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Warm start problem but coldstart ok

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Old 02-15-2018, 04:56 PM
  #16  
GerritD
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Originally Posted by allan29 View Post
For the residual pressure test , you don't need to have the engine hot !
Disconnect the WUR and the additionnal air valve , put pump on without start the engine during 2 minutes minimum and stop the pump .
Watch the pressure after 10 , 20 and 30 minutes . You can see 2,7 Bar , and 2,6 bar and 2,5 . If less, it's not good .
All CIS system have a pressure accumulator , it's hère to resist to the vapor lock .
If you don't have , you need one !
Before incriminate the fuel distributor , check the pressure valve and piston O ring in !
If you speak French language , email me , I'm better ...
You have a problem with your WUR too .
The high cold pressure is a problem .
Your engine run fine when hot ?
The test was with vacuum ?
Clamp the hose of the pump is a good solution , but you cannot know if the problem is the fuel return valve or the pressure accumulator .
As for the fuel accumulator, I never had one on my previous engine and this engine was also a CIS Kjet but 4.5L 240Hp and I never had issues with
the warm start of the engine...how is this possible??
Can the fuel accumulator easily be installed afterwards? Is the part easy to get?

My engine runs fine when hot.
Test was done without vacuum.

So I think I need to do the following steps :
1. install a fuel accumulator
2. perform a pressure check (cold + warm)
3. check also my hot start valve ( I never checked this)
4. If still issues, replace relieve valve O-ring of my fuel distributor

What is your opinion?

kr
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Old 02-15-2018, 06:56 PM
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The charts for WUR are with Vacuum . Without , 0,5 or 0,6 bar less
.
The accumulator is front of the rear passager wheel .


Here an earlier version with fuel filter .



Number 4 is the pressure accumulator .

Last edited by allan29; 02-15-2018 at 07:27 PM.
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Old 02-15-2018, 07:11 PM
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To check the thermotime switch for cold start injector ...




In French ...




General wiring :
#1 contact
switch
#2 Cold start valve
#3 Thermotime switch

#4 Fuel pump relay
#5 Fuel pump
#6 and #7 WUR and additionnal air valve for cold start





Last edited by allan29; 02-15-2018 at 07:31 PM.
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Old 02-15-2018, 07:17 PM
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The thermotime switch work only during the 2th or 3th time first start ... after he's hot !
And you need stay few minutes for recold wihtout start again if you want check .

Other option , if the WUR pressure is too high when cold and sometime hot , it's very very hard to start !
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Old 02-15-2018, 07:23 PM
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The following steps :
1. install a fuel accumulator "or find it and check it "
2. perform a pressure check (cold + warm) " take care with or without vacuum "
3. check also my hot start valve ( I never checked this) " and the thermotime switch "
4. If still issues, replace relieve valve O-ring of my fuel distributor " yes"
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Old 02-15-2018, 08:09 PM
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Originally Posted by allan29 View Post
The following steps :
1. install a fuel accumulator "or find it and check it "
2. perform a pressure check (cold + warm) " take care with or without vacuum "
3. check also my hot start valve ( I never checked this) " and the thermotime switch "
4. If still issues, replace relieve valve O-ring of my fuel distributor " yes"
Wow, Allan, this is so much information that will really help me. I already thank you for this.

Si je peux t'aider avec qq ch autre, ne m'hésite pas de contacter.
Tu peux me joindre sur mon Addresse email, m'envoie un message via mon compte Rennlist et je te Donne mon email.
J'ai restauré mon 928S moi-même :
- nouveaux freins disques, nouvelle peinture, toute électricité renouvellée, nouvelle pompe essence, nouveaux échappement, boîte automatique
est refaite, nouveaux tapis, remplacé moteur 4.5 240ch par moteur d'origine S 4.7 300ch et j'ai restauré le moteur S : nouveaux bièlles, segments cilindres
joint de coulasse, Pompe à eau, courroi de distribution et j'ai installé le système PorkenTensioner de 928 Motorsports...

Ici qq photos :










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Old 02-16-2018, 08:25 AM
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Ohhhhh.

That's a nice one.

I have no info to add about the CIS, but I wanted to say how much I like your car.

You are in France, but you don't have the yellow bumper lights. How did that happen?

And your air filter is upside down. The 'hump' should be up. Ignore the arrows on it. Don't flip the one that's in there, but when you get a new one, put it in right side up.
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Old 02-16-2018, 07:18 PM
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Originally Posted by Wisconsin Joe View Post
Ohhhhh.

That's a nice one.

I have no info to add about the CIS, but I wanted to say how much I like your car.

You are in France, but you don't have the yellow bumper lights. How did that happen?

And your air filter is upside down. The 'hump' should be up. Ignore the arrows on it. Don't flip the one that's in there, but when you get a new one, put it in right side up.
Thanks Joe! Of all Porsches the 928 is my favourite (Power, comfortable and eye catcher). I just love the V8.
No, I live in Belgium and work in Brussels which is the capital city of Belgium.
Since Brussels has 2 spoken languages, French and Dutch, I speak both of them and also German since I live near the border ( about 15 miles)
of Germany.

thanks for the remark about the air filter, I never knew this.

kr
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Old 02-17-2018, 07:15 AM
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Gerrit , I made the same work on my 928 S of 1982 !
Rebuild engine , drive train , wires , interior trim , leather ...
Next step , the body painting , big brakes , X pipe and ...

Some pics :



On race track ...


With my 944 and back the Opel GT ...



German's family ! My Mercedes CLK miss in this picture !
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Old 02-17-2018, 07:26 AM
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I try new part from Mercedes ...


I check pressure . I rebuild all my CIS and now , it's my job ... Thanks 928 !
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Old 02-17-2018, 07:28 AM
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Your car looks like a 928 non S , baby without side moulding and the position of your WUR , with aero kit option of "S" model .
I like without side moulding .
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Old 02-17-2018, 07:50 AM
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Originally Posted by GerritD View Post

Hi fellow 928-colleagues,

can perhaps someone point me to the right direction, as in which component could be the culprit for my warm start troubles :
1. I have a 928S euro of 1980, 4.7L 300Hp 3sp AT with K-Jet
2. cold start is no problem. Engine fires up right away without pressing throttle pedal
3. once engine is warm and I shut engine off, I can easily start after 5 to 10min, without pressing throttle pedal
4. however, when engine is warm and I shut it off for more than 30min, I cannot start the car again, not even when pressing pedal to the metal
I can hear engine wanting to start up but no luck. At the same time I can smell fuel at the exhaust.


Here is what I already did :
- check injectors : they are not leaking
- check system and control pressure when engine is cold and is not running : pressure within specifications
- I replaced diaphragm and seals of the WUR
- I replaced my ignition coil
- I replaced distributor rotor
- I replaced ignition leads
- I replaced my spark plugs
- I checked my emission value and it is 2% CO, so within specification of Porsche (between 1,5 and 2,5)

Is a bad WUR the culprit?
Or should I look for other failing components....
Hi Gerrit,

I have the same exact issue in my 83S Euro CIS.
I've replaced the fuel pump check valve, the fuel accumulator and the cold start valve but the problem remains.
I already have new injectors to replace sometime in the future.
It's very annoying when the car is warm and doesn't want to start, mine only starts when I press the accelerator pedal all the way down.
By te way, in my car the fuel accumulator is located on the rear fender on the passenger side.
Good luck to solve this problem.

Regards
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Old 02-17-2018, 05:41 PM
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Originally Posted by R.Pires View Post
Hi Gerrit,

I have the same exact issue in my 83S Euro CIS.
I've replaced the fuel pump check valve, the fuel accumulator and the cold start valve but the problem remains.
I already have new injectors to replace sometime in the future.
It's very annoying when the car is warm and doesn't want to start, mine only starts when I press the accelerator pedal all the way down.
By te way, in my car the fuel accumulator is located on the rear fender on the passenger side.
Good luck to solve this problem.

Regards
Hi Ricardo,
that's a shame that you could not solve the issue. Are you living in a warm climate ? Here in Belgium it is 5 degree Celsius in winter season
and I have the hotstart issue in current winter season.
But I am determined to solve the problem
I already have some root causes to check :
- relieve valve Fuel Distributor
- hot start valve
- WUR

I keep you posted with my test results

kr
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Old 02-17-2018, 05:49 PM
  #29  
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Originally Posted by allan29 View Post
Your car looks like a 928 non S , baby without side moulding and the position of your WUR , with aero kit option of "S" model .
I like without side moulding .
Well, first 928S from 1979/1980 did not have side moulding. I like old school cars , as 928 should be.
but you also have some damn fine cars. nice colours.

And Germans did build very good and reliable cars, they still do, but in the old days the design was very nice to look at

kr
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Old 02-28-2018, 12:09 AM
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Originally Posted by allan29 View Post
The charts for WUR are with Vacuum . Without , 0,5 or 0,6 bar less
.
The accumulator is front of the rear passager wheel .


Here an earlier version with fuel filter .



Number 4 is the pressure accumulator .
Hi Alan,

I am currently trying to acquire a fuel accumulator . Not easy as it as hard to get the correct one (0438 170 026) and it is quite expensive.
Can't I use another one from a 911? isn't fuel pressure coming from fuel pump the same for 911 & 928?

Why isn't fuel accumulator closer to the engine instead of at the back of the car?

I also replaced my fuel lines couple of years ago by PTE race fuel lines. So flexible lines covered with RVS protection.
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