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  #1  
Old 05-26-2008, 09:38 PM
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Join Date: Aug 2007
Location: Sealy, Texas
Posts: 58
260e

I'm still working on this car.
I have duty cycle readings hovering between 42.5 - 54.6 a vacuum gauge that reads a steady 15 in. This is all at idle. As soon as I increase the revs I get black smoke out the back of the car. Today I hooked a fuel pressure gauge to the cold start outlet of the fuel distributor and got a reading of 80psi. I do not have a CIS fuel pressure gauge set so I don't know if this reading has any validity. I can't drive this car anywhere because once I have traveled 10 miles the plugs are sooted up and she will barely pull away. I'm baffled. Changed the fuel dist. and idle valve for used units absolutely no change. Went back to the old units, no change. New 02 sensor, no change. Cap and rotor, no change. I'm on my 4th set of plugs all different makes, no change. I can't get non resistor anywhere so I'm using NGK. All compressions around 155 hot/warm engine. Valve stem seals changed, no change.

Is there anyone out there that can point me in a new direction?

Michael


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  #2  
Old 05-27-2008, 08:08 AM
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Have you tried disconnecting the vacuum line to the charcoal cannister?
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  #3  
Old 05-27-2008, 01:44 PM
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Location: Sealy, Texas
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Thank you for the response M.B. Doc. I couldn't find the canister but I did find a plastic vacuum line buried along side the fuse box that was obviously broken (fuel tank vent line??) I capped the end and started the vehicle. I'll report the findings.
Thanks again.
Michael
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  #4  
Old 05-29-2008, 05:29 PM
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Location: Sealy, Texas
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Still no change in the vehicle. On acceleration or higher revs. black smoke pours out of the tail pipe. I'm clutching at straws now, the speedo does not work, are there any inputs for vehicle speed that the F.I. computer would need to see?
Is there a starting point on the fuel distributor in regards to how much it should travel before the arm moves the central plunger.
My test results abeit with home tools are: fuel pressure at cold start supply, 80lbs, duty cycle around 42.6 - 54.6 vacuum gauge reads 16" (picked up an inch when I found the broken line leading to rear of car) steady. Idle is 750rpm. When I increase the revs, all those reading are useless and black smoke pours out of the tailpipe. The above letters list what has been changed.
Would a faulty fuel injection computor cause these kind of problems

Michael
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  #5  
Old 05-29-2008, 07:24 PM
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Location: Montreal, Quebec
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Have you looked at your air intake system?????
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  #6  
Old 05-29-2008, 08:44 PM
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Join Date: Aug 2007
Location: Sealy, Texas
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Jackd,
What do you mean "air intake system" if you are referring to the possibility that the air filter is clogged, the filter is brand new, but I haven't even been able to run with it, as I'd spend too much time removing it to make adjustments. The air sensor plate and all other components have been checked. no leaks nothing binding, no vacuum leaks (now that I found the one MBDOC referred to) all potentiometers read correct as per my 'Mitchel on demand' manual.
It feels as though when I accelerate the central plunger opens up the slits in the feed lines of the fuel distribution unit too much and nothing in the system is able to overcome it. So huge amounts of raw fuel get sucked into the cylinders and the spark is unable to cope and eventually the motor stops running. Screw in new clean plugs and I can get it home.
There has to be something obvious that I'm missing.
Michael
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  #7  
Old 05-29-2008, 09:26 PM
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Location: Montreal, Quebec
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Another (remote) possibility.
What if the cold start injector was running full bore full time?....just a thought
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  #8  
Old 05-29-2008, 10:32 PM
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Join Date: Aug 2007
Location: Sealy, Texas
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I had the same thought, its been disconnected for some time now.
Do the injectors on these motors wear out? They'd have to all be worn out for the amount of smoke I'm producing.
I've no idea of the mileage.
I also checked to see if the injectors were dripping fuel when the throttle was closed, no drips.
Hang in there with me please.
Peace in my household rests on this cantankerous automobile.
Michael
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  #9  
Old 05-30-2008, 05:46 PM
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Location: Matthews, NC
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Michael
If it will idle then I would say the injectors are OK. If I were working on your car I would check the duty cycle at the higher RPMs where you have the problem. I'm sure they will be off by quite a bit. If every thing is working as it should the duty cycle will stay aproximattly the same at any speed. All that being said I think there is a vacuum leak some where and the fuel dist is adjusted to compensate for it. At higher RPM the vacuum leak won't effect the engine as much so with the fuel dist mal-adjusted the misture is now too rich. On these injection system I will purposly adjust the mixture to a very lean condition then carefully spray carb cleaner around and will usually find a spot where the engine speeds up. That is the spot. Also disconnect the brake booster and block the line. There are a lot of little things like this you can do and hopefully will find something that changes how the engine is running. I hope you can make some sense out of this. Sometimes I have a hard time discribing something I do every day.
Paul
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  #10  
Old 05-30-2008, 08:16 PM
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Location: Sealy, Texas
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Paul, thanks for joining the fray.
With regards to vacuum leaks, I have tried the carb. cleaner spray around technique. If I loosen the brake boosters vacuum supply at the manifold I get a significant increase in revs., and as mentioned in a previous post above the duty cycle etc. go completely haywire.
New track I might try that was suggested to me today. I don't know the previous owner or the service history (if any) this vehicle has been subject to, with that in mind if the mixture has been off for some time and misfires etc allowed to continue its possible that the catalytic converter may be stopped up. It will idle fine, but as soon as I try to put more air through the system that's when it starts to choke up. So I'll disconnect the pipes and see if it helps. I live deep in the country so noise is not a problem.
Your thoughts.
Michael

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