Fuel getting into modulator vacuum line
This 54 that I have been working on has fuel getting into the vacuum modulator line causing shifting problems. I have no idea how fuel is getting into this line. This 54 modulator line is routed from r/h side of trans goes under trans and up the left side of engine to the top of the intake manifold. Does this routing sound correct. I have not checked fuel pump yet. Thanks Ed
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Re: Fuel getting into modulator vacuum line
It is gas for sure. I have not started to troubleshoot this yet just looking for ideas. The only thing that I could think of is improper routing of vacuum lines intersecting with the fuel pump vacuum for the wipers. But from quick look the modulator line is routed as described above. The modulator line has a connection under the trans and when you break this line fuel dribbles out. EdComment
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Re: Fuel getting into modulator vacuum line
I just cant see how that's can be , or a lot of gas vapors lingering in the intake when you shut down. The carbs are closed at that point. How long does it take to fill the line?Comment
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Re: Fuel getting into modulator vacuum line
Ed, the car must be dumping fuel somehow when engine is shut down, and getting into the modulator vaccum hose, when engine is started the fuel thats is the hose must be drawn into the intake because as ray says it creates a vaccum for the modulator to work.so the only possiablity is fuel is somehow being dumped into the line. P.S. im not a C-1 guy but have been working on cars for a living. 40 yrs.
Maybe try taking car for a run and after disconnect modulator line and see if fuel maybe dribbles onto a paper towel or some to absorb. the fuel.New England chapter member, 63 Convert. 327/340- Chapter/Regional/national Top Flight, 72 coupe- chapter and regional Top Flight.Comment
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Re: Fuel getting into modulator vacuum line
Yes that is what happens moved car around in driveway and then removed line after shutdown to find fuel in line. Dont need a paper towel to see the amount of fuel that comes out its obvious. Very strange deal. Will look into futher but the storm will hamper any driving here in Delaware. If you drive car to much the fuel in the line starts causing shift problems till drained. EdComment
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Re: Fuel getting into modulator vacuum line
Man you got me stumped! The vacuum line routing you describe sounds right on. Since the fitting is on the top of the intake manifold the fuel would seem to have to fill the entire intake log in order for it to get high enough to overflow into the metal line. That would cause tons of other problems you don't have. Also, as others have mentioned, the line should be carrying a vacuum pulling toward the intake. Don't see how fuel can flow against that pull.
There is a smaller vacuum line under the center carb that feeds the distributor vacuum advance. I could see how one could get fuel in this line. Are you sure the line to the modulator is not connected here instead of on top of the intake?Comment
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Re: Fuel getting into modulator vacuum line
I will check on that later today. Thanks EdComment
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Re: Fuel getting into modulator vacuum line
Ed, does the car have any running problems, with the extra fuel in the line I would think the car may start hard after shutting downand maybe a little black smoke.
the easiest way to locate the fuel source would be to block off all vaccum soruce hoses and start car and run for a minute, then shut down and removed the lower vaccum block offs on the intake. to see if there is fuel being dumped, you may have something stuck in the needle and seat of one of the carburators. hope this makes since.New England chapter member, 63 Convert. 327/340- Chapter/Regional/national Top Flight, 72 coupe- chapter and regional Top Flight.Comment
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Re: Fuel getting into modulator vacuum line
Yes it makes some sense. I pulled both vacuum lines off of the bottom of fuel pump and they are dry. This car has had junk stuck in float before in rear carb causing fuel to run out air horn. I think maybe #1 carb has crap in needle causing fuel to flood down inside intake in stead of out horn. Car now has new fuel lines and filter. That work was done recently so maybe something got by during that work. I removed the intake vacuum fitting and I can see fuel laying in the bottom. Storm to nasty to run today hell every time I try to get to garage I have to shovel a path. Thanks EdComment
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Re: Fuel getting into modulator vacuum line
Hello Ed;
Don't know if this will help. C2s have modulator line routing with a loop to stop fuel and fumes from getting to the transmission.
Back in the day we also created a loop in vacuum advance lines to stop fuel fumes.
Think there was a TSB at the time because of duplicate warranty applications for vacuum canisters.
RayAnd when you get the choice to sit it out or dance
I hope you dance
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Re: Fuel getting into modulator vacuum line
If there are shifting problems, because of fuel getting into PG Trans, you better check the trans fluid/gasoline level.... Correct the fuel problem & "change" the PG Trans fluid before you burn out your Transmission....SamComment
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Re: Fuel getting into modulator vacuum line
Roger that, this whole problem came up after transmission rebuild. Update I checked all three carb floats and seats no problems found nice and clean and float levels look good. I think my next step is to check fuel pressure when I can. EdComment
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Re: Fuel getting into modulator vacuum line
Ed,
You've got me really curious about this issue. Any news to report?Comment
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Re: Fuel getting into modulator vacuum line
No sorry no news just got back from xmas trip an hour ago to myrtle beach. I will check fuel pressure as soon as I rig something up to test with. EdComment
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