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Possible Purchase - '81 931
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5thlilpiggy  



Joined: 12 Jan 2015
Posts: 13
Location: minnesota

PostPosted: Tue Jan 13, 2015 2:28 am    Post subject: Possible Purchase - '81 931 Reply with quote

Hi All

Someone is selling a 931 on the outskirts of the metro area here.

Speedo shows 68k miles, and (supposedly) winter stored, but the drivers seat is pretty beat, so dunno about the legitimacy there...

Last tabbed in 2011. Has not been running in over a year (at least) and being stored in a barn/shed.

Initially would not start. New gas was put in, and alarm wiring was disconnected.

Now, it supposedly starts with starter fluid and will idle great.
When you give it throttle, it stalls out and dies.

I realize it is a big DIY project, which is part of the fun. Given the symptoms, I am worried about possible DITC headaches, which does not sound fun.

They are asking around $2k. Would like some advice from you fine folks.

Try to bargain? Run away in terror?
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jason c  



Joined: 13 Jan 2014
Posts: 1018
Location: Nwi

PostPosted: Tue Jan 13, 2015 9:01 am    Post subject: Reply with quote

Post pics of the car, your mechanical ability, depth of your pockets & we'll give you an answer.
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fiat22turbo  



Joined: 18 Jan 2006
Posts: 4040
Location: Portland, OR

PostPosted: Tue Jan 13, 2015 9:31 am    Post subject: Re: Possible Purchase - '81 931 Reply with quote

5thlilpiggy wrote:
Someone is selling a 931 on the outskirts of the metro area here.


*shudders*

5thlilpiggy wrote:
Speedo shows 68k miles, and (supposedly) winter stored, but the drivers seat is pretty beat, so dunno about the legitimacy there...


The vinyl stitching fails on all of them, but the odometer gears have been known to fail.

5thlilpiggy wrote:
Last tabbed in 2011. Has not been running in over a year (at least) and being stored in a barn/shed.


Do not start/run it again without replacing the timing belt, tensioner and water pump. Or you'll get to replace the valves, repair the head, replace the head gasket and the timing belt, tensioner and water pump (among other things)

5thlilpiggy wrote:
Initially would not start. New gas was put in, and alarm wiring was disconnected.


Yep. Sounds about right for a CIS car. They do not like to sit. AT. ALL.

If you go ahead with the purchase, plan to either drive the car regularly or plan on draining and flushing the fuel system regularly.

5thlilpiggy wrote:
Now, it supposedly starts with starter fluid and will idle great. When you give it throttle, it stalls out and dies.


If they removed the upper intake tube to spray starter fluid into the throttle body, it will stall and die with throttle movement because the flapper in the CIS fuel distributor didn't see any vacuum. Reinstall the intake system and then see if it works better.

Expect to buy a set of CIS fuel pressure testing gauges and various books on the 924 and the Bosch CIS injection system before you go at it with tools and other implements of destruction.

5thlilpiggy wrote:
I realize it is a big DIY project, which is part of the fun. Given the symptoms, I am worried about possible DITC headaches, which does not sound fun.


Folks who have DITC issues either have a minor failure of the connector or wiring which simply requires cleaning and lubrication of all the connections or they have a hard failure of the pickup/ECU and they get to move to aftermarket ignition (or even EFI if they are so inclined).

5thlilpiggy wrote:
They are asking around $2k. Would like some advice from you fine folks.

Try to bargain? Run away in terror?


Biggest issue with the 924 Turbo is the engine. Internal parts and 924 Turbo (931) specific parts getting harder to find (hope you don't have to rebuild the bottom end, replace the followers or find an uncracked exhaust manifold or turbo housing. Many of the more handy folks here have worked around those issues (ensuring the followers are properly oiled and adjusted, letting the turbo cool down before shutting it off, build their own exhaust manifold, etc.)

Otherwise the car is the precursor to the 944 and 944 Turbo, so not only is it rare in terms of the Porsche world, it shares much of its lineage and underpinnings with its children making improvements in many areas fairly straight forward.

I can't comment on the price without seeing pictures/video, but that seems to be about the going rate for a running 931 that needs some work.
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5thlilpiggy  



Joined: 12 Jan 2015
Posts: 13
Location: minnesota

PostPosted: Tue Jan 13, 2015 10:03 am    Post subject: Reply with quote

Pics:

Sorry, I didnt take any. After seeing it in person, the craigslist pics make it look quite a bit better than it actually is. Part of that is due to the windows currently being frosted over and the tires caked with mud (again, stored in a barn).




Ability:

Above average. Timing belt on a Volvo S70. Fuel pump, brake calipers, suspension, exhaust and learned to weld on a rusty Rover D1. Head gaskets and suspension on a Rover D2. Starter (gotta take off the intake), rotors/pads on the Cayenne. Lots of general maintenance stuff on all of the above as well, of course.

Im no master, but Ive learned my way around the inner and under of an automobile

Pockets:

I realize it would be just the beginning, but would be hoping to at least get the engine running for under $1k.
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5thlilpiggy  



Joined: 12 Jan 2015
Posts: 13
Location: minnesota

PostPosted: Tue Jan 13, 2015 10:23 am    Post subject: Re: Possible Purchase - '81 931 Reply with quote

fiat22turbo wrote:

the odometer gears have been known to fail.

Seller claims that the 10,000 digit will be slightly off kilter after 100,000k is passed. Is that true?

fiat22turbo wrote:

Do not start/run it again without replacing the timing belt, tensioner and water pump. Or you'll get to replace the valves, repair the head, replace the head gasket and the timing belt, tensioner and water pump (among other things)

...

If they removed the upper intake tube to spray starter fluid into the throttle body, it will stall and die with throttle movement because the flapper in the CIS fuel distributor didn't see any vacuum. Reinstall the intake system and then see if it works better.


So, should I have them show me that it starts and idles and try the intake reinstall, or let it be?


fiat22turbo wrote:
Yep. Sounds about right for a CIS car. They do not like to sit. AT. ALL.


Is that cause of the vacuum lines?

fiat22turbo wrote:

Expect to buy a set of CIS fuel pressure testing gauges and various books on the 924 and the Bosch CIS injection system before you go at it with tools and other implements of destruction.


It looks like you can build one just by hooking a T up to a regular fuel pressure tester, no?

And yeah, Ive been doing a ton of internet research. Downloaded the factory 924 manual as well as the Model '81. Would get the Haynes too if I bought the car.


fiat22turbo wrote:
Folks who have DITC issues either have a minor failure of the connector or wiring which simply requires cleaning and lubrication of all the connections or they have a hard failure of the pickup/ECU and they get to move to aftermarket ignition (or even EFI if they are so inclined).


Yeah, saw that, and the bold is my biggest fear. Sourcing a "new" DTIC and cable looks difficult and pricey. Also, Ive never dealt with a distributor system, so installing a whole new one is daunting.


fiat22turbo wrote:

that seems to be about the going rate for a running 931 that needs some work.


Would you consider this one "running"?
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jason c  



Joined: 13 Jan 2014
Posts: 1018
Location: Nwi

PostPosted: Tue Jan 13, 2015 10:24 am    Post subject: Reply with quote

Its looks good in the pics. If the car runs with starter fluid, it has spark & the DITC is working.
As fiat said, CIS cars do not like to sit. Plan on doing a lot of fuel system cleaning.
The timing belt is a must do before you run it. Its not complicated, should be no problem for you.
Do a good PPI and negotiate accordingly.
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Grenadiers  



Joined: 20 Feb 2007
Posts: 3222
Location: Nelson, WI & Prescott, AZ

PostPosted: Tue Jan 13, 2015 10:31 am    Post subject: Reply with quote

Two grand is way too much for this car. Looks like all of the engine components in the CIS system are original. Meaning, you'll have to replace or clean quite a bit of that ancient system. Sounds like it has potential to run, but starter fluid starts doesn't make a car. Too many variables that will drive you nuts trying to figure out. The PO senses big money with the Porsche marquee, however, he's delusional in that respect. You'll have to decide on how badly you want this car, and how much that is worth to you. To some of us with parts and knowledge on fixing it, 500-1000 would be tops. And, the interior is another area of concern too.
_________________
'83 944 Track car.
'88 924S Track car.
'89 944 Turbo
2004 Winnebago Vectra monster RV
2012 Jeep Wrangler
2014 Kia Soul
2001 Ford F350 powerstroke
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5thlilpiggy  



Joined: 12 Jan 2015
Posts: 13
Location: minnesota

PostPosted: Tue Jan 13, 2015 10:38 am    Post subject: Reply with quote

jason c wrote:
Its looks good in the pics. If the car runs with starter fluid, it has spark & the DITC is working.


The pics are doing a lot of justice, The exterior isnt too bad, but the interior is not exactly inviting.

Just to be clear...if it idles, the DITC works and the stall with throttle is due to vacuum/CIS?
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5thlilpiggy  



Joined: 12 Jan 2015
Posts: 13
Location: minnesota

PostPosted: Tue Jan 13, 2015 10:44 am    Post subject: Reply with quote

Grenadiers wrote:
Two grand is way too much for this car... To some of us with parts and knowledge on fixing it, 500-1000 would be tops.


Thanks, I was looking for this kind of blunt price analysis!

The thing is, they paid about 1600 for it thinking they could flip it. Will be tough getting them below that and would suck if they decide to part it.

Grenadiers wrote:
Looks like all of the engine components in the CIS system are original. Meaning, you'll have to replace or clean quite a bit of that ancient system.


So, there would be a bit more involved than replacing all the hoses?
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jason c  



Joined: 13 Jan 2014
Posts: 1018
Location: Nwi

PostPosted: Tue Jan 13, 2015 11:01 am    Post subject: Reply with quote

The DITC (digital ignition timing control) is this cars ignition system. The biggest area of concern is the pickup sensor on the flywheel which is NLA. If the car runs on starter fluid, the ignition system is making spark. If your getting spark, the DITC is working.

The reason it can't be revved up could be vacuum related. It likely fuel starvation. An engine can run with no intake system at all if its fed the proper amount of fuel. With no intake, you have no throttle body/plate, without it the engine will run wide open though.
Fuel delivery is critical on these engines, it will not run properly on too much or too little. Starting fluid is not intended to keep any car running, its difficult to feed the proper amount in and its not good for the engine anyway.

If you purchase this car you'll likely have to change some if not all the vacuum lines/hoses anyway, heat & age kills them. If it hasn't ran in awhile, its also likely the fuel distributor, warm up regulator and cold start valve may need rebuilding or replacing in addition to cleaning out of the fuel tank, lines & injectors.
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5thlilpiggy  



Joined: 12 Jan 2015
Posts: 13
Location: minnesota

PostPosted: Tue Jan 13, 2015 11:39 am    Post subject: Reply with quote

Just to clear up any misunderstanding...

They drained the tank and put fresh gas in.

They then started it with starter fluid.

At that point it will idle, in his words, "all day long", but if you give it gas it will die.
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5thlilpiggy  



Joined: 12 Jan 2015
Posts: 13
Location: minnesota

PostPosted: Tue Jan 13, 2015 11:56 am    Post subject: Reply with quote

I sincerely want to thank everyone who responded, especially jason c. It has all been very helpful.

So, last 2 questions:

1. Is $1500 absurd, or just a little high?

2. At $1500, worst case is I could make over half of that back by selling just the DITC/crank sensor and wheels, right?
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jason c  



Joined: 13 Jan 2014
Posts: 1018
Location: Nwi

PostPosted: Tue Jan 13, 2015 12:45 pm    Post subject: Reply with quote

Value depends on who you ask. Value to you should be what matters. However, a lot of people lose their shirts on these cars because of the lack of understanding. This is not a cheap car to fix unless you have knowledge, ability & resources. I think all of us have more into our cars than their "worth" but thats pretty much the same for all car enthusiasts.
If you can post pics representative of the cars condition, we can give you a better idea on value.

Don't expect to get this car as an investment.
As a parts car; the crank sensor will sell fast. The turbo (if still good), head, nose panel and hood (if you have a close buyer) will sell quickly at fair market prices. The rest of the stuff is a dime a dozen & will take you forever to get rid of.

Its a good sign if it idles on its own. The cold start system has a problem if starting fluid is needed to get it going.
If its not cold starting on its own and is starving for fuel when revved, I would check fuel pressure & delivery and hot & cold control pressures to start with. There's likely a problem with the wur from sitting.
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MikeDanger  



Joined: 21 Nov 2002
Posts: 490
Location: Denver

PostPosted: Tue Jan 13, 2015 4:20 pm    Post subject: Reply with quote

the 931 isnt a car to make money on. you could make more (flipping) a 924na.
with a 931 your selling/buying a box of potential problems!

2k is too much for a car that wont start and run. especially for someone that doesnt know anything about them.
A car that wont start/run is about 5-600, a "decent" condition car is 1500-2000.
The CIS is a pain in butt.

They were stupid for paying 1600 for it.
If you think it might run offer 1k or less. No one is going to jump to pay 2k let alone 1600, tell them if they want to cut their losses to call you, and walk.
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morghen  



Joined: 21 Jan 2005
Posts: 8167
Location: Romania

PostPosted: Tue Jan 13, 2015 6:32 pm    Post subject: Reply with quote

Weather you buy it or not, the timing belt must be changed ASAP, don't turn the motor over anymore unless you properly replace the timing belt. Its cheap and easy and it saves the car.

DITC either works or does not...it will not cause the car to idle but stall on acceleration.
CIS on the other hand can do this...probably a vacuum leak from cracked hooses tho..but could be fuel related as well...things need to be checked and understood...and if you have a Haynes manual and just a tiny amount of brain you can sure make it work as it should.

A 931 is a car gaining value, money like 1000-1500 is cheap...1000 is money you spend in a month on food and gas..its not real money..and you are buying a car that can put a smile on your face for 1-2 month food money.
I know US is a different story, but in Europe good condition 931 sell for 5-6k easy, while excellent condition ones close in on 10k.

The "not running" idiot theory is a big mistake in my opinion. Without actually knowing whats wrong with the car you might be tossing a great deal. Maybe its just a loose hoose connection or a cracket vacuum line...or it might be that you need to spend a few hundred dollars on a fuel pump, some cleaning substances and who knows, maybe even a WUR rebuilt...it will not cost you a fortune and if you can afford to toss 1500-2000 on a car you can afford to spend another 500 on making it run properly.
If your total money is 1500-2000, take the bus.

Good luck with the car !
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