I have a 1985, 318 eng, 2 bbl carb, Dodge ram with a hot start problem. Summer time 100 degree temps are a killer. It always starts immediately after sitting all night. It runs perfectly for as long as I care to run it. When I shut it off, it will start with no problem, as long as I restart it within 5 minutes. If I wait 15 or 20 minutes, it usually will not fire. About 1/2 of the time if I hold the accelerator to the floor and continue to crank it, it will start. The other 50% of the time it will not fire and start until it cools off. (sometimes hours) If I let it idle for 20 or 30 minutes when the temps are extremely hot, it runs rough and hesitates for a couple miles until the engine cools some....then it runs ok again. Almost acts like it is trying to vapor lock.
Anyone have any ideas?

I have the carb bowl vent to cannister disconnected. The hose is not plugged. It has started and run ok today in 90+ temps. I cannot see any fuel dripping in intake after the engine is stopped, causing it to flood. Pulled a plug wire off and it will spark 1/2 inch when running. I will check again for spark next time it won't start. Whenever that may be...... I have replaced no less than 3 new ECM's & pickup modules, ignition switch, and a ballast resistor or 2, trying to fix the problem. I also replaced the engine wiring harness, thinking it may have a broken wire causing an intermitent electrical problem. Pulled 3 plugs and did a compression check for the heck of it. The average was 95 psi.

 

I have a 97 3/4 ton 4x4 318 with the same issue. If I shut it off and restart immediately it will start, how ever if I wait a minute or so, it will take 3 hours for engine to cool enough for a restart. The engine cranks, I can hear the fuel pump prime with the engagement of the ignition, but it appears to not have any spark. I am thinking a coil issue, possibly a ignition module (does Dodge have one and if so where is it's location?) possibly something within the distributor cap. My though is something electrical is getting hot, and so long as it is hot it will not allow spark. I live in Michigan average temps has been in the mid 80s during the day this summer. this is a new issue, been going on a couple of days. I am flat broke so can not afford to experiment.

 

I had a '97 Grand Cherokee that did it. Ended up being the crank position sensor. Was breaking down when getting hot, causing the ignition to not know when to fire. Obviously won't be the issue with the '85, sounds like vapor lock or coil maybe. A good manual usually gives ways to troubleshoot and test specific items, otherwise you're kinda taking shots in the dark.

 

i would maybe try disconnecting the oil pressure sensor or coolant temp sensor if it is not starting while it is hot. i think i remember a friend saying some of the older dodge engines not starting because of one of the oil sensors.

 

Glad to hear that I am not the only one in this battle. I have replaced both the coil, and distributor cap within the past year. The old dodge is a carb model with a mechanical fuel pump. The carb was also rebuilt a year or so ago, and a new needle & seat was installed. (thought it might be flooding) It always fails when I am by myself, so I can't crank it and check for spark and fuel. I highly suspect it is electrical, while at the same time I don't understand why holding the accelertor to the floor seems to help. That usually indicates a flooding problem. I have been purchasing the replacement ECM's from Napa, and Autozone. I have noticed they have all been imported. I wonder if Mopar still sells a factory ECM?

 

Ok, I replaced the coil to no avail. going after the crank position sensor and distrib cap next. It does not make a bit of difference if I hold the gas peddle down or not. turn it off for 15 seconds and wait 2-3 hours for a restart. But it will turn off and restart within that 15 second window. I will look into the oil sensor unit as well.

 

I just purchased my first Dodge truck. 87 Dodge 1500 short bed with 318. Women got tired of , "will not start when hot," issues. Great deal and one fuel pump later , it is fine. Proper sucking from tank and very low pressure to carb, was the issue. Ran fine and started in the morning, but any gaps of time, and it would not get fuel.

 

Try the above suggestions and check your thermostat, rad hoses for collapse and make sure you have the proper thermo barrier in between your carb and intake