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Fuel enrichment for cold starting?

I drove my 930 out to my folks house on Thanksgiving. When I left, it was about 25 degrees out and I didn't think the car was going to start. Normally it pops right off, but I had to crank it for about 5-6 seconds, then again for about the same ...... finally on the third attempt it fired after about another 5 second crank.

I wonder what the deal was? Do these 930s typically not like cold weather?
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Old 12-02-2008, 05:50 AM
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Could be an isolated event.
If not then check the spark and cold start fuel function. The cold start valve helps to fire off quicker and the fuel pressure must be within spec for the temperature. If the fuel pressure is high (off spec) then the engine will put-put-put to life.
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Old 12-02-2008, 05:59 AM
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My mechanic said that these cars are not eager to start much below freezing (bearing in mind that I have the earliest form of WUR on my 1976)...
Old 12-02-2008, 07:50 AM
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Thanks.....

When it did fire, it fired right up, but it was after a LOT of cranking. Maybe I will try it again in the safety of my garage to see if it is a reoccuring issue, or if it was a one off event.

I don't plan on driving the car much in the freezing temps anyway, but it's not much fun to think you could get stranded because of something like that.
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82 Porsche 930 Euro, black, 31K miles.
Factory stock other than k27 turbo, B&B headers, GHL exhaust, Tial F40, 1 bar wastegate, MSD 6A ignition, 8" and 9" Fuch upgrade, H4 Xenon headlamps and a 930S steering wheel.
Old 12-04-2008, 06:04 AM
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It should fire right up in the cold. Mine starts withing 3 seconds nomatter what the temperature, and that is without the AAV. When I lived in IL the car was started once a week all winter long.
If your engine did not chug to life when it fired up I would suspect the cold fuel pressure is OK. That leaves the cold start valve and spark. There is always the looming odd issues caused by vacuum leaks as well.
Do report back if you can get it to repeat and what your findings are. Good info for aging cars.
One more thing I just thought of, check valve. If your fuel pressure drains off completely when cold it will take longer to start. This condition however is not dependant on temperature.
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'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8

Last edited by RarlyL8; 12-04-2008 at 06:16 AM.. Reason: Ad to post.
Old 12-04-2008, 06:13 AM
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Rarlyl8

Brian,

I was just reading this thread as I am having "cold start issues" and noticed your last post where you mentioned the check valve... I thought our cars did not have them. Mine is an 87.

Can you clarify?

Maxx1, did you ever figure this one out?

Thanks guys,
Bryan
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Current cars: 2012 Cayenne TT, 1997 993TT, 1984 Jeep Grand Wagoneer, 94' 928 GTS, VW GTI
Old 10-31-2009, 07:41 AM
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Quote:
Originally Posted by x98boardwell View Post
Brian,

I was just reading this thread as I am having "cold start issues" and noticed your last post where you mentioned the check valve... I thought our cars did not have them. Mine is an 87.

Can you clarify?

Maxx1, did you ever figure this one out?

Thanks guys,
Bryan
Bryan,
The check valve is located up front, connected to the output of the front fuel pump. If you have a faulty check valve, you will see the residual fuel pressure drop precipitously after the engine is shut off. There are specs in the Porsche shop manual for the amount of pressure drop vs. time. I'm on the road so I don't have access. Maybe someone else has spec?
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Old 10-31-2009, 08:26 AM
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Fuel pressure should drop and hold at 2.5bar after shut down. If not start up will require a lot of cranking. Check valve in fuel pump and fuel accumulator perform this function.
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'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
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Old 10-31-2009, 11:42 AM
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Guys

Thanks for the help. I have replaced my fuel accumulator because I had a hot start issue at one point but now that the weather is getting colder here at night I find myself cranking the engine over in the morning and it sputters to life eventually and then runs fine after that in any condition... only the first time in the morning when cold.

I will check cold pressure and check valve. Does anyone have a picture of the check valve and where to hook up lines for cold pressure??

Thanks again for the quick replies.

Bryan
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Previous cars:
2007 GT3, 2006 Cayenne TTS, 1991 928 S4, 1987 930, 1975 914 2.0, 1989 944 Turbo S, 1991 964 Targa, 1991 964 Convert, 2004 996TT Convertible, 550-6 Spyder with a 2.4 liter twin plug "S-spec'd motor"
Current cars: 2012 Cayenne TT, 1997 993TT, 1984 Jeep Grand Wagoneer, 94' 928 GTS, VW GTI
Old 10-31-2009, 01:39 PM
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"Sputters to life eventually" sounds like the put put put cold start of a lean AFR. Typical problem is high fuel pressure from the WUR. Is yours adjustable?
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'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 10-31-2009, 07:24 PM
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Don't we also have a thermotime switch and cold start injector that should energize for a few seconds on cold starts? Or was that just for US cars?
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Old 11-01-2009, 04:55 AM
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Typically when the CSI fails you just have to crank a little longer but the engine still fires and runs.
The TTS shuts down auxilliary air devices once up to temperature. These devices simply raise the idle.
If you are experiencing the "put put put" to life and a low idle at cold start only it is typicaly AFR related.
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'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
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Old 11-01-2009, 05:43 AM
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Question

Brian,

I have an AFR gage in the car. Once the car finally starts the AFR's are great around 12.5 or so (being cold and all). Once the car settles down from the high revs after 30 seconds it then will go a little lean (around 16.5 or so) and then eventually it will be fine (in the mid 14's).

How comfortable do you feel that this is purely a WUR related symptom or do you think it still could be the check valve... since I have already replaced the Accumulator.

Thanks for everyones input on this. Other than this one hick-up the car runs perfectly.

Bryan
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Previous cars:
2007 GT3, 2006 Cayenne TTS, 1991 928 S4, 1987 930, 1975 914 2.0, 1989 944 Turbo S, 1991 964 Targa, 1991 964 Convert, 2004 996TT Convertible, 550-6 Spyder with a 2.4 liter twin plug "S-spec'd motor"
Current cars: 2012 Cayenne TT, 1997 993TT, 1984 Jeep Grand Wagoneer, 94' 928 GTS, VW GTI
Old 11-03-2009, 03:43 PM
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Update

Well,

I changed the $25 check valve in the front of the car. That was not it. I even unplugged the sensor behind the CIS so the fuel pumps run all the time.

It still starts horribly on first morning starts. So, this has to be either WUR related correct? It doesn't seem even if the CSV was not working that it would take 10 tries to start since there would be plenty of fuel in there at that time, correct?

Thoughts?

Bryan
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Previous cars:
2007 GT3, 2006 Cayenne TTS, 1991 928 S4, 1987 930, 1975 914 2.0, 1989 944 Turbo S, 1991 964 Targa, 1991 964 Convert, 2004 996TT Convertible, 550-6 Spyder with a 2.4 liter twin plug "S-spec'd motor"
Current cars: 2012 Cayenne TT, 1997 993TT, 1984 Jeep Grand Wagoneer, 94' 928 GTS, VW GTI
Old 11-12-2009, 06:26 PM
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Bryan,

I can have my car mimic your exact symptoms by simply raising my cold pressure in my WUR 0.5 bar. I know this, because I did it this past weekend...

E.g. - - > Right now, my car starts and idles perfectly when cold. My cold control pressure is 2.3 BAR. It starts there and slowly rises to 3.8 bar over about a 3 minute period.

However, if I was to raise my cold control pressure to 2.8 bar, I would experience the same problems you are having at initial startup... [the ole "put put to life" thing...]

The 0.5 bar decrease is all I need to go from terrible cold running [very lean and barely staying alive] to purring like a kitten... If you don't have an adjustable WUR and a set of CIS gauges, I'd get some...

Once you have them in hand, feel free to contact me on how to adjust.
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Old 11-12-2009, 06:53 PM
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Thks

Mooney,

That is exactly what I wanted to hear. So is your advice to send the WUR to Brian Leask to rebuild and make adjustable or should I just rebuild my WUR with no adjustability?

Thanks,
Bryan

Also, best place to buy gages and hoses and also where to hook into?
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Previous cars:
2007 GT3, 2006 Cayenne TTS, 1991 928 S4, 1987 930, 1975 914 2.0, 1989 944 Turbo S, 1991 964 Targa, 1991 964 Convert, 2004 996TT Convertible, 550-6 Spyder with a 2.4 liter twin plug "S-spec'd motor"
Current cars: 2012 Cayenne TT, 1997 993TT, 1984 Jeep Grand Wagoneer, 94' 928 GTS, VW GTI
Old 11-12-2009, 07:18 PM
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Like others have previously posted: the "put put put to life" is typically a symptom of high control pressure under the "cold" phase of the WUR. If this is what you have, then you'll need to adjust that...

Our host has the gauges: TOL-TA33865 for $99

I had BL send me a programmable WUR [I think I had to give him the part number off of mine so he could match it] and I simply mailed him mine once I got his installed.

I wouldn't know the first thing about rebuilding a WUR, myself... So, can't help you there...

Because I have a wideband AFR, I enjoy instantly seeing the results of my adjustments [either: cold, warm, or enrichment].

Because this is my first year with the 930, I noticed that as the weather cooled off [90's to 60's], I had to lower my cold control pressure setting to get a smooth warm up [from 60-F].
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Old 11-12-2009, 08:50 PM
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Got my CIS gauge from jc whitney and iirc it was $60. Quality is fine and I hooked the gauge up at the WUR.
Old 11-12-2009, 11:57 PM
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Typical cold pressure target is 2.5bar as previously stated. With these aging systems I throw out the book and tune to what works best in the environment driven.
You don't necessarilly have to have an adjustable WUR to adjust the cold pressure. There is a plug over the bimetal spring that you tap down to richen. Tap too far and you have to take the WUR apart to tap back the other way. If you put the gages on you can see the change in pressure as you tap so it is not difficult if you go slow. Nothing to loose ...
Do verify your pressure before doing anything to isolate this as the problem.
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'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
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Old 11-13-2009, 05:04 AM
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Ok.. thanks

Mooney,

Yes, I have no idea how to rebuild either so that is not an option. I will reach out to Brian Leask (anyone have his email) and see what he has for me. I also have an Innovate Wide band AFR that is hard mounted so I can also see real time the issue... but not until the car actually starts. When it finally starts (and then running well) it is around 11.5 or so then creeps up from there.. but by this time haven't I already overcome the pressure issue and that is why the car started?

RarlyL8,

Where is the plug that you are referring to and what tools do you to use to tap to introduce enough force but not too much? I will absolutely attach the gages first but want to make it is not too late... since it is a cold start issue and I cannot tell the actual pressure until the car if running correct?

Thanks for the help guys,
Bryan
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Previous cars:
2007 GT3, 2006 Cayenne TTS, 1991 928 S4, 1987 930, 1975 914 2.0, 1989 944 Turbo S, 1991 964 Targa, 1991 964 Convert, 2004 996TT Convertible, 550-6 Spyder with a 2.4 liter twin plug "S-spec'd motor"
Current cars: 2012 Cayenne TT, 1997 993TT, 1984 Jeep Grand Wagoneer, 94' 928 GTS, VW GTI
Old 11-13-2009, 06:38 AM
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