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Gasoline smell but runs well enough

Started by CudaMoparRay, January 12, 2018, 02:48:06 PM

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CudaMoparRay

Trouble shooting gasoline smell sometimes dieseling after shut down.  No visible gas leaks.
My guess is needs carburetor float adjustment and distributor timing.
Appreciate comments, thanks in advance.
Hint: Fuel, tach and oil pressure gauges show slight back and forth readings.
[video]https://forum.e-bodies.org/gallerypics/videos/283_12_01_18_2_34_23.MOV[/video]



Cuda Cody

Can you remind us of your build?  Engine, intake, carbs, ect...  Is the engine changing RMP by itself or are you blimping the throttle?  If it's doing it by itself, it might be an intake leak causing the RPM issue?

Is the smell from the exhaust like it's running rich?



dodj

I'm thinking you have a distributor/timing issue. I would definitely check the fuel bowl level though.
"There is nothing your government can give you that it hasn't already taken from you in the first place" -Winston Churchill

Chryco Psycho

Dieseling is related to idle speed , timing & mixture .
Many cams with long duration cams will misfire / lope at idle this pushes raw fuel into the exhaust so the smell can be normal at idle .
Start by checking float level as it affects everything else .
Generally you want the timing at idle to be 12-16 * , depending on the cam but you do not want more than 36* at high rpm so you may need to weld the advance slots to keep it from over advancing , you can also limit vacuum advance but inserting an allen wrench where the hose connects & turning the screw inside clockwise .
  Idle mix should be as lean as it will go before the idle speed starts to drop .

cudabob496

I'd inspect the whole outside of the fuel system first,
for obvious leaks. fuel pump, hoses, etc
72 Cuda, owned for 27 years, 496, solid roller, 3500 stall, 3.91 gears, ported Stage VI heads, 3 inch X-pipe exhaust, 850 DP, ram air setup, fuel cell, batt in trunk,
Wilwood brakes, Weld wheels, MT ET Street tires, fiberglass hood, Alum radiator.

CudaMoparRay

Quote from: Cuda Cody on January 12, 2018, 03:03:18 PM
Can you remind us of your build?  Engine, intake, carbs, ect...  Is the engine changing RMP by itself or are you blimping the throttle?  If it's doing it by itself, it might be an intake leak causing the RPM issue?

Is the smell from the exhaust like it's running rich?

Engine is 360, Intake is Weiand 2P 180 #8007, carb is Edelbrock Performer Series 1405 600cfm 4 bbl.
Just idling no throttle.
No smell in particular from tail pipe just engine bay area makes eyes cry and dissipates after a day in the garage.



CudaMoparRay

One more maybe very important detail or not?
I have the vacuum advance hose off and both sides it connected to with a plug.
Will reconnect a vacuum hose and test that way later.

73chalngr

I had a similar problem could not figure it out.did a carb swap problem went away so i rebuilt the bad one .something is sticking putting too much fuel to the motor  choke, float .

Chryco Psycho

The 1405 is one of the worst carbs ever made , adding the vacuum advance will not help


CudaMoparRay

Quote from: Chryco Psycho on January 14, 2018, 06:01:54 AM
The 1405 is one of the worst carbs ever made , adding the vacuum advance will not help

Well, that might explain a lot. Might try another carburetor instead like suggested.

RUNCHARGER

It's idling way high for a start. Do you know what is in it for a camshaft? You will have to start from square one to tailor your spark curve and carb calibration to the engine setup. Myself I start with the distributor and go from there. As CP suggested somewhere from 15 to 20 degrees of initial advance, 34-38 degrees total advance brought in as quickly as possible without pinging. Then it's on to the carb. With the distributor dialed in you should be able to slow down your idle speed, make sure it is actually idling on the idle circuit and go from there.
The video shows idling at 1100rpm, Unless you have a verrry radical camshaft you should be idling at somewhere from 700RPM to 850RPM (just guessing here as we don't have camshaft specs). At your idle speed the butterflys are open and you are not even on the idle circuit.
Sheldon

Chryco Psycho

If you have a decent cam in the engine the eddy carbs simply are not adjustable to work with low vacuum & long duration .
If you want a tunable carb try Proform or Quickfuel  :bigthumb:

CudaMoparRay

As far as I know it is a stock cam. I will ask the original owner when I talk to him next and also take the car out next week again to test it.
Thanks to all for your great help.