1981 930 Turbo problem

[jdisterdick]

I have a 1981 930 Turbo that is blowing black smoke out the exhaust when accelerating I am told it is dumping too much fuel into the motor and several mechanics have tried to find the problem without success. I'm no mechanic but hoped someone might have a suggestion as to what might be the problem

[Rich76_911s]

First, welcome to the forums!

I'm sure other more knowledgeable people will chime in, but I am chasing down similar rich conditions. Here is where I am starting:

1. I installed an air/fuel ratio (AFR) gauge. This showed me that I was rich for the full range of operation, not just on boost or accelerating. I was getting black smoke on acceleration too.

2. I am checking my CIS fuel Pressures.

3. I also want to check my fuel pumps to make sure I am getting adequate fuel delivery.

4. Air leaks after the fuel metering plate.

5. I did also swap out the DME that controls the lamda system with a known good one, but this had no effect for me.

This is just where I am starting and like I said others will probably have better information and I'd follow their lead.

[Norm K]

Originally Posted by jdisterdick

I have a 1981 930 Turbo that is blowing black smoke out the exhaust when accelerating I am told it is dumping too much fuel into the motor and several mechanics have tried to find the problem without success. I'm no mechanic but hoped someone might have a suggestion as to what might be the problem

First, welcome to the forum. Second, you'll quickly find that few here will believe your 930 actually exists until you post pics.

The CIS (assuming your car is pretty much stock?) on these cars, while reliable, is certainly capable of delivering an over-supply of fuel. In fact, it seems designed to do just that when approaching full boost.

Has this been a gradual thing or did it come on suddenly? Agree on the AFR gauge suggestion - absolutely critical on these cars. Confirming fuel pressure is a necessary diagnostic step on most fuel-related matters. So, a couple of hundred dollars for an AFR meter, a hundred and a half for a CIS test kit and you're on your way.

Plenty of folks here who are more than willing to share their expertise, many of whom have it in spades.

Good luck and get those pics posted!

[Ronnie's.930]

JD, if your car is a Euro model, as noted in your "poll" info, then there is no O2 sensor present - the Euro fuel head is non-Lambda, so no O2 sensor or frequency valve.

Also, when the black smoke is evident under acceleration (I assume this means under full boost, too?), does the engine misfire (does it "bog down" and basically stop accelerating for a moment)? I ask, because an overly rich condition like you mentioned will cause significant misfiring during high load conditions - such as full boost in 4th gear.

And like the other guys mentioned, without an on-board air/fuel meter, you end up doing a lot of guesswork when trying to diagnose fueling problems.

[Strygaldwir]

I'd make sure the vacuum line between the throttle body and the Warm Up Regulator (Control pressure regulator) is in place and not leaking. If that is not it, full diagnosis on the WUR is probably indicated. Cold Control Pressure, Warm Control pressure and System pressure to begin the process.

I didn't think you had a O2 sensor in the Euro 82 model...

[tops911]

mine was rich due to the WUR staying in start up mode; no power to heat up the bimetallic spring. That was caused by a faulty relay, I read that the fuel pump relays were supposed to be red in color. So I replaced the black relays with red and had a rich problem. I replaced the new red relay with the old black relay and then rich issue went away.
Just one of several possibilities, good luck

[jdisterdick]

Happened sudden
How do you post pictures?

[jdisterdick]

Originally Posted by Ronnie's.930

JD, if your car is a Euro model, as noted in your "poll" info, then there is no O2 sensor present - the Euro fuel head is non-Lambda, so no O2 sensor or frequency valve.

Also, when the black smoke is evident under acceleration (I assume this means under full boost, too?), does the engine misfire (does it "bog down" and basically stop accelerating for a moment)? I ask, because an overly rich condition like you mentioned will cause significant misfiring during high load conditions - such as full boost in 4th gear.

And like the other guys mentioned, without an on-board air/fuel meter, you end up doing a lot of guesswork when trying to diagnose fueling problems.

Yes it bogs down and stops accelerating but doesn't seem to misfire. Black smoke come under acceleration but it never gets to full boost. If acceleration is very modest it doesnt seem to happen but when given more throttle it bogs and dumps the black smoke

[pkabush]

!st off from a fellow 81 930 brother, welcome to the forum. Nice pic, she's a looker with her gold shoes n all. Not a fan of the black bra but, I get the logic.

2 - Find a trusted Porsche only mechanic. Whoever worked on your car wasn't or they would have been able to tell you for certain why your condition exists.
What city are you in/near ?

3 - If you want to tackle this yourself your in the right place. But as mentioned you'll def wanna invest in cis gauges and a AFR meter mounted in your car.
Personally I'd find a mechanic to get your car sorted so you can start enjoying it. You'll have a hard time wiping the s*** eatin grin off your face. Whereas trying to sort this yourself likely wont produce the same results. Really satisfying in a masochistic sort of way though. Good luck whichever rout you go.

[mark houghton]

I need to start spending more time here, getting up in the middle of the night so as to beat all of youze to the punch with diagnoses.

I can't add much to the ideas already suggested....all of which are spot-on. Do indeed make sure all your hoses are tightly connected, and do make sure your intercooler o'rings are in good shape and properly seated. With CIS, if you have a substantial air leak in the intake system, it will cause a major pig rich condition when boost begins to build - getting progressively worse as boost builds. Once all connections are confirmed to be good, then start looking at your WUR. Could very well be stuck in cold warmup mode....either a faulty internal mechanism, or no power to it (power comes from the rear fuel pump relay when the engine is running). Definitely, knowing what your system and control fuel pressures are will put the WUR question to bed.

Rich, there isn't a DME relay on CIS cars, since they're not electronically fuel injected. I think you're referring to the overspeed relay or the Lambda computer itself under the drivers seat.

[RarlyL8]

There are several things that can cause an overly rich condition when on boost. Symptoms come in packages so the answer can be found through elimination.
Does the engine run perfectly off boost?
Any starting issues, cold or hot?
What is the system fuel pressure?
What is the warm control pressure?
What is the gross fuel flow/30 seconds?
How many volts to each fuel pump while the car is running?
Answer these questions and you will have your culprit.

[cmarkin]

Having a 1984 Euro model myself - I have to ask...

Is this a gauge that I can install in my 930?

[RarlyL8]

AFR won't tell you as much as fuel pressure in this situation. FP gage is used in the engine compartment.

[klefroid]

very interesting thread as I am having exactly the same problem. I have the afr gage so only need to get a cis tester.

Good luck!

[klefroid]

Originally Posted by RarlyL8

There are several things that can cause an overly rich condition when on boost. Symptoms come in packages so the answer can be found through elimination.
Does the engine run perfectly off boost?
Any starting issues, cold or hot?
What is the system fuel pressure?
What is the warm control pressure?
What is the gross fuel flow/30 seconds?
How many volts to each fuel pump while the car is running?
Answer these questions and you will have your culprit.

I'm having the hot starting issue! :-)

? ... :-D

[RarlyL8]

Describe the hot start problem. Does it start and then run badly, require lots of cranking to start and then run OK, start or not start intermittently, or require lots of cranking to start and then run badly for a couple minutes before clearing up?
What does your AFR meter read after a hard start?

[klefroid]

require lots of cranking to start and then run badly for a coupe minutes before clearing up?
What does your AFR meter read after a hard start? I think it was lean if I remember



I had to try for 3 min. or so. and then it runs like crap for about 30 seconds.... I did not have this problem before, It was running to rich so I had to adjust the mixture screw to make the car more lean.
AFR stationary : 13.5
Off boost : 13
On boost : Less the 10 (seems like my gage doesn't go any lower the 10) and little black smoke visible.

Is there also a possibility that the spark is to weak on boost?
That would not explain the hard start when warm....

[RarlyL8]

You should not have to adjust the idle mixture unless a change is made to the engine. An intermittent rich condition will become an intermittent lean condition.
Answer the same questions I listed above and the culprit will be exposed. Rich start and boost point towards WUR/FD or weak ignition issues. If these were isolated, boost OR start, the options change.

[klefroid]

Originally Posted by RarlyL8

You should not have to adjust the idle mixture unless a change is made to the engine. An intermittent rich condition will become an intermittent lean condition.
Answer the same questions I listed above and the culprit will be exposed. Rich start and boost point towards WUR/FD or weak ignition issues. If these were isolated, boost OR start, the options change.

That makes sense. The car in in a winter sleep now. When it get warmer I will first buy a Cis tester and check the wur and feul/system pressure. I might order one right now.
I had a change because of a new turbo and cams. You got a replacement if the wur is the culprit? If so the I get back to you soon...

[Miguel Antonett]

Originally Posted by jdisterdick

Yes it bogs down and stops accelerating but doesn't seem to misfire. Black smoke come under acceleration but it never gets to full boost. If acceleration is very modest it doesnt seem to happen but when given more throttle it bogs and dumps the black smoke

Prrrrrreeeeeettycool!

Welcome to the forum!

Nice machine you have there... you'll learn a lot in here; meanwhile, I recommned you to remove the poll from the thread, it makes no sense, you'll figure that out as you learn 930s. Similarly, the pros and cons of bras... Enjoy it!