Make my day! Hard start!

[ras911]

Here’s my story sad but true

Picked up my 1983 911SC ( muhahahahhhaaaaa) two weeks ago, drove her home 1337 miles , purred like a tiger the whole way home . Before I picked up the car I had a local respected mechanic adjust the valves,update to carrera tensioners changed the tranny fluid , flush brakes install a popoff and remove the ecrunbling engine pad . The PO had put in a new o2 sensor, new plugs fuel filter , air filter etc .I’m thinking for all intents and purposes, outside of brake pads and tires, this car should not need a lot of attention outside ofd routine items until the 60k service in 3 years. Great!
Alas, the next morning I had difficulty starting her up . Some backfires, a little uneven idle and roughness . Five minutes later beautiful, thank you Ferry.
Later that day, one of my Porsche buddies wants to see the car ,and what do you know - no start, well at least a hard start. Okay , I called the mechanic who had worked on the car and he suggested a bad tank of gas on my way home . Suggested blowing out a couple of lines from and to the accumulator. I figured I would get it to my mechanic in due time.
Not a big deal until yesterday when I went out to start the car and …….nothing, no start. Plenty of crank no start. - I check the basics – relay , fuses, gas in tank. Raise the sensor plate and the fuel pump fires right up. After messing about a bit I finally press the pedal to the floor and crank and she starts sputtering, dies and catches , I rev her up and a minute later lo and behold , smooth as silk! Drives b eautifully , pulls smoothly through the tach. Let her sit for a couple of hours she starts but not without adding pedal. This morning same thing . She doesn’t want to start ! Peddle to the meddle and crank and she finally catches on . Check electrical connections look(feel) for leaks
So hears my thinking , either the car has not adjusted to the climate change well between old home and new and is running too lean , or the cold start system has a gremlin.

I will probably not attempt to correct this on my own, I don’t have testing tools for a fuel injection system nor the experience and I would not feel comfortable attempting to diagnos and fix a complex system such as CIS. I was thinking of perhaps changing the cold start valve but maybe this is just a simple adjustment that is needed.

You guys seem to know these systems very well, perhaps with the description above you could take a shot on internet diagnosis as an exercise !! If there is a simple solution maybe I could handle it . BTW is that cold start valve at the front of the system ( a reach around from the back?

Go ahead make my day!

[Joeaksa]

Bob,

Wonder if you have a fuel pump or pump relay going bad? Just a guess but the backfiring makes me wonder if your pump is working part time and not delivering enough fuel all the time...

JoeA

[ras911]

Hey Joe
The backfire is only on the start up. Once she is settled in ( 1 minute) she is great. Changed the relay , checked the fuses. When the Sensor plate is lifted with the ignition on, car not running , it sounds pretty good . Thanks , The fuel pump was my initial thought too.

[Paulporsche]

Bob,

You should do a search . There are quite a few threads on these symptoms. If the car starts, usually your cold start valve is working. You should have your control pressures (especially cold) checked. The most common cause would be an out of spec WUR. However, it's possible your mixture is just too lean for your car's new home. You can try enrichening in small increments and see if it helps. If the car wants to stall after revving or has a hunting idle, go slightly leaner.

That is probably the CSV that you are describing. It has a blue "collar" around it.

[ras911]

Paul, how would I make the mixture richer? I am used to truing bicycle wheels , which is also done in small increments . I would like to give that a shot

[Paulporsche]

There is an adjustment screw accessible from the top of the mixture control unit. In your car it may be capped by a plug that has to be drilled and pulled out, or you may find a hole there, or even a removable plug that has been inserted by a PO or mechanic. The adjustment is made by a long 3mm Allen wrench. By small increments, I mean nudges, like 1/32 or 1/16 of a turn, since 1 complete turn
could produce a change in CO of between 8 and 12%--a HUGE amount.

A search will tell you more. Since this is new to you, you may want to go to a mechanic. He can check the pressures w/ the gauges and see if your WUR and AAR are OK. He can also set your CO for you. It won't be expensive, and if you observe, you will then know what to do for future reference.

BTW turning the screw clockwise as viewed from above richens the mixture.

[ras911]

Paul
I think I know what you mean . Probably best to leave this in the hands of a pro. I am also sitting here wondering if it could be the check valve on the fuel pump. It could be a pressure issue , I will have it checked. Thanks

Bobn

[Paulporsche]

The check valve and fuel accumulator are possible culprits. This is why checking the fuel and control pressures will give you insights.

Usually, if it starts, ridles rough when cold, and then OK when warm, then it is probably lean when cold, so either the mix setting is off or the WUR is leaning the mix. If the cold idle is low but the warm idle is OK then look to both the WUR and AAR.

[ras911]

Paul
Looks like you were on the money. The mechanic is blaming it on old fuel and a bad WUR. I will know for sure later.

[ras911]

Update on the symptoms
So any way the wrench paints a freakin' doomsday scenario ; rusted gas tank , clogged fuel distributor and injectors, varnish in the entire system from old gas yada yada yada!
I am totally depressed . He then revises says I need a new WUR , charges me a shi-load for the part and the labor and it pretty much seems unchanged . His plan is to finance his track days from Bob's 911 or so it seems to me until..................he suggests putting in a can of BG 44k and running the hell out of the car. Seee what happens he says . Well I'll tell you what happens , I bug out of work load up the tank with a couple of gallons and a pint or so of this BG snake oil and go on a redline binge . Of course it about 100 degrees the day I do it , but the engine is suprisingly cool , but not me no way ... I am sweating my butt off.

Lo and behold it seems much better and I am getting optimistic . So I get some more gas in the tank and add a little fuel fresh , now she is starting on the second key turn . I park her out front after a grocery run with my favorite little co-pilot, my 8 YO on Father's day . You know the drill the grocery is up the street but somehow we put 8 miles on the odo. Okay now I am getting pumped because the start situation is improving . I go out to the car to put it away for the night and OH NO , she cranks and cranks without a hint of wanting to start. I woke up several times last night thinking I am totally messed up here . Try it this morning - no go . Now the temp last night and this morning was probably low 60s.

So I do a few searches - figure I will check for vacuum leaks etc , not really expecting anything because of what the mechanic told me about my varnished up system . Any way It's about 80 when I get home. I put the key in fire it up and she sounds hopeful - I then turn the key a second time and she fires right up!!!!
Later or should I say earlier tonight I took a nice 25 mile jaunt around the Capitol, Va and back to MD . Running very nicely indeed . SO WHAT GIVES?

Paul , Vash??? CIS DUDES?????

Thanks guys

[Paulporsche]

Did this mechanic ever check your control pressures after installing the new WUR? Especially your cold control pressure on a cold morning?

Did anyone ever check to see if there was any rust in the tank or the other components you mentioned?

[echrisconnor]

I'm with Paul on this one. You have to check the pressures to get a clue here. It sounds like the classic symptoms of a bad WUR or leaking check valve. You've replaced the WUR so that makes it less likely to be the culprit. If you're in the replace without checking mode, then replace the check valve next. However, I'd get ahold of CIS pressure testing tools first and definitively find the problem. Your mechanic should be able to do this sort of a test very easily, or you can absolutely do this yourself. If you just dropped $400 on a new WUR, this $60 for the CIS tester is money well spent. There are numerous posts on how to check pressures and what various test results mean.

[ras911]

Believe me I am not in the mode of replacing things. This CIS is beyond me as noted in my post . We havent had any cool weather to think of except for the other night and I believe they checked the pressure after letting it sit overnight when it was in a couple of weeks ago

The check valve is not temperature related is it?

I will have to get it checked , not sure of my faith in this mechanic.

Fuel tank checked for rust found nice and clean, not an issue.

Where do you get those gauges?

[stealthn]

Here's my 2 cents (CDN), replace the fuel filter and accumulator, throw a can of techron in the tank and drive the crap out of it. If it doesn't make any difference, check fuel mixture and pressure.

Good luck and let us know.

[echrisconnor]

Gauges can be bought through JC Whitney for about $60. Or, if you search under my name, there's a post on how to cobble together a set from a few used parts and things from the hardware store for about $20.

The pressure test shoud be done with a cold engine at first to see the fuel pressure values with a cold engine, and then as it warms up. This is most relevant for checking the mixture and not so much for hot starting. The residual pressure test should be done with a warm engine and will tell you if fuel pressure is dropping too quickly with a hot car. This is what gets you on the hot starts.

CIS is actually pretty simple once you get a few of the basics.

[Paulporsche]

Did you ever try simply richening the mixture. It could be just that simple, as the new WUR would have probably changed the control pressures. Try setting it to just shy of getting a fluctuating idle on a hot, humid day.

[enolam]

Maybe the Cold Start Valve is not working. Could be unplugged or not getting signal from switch. Or Aux Air Regulator not working which lets more air in for smoother, faster idle when cold.
Anybody with CIS needs the test guages sooner or later.

[Paulporsche]

-If the car starts, usually the CSV is working. See approx 10 posts back.

[ras911]

I will try the mixture Paul.
I think I will also attempt the gauge thing , although I feel somewhat intimidated by the procedure . I will check back , but have work, vacation etc to deal with as well , so it might not be in the near future .

This AM 71 degrees no start. Can't wait to get home with temps in the 80s and see what happens!


The best thing about all this is I think the diagnosis from the mechanic about the fuel distributor, injectors etc is off the mark and a fix may be relatively inexpensive . Thanks A LOT for all the input . Truly appreciated!!!

[ras911]

WTF

Sure as the sun does shine

Got home 84 degrees - she STARTS right up! WHAT THE HECK IS THIS ALL ABOUT???
I'm going to check the thermo time connections , the temp switch , maybe check to make sure I am not living in a parallell bizarro world, etc.


Guess I can only use this car on Hot Days or I need to move to the deep south.