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  #1  
Old 10-18-2008, 04:07 PM
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Okay.. I'm losing it. '69 250 auto

I replaced the gaskets on the rear carb, as the spacer/gasket between the throttle plate and carb was apparently leaking, causing an air leak, and I think that had part to do with why it would die when putting it in gear. Now it sometimes goes into gear. If I spray carb cleaner around the rear carb, it still revs up a little bit, but I have replaced every gaskets, and every bolt/screw is tight. I am not sure what else I can do??

When the car is at idle, if I block the rear carb's idle air bore, the car revs up. When the car does go into gear, it runs fairly rough. If I block that rear idle air bore, it runs good. I don't necessarily think it has to do with the idle circuit, but I'm sure this bit of info is telling me the problem but I just can't figure it out!

Last question, on the Zeniths, are both carbs supposed to have the same gaskets throughout? Particularly the uppermost gasket. I assume so, but just double checking.

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  #2  
Old 10-19-2008, 05:31 PM
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Well I believe I have fixed even more vacuum leaks, as the car doesn't rev up when I block that hole now. Didn't really fix my dying when put in gear problem. I have the RPMs set @ 800 or so in idle, and 1200 when the dashpot is fully extended. I can put it in gear the first time I start the car, and can usually keep it there with a little bit of coaxing, but any time I try and put it back into gear after that it stalls out.
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  #3  
Old 10-20-2008, 08:01 AM
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I'm having this SAME problem with my Twin Zenith Finny auto.

Idles fine and low in Park or neutral....just DIES in gear.......SOMETIMES.

My spidey senses were telling me it was a vacuum leak......related to auto vacuum demand.....???

When I checked the 'rear of intake manifold' to auto vacuum supply tube 'banjo fitting, it seemed a tad loose.

When i put the 14mm spanner on it...the head just broke straight off (and NOT coz I had eaten too much of Popeye's spinach). Seriously NOT COOL for my delicately balanced and extremely sensitive Zeniths!

Took the same bolt off the parts car and it was fixed.....for about 30 mins driving...she ran like a DREAM.

Now my fuel pump is sucking OIL out of the sump (through a stuffed and "no longer available" diaphragm???? I noticed a tiny little bubble of insoluble liquid in my glass pre-fuel pump filter, The pump seems to "lose prime" when let sit, and today I saw the glass filter fill with air bubbles immeadeately as I pulled the dipstick out .....Ah HUH !!!!!) and feeding it to my DELICATE carbs....so I have cleaned the fuel pump with the little 'hand-prime' lever off the parts car and will install after I get the little cork gasket that lines the mesh filter screen!

I don't know if this little tale helps YOU at all....but I feel much better!

Last edited by V8Finny; 10-20-2008 at 08:07 AM.
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  #4  
Old 10-21-2008, 12:34 AM
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Now my fuel pump is sucking OIL out of the sump

Usually, the gas flows into the oil sump, increasing the volume of oil.

Additionally, if the heat riser valve inside the exhaust manifold is frozen closed, engine performance under load is greatly diminished (aka the potato in the exhaust pipe effect)
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  #5  
Old 10-21-2008, 12:48 AM
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"
Quote:
Originally Posted by MunichTaxi View Post
Now my fuel pump is sucking OIL out of the sump

Usually, the gas flows into the oil sump, increasing the volume of oil.

Additionally, if the heat riser valve inside the exhaust manifold is frozen closed, engine performance under load is greatly diminished (aka the potato in the exhaust pipe effect)
"

Now my fuel pump is sucking OIL out of the sump (through a stuffed and "no longer available" diaphragm???? I noticed a tiny little bubble of insoluble liquid in my glass pre-fuel pump filter, The pump seems to "lose prime" when let sit, and today I saw the glass filter fill with air bubbles immeadeately as I pulled the dipstick out .....Ah HUH !!!!!) and feeding it to my DELICATE carbs
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  #6  
Old 10-21-2008, 04:08 AM
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Quote:
Originally Posted by Ruman999 View Post
I replaced the gaskets on the rear carb, as the spacer/gasket between the throttle plate and carb was apparently leaking, causing an air leak, and I think that had part to do with why it would die when putting it in gear. Now it sometimes goes into gear. If I spray carb cleaner around the rear carb, it still revs up a little bit, but I have replaced every gaskets, and every bolt/screw is tight. I am not sure what else I can do??
Did you check how flat the base of the carb is? .A little warp will cause an air leak. Tighten the base bolts too much and you will warp the base.
Quote:

When the car is at idle, if I block the rear carb's idle air bore, the car revs up. When the car does go into gear, it runs fairly rough. If I block that rear idle air bore, it runs good. I don't necessarily think it has to do with the idle circuit, but I'm sure this bit of info is telling me the problem but I just can't figure it out!
Disconnect the front carb from the throttle linkage and try again.
If it's still running the same ,unscrew the throttle stop until the throttle plate is closed dead shut. make sure the secondary throttle plate is closed shut .
Screw the rear carb idle mixture screw home ,but not tight because you will destroy the seat.
Did you set the fuel level correctly in the float chamber?
Once you have that checked start the engine and check the idle. it should be idleing on the front carb at 700 RPM. turn the idle down if it exceeds this.
Now open the throttle with the idle stop screw on the rear carb until you can hear it hissing .If the idle speeds up a lot (e.g 200RPM increase)you are running a bit rich meaning the float level is wrong or the idle mixture screw is not screwed in far enough.
If the idle is rough,unscew the idle mixture screw slowly until the idle evens out.
if this doesn't make any difference ,you have a blockage in the idle circuit which needs to cleared.
At this point you need to synch the carbs to get them opening at exactly the same point to ensure you get full performance. [/quote]

Quote:
Last question, on the Zeniths, are both carbs supposed to have the same gaskets throughout? Particularly the uppermost gasket. I assume so, but just double checking.
Both the same.
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  #7  
Old 10-25-2008, 03:21 PM
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I tried that trick and I don't believe the idle air circuit is clogged. I am thinking it might be a leak in the intake manifold gasket? I have roughly 17 vacuum in idle, and it drops to 9-10 in gear(when it goes in gear). What would cause the drop only when it's put into gear??
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  #8  
Old 10-25-2008, 04:48 PM
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Why don't you believe that it is blocked? . Try what i suggested then use the vacuum guage ,which by the way ,is pretty pointless if one carb is not working correctly.
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  #9  
Old 10-27-2008, 09:33 AM
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You said sometimes it stalls? Could it have something to do with pressing the brake? Try plugging off the brake booster...
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  #10  
Old 10-27-2008, 04:11 PM
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hmm,could have a point there,perhaps if he stopped using the brake it may fix it completley.
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  #11  
Old 10-28-2008, 11:51 AM
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Haha, either way the problem would go away near the first large tree ;-)

There's always the umbrella handle under the dash!

All kidding aside, I've actually driven mine around town without the booster attached before. It's hardly noticeable at those speeds, but obviously should be remedied for regular use.
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  #12  
Old 10-29-2008, 12:37 PM
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Another thing to check is that you used the same exact looking gaskets from your new carb kit that came out of the carbs. The carb kits I have bought in the past have two extra styles of the uppermost gasket. I discovered that if you don't use the one that is exactly like the one that came out of your carb, it will not idle.
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  #13  
Old 10-30-2008, 10:27 PM
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The brake booster has been blocked off for a couple of weeks now. I dont' believe it's leaking but I am eliminating that completely from the problem. It just idles bad in gear, if at all. I think it's a vacuum leak. The intake manifold seems to be leaking near the rear carb some. I am going to replace it to eliminate that from being a problem. I will mess around with it more this weekend.

The rear carb does still seem to be leaking when I spray carb cleaner. I can't quite figure out where from. It idles great in park.

Another odd thing, too, is that when I have the brake pushed in, car in gear, I can floor the gas and it only gets up to maybe 1500 RPM tops.
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  #14  
Old 10-31-2008, 05:20 PM
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Quote:
Originally Posted by Ruman999
I replaced the gaskets on the rear carb, as the spacer/gasket between the throttle plate and carb was apparently leaking, causing an air leak, and I think that had part to do with why it would die when putting it in gear. Now it sometimes goes into gear. If I spray carb cleaner around the rear carb, it still revs up a little bit, but I have replaced every gaskets, and every bolt/screw is tight. I am not sure what else I can do??
Did you check how flat the base of the carb is? .A little warp will cause an air leak. Tighten the base bolts too much and you will warp the base.
Quote:

When the car is at idle, if I block the rear carb's idle air bore, the car revs up. When the car does go into gear, it runs fairly rough. If I block that rear idle air bore, it runs good. I don't necessarily think it has to do with the idle circuit, but I'm sure this bit of info is telling me the problem but I just can't figure it out!
Disconnect the front carb from the throttle linkage and try again.
If it's still running the same ,unscrew the throttle stop until the throttle plate is closed dead shut. make sure the secondary throttle plate is closed shut .
Screw the rear carb idle mixture screw home ,but not tight because you will destroy the seat.
Did you set the fuel level correctly in the float chamber?
Once you have that checked start the engine and check the idle. it should be idleing on the front carb at 700 RPM. turn the idle down if it exceeds this.
Now open the throttle with the idle stop screw on the rear carb until you can hear it hissing .If the idle speeds up a lot (e.g 200RPM increase)you are running a bit rich meaning the float level is wrong or the idle mixture screw is not screwed in far enough.
If the idle is rough,unscew the idle mixture screw slowly until the idle evens out.
if this doesn't make any difference ,you have a blockage in the idle circuit which needs to cleared.
At this point you need to synch the carbs to get them opening at exactly the same point to ensure you get full performance. [/quote]

Quote:
Last question, on the Zeniths, are both carbs supposed to have the same gaskets throughout? Particularly the uppermost gasket. I assume so, but just double checking.
Both the same.


Add to the above.
Once you have followed what i have said ;
With the engine off ,get an assistant to push the acelerator to the point where the pedal is JUST TOUCHING the kick down switch.
Use a flashlite and see if the carbs are opening fully.
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  #15  
Old 11-07-2008, 10:37 PM
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checking & fixing zeniths..

Normally most zenith faults are cured by doing two things; stalling is caused by the idle tube getting partially blocked and the lower transition bores for the idle section getting carbon blocked. causes all sorts of weird symtoms.

simply remove both the idle mixture screws .generously spray carb cleaner to clean out the idle bores. next clean out the idle air tube . thin brass rod like 30mm or so. it can be accessed by removing the top cover .for later use mark out its air hole in the cover so that it can be sprayed directly without removing the cover.

start the car readjust the mixtures and all should be well.

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mak
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