Difficult start, cold or warm

[karmannghia60]

1979 SC (CIS)
Difficult to start regardless cold or warm/hot. Maybe more difficult warm/hot
It will take atleast 30 seconds of cranking few times before it starts. Once it starts, it runs fine
Initially I thought the problem is warm start only so I replaced the accumulator
I checked the connection on the WUR
Fuel pump is new
Taking the air filter off and lifting the lever makes no difference. I will hear the sound of fuel pressure but the car still won't start

Where to from here?

Thanks in advance

[T77911S]

start with ignition:
new plugs, cap, rotor and wires if needed.
then set the timing and check the advance.

CIS:
check for air leaks.
check pressures. warm cold and system
check mixture setting.


in that order.

[Bob Kontak]

Originally Posted by karmannghia60

Where to from here?

If your ignition and timing are perfect, I would look at the two things that CIS-wise make starting difficult.

Cold - Does the cold start valve blast the fuel into your air box when you crank the engine?

After warm-up the cold start valve can't work because the thermo-time switch on the left side chain cover is too warm and will not allow the connection for the CSV to fire when you crank.

Warm - You have lost rest/residual pressure in your system which is required for a quick start.

For a quick test, disconnect the wires on the thermotime switch and see if the cold start symptoms are the same. i.e., 30 seconds. Does not guarantee it's your problem but raises an eyebrow as to a potential cause.

Residual pressure has to be tested with pressure gauges.

[tirwin]

Why is it that a lot of people start posts with CIS problems with "I replaced the fuel accumulator and it didn't fix the problem"?

Tony has been preaching this for years. Start with the basics! That's an expensive part to replace to not fix the problem...

Sorry, kharmannghia60, I'm not trying to pick on you. I have seen a lot of people do this only to find it has nothing to do with the problem. You got great advice already. Listen to what they told you.

[T77911S]

T, i see it all this ALL the time and i just shake my head when i see people just replace stuff. another big one is the ICV on motronic systems.

the OP could have bought a set of gauges for the price of the ACC. at least thats the way i look at things. buy a tool that will help fix the problem if needed.


see my 1st post.

[boyt911sc]

Originally Posted by tirwin

Why is it that a lot of people start posts with CIS problems with "I replaced the fuel accumulator and it didn't fix the problem"?

Tony has been preaching this for years. Start with the basics! That's an expensive part to replace to not fix the problem...

Sorry, kharmannghia60, I'm not trying to pick on you. I have seen a lot of people do this only to find it has nothing to do with the problem. You got great advice already. Listen to what they told you.

Tim,

I've been trying to get the attention of CIS troubleshooters for years and when you initiated the 'thread', I was relieved to see it. Many has benefited from your thread and a lot more people needed to use it as reference. CIS troubleshooting posts become popular at fall and spring seasons. Why? When the weather starts to get cooler in the fall, people with CIS engine problem/s noticed irratic performance that was not observed in hot summer months.

Instead of using a tool (fuel pressure gauge kit) to diagnose the problem, people like to replace parts after parts to fix the problem/s. Sometimes you get lucky and makes the car run better. But you can not rely on luck for a systematic diagnosis unless you want to spend unnecessarily for parts.

I received a lot of emails and phone calls from fellow PP members regarding their CIS woes. Like a broken record, I keep repeating "I've been looking for a CIS problem that a typical DIY'er like you or me could not diagnose correctly. And still looking........" Test and confirm. Stay away from quess-work and the culprit would come out like a sore thumb.

Tony

[karmannghia60]

Will this kit be suitable to check the pressure?
NEW Universal Fuel Injector System Pump Gauge Pressure Tester Test KIT Tool SET | eBay

I am in Australia so shipping from America is very expensive, need to find something local

[universeman]

That looks a lot like the Harbor Freight kit that everyone here swears by. Probably also made in China but cheap/good value. No idea how you could confirm that, maybe ask the seller? Good luck!

[universeman]

Not exactly the same...
Master Fuel Injection Pressure Test Kit

[kach22i]

Seasonal changes in temperature affect my fuel/air ratio.

I typically have to adjust it when it gets warm for the summer, and when it gets cold again late fall and stays cold.

I'm sure there is something which is not working right which forces me to do this manually but I haven't found it yet, and it's not very often a problem.

[karmannghia60]

Ok I think I am on to the reason
The car ran like a dream for 3 weeks, hasn't missed a beat
Then yesterday on the freeway, it just died, completely with no warnings whatsoever. So I figured out this can't be a fuel issue, must be ignition
Few tests later and I discovered that the power to the rear fuse box has died hence no power to the Bosch ignition module nor the coil
I hot wired it to a live wire and bang, the car starts on first click
Now I am trying to figure out what's wrong with the red wire that goes into the rear fuse box
From following the wiring diagram, it seem that the red wire goes to the same fuse as the fuel pump on the front fuse box, is this correct?
If not, where is the origin of this red wire?
Alternatively if I can't fix it, can I just run another wire which is live with ignition to the rear fuse box?
Thanks

[timmy2]

Power to the CDI box comes from the white T shaped 2 pole connector located just below the CDI box.
The power to that connector comes directly from fuse 18 in the front fuse panel.
It splits off at the white T connector and feeds fuse S22 on the rear fuse panel providing power to the heater blower relay J14 and the CDI .
Line 126 on the schematic shows T2a (white T connector) and S22 the power to the CDI splitting off from T2a to terminal 15 of N15 (CDI box)

So, check to make sure fuse 18 in the front is clean and seated well, and check the T connector and red wire to CDI are connected securely.

[Joe Bob]

CIS is ALL about fuel pressure and vacuum leaks. START there and THEN throw parts ($$$) at it. Buy some fuel pressure test gauges and search for leaks.

[karmannghia60]

Thanks Timmy, that's what I needed to know, where the red wire starts at the front. However, according to this Fuse diagram
Fuse 18 is for interior light and its from the battery not only at ignition. Am I missing something?
My car doesn't have the CDI anymore, the PO replaced it long ago. It has the small black Bosch module. But doesn't matter, its not the problem
Red wire is losing power and thats the problem

[karmannghia60]

Thanks Timmy, that's what I needed to know, where the red wire starts at the front. However, according to this Fuse diagram
Fuse 18 is for interior light and its from the battery not only at ignition. Am I missing something?
My car doesn't have the CDI anymore, the PO replaced it long ago. It has the small black Bosch module. But doesn't matter, its not the problem
Red wire is losing power and thats the problem
And I checked the connection at the back, all good

[timmy2]

Use the '78 schematic for your '79.
Things changed after 1980
Download it from our host here:
Pelican Parts - Porsche 911 Parts Listings & Diagrams

[rusnak]

Originally Posted by Joe Bob

CIS is ALL about fuel pressure and vacuum leaks. START there and THEN throw parts ($$$) at it. Buy some fuel pressure test gauges and search for leaks.

I was going to post this.

I would also break out the LM-1 and check fuel air ratio, but only because I already have one.

[timmy2]

Guys, read the whole thread.
Car runs great now but cut out due to power failure to CDI.

[karmannghia60]

Correct, nothing to do with fuel pressure

[karmannghia60]

ok, after months of frustration, i found the problem. for some reason, someone at some stage in the past rewired the wire at the front fuse box using a scotch lock. which, as most of them do, went bad and caused erratic connection
removed it and will see how the car behaves over the next few weeks