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Starting problems 911sc

Hi guys!
Been Reading all posts I've found about 911sc starting problems on this site and others and i think i have a few suspects, but I'm still not sure because i seem to have both Cold start and warm start issues which puzzles me.

Bought the car about 1 1/2 years ago and it started up great, the Engine ran abit lean so i adjusted that and all was great. Sadly i had to have it outside wintertime but under a roof but no walls or heat. It slowly got harder and harder to start till I just couldn't start it anymore. I jump started it and it ran great, no surging or any problems at all, shut it off and it wouldn't start even though it was warm and had been running 30+ minutes.

When I try to Cold start it, it almost starts at the first crank, second abit further away from starting and third its nowhere near. I suspect it gets to much fuel, it smells alot of it.

Been searching alot online and I have a few prime suspects but would appreciate help with this.

Suspects:
Fuel accumulator
Fuel check valve
Cold start valve
WUR

Any ideas??
appreciates any help.
tnx Ola
Old 01-14-2016, 10:30 PM
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Bought the car about 1 1/2 years ago and it started up great, the Engine ran abit lean so i adjusted that and all was great. Sadly i had to have it outside wintertime but under a roof but no walls or heat. It slowly got harder and harder to start till I just couldn't start it anymore. I jump started it and it ran great, no surging or any problems at all, shut it off and it wouldn't start even though it was warm and had been running 30+ minutes

jump start it again . if it runs fine do battery load test.
Old 01-15-2016, 12:43 AM
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if it will not start after it is hot you have residual fuel pressure problem.
with the key on, (when it will not start), try lifting the sensor plate for 2-3 seconds, or until you hear the injectors squealing.
then start it.
if ti starts its either the accumulator or the check valve at the fuel pump.

"it was ruinning lean and i adjusted it".
not always a good idea.
if it was running lean, WHY was it running lean. usually an air leak.
now you have just covered up a problem so you need to find out why it was running lean.
also, how did you know it was lean?

surging is a rich condition.
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Old 01-15-2016, 02:41 AM
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Quote:
Originally Posted by T77911S View Post
if it will not start after it is hot you have residual fuel pressure problem.
with the key on, (when it will not start), try lifting the sensor plate for 2-3 seconds, or until you hear the injectors squealing.
then start it.
if ti starts its either the accumulator or the check valve at the fuel pump.

"it was running lean and i adjusted it".
not always a good idea.
if it was running lean, WHY was it running lean. usually an air leak.
now you have just covered up a problem so you need to find out why it was running lean.
also, how did you know it was lean?

surging is a rich condition.
You're right, shouldn't have touched it but I did. I'll try what you suggest with the pressure plate, I also noticed that the pressure plate isn't totally smooth moving up and down, shouldn't it be really smooth?
Anybody have any experience with the cold start valve? read that if it leaks it'll flood the cylinder and when choke kicks in it gets to much fuel which would explain the smell and that it's the closest of starting on the first crank.
I'd like to clarify that it always turns over so battery is good, its new.
Old 01-15-2016, 05:23 AM
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the CSV does not go bad very often. i wuold look elsewhere first.

the sensor plate should move smoothly but it should also have a lot of resistance as long as the fuel pump (the key) is on. there should NOT be any free play before you feel resistance. if the plate moves freely then has resistance the plunger is not coming all the way down.

with the key off the plate will move very easily. it may bleed off any residual pressure at first but once that is gone it should jsut flop around
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86 930 42kmiles [__] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD
88 BMW 325is 200K+ SOLD
05 BMW 330CI 130K:: [__] RUNNING: [__] NOT RUNNING:
08 VOLVO V70 190K:: [__] RUNNING: [__] NOT RUNNING:
90 B2200[__] RUNNING:[] NOT RUNNING:__2000 MER E320 WAGON [] WRECKED:[]RUNNING:
Old 01-15-2016, 05:32 AM
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Don't mind

SC is my fifth car equipped with K-Jetronic ignition and stays outside since nine years, like the previous others.

Clean fuel accumulator, change fuel filter, verify injectors, fuse end relais of the fuel pump. Don't touch any, unless you already verified these things

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Old 01-15-2016, 10:32 AM
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Having just done this on my '83 SC here is what I would recommend:
1. Drain the tank, remove strainer and flush.
2. Remove fuel level sender tube and clean up rust particles that accumulate around connections.
3. Replace fuel filler hose (it dries out and cracks on the underside that you cannot see)
4. Install new strainer and gasket
5. Replace short hose from tank to pump
6. Replace fuel pump check valve. Be careful not to allow pump to rotate when breaking connections as your output hose is probably as hard as rock and will split easily.
7. Replace fuel filter
8. Remove accumulator and flush
9. Remove fuel input line to WUR and clean out fine metal mesh filter (mine had 1/4" of rusty particles)
10. Clean around sensor plate and lubricate hinge if necessary so action is smooth
11. Refill tank and then check pressures with CIS gauges

I initially tried step 11 first and my readings were way off because of issues upstream. Steps 1 through 10 give a good base for your readings. Good luck. Not real hard stuff but a little time consuming.
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Old 01-15-2016, 05:31 PM
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Three basic steps.......

You need just do these three (3) basic tests before going to the details of checking the CIS components:
1). Make sure you have a fully charged battery.
2). Check using an inductive timing light for ignition.
3). Hook up a pressure gauge and check your fuel pressures (control, system, and residual). Make sure you have plenty of gasoline in the tank. For this step, you need to know how to test run the FP using the FP relays socket's terminals 87A & 30.

If the above are all good, your engine should start and run unless you have a significant source of unmetered air going to the system.

Tony

Last edited by boyt911sc; 01-16-2016 at 12:50 AM..
Old 01-15-2016, 06:21 PM
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Old 01-15-2016, 07:26 PM
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Quote:
Originally Posted by woland View Post
Don't mind

SC is my fifth car equipped with K-Jetronic ignition and stays outside since nine years, like the previous others.

Clean fuel accumulator, change fuel filter, verify injectors, fuse end relais of the fuel pump. Don't touch any, unless you already verified these things


Tnx for response and tips, I'll do that.
I'm sure outside would be no problem if you drive the car regularly. But if it sits it might be a problem.
Tnx Ola
Old 01-16-2016, 02:29 AM
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Quote:
Originally Posted by kiwiokie View Post
Having just done this on my '83 SC here is what I would recommend:
1. Drain the tank, remove strainer and flush.
2. Remove fuel level sender tube and clean up rust particles that accumulate around connections.
3. Replace fuel filler hose (it dries out and cracks on the underside that you cannot see)
4. Install new strainer and gasket
5. Replace short hose from tank to pump
6. Replace fuel pump check valve. Be careful not to allow pump to rotate when breaking connections as your output hose is probably as hard as rock and will split easily.
7. Replace fuel filter
8. Remove accumulator and flush
9. Remove fuel input line to WUR and clean out fine metal mesh filter (mine had 1/4" of rusty particles)
10. Clean around sensor plate and lubricate hinge if necessary so action is smooth
11. Refill tank and then check pressures with CIS gauges

I initially tried step 11 first and my readings were way off because of issues upstream. Steps 1 through 10 give a good base for your readings. Good luck. Not real hard stuff but a little time consuming.
Long list let's hope I won't need to do it all. But it's great to know we're to start if we keep having the problems.
Tnx
Old 01-16-2016, 02:32 AM
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Quote:
Originally Posted by T77911S View Post
the CSV does not go bad very often. i wuold look elsewhere first.

the sensor plate should move smoothly but it should also have a lot of resistance as long as the fuel pump (the key) is on. there should NOT be any free play before you feel resistance. if the plate moves freely then has resistance the plunger is not coming all the way down.

with the key off the plate will move very easily. it may bleed off any residual pressure at first but once that is gone it should jsut flop around
Big tnx! We now where to start now, I'll get back to you with the results.
Tnx
Old 01-16-2016, 02:33 AM
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Quote:
Originally Posted by boyt911sc View Post
You need just do these three (3) basic tests before going to the details of checking the CIS components:
1). Make sure you have a fully charged battery.
2). Check using an inductive timing light for ignition.
3). Hook up a pressure gauge and check your fuel pressures (control, system, and residual). Make sure you have plenty of gasoline in the tank. For this step, you need to know how to test run the FP using the FP relays socket's terminals 87A & 30.

If the above are all good, your engine should start and run unless you have a significant source of unmetered air going to the system.

Tony
Thank you! Hopefully we'll solve it with all of your tips and tricks.
Old 01-16-2016, 02:35 AM
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Checked the car today, it started when moving the sensor plate. It backfired pretty bad though thru the pop off valve, also noticed the lid on the popup valve was broken, some I'm guessing the air leaks in there and results in backfire???
Old 01-19-2016, 07:58 AM
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Pressure test.......

Quote:
Originally Posted by Porscher View Post
Checked the car today, it started when moving the sensor plate. It backfired pretty bad though thru the pop off valve, also noticed the lid on the popup valve was broken, some I'm guessing the air leaks in there and results in backfire???






Porscher,

Remove the CIS rubber boot between TB and AFM unit. And do a pressure test. You just need a continous flow of pressurized air (no more than 5 psi.) to pressurize the air box and the intake manifolds. Plug the two (2) vacuum hoses that go to the CIS boot (Pope), POV, and throttle body. A latex glove over the TB is one option. And keep us posted.

Tony
Old 01-19-2016, 08:44 AM
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Just had s mechanic do a fuelpressuretest, pressure dropping fast after shutting it off. Isn't that a faulty accumulator symptom?

PS.
Oh You mean a test for airleaks right, read to fast. TB? Not really sure I understand all those steps though.

Last edited by Porscher; 01-19-2016 at 08:57 AM..
Old 01-19-2016, 08:48 AM
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Residual pressure loss....?.

Quote:
Originally Posted by Porscher View Post
Just had s mechanic do a fuelpressuretest, pressure dropping fast after shutting it off. Isn't that a faulty accumulator symptom?

PS.
Oh You mean a test for airleaks right, read to fast. TB? Not really sure I understand all those steps though.




Porscher,

There are three (3) common culprits for sudden residual fuel drop if you exclude fuel leak from hoses or fittings. They are:
1). Defective fuel accumulator.
2). Defective fuel pump check valve.
3). Defective return valve inside fuel distributor. This is the least common culprit.

FA and FP check valve are the 2 most common culprits. You could bench test all the above culprits and don't replace parts unless confirmed and verified defective. Unless you want to spend unnecessarily by replacing parts after parts. Keep us posted.

Tony
Old 01-19-2016, 09:08 AM
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My mechanic checked the fuel valve and it was OK, we'll check the accumulator next time I'll go to the car. The mechanic thought it was the distributor.
Old 01-19-2016, 09:41 AM
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check injector pressure... one or more might "now" be leaking off the pressure which leads to cold and warm start issues. When its one, it's not so bad but when several start to leak it gets frustrating...
Perhaps you can get your hands on a another set of injectors that are known quantity, that you can try in your SC...
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Old 01-19-2016, 02:32 PM
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My vote is for 2) but be careful with those hoses!
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Old 01-19-2016, 06:12 PM
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