Troubles after winter storage...

[azasadny]

I took my 1974 911 (2.7 CIS) out of winter storage a month ago and put in a new battery and it started right up on the first try. I had put a bottle of StaBil in the tank last November when I stored the car. I started noticing that the car would have troubles starting cold, but once the car warmed up, it would start fine. Now, the car is hard to start (takes at least 20 cranks) and then backfires! After a backfire or two, the car starts and then runs smooth with no problems. Another problem is that the car idles at 1900 rpm after it warms up.

Could these two problems be related? Last summer, I replaced the plugs, wires, CD unit, coil, points and dist cap and rotor, cold start valve, set the timing. I thought i had everything covered, but the starting problems and backfires drive me crazy, especially since the car runs great after it does get started and never misses a beat when I'm driving it.

I would appreciate any advice as I'm a novice and this is really baffling me. I smell gas and hear the whine of the CD unit and know I'm getting spark, but what is causing this? Thanks in advance!!!

[Rob McKibbon]

Az,
Same car as mine. Touchy little buggers though?
I had similar problems before I rebuilt my engine this winter.
However, upon refitting the CIS we discovered the PO had installed some low budget fuel lines and clamps. The fuel lines can run up to 80 Lbs of pressure...... anyway my mechanic installed a pressure gauge into the fuel line system and discovered a "faulty" fuel regulator. It was not holding the proper fuel pressure, which makes cold starting more difficult. These CIS systems can be very tricky and I don't really understand how they work, but they do deliver different pressures of fuel depending on the RPM's and Engine Temps? You can pick gauges up fairly cheap; install the gauge. After warming the engine, the pressure should be maintained overnight. Mine was dropping off.

Some testing also exposed that my brand new fuel sender (the one under the car behind the drivers seat) wasn't holding pressure either. They're famous for this, at this year too. No gaurantee a replacement would work either, so we installed a one way check valve in the fuel system too.

Car runs like a dream now, can't believe how easily it starts whenever!

(Now I think I have a problem with the starter overheating and not engaging when hot? Hasn't happen since learning how to check it, thanks to Pelican BBS)

Good Luck!

[azasadny]

Rob,

Thanks for the good advice! I replaced the fuel filter last summer, but the fuel regulator could be the culprit! I really appreciate the advice and I will look into this. Funny, as the car runs so well after it starts, you'd think a fuel pressure problem would prevent the car from running well. I don't understand the CIS system either, I just didn't want carburetors to adjust! There is always something to tinker with!!!

Thanks again!!

[Rob McKibbon]

Forgot.... when replacing my fuel regulator, my mechanic ordered a 1978 one; he said they improved the design of them in that year. Still waiting for the replacement, but installed a temp. used one until it arrives....

Gauge installed:


This is the fuel regulator:

[Jdub]

You haven't mentioned if you have freshened the gas, etc.

Pick a free day, top off with fresh gas, and drive the car for well over an hour. You have got to drive out all the crap and varnish. When you get home, drain the oil and put in fresh oil and filter. Then, with a near-empty tank, put in 20oz of Techron and fill it up.Again, drive the car for a minimum of one hour in a spirited manner.

Don't spend money on things you may not need to. Give the car a chance to wake up first.

John

[azasadny]

Jdub,

I failed to mention that I ran 1/2 the tank of old gas (by driving), then put in fresh gas and Techron. I now have a full tank of fuel that is fresh and I have driven the car about 100 miles total since taking it out of storage, but now the "intermittent" starting problem has now progressed to a constant problem. If I let the car sit for longer than 1/2 hour, it gives me fits when I try to start it again. Once the car starts, it runs great, so this is really frustrating me.

The next step is to replace the fuel accumulator (I just ordered it from Pelican Parts), then try it and if that doesn't work, I'll check the fuel/air mixture (but I don't know how to do that).

[Jdub]

Sounds like you are on the right track. For the CO, be sure to have the car well warmed up and have a pro. set it for you. JohnW sets my CO at 3.5% but your car may require different - I don't know (mine is a '78SC).

John

EDIT: do put in a fresh gas filter.

[azasadny]

Jdub,

I changed the fuel filter last summer when I replaced the PermaTune CD unit. I figured that I may as well change it while I was there. I replaced alot of vacuum hoses, clamps and fuel lines as well...

[Jdub]

Heck, I replace the fule filter twice a year to correspond to the shift to oxygenated fuel. It's cheap insurance and I recommend that same schedule for others running our CIS systems because it is SO sensitive to impurities.

Just a thought,
John

[azasadny]

Well. i replaced the fuel accumulator, then jumped the car today and after 10 or so cranks, the car started and ran great. I drove for about 1 and ½ hours, all over the area. The car used to idle at 2000rpm after it warmed up and it didn’t do that at all. The idle is about 800rpm, so I need to adjust that. I tried to restart the car immediately after parking it in the garage and it started right up o the first crank. One half hour later, I tried it again and the car won’t start, so I’m back at square one and don’t know what to do next. I may have to get the car started and then take it to a shop , although I really don’t want to do that. I sprayed degrease solvent in the hole next to the fuel distributor and I was able to turn the idle speed set screw….. it wasn’t easy and seems very hard to turn. any ideas on what I should try next? do I need to get a pressure gauge for CIS troubleshooting? And if do, any particulat recommendations as to source and brand? Thanks!

[ruf-porsche]

Originally posted by azasadny
do I need to get a pressure gauge for CIS troubleshooting? And if do, any particulat recommendations as to source and brand? Thanks!

First you should determine if it's a fuel problem or no spark problem. Don't assume that just because the car doesn't start it's a fuel problem.

Does your fuel pump have a check valve? Could be that the check valve is no good and the pressure in the fuel line is slow dissipating as the car sits. Another way fuel pressure could dissipate is through leaky injectors. When you were able to get the car started was there a lot of black smoke? Black smoke indicates a very rich or flooded condition.

If you are going to be working on your car, a good set of tools and test equipment is invaluable.

J.C. Whitney has a CIS pressure gauge. It was mention in several previous posts. Poster I believe was SOUK.

[azasadny]

Ruf-Porsche,

Last summer when I bought the car, I replaced the CD unit (PermaTune), installed the Pertronix unit, new plugs, cap, rotor, fuel filter, etc... and tuned the car and put in a new Optima battery this spring. I'm getting a good spark and I am getting fuel to the fuel distributor and can smell gas. Once the car starts (eventually), it runs smooth and powerfully without any flat spots, but getting it started is the problem. I'm thinking the problem has got to be in the CIS system, maybe the WUR? I'm getting the CIS pressure tester and possibly the CO analyzer (If I can even find one). I also repleced the cold start valve last fall when the "intermittent cold start problem" began. Now the problem is constant. When I try to adjust the idle speed control (mixture) 3mm Allen screw next to the fuel distributor, I have a very difficult time getting the Allen wrench to seat properly and it's very difficult to turn. One of my new "Porsche buddies" drove over yesterday to help and he said it's much more difficult to turn my Allen bolt than his. He thinks mine is gummed up with carbon and I sprayed some Gumout to try and loosen things up a bit. I can restart the car easily with 15 min or so after driving, but after that it's back to the "crank 30 or 40 times to get it started" routine. Very frustrating!!

[bigchillcar]

Azasadny,

I likewise have a '74 911 and do all my own work. Just a couple quick observations. In your pic you posted, your arrow points to what you call the 'pressure regulator'...this is in fact your fuel accumulator! When you say 'pressure regulator', I think you refer to the infamous 'warm-up regulator' (sorry no pic, but look for a pic in Pelican's parts section). The warm-up regulator has an internal element which senses changes in engine block temperature and adjusts fuel pressure accordingly. If this unit ($350 I think) has failed, it could mean that it's supplying insufficient fuel pressure while cold AFTER startup.

You mentioned that you replaced the cold start valve...was the thermotime switch replaced concurrently? They work together. The thermotime switch checks when starter power is applied to see whether or not the block temp. is 90 degrees or greater. If not, it opens the cold start valve which acts like an extra injector. If less than 90, it will not...it thinks the car is warm and doesn't need it.

Another point...the screw you refer to on the fuel distributor, accessed with an allen wrench is the mixture - not idle screw. If you have played with it too much, you'll have CO mixture problems galore. It is very sensitive and without a gas analyzer, may need a tech to reset properly to 3.5% (memory). What you need to look for is called the idle air-bypass screw (about the size of a dime). Look for it where you see your throttle linkage...it has a tension spring to prevent it from moving or backing out once it is set.

Finally, you haven't mentioned your hand throttle, but its function is an important one. It must be up for starting at anytime - whether hot or cold, per manual. As it warms, adjust it down until not needed. Check idle speed at 180 degrees. At this temp., turn the idle air bypass screw until idle reads ~ 950 rpm's. Idle is now properly set. The hand throttle is genrally needed for the firsy 10-15 minutes, after that the car is warm enough not to require it any longer. Hope this helps!
Ryan

[azasadny]

Ryan,

Thanks for the info, sorry for my confuding posts, I'm a clueless newbie and it shows! Yes, the fuel accumulator was what I replaced the other day and it didn't help (I really didn't think it would). I replaced the thermotime switch at the same time I replaced the cold start valve. I have to check my hand throttle because i use it, but I don't think it's doing anything. I have monkeyed with both the mixture and idle screws, but my allen screw for the mixture is really hard to move. I have moved it one-half turn clockwise to richen the mixture as my car was backfiring, whch I though indicated a "too lean" condition. I'm contemplating buying a Gunson CO analyzer and I'm bidding on a CIS pressure tester on eBay right now. Am I missing anything else? I'm getting spark and fuel but still incredibly difficult to start. When the car does start, it runs great! Thanks for your help, you guys are great and I don't know where I'd be without you!!

[bigchillcar]

Azasadny,
How much is the CO analyzer going to cost you? My impression is that this would be too costly to justify purchase unless one went into business with it. It's probably a lot cheaper just to let a knowledgable tech do his job and set it properly. I don't have that equipment and since the adjustment is SO sensitive, I happily let a tech do the job. Perhaps you've turned the screw to the stop? My thoughts are that if the car was generally running fine before storage, then the mixture should have remained ok and didn't require adjustment. One way to confirm this is to check your spark plugs' condition. Wet, black plugs indicate a mixture that has long been too rich...white plug residue? Too lean. If they look dry and generally in between this condition (lots of books with these pics available) then your mixture was probbaly fine before setting. I would have checked this before adjusting, if they look fine, probbaly no need to investigate further. When they don't I'd take it to a tech for analysis. That's an easy and free diagnostic (well, plugs are never easy to remove from these cars ).

As for the hand throttle. When starting with it all the way down, it should idle poorly if at all. When up and started as it warms, you should hear the idle speed increasing. It's not a choke - all it does is provide a separate access point to your throttle linkage. Its the same thing as holding your foot on the pedal! It just removes the work in doing so. There is a plastic bracket that connects this hand throttle to the actual throttle cable. It's just underneath the hand piece (white plastic). Remove the three screws that hold the emergency brake bracket to the body and you should see it. I discovered last week that a friend's '74 has this piece broken and so his hand throttle does nothing. It makes it kind of hard to drive until warmed up. FWIW, this only came on the '74 car. After this year, they installed the 'auxillary air valve' to do this job automatically with vacuum. I personally prefer the hand throttle because I can control my idle to suit me. When at a stop light, if the idle is low and its night and i have my lights, radios, etc. on, the load can literally turn off the radio. I reach down and pull up a little on the hand throttle and I've got tunes again!
Ryan

[azasadny]

Ryan,

Thanks again for the good advice! The Gunson CO analyzer is available on eBay for about $120, which is less than the cost (and more convenient) than taking the car to a shop. The closest Porsche shop is about 50 miles from me.

I'll check the hand throttle and see if it's broken because it doesn't seem to do anything at all. The car had an intermittent cold start problem last fall, when I put the new battery in it this spring to take it out of storage, it started on the first crank! I thought my problems were over, but the problem returned and now it's constant instead of intermittent. When I put the new plugs in last summer (lots of fun and scraped knuckles!), the old plugs looked good with no signs of fouling.

[bigchillcar]

Hi,
I would guess you're correct and your mixture was probably fine before 'adjusting it'

If you've driven 100 miles with a very lean condition that would certainly cause backfiring as described, I would check at least one (the easiest to access) and see what it looks like. If you get the chance, let us know the condition.

A quick check if your hand throttle is at least connected...remove the four screws from the plate in the floorboard of the backseats (where your shift coupler resides). There you will find the throttle cable (more on the driver's side of the tunnel). Watch or feel it move by pressing the acc. pedal. Then do the same working the hand throttle. If nothing happens with the hand throttle, my guess would be that it's either way out of adjustment or that plastic part described earlier is broken!
Ryan

[caliber60]

You should not top off old gas with new gas. Drain the old gas completely. My was stored for 5 years.

[azasadny]

Caliber60,

Prior to storing my car for four months, I filled the tank and then put in a bottle of StaBil. The car started the first crank after sitting for that time. I just checked and my hand throttle isn't connected to anything, so I've got to fix that ASAP. Thanks!

[azasadny]

Bigchillcar,

The plastic piece that is supposed to be attached to the hand throttle lever is nowhere to be found, looks like I need to order one! The cold-start relay in the rear electrical shelf was also "missing" and I installed a new relay, but there are a few loose wires back there that I need to trace and figure out. You don't happen to have a wiring diagram that shows where the wires in the engine compartment are supposed to go, do you? Thanks again!