E9 running issues!!!!

Jacquescs

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My solved nightmare was a rebuild of both carbs.
Make sure that all the parts did have a proper ultrasonic clean, and that the flat sufaces of the carb housing parts are polished and 100% flat. If not you might get a false airintake isue.
Also make sure that you have the correct gasket between your carb and airintake. There is a little rubber ring in it and this will get out of position when older and will block a line for fuel consumption.

I hope my story is clear as my English is not so good...

Good luck!
 

teahead

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what's odd is that it works good, but then later it runs like crap?

Hmm...sux throwing parts at the problem. Stock ignition or Pertronix and/or 123?

Ya, check the fuel pressure for sure.
 

Boobouna

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what's odd is that it works good, but then later it runs like crap?

Hmm...sux throwing parts at the problem. Stock ignition or Pertronix and/or 123?

Ya, check the fuel pressure for sure.

Stock ignition. Yes odd it works then runs crap after 20min.


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61porsche

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Ifin we were just talking:

Works fine cold.....rich enough to run,,,, gets hot.... likely lean.....not firing on all cylinders...pull a plug wire.. likely cyl 1 or 3 .. 4 or 6. Because of the manifold design, the outside cylinders are the first to see lean. Adjust the mixture or find the vacuum leak.

Find the carb that's acting up.....
 

DaSurfa

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I have the same exact issue as you. My car would not stay running starting last year and over the summer my friend rebuilt both my webers and got my car running again. Tried to tune and drive it but every time I come to a complete full stop, engine rpm will drop and slowly die and shut down. Only way to stop it is if I blimp the throttle and then engine will settle to a idle and keep it. Finally we figured out my rear carb had a vacuum leak cause whenever I place my hand over the carb, idle will raise.
 

deQuincey

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Yeah, this sounds like a fuel delivery issue. The first thing I would do is to again go through and check the filters/screens in your fuel system including the little screens in the carbs (if Zeniths have them; I have Webers).

Next, I would look at your fuel lines. Normally it is unlikely that debris can get caught in the fuel lines, but I had a dented fuel line in my car near the rear subframe mount that I cut out and fixed after I fixed the rust in my tank specifically because I was concerned that something might get stuck in the lines there.

Also, I would take another look at the floats in your carbs. I don't have Zeniths, so I can't give you specifics, but one thing to consider is that the original data for our cars is based on gasoline that had a different specific gravity as compared to today's fuels. So the floats may be set to the correct original specification, but may act differently because the fuels we have to use differ from fuels in the 1970s. You may need to alter your floats to take the ethanol into account.

well spotted, but our friend has a filter in the fuel line before the carbs, if debris came from reservoir, it should have stopped there, thus there is no need of a second rebuild of those zeniths

p.s. zeniths floats can not be adjusted as for example the bing carbs for my r45 motorbike, i do not think anything can bej done to adjust to new fuel, and in any case that will create a problem since minute one
 

deQuincey

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My solved nightmare was a rebuild of both carbs.
Make sure that all the parts did have a proper ultrasonic clean, and that the flat sufaces of the carb housing parts are polished and 100% flat. If not you might get a false airintake isue.
Also make sure that you have the correct gasket between your carb and airintake. There is a little rubber ring in it and this will get out of position when older and will block a line for fuel consumption.

I hope my story is clear as my English is not so good...

Good luck!

jacques, he rebuilt his carbs, we have to think he did it well with the proper gaskets

good point on the air leaks

BTW, i have rebuild a dozen of these zenith carbs and i strongly recommend NOT to use ultrasonic clean, the liquid used in this type of cleaning will attack the aluminium body of the carbs leaving rough surface, clean them by hand with steel wool and tiny brushes, there are sets of 20cm long twisted wires with brush hair on them these sets have different diameter brushes, from 3mm up to 10, then orthodontic brushes work very well for extra tiny holes and copper wire for ultra tiny ones
 

deQuincey

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Ifin we were just talking:

Works fine cold.....rich enough to run,,,, gets hot.... likely lean.....not firing on all cylinders...pull a plug wire.. likely cyl 1 or 3 .. 4 or 6. Because of the manifold design, the outside cylinders are the first to see lean. Adjust the mixture or find the vacuum leak.

Find the carb that's acting up.....

so nice to read you again ! :)
could this be something that happens after 20 minutes of good driving dear Master ?
 

61porsche

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Oh yes.

Rear sees the build up of heat. Usually that carb runs rich - the fuel level rises from the heat.

Since the carbs were rebuilt, the base plate can get loose. The screws just don't hold well unless you set them by torqueing waiting, repeat. The gasket compresses more. The base plate is your idle circuit.

But find the air bleed jet and put your finger over it. Smooths out- you're lean.
 

bavbob

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DeQ help me out here. The Zeniths have a thermo switch which basically is a cold start valve that should close when the car warms up. Seems this is a fuel starvation issue but can it be too much fuel, switch not closing? Pull the plugs and take a peek. Switch can be removed and while the car is warming, the internal spring should start to wind and is easy to see.

Other thing, cap is new? On the e24's the cap gets enough heat and if there are micro cracks, the car runs well cold but then the car can misfire and run like crap as the cap heats up.

Had a 320i that would run poorly when hot, sometimes just die instantly. Copper coil in the distributor can also get small cracks that cause issues when they warm up.
 

Boobouna

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DeQ help me out here. The Zeniths have a thermo switch which basically is a cold start valve that should close when the car warms up. Seems this is a fuel starvation issue but can it be too much fuel, switch not closing? Pull the plugs and take a peek. Switch can be removed and while the car is warming, the internal spring should start to wind and is easy to see.

Other thing, cap is new? On the e24's the cap gets enough heat and if there are micro cracks, the car runs well cold but then the car can misfire and run like crap as the cap heats up.

Had a 320i that would run poorly when hot, sometimes just die instantly. Copper coil in the distributor can also get small cracks that cause issues when they warm up.

Are you referring to distributor cap when you say cap? Yes new.


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deQuincey

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Oh yes.

Rear sees the build up of heat. Usually that carb runs rich - the fuel level rises from the heat.

Since the carbs were rebuilt, the base plate can get loose. The screws just don't hold well unless you set them by torqueing waiting, repeat. The gasket compresses more. The base plate is your idle circuit.

But find the air bleed jet and put your finger over it. Smooths out- you're lean.

thank you jerry,

i see, that is a good point, " rear sees the build up of heat", problem might be how to take that into cosnideration when tuning them...

good note on base plate, i leave some days between the rebuild of a set of carbs and their installation, usually two more turns of torqueing, and not only the four bolts at the botom, but the nine bolts at the top aswell, and yes, gaskets do compress quite a bit.
 

Luis A.

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Great suggestions all.

Can you describe in detail the ignition system and age/condition of the components. One of the most confounding problems I ever had was poor running such as yours. It occurred only after running a while and took a few drives (100s of miles) before this happened. It was ignition related.
 

Boobouna

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Great suggestions all.

Can you describe in detail the ignition system and age/condition of the components. One of the most confounding problems I ever had was poor running such as yours. It occurred only after running a while and took a few drives (100s of miles) before this happened. It was ignition related.

Ignition system is same as factory set up. All new components.


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Boobouna

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Ignition system is same as factory set up. All new components.


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I thought I would test out the car tonight when I got home. To my surprise the car started first turn. I let it warm up for 5min then went on my way. Got out of my building and went through some back streets then down the road. 5 min later as soon as I hit a stop sign the car revs started to drop well below the min causing the car to struggle to stay running. So I turned back and went home. As long as you keep the car moving it will get you home. As soon as you stop it starts to get scary.


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Luis A.

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Easy test to tease out ignition issues. Clamp a strobe timing gun on each spark plug HT lead and eyeball that all the cylinders are getting spark when it's running rough. It's the fact that it doesn't do it until a few minutes/miles that makes me think ignition issues need to be ruled out. Plus they are far easier to ID than carb issues... most times.
 

jefftepper

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Since the prior posts in this thread cover all of the "usual suspects" let me suggest a couple of things that might be very unlikely. If the power brake booster has a leak (vacuum) and your foot is on the brake, as when you are slowing or stopped, the excess air sneaking into the intake manifold might be leaning out the engine to the point it stalls. On an automatic transmission with a vacuum modulator (do these cars even have such a thing?) a bad modulator can likewise be the source of a vacuum leak. Note that in such a circumstance, the leaking modulator may actually allow ATF to be sucked into the intake and then out the exhaust with no visible leaks on the floor. Check the ATF level to see if lost ATF is a possible factor in this situation. Good Luck
 

Ohmess

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Further to the comment about the brake booster circuit may be your vacuum leak, pull and test the check valve and look closely at all the connections between the manifold and the brake booster itself. If any of those connections are leaking, they are much cheaper to fix than a brake booster.
 
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