Vapor lock?

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Joel Chapman

Joel Chapman

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Mountain Home, ID/ Hughson, CA
So I have a 71 Dodge Dart with a 360 engine/570 street avenger carb/1/2” spacer/Holley mechanical pump. I have a rubber fuel line running in the similar fashion that the stock line went. After I installed the headers I started having starting troubles when the engine is up to operating temperature. It cranks and cranks but is acting like it getting no spark. Some times it responds well to putting the pedal partially down other times not so much. Am I experiencing vapor lock? Should I reroute the fuel line? Just trying to figure out where to start looking to get it to start more consistently. It will eventually start after I play with it for a little bit which makes me think vapor lock, but I’m not Sure.
 
Next time you suspect it might act up, look down the carb and move the throttle to wide open you should see a good shot of fuel from accelerator pump.

If you do you have fuel in the carb.

Have you checked that the coil is getting battery voltage during cranking and post ballast resistor voltage (about 8 or more) volts during run.
 
Joel Chapman said:
So I have a 71 Dodge Dart with a 360 engine/570 street avenger carb/1/2” spacer/Holley mechanical pump. I have a rubber fuel line running in the similar fashion that the stock line went. After I installed the headers I started having starting troubles when the engine is up to operating temperature. It cranks and cranks but is acting like it getting no spark. Some times it responds well to putting the pedal partially down other times not so much. Am I experiencing vapor lock? Should I reroute the fuel line? Just trying to figure out where to start looking to get it to start more consistently. It will eventually start after I play with it for a little bit which makes me think vapor lock, but I’m not Sure.
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Shouldn't matter if the fuel line and hose is in/routed the same as factory. It's a float or heat soak at the carb.. perhaps.
Heat temp does it run at sitting at idle in heat and cruising down the hwy?
Engine may be heat soaking/temp rise an excessive amount after shut down and maybe an increase in cooling capacity could be the cure... but things like and initial timing increase can help.
Maybe fuel is being pushed , look down the carb after shut down for dripping fuel.
Just start with the easy and go from there
 
I'd be surprised if it's really vapor lock. It's pretty rare.
 
RustyRatRod said:
I'd be surprised if it's really vapor lock. It's pretty rare.
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That's what I seem to have seen, and heard also. Now, I've had a bad coil kinda act that way before....I know I gets hot up there where Y'all are, it gets pretty darn hot down here too...I'd think you would have to have a winter blend gas in the heat, some weird fuel line routes, or something.... I dunno, Yer the Pro!
 
I hav
Dana67Dart said:
Next time you suspect it might act up, look down the carb and move the throttle to wide open you should see a good shot of fuel from accelerator pump.

If you do you have fuel in the carb.

Have you checked that the coil is getting battery voltage during cranking and post ballast resistor voltage (about 8 or more) volts during run.
Click to expand...
I haven’t checked the coil because it’s a brand new (well less than 500 miles new) msd coil. It sits where the stock coil sat on the intake manifold. Will check the carb next time i try and start it back up when it’s at operating temp.
 
MOPAROFFICIAL said:
Shouldn't matter if the fuel line and hose is in/routed the same as factory. It's a float or heat soak at the carb.. perhaps.
Heat temp does it run at sitting at idle in heat and cruising down the hwy?
Engine may be heat soaking/temp rise an excessive amount after shut down and maybe an increase in cooling capacity could be the cure... but things like and initial timing increase can help.
Maybe fuel is being pushed , look down the carb after shut down for dripping fuel.
Just start with the easy and go from there
Click to expand...
Right now the car seems to like to cruise around at 190 and Idling in the heat here sometimes it creeps up to 200. Im thinking that I may need a new radiator, right now it still has the stock three row from 71. Also as far as timing last I checked it was set at 10 degrees I believe should I bump it up some?
 
Joel Chapman said:
So I’m still learning a lot about this stuff so I thought vapor lock and heat soak where the same thing…
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Vapor lock is when fuel gets hot, boils and turns to vapor, just like the name implies. The fuel pump cannot pump vapor. The carburetor cannot move vapor. So if either or suffers vapor lock, the car will stall. I don't really know what the clear definition for heat soak is, because many people use it to describe many different things. I know what MY definition of it is and it's not the same as vapor lock.
 
Update for everyone. I believe it is a coil issue. Removed the plug wire from the coil and placed it on the cowl. There was no spark when cranking only once I let the key off from trying to start it did I get a spark.
 
Joel Chapman said:
Update for everyone. I believe it is a coil issue. Removed the plug wire from the coil and placed it on the cowl. There was no spark when cranking only once I let the key off from trying to start it did I get a spark.
Click to expand...
Ballast resistor. If it was the coil you would not have a spark at all.
 
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