CIS Question...81 SC - Page 2

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by Westy

That's the one. I'm trying to figure out why I have a warmup issue. So I pulled both Wuhr hoses off to give them the old mouth-suction test. Both held up fine, and I'm learning to love the taste of gas. But when I put it back on, it was leaking a little. So I put the 14mm wrench on it and really had to crank it down hard to stop the gas flow. That's a tapered fitting, and it seems it shouldn't require that much force to seat it. At least that's where my brain cells were focussing!

Westy,

Read and re-read again LJ's post. He explains the messages clear and simple than anyone I've seen in this forum. Others have a different approach to tackle the problem. Before you go and start doing some suggested procedures to identify the culprit, I strongly suggest that you fix the fuel leak first.

Get familiarize with the CIS set-up of your engine. Get a good reference maintenance manual like Bentley and the like. Read posts pertaining to CIS woes and problems. They become boring to read once you understand the basic principles about CIS. Tim Irwin has a nice thread about CIS troubleshooting for Dummies.

If you don't have a set of fuel pressure gauge to use for your troubleshooting task, you are wasting your valuable time. If you could get the engine to start from cold, you are ahead of the game. If you can not, that a different story. Keep us posted.

Tony

Westy · 04-06-2015, 08:00 AM

Distributor vacuum test - Negative change
Brake cleaner test - no change. Checked to see if it was volatile enuff by spraying in the intake and yup, RPM increased. I sprayed everywhere. This doesn't surprise me, as a few years ago I dropped the motor and replaced a few runner boots and injector O-rings and other little stuff. This problem is lasting for shorter periods of time. Today it lasted about 5 seconds and then idled fine. I dunno. As was suggested, it might be fuel pressures. I know my mechanic pretty much only works on older cars, a lot of them CIS. He said it was the WUR (AGAIN!!!) but I have no idea how he determined this. Haven't been up there in a few years. The car warms up quickly, so I have to let it completely cool down once I've done a test. The vacuum line slid right off. I need to trace it back to the other end. It's old hose, maybe it's cracked at the other end,,,although the brake cleaner test didn't indicate this.

Westy · 04-06-2015, 08:07 AM

Why can I not find Tim's article? Am I challenged??

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by Westy

Why can I not find Tim's article? Am I challenged??

Westy,

Go to SEARCH, select Advanced Search, and type Tirwin. Select 'started by....'. You'll find all the threads started by Tim Irwin. Keep us posted.

Tony

Westy · 04-06-2015, 08:19 AM

Also I want to repeat....I'm not keeping the car, sad as that is. BUT, I'm not going to try and cover up an issue so some happy buyer turns his bank account into a black hole. If it's bad fuel pressure but only at startup, then I think we'd be getting into areas where I would be better off keeping my hands off of it. This car has appreciated significantly since I bought it. If it's gonna cost me a few hundred to fix, then so be it. I have the Bentley manual, so I'll go do some reading. I have an appointment with IPB Autosport in Sacramento on the 15th. If I can figure it out B4 then, I can cancel. Right now I'm gonna go read up on how to test the cold start gizmo!

T77911S · 04-06-2015, 08:57 AM

let me repeat it.
if the car starts, as his does then dies, it is NOT the CSV.
with a bad CSV the engine will crank and crank and crank. lifting the sensor plate will make it start. (good test for the CSV circuit).
telling someone to make their WUR adjustable is NOT checking pressures.

i dont suggest brake cleaner. brake clean csn mess up rubber a lot more than carb cleaner can. spray a rubbber O ring and watch it swell.

if you feel pretty confident you do not have an air leak then its time to check pressures. you just cant do anything else at this point.
i could tell you things to do to determine for sure if you are lean but none will tell you why.
its the process of elimination thru testing instead of buying parts.

assuming everything is good after each test i would:
check air leaks
check pressures
check dwell on frequency valve
check mixture setting
check injectors
check air leaks.

check the intake bolts again. they came come lose.
check the rubber "turtle" that goes from the AFM to the throttle body. look for cracks.
if your oil tank is vented to the "turtle" or any other hoses go to the turtle, check them.
check the oil tank cap. it should have a gasket in the cap.
you have a lot of vacuum plumbing behind the intake that can leak. its a pain but it needs to be checked.

unless you have gauges about all you can do is look for air leaks.

otherwise sell it as it is.
i would buy a car that has bad cold running/ but i would expect to spemd $$ on a WUR, perhaps the time to take the engine out and reseal everything on the intake. but to me thats not that big a deal and i would rather start with everything working so that if i did have problems down the road my list of ssupected problems would be shorter.

Westy · 04-06-2015, 09:02 AM

OK. Everything you say makes sense. I'll piddle around with it' I know I'm not dropping the motor again. Did that years ago when the back was in better shape, and it wasn't easy then. I'll get my wrenches out and tighten stuff down, check some more vacuum lines. I DID remove the oil cap and there was little if any change in RPM. The motor was warm, and didn't care if it was on or off. I'll check the seal.

paul.911 · 04-06-2015, 09:43 AM

Stick with your gut, I had trouble with my 81 SC. Got a rebuilt wur, retuned and it still wasn't 100% there. My fuel line seemed fine but I replaced it anyway and now the car runs a lot better. Maybe gunk builds in the line or the fitting?

tirwin · tirwin's Garage

CIS Troubleshooting for Dummies

Westy · 04-06-2015, 09:51 AM

Thanx T I found it. And thanx for showing me how dumb I really am. Right now I just have visions of a 993 or 996 floating around in my head!!

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by Westy

OK. Everything you say makes sense. I'll piddle around with it' I know I'm not dropping the motor again. Did that years ago when the back was in better shape, and it wasn't easy then. I'll get my wrenches out and tighten stuff down, check some more vacuum lines. I DID remove the oil cap and there was little if any change in RPM. The motor was warm, and didn't care if it was on or off. I'll check the seal.

Westy,

You just demonstrated in your last post that you have unmetered air in the system. The question is where is this coming from? A simple way to locate it is by pressure testing the system with a continuous supply of low pressure air (5 psi or less). Spray soapy water on suspected areas and the leak would show up (if any). With the engine in place, it is almost impossible to have a good and reliable test specially if the leak is underneath or behind the air box. Not until you have tested and confirmed that the air box is leak-free, the air box is a subject of interest.

Tony

fred cook · fred cook's Garage

Quote:

Originally Posted by Westy

Fred, you're only a few thousand miles away. Come on out and we can work on it together. I'll serve you up some great burritos and cold beer.

Wish I was closer, would be glad to help! The burritos and beer sounds good!

Westy · 04-06-2015, 11:01 AM

OK. The car is at the mechanics getting smogged. I'll let him do the oil and filter, too. I explained the problem to him. Told him to check and see if he can figure it out. If it's fixed, I'll figure my price and post it for sale. If not, then I'll drop 1k off the price. That should more than cover it. FYI, when I dropped the motor, it was to replace a cracked airbox and pop off valve. No more motor drops for this oldin'!!