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ivanuf's Avatar
 
Join Date: Jun 2004
Location: Puerto Rico
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$100 Prize for the Guru that solves my Itermittent long cranks problem!

First let me clarify that this has been going on for a couple of years, and during that time I have read all topics on this forum of no-start, cold, warm, you name it I have read it.

The car:
1977 930 with 3.3 Pistons, and Ignition (counter-clockwise rotation, dual vac.) and all
The 77 CIS including 8-pin CDI with replaced internals with modern electronics by another vendor. Engine out all new top end service. The car runs great and it always starts.

Sometimes it will take just a touch of the key and it will start right up, cold or warm. Quick after a drive or after a couple of weeks parked it does not matter, if it in the mood it will start right up.

But 1 out of 3 it fells like it misses that sweet spot and you will have to crank it for several long no-start cranks until it starts. The amount of time it takes is completely random. It could be warm, or cold it does not matter.

What I have troubleshooted and replaced during the last 2 years.

1. Both fuel pumps and check valves.
2. Fuel Distributor and WUR set to Tony to repair and calibrate.
3. Removed MSD and replaced with CDI with modern internals.
4. New Distributor for 3.3 bottom end
5. New engine wire harness
5. Spark plugs and cables with proper OHM ends
4. New coil and coil wire proper OHM end
5. Ignition switch
6. Fuel Filter and New Fuel Accumulator
7. New high torque starter.

Ignition timing: I do not recall now, but we have verified several times and it is within specs.

Fuel Pressures: Also all values are in spec as per my WUR as per CIS Primer hand notes for Turbo Cars.


It is not a big deal because it always starts, but if really frustrating having this issue plus my SC starts right up every single time and it just feels good.

Any suggestions on what to try or test next, I ran out of options. The person that submits a suggestion or proper help to solve the problem will receive $100 via paypal as a token of my appreciation.


Merry Xmas!

Ivan




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Old 12-24-2020, 04:12 AM
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Somehow you have to find out if it's spark or fuel. On one of the times it wont fire right up check for spark. If you have a strong spark then you know it's fuel related and you can proceed from there. Do you have a fuel pressure gauge? If yes install it and drive the car until you have the issue then check the the pressures.
Old 12-24-2020, 05:13 AM
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the green ignition wire,, mine was always a problem..
Old 12-24-2020, 05:19 AM
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Distributor
Old 12-24-2020, 05:42 AM
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My 86 930 does this too. I kinda think it’s related to the massive inter cooler I have in it. I *think* you need to have vacuum for the distributor to have the correct advance to start.

Having no IC on your 77, this may not be the case.

I would start by checking for vacuum leaks if I was you, particularly your Turbo which were notoriously bad on the 76 and 77 cars. I know the turbo on my 86 needs to be rebuilt and I think this is my issue.
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Last edited by unclebilly; 12-24-2020 at 06:13 AM..
Old 12-24-2020, 06:08 AM
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I had similar symptoms with my 77 930.
Turned out to be that the front fuel pump had a mind of it's own.
The car will run fine with just the rear pressure pump working.
Take away the front suction pump, for whatever reason, and the car may take several long cranks to fire up. When it finally fires, it ran like it was only firing on 3 cylinders until the lines filled up, and the rear pump built up enough pressure.
Just because you have replaced the pumps does not mean that they are performing as designed.
Bill K
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Last edited by bkreigsr; 12-24-2020 at 08:37 AM..
Old 12-24-2020, 07:27 AM
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Quote:
Originally Posted by 991gts6s View Post
the green ignition wire,, mine was always a problem..
It is new
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Old 12-24-2020, 08:11 AM
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Quote:
Originally Posted by Dpmulvan View Post
Distributor
It was purchased new for the 3.3 bottom end. How can we confirm that is having issues?
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Old 12-24-2020, 08:13 AM
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Quote:
Originally Posted by gomezoneill View Post
Somehow you have to find out if it's spark or fuel. On one of the times it wont fire right up check for spark. If you have a strong spark then you know it's fuel related and you can proceed from there. Do you have a fuel pressure gauge? If yes install it and drive the car until you have the issue then check the the pressures.
.
I have done that several times and fuel pressures are on spec. So I eliminated fuel as the reason. Also on the long cranks you smell the fuel fumes.
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Old 12-24-2020, 08:14 AM
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Quote:
Originally Posted by bkreigsr View Post
I had similar symptoms with my 77 930.

Turned out to be that the front fuel pump had a mind of it's own.

The car will run fine with just the rear pressure pump working.

Take away the front suction pump, for whatever reason, and the car may take several long cranks to fire up. When it finally fires, it ran like it was only firing on 3 cylinders until the lines filled up, and the rear pump built up enough pressure.

Just because you have replaced the pumps does not mean that are performing as designed.

Bill K
I thought about this, the only way to make sure I guess it will be to install 2 pilot lights inside the car form the 12V of each pump, that way I can confirm that both pumps are working when cranking. Any better Idea to discard this option?
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Old 12-24-2020, 08:18 AM
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I will put the fuel gauges back (again) and post the numbers. I will also try to install the (2) lights for the fuel pumps (or better idea) to have all the fuel data for reference.
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Old 12-24-2020, 08:22 AM
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Quote:
Originally Posted by unclebilly View Post
My 86 930 does this too. I kinda think itís related to the massive inter cooler I have in it. I *think* you need to have vacuum for the distributor to have the correct advance to start.

Having no IC on your 77, this may not be the case.

I would start by checking for vacuum leaks if I was you, particularly your Turbo which were notoriously bad on the 76 and 77 cars. I know the turbo on my 86 needs to be rebuilt and I think this is my issue.
I have smoked and applied carburetor cleaner all over the engine after assembly and so far have not found any leaks. But I am always looking.
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Old 12-24-2020, 08:31 AM
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Have you verified control pressures on the WUR?
Have you verified the air flow metering plate is moving while cranking?
Have you verified that the air flow metering plate is moving off the fuel pump switch?
Have you cleaned the fuel distributor - especially the fuel plunger rod and matching cavity?
Have you verified the CIS injector flow pattern?

Does this happen with full or empty fuel load?
Have you cleaned the siphon screen on the fuel tank?
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Old 12-24-2020, 08:41 AM
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Old 12-24-2020, 09:02 AM
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Quote:
Originally Posted by jpnovak View Post
Have you verified control pressures on the WUR?
Have you verified the air flow metering plate is moving while cranking?
Have you verified that the air flow metering plate is moving off the fuel pump switch?
Have you cleaned the fuel distributor - especially the fuel plunger rod and matching cavity?
Have you verified the CIS injector flow pattern?

Does this happen with full or empty fuel load?
Have you cleaned the siphon screen on the fuel tank?

He stated that Tony rebuilt and checked the FD and the WUR.

I like the siphon screen idea though.
Old 12-24-2020, 09:11 AM
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Just a thought, have you checked or replaced the fuel pump relays? I believe there's a upgrade kit for the turbo fuel pump relays.

Here it is: https://www.google.com/search?source=univ&tbm=isch&q=1977+porsche+turbo+fuel+pump++relay+upgrade+kit&client=firefox-b-1-d&sa=X&ved=2ahUKEwjakp62neftAhVFElkFHTpADOQQjJkEegQIBhAB

And there's this: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwjakp62neftAhVFElkFHTpADOQQFjALegQICxAC&url=http%3A%2F%2Fforums.pelicanparts.com%2F911-930-turbo-super-charging-forum%2F424622-930-fuel-pump-relay-wiring-once-all.html&usg=AOvVaw3fijoEBWsK4b9U5kUoIcxX

The issue is fuse 16 gets overheated.

Last edited by gomezoneill; 12-24-2020 at 09:21 AM..
Old 12-24-2020, 09:15 AM
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Flaky WUR. The diaphragms can be good but the bi-metallic thing can be erratic.
If I’d done everything you’ve done ignition wise, I’d borrow or plunk down for another WUR.
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Old 12-24-2020, 09:19 AM
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Check these suggestions......

Quote:
Originally Posted by jpnovak View Post
Have you verified control pressures on the WUR?
Have you verified the air flow metering plate is moving while cranking?
Have you verified that the air flow metering plate is moving off the fuel pump switch?
Have you cleaned the fuel distributor - especially the fuel plunger rod and matching cavity?
Have you verified the CIS injector flow pattern?

Does this happen with full or empty fuel load?
Have you cleaned the siphon screen on the fuel tank?

Ivan,

Install the CIS gauge and measure:
  • CCP (cold control pressure) electrical plug to WUR disconnected.
  • Check the system pressure.
  • Install the WUR electric plug and start the motor.

Have you done a smoke test to verify the absence of unmetered air going into the system? I would be curious to know how the CSV and fuel injectors delivered fuel looks like during the initial start stage. You want a mist-like V patterns and not a jet-like flow spray pattern. Keep us posted. Thanks.

Tony
Old 12-24-2020, 10:46 AM
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Cold start injector working?
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Old 12-24-2020, 11:51 AM
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Sounds like you’ve taken a thorough approach.

What about the basics?
Leak down and compression numbers?
Valve adjustment?
Cam timing checked?

Usually temperature based?

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Old 12-24-2020, 11:57 AM
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