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post #1 of 9 (permalink) Old 03-05-2016, 09:04 AM Thread Starter
CPL
 
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old topic,fuel bleed back

God morning.i installed the inline fuel return filter ,it took care of my fuel over heating of and the vaperlock it is running great.however once in turn off the engine it's dieseling,then the gas bleeds back and I have to crank it over and over untill the gas gets back to the filter and into the carb.
Any ideas would be Appreciated
Thanks
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post #2 of 9 (permalink) Old 03-05-2016, 04:51 PM
 
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Originally Posted by CPL View Post
God morning.i installed the inline fuel return filter ,it took care of my fuel over heating of and the vaperlock it is running great.however once in turn off the engine it's dieseling,then the gas bleeds back and I have to crank it over and over untill the gas gets back to the filter and into the carb.
Any ideas would be Appreciated
Thanks

Need a lot more info about your car. What size engine again? What year? Compression ratio? Iron Heads? Carburetor type? Gas octane you are using? Points or HEI distributor? Timing settings? Type of spark plugs & heat range? What temperatures are you seeing on the water temperature gauge -running & shut down?

Primary problem, if I were to guess, is the carburetor.

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post #3 of 9 (permalink) Old 03-05-2016, 05:36 PM Thread Starter
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Originally Posted by PontiacJim View Post
Need a lot more info about your car. What size engine again? What year? Compression ratio? Iron Heads? Carburetor type? Gas octane you are using? Points or HEI distributor? Timing settings? Type of spark plugs & heat range? What temperatures are you seeing on the water temperature gauge -running & shut down?

Primary problem, if I were to guess, is the carburetor.

original 326 rebuilt 30 over about 350 miles on it .put in a mild cam, original iron heads new valves rockers, springs , and hard valve seats so I can burn unleaded ,Im using the highest octane ,super premium .2 barrel carb it was rebuilt.
thanks
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post #4 of 9 (permalink) Old 03-05-2016, 11:39 PM
 
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OK, thanks. Still sounds like a carb problem even though it was rebuilt -plenty of bad rebuilt carbs. You should be able to shut it down and fuel remain in the bowl of the carb. That said, it should fire right up and run with the gas in the bowl while the fuel pump draws gas into the line to continue the flow of gas to the carb.

If there is a leak within the carb, the gas could be running dry in the bowl. Do you see any white wispy "smoke" rise up out of the carb when you shut the engine off? You will need to remove the air cleaner just before you shut the engine off to see this. The heat from the warmed up engine will evaporate the gas as it leaks out the carb. If it is leaking, MAKE SURE you have a FIRE EXTINGUISHER on hand when you remove the air cleaner, shut the engine off, and observe the carb.

When you shut the engine off and it diesels on, it is because it is still getting fuel/air. One of the ways this happens is that the throttle plate is not fully closed and the engine draws air past the plate. If you have a gas leak, gas is also being drawn in and the engine will continue to run on.

Does your car have an electric idle stop solenoid?

This info below is from a 1968 -1973 Chilton's Repair & Tune-Up guide which only has the 350CI and not the 326, but some of this should still apply. You did not say what year the engine was.

Timing for the 326CI shows to be 6 degrees Before Top Dead Center at the crankshaft pointer. Make sure yours is the same.

What is your engine idle speed when the car is in Drive (automatic?)? Idle speed in Drive for an automatic with the electric idle stop solenoid is 500 RPM's with it disconnected, and 650 RPM's with the solenoid energized. (100 more RPM's if your car has A/C)

Did you adjust your idle mixture screws? If they are running too rich, these can provide extra/available gas to the engine when you shut it off. I usually turn the screws in all the way until they stop - do not force them closed or run them down real tight, just turn them in gently until they stop. Then back them out 4 turns to get an initial setting. Then I screw one in at a time until the engine runs poorly (you will hear it) and then back it out to the point where the engine runs smooth and then stop. Then do the other idle mixture screw the same way.

If you installed a mild cam, you may not be able to drop your idle RPM's low enough using your idle speed screw on the side of the carb - which can cause a dieseling effect because the setting requires the throttle plate to be open more to get your engine to idle high enough with the mild cam so it does not stall out.

This is where an electric idle stop can be used if you do not have one. This is also why Pontiac used them. You can set the electric idle stop to completely shut off the throttle plate so no air can get into the engine and cause the dieseling when you shut the engine off.

So, check your timing. Check to see if your carb is leaking gas into the engine. Check & adjust your idle speed screw to get your RPM's down to 500 RPM's in Drive (100 more RPM's with A/C). Check your idle mixture screws and adjust.

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post #5 of 9 (permalink) Old 03-06-2016, 09:12 AM
 
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You could not pay for that excellent advice that PJ just gave you on the carb....he is as usual spot on. Most likely it is a carb problem.

Just to build on what Jim said, try not to read too much into looking at the fuel in the filter as the fuel in the fuel bowl should start it even if the filter was empty and like Jim said the pump would fill that quick. It really sounds like you may be running too rich and the you have too much gas .....you didn't say if this problem was at hot start or cold....

In addition die selling or run can also be caused by overheated engine and since it is so new, the reason is that parts gets so hot in the cylinder that they can glow and loosely fire the mixture in the cylinder...so just sometimes it is overheating. Also the wire from the alternator, the brown wire that runs to your idiot light in the dash must be hooked up and you must have a bulb or that line must have a resistor or the car will diesel...

That line from the alternator must be hooked up right....

But dieseling is caused by a mixture left in the cylinder and something there a spark, something hot firing it.....so you have start where Jim said is it too much fuel.....makes sense, when you go back to start it it is flooded and won't start,

Or is it overheating? Or is the alternator wire not hooked up right?......

I don't think that fuel in the filter draining back is related, I could be wrong, but you are reading that as causing a lean condition....and a lean condition does not cause dieseling....it is too much fuel, too much heat, or leftover spark...not completely shut off
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post #6 of 9 (permalink) Old 03-06-2016, 10:47 AM Thread Starter
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Thanks ,Jim,Thanks Lemans guy.
It's a 1965 Lemans ,326 .it happens at cold start and when it's at running temp..i hit 350 miles yesterday the running temp dropped about 5 degrees .after reading yalls advice it dose sound like a carb issue ,gas not staying in bowl.I will try all yalls suggestions and let you know.
Thanks
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post #7 of 9 (permalink) Old 03-06-2016, 07:21 PM
 
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Also, if you are running stock exhaust manifolds, it may have the exhaust butterfly valve that operates off of a bi-metallic spring. If this is not operating, ie stuck closed or stuck partially closed, it will push the exhaust out & through the intake manifold heat crossover which goes under your carb and get both the manifold and carb pretty hot - which will also create a similar problem with gas boiling out or even vapor lock.
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post #8 of 9 (permalink) Old 03-06-2016, 08:29 PM Thread Starter
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No I'm running hooker headers
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post #9 of 9 (permalink) Old 03-14-2016, 09:50 PM
 
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Check to make sure the tank vent is not clogged. That would cause the vacuum created in the tank which would suck the gas back. Not sure about the deiseling though but that seems unrelated.

It doesn't have nitrous. It has cubic inches.
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