three weeks, I again towed the car, and this time my mechanic told me that he found that there was some rust in the gas. At that time, at his suggestion, we replaced the fuel tank, rebuilt both carbs and cleaned all the lines...and rebuilt the reserve cut off. Also, I think he cleaned the ignition switch. Two weeks ago, it wouldn't start again. So another towing, this time my mechanic said he noticed that one of the 'new' floats was in fact leaking and had gas in it. ( He apparently had bought this float at a parts swap and it was supposed to be in great shape!) He replaced the float and felt all was ok. I drove the car after that, and while it wasn't easy to start, I did manage to start it and go on a long coastal drive. The car drove great. Today, I tried again to start it...and the rest is history.
Unfortunately, I don't drive this car every day...it's not my daily driver. Nonetheless, I am feeling pretty certain that it is not the ethanol gas that is the culprit..or the fact that I don't drive it that often.

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Ron LaDow
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Re: 356 C Cab won't start when cold, what's going on??

#18 Post by Ron LaDow »

Dave,
Is the electric fuel pump the sole source of fuel to the carbs, or a starting bandaid? And when was the last full (and by progression) tune up was done?
I know this sounds like a third degree interrogation, and I mean no offense, but I can't count the number of times folks here have head-scratched and offered suggestions only to find at the end 'I forgot to tell you it's a 2.8L Type-4 VW with a turbocharger' or some such.
ANY additional data (your turn to head scratch) will help and Sebastian is at least correct (I might go a bit higher...).
Added by edit:
An IC engine will run (maybe not 100%) if:
1) There is compression.
2) There is some fuel in the mixture (and it doesn't have to be close to at least fire).
3) There is a spark somewhere close to where it needs to be (ditto).
I'd make sure #3 is good before any other fiddling. And I mean I would MAKE SURE it was good.
Added by second edit:
"It didn't start"
Did it not turn over?
Did it pop once and then continue to spin with nothing else?
Give us some data, please.
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Toby Brown
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Re: 356 C Cab won't start when cold, what's going on??

#19 Post by Toby Brown »

After having gone through almost everything that you have we concluded it wasn’t the fuel system but it was the ignition. Checked timing, etc etc, replaced coil and then we tried a new condenser and its been perfect ever since. Check your condenser when all else fails. Good luck

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Dave Finburgh
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Re: 356 C Cab won't start when cold, what's going on??

#20 Post by Dave Finburgh »

Ron and everyone, thanks for the help...really appreciate it.
The engine turns over, but doesn’t start. Doesn’t seem like it is even firing at all, not even close to catching. Plenty of cranking and cranking power. Battery is a newer 6volt Optima.
Occasionally in the past, I have heard it begin to start,then backfire and not start.
When I did manage to get it started, it ran sluggish for a few minutes and then seemed to be ok.
At this stage, im going to make sure my mechanic checks the electrical....and that the timing etc is ok.

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Re: 356 C Cab won't start when cold, what's going on??

#21 Post by George Hussey »

as I remember zenith carbs sometimes have an internal plug that lets them leak down making it incredibly hard to start when cold, someone who knows this problem precisely can chime in
George Hussey

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Ron LaDow
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Re: 356 C Cab won't start when cold, what's going on??

#22 Post by Ron LaDow »

Dave,
Got it; thanks for the info. You can start by just pulling a plug lead, sticking a spare plug in it, leave it on some bare metal and cranking the engine.
No spark, work back until you find a signal, or (per Toby) swap the condenser.
If you have a spark, it's probably totally off in timing.
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Hugo Karasawa
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Re: 356 C Cab won't start when cold, what's going on??

#23 Post by Hugo Karasawa »

I hope this does not sound disrespectful.
Your problem lies with your mechanic.
Is he an experienced mechanic ?
With all the parts that he has changed and checked your car should start immediately .
Where are you located ? most probably somebody will suggest a good mechanic that understands 356s.

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Dave Finburgh
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Re: 356 C Cab won't start when cold, what's going on??

#24 Post by Dave Finburgh »

Hi Hugo,I have spent thousands of $$ with this issue. To say that I am frustrated with it would be an understatement. My mechanic is actually well known in the 356 circles. I do think that he tries his best, and that he is accommodating to me, but the problem seems to be very esoteric and difficult to diagnose. Both my mechanic and others are sure that it relates to the ethanol gas that we are all now using....Perhaps, but I somehow doubt it.
Meanwhile, I have reached out to another mechanic who is local and he seems willing to help me...we shall see. :D

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Dave Finburgh
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Re: 356 C Cab won't start when cold, what's going on??

#25 Post by Dave Finburgh »

Ron, quick question...since in the recent past when it has started, even though having been extremely difficult to do, it has run pretty well after warm up. Would this still indicate that the timing is out, or that there could be an electrical issue? :?: :?

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David Jones
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Re: 356 C Cab won't start when cold, what's going on??

#26 Post by David Jones »

Dave, I still think it is fuel related in that there is just not enough available for a cold start. Yes it could be ignition but ignition problems which are intermittent usually tend to occur when the engine is hot and a rebuild of the distributor or even a quick check for spark can eliminate that item. Bad timing is off the table as it runs well when started but running well once started does not necessarily relate to bad starting. As I said before I am inclined to think weak fuel pump and poor accelerator pump performance. Try throwing a splash of raw fuel down the carb throats on a cold start. Do not use starting fluid as that can be too volatile and can cause fires when misused.
You can also try a hand choke by getting someone to spin the engine over while you hold your hand on the carb top to suck some extra fuel in just like a manual choke on many other cars of pre injection era.
If I had known I would live this long I would have pushed the envelope a little harder.
Cymru am byth
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Hugo Karasawa
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Re: 356 C Cab won't start when cold, what's going on??

#27 Post by Hugo Karasawa »

I think the gasoline in USA does not have enough ethanol to cause problems in starting our engines.
If it were Brazil that would be other story, they even had two gas tanks in some cars, one with gasoline to start the car and one with ethanol to continue driving the car after it started.

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Re: 356 C Cab won't start when cold, what's going on??

#28 Post by John Jenkins »

Dave, I read all the replies so far. Some will save me some time. See you after Wednesday.
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Jon Schmid
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Re: 356 C Cab won't start when cold, what's going on??

#29 Post by Jon Schmid »

No expert here, but based on my recent experiences with both of my 356's I would put a sharp eye on the condenser, especially if it's a Turkish made Bosch. Even new ones are suspect. Good luck!!

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Re: 356 C Cab won't start when cold, what's going on??

#30 Post by Heidi Frances »

Hi Dave, I think Dave Jones is on the right track... When the car has sat for a while (or you could just drain the carbs to test), try a small squirt of fuel in both carb throats. If all else is good it will fire and then stall. If not, then it is an electrical issue. Check spark from the coil, then to the plugs to box in an electrical issue. A bad condenser will allow the car to idle but will backfire on acceleration and you will smell unburnt fuel. Now, if your car does fire and stall, then it is fuel. With the carbs both still dry, and the engine off, run your electric pump until it shuts off (stops clicking). The car should fire right up. If not, drain the carbs again to be darn sure the pump filled them. If they are full, then your issue is within the carbs, but that is a bit unusual for both to go bad simultaneously - especially if it is running once warm. It has to be delivery... How is that mechanical pump? Have you verified it is pushing at 2.5 psi or so? You say the car runs fine when it is warm, but it may be that your pump is weak as well or partially blocked? The electric should push right through it. It is easy enough to verify all possible failure points, just isolate them. With the float bowls completely dry, pull the tops off and fill them with a small cup. Put the tops back on and it should start. Just isolate each step along the way. You'll find it...

Franny
 

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