Heat Soak/Vapor Lock Solution??

-
MOPARJ

MOPARJ

What can I upgrade now?
Joined
Nov 3, 2006
Messages
861
Reaction score
7
Location
Thousand Oaks, Ca
I noticed the past few days that my 318 on my duster has been not acting itself. It has an Edelbrock 600, Performer intake, stock fuel pump. The problem only occurs when its warm to hot. What will happen is the idle will come way down and if you give it a hard shot of gas, it will die, cleanly. If it starts again, it may hesitate if you give it gas. If you let it cool down, it is fine again until it gets hot again. I replaced the stock pump with another stock replacement, replaced the filter with a clear unit. That has not helped. The one thing that i noticed yesterday is when cold, the filter is full, but when its hot and starting to act up, the filter is either near empty or sometimes it spits little spurts of fuel into it, but not much, as i f there is an air bubble when hot. It runs great before it gets hot and acts up. Dont know the fuel pressure yet, but i know its not much obviously. The plugs are dry.My hunch is that there is vapor lock, or severe heat soak going on. I just have a standard carb base gasket, not a heat-proof gasket, or a heat shield. I also am thinking about moving the filter after the pump, instead of before the pump. Does this sound like vapor lock too y'all too? The cam eccentric is fine. What gasket or shield should i use? Can i get it at a local parts store? The motor has 83,000 miles and has stock manifolds, if anyone cares or needs to know. Thanks. (Also, it has always been harder to start after it sits for a while when hot, after i put this intake and carb on, which is a biproduct of alluminum i guess).
 
If it starts right up after it cools down I would rule out a fuel problem. If the carb was getting heat soaked it would evaporate the fuel out of the carb. So there would be no fuel for it to start right up. I thinking you may have coil going bad. Coils going bad can do this when warm but fine when cooled down. Electrical devices do not like heat and when they start going bad it usually shows when the item is warm or hot.


Chuck
 
Funny you should mention...it has always had heat soak, causing hard starting when warm, but these recent problems surfaced the same day that i installed am Accel Superstock coil. I did it just for kick, not because the stocker was bad. What the hell? I had an Accel go bad on my dads Coronet. It would backfire through the carb. Is this one bad too? The coil is hot to the touch, as its chrome. I was trying to doubt that, but maybe i shouldnt. There still isnt a lot of fuel in the filter, so i will probably place it after the pump and add a phonolic spacer when i get one. Now what do you think? LOL. Thanks for addtional info. (p.s., the idle comes down when hot, it stumbles when you give it gas, then if you shut it off, it may restart, but it will die as soon as you give it gas-when it cools off, its fine again for a while...also, above 3500 RPM, it starts missing, then cuts out at 4000. when cold or cooler, it revs to 5000 no problem). Thanks.
 
It sure seems ignition related. A fuel pressure gauge will definately tell you if it is fuel related or not, I'm thinking not, but I would confirm this with a gauge. I had a MP coil go bad after running the motor 30 seconds. So it's just not Accel that can have problems.


Chuck
 
I had vapor lock issues out in vegas. It would get 113* or so in the summer, cuda was my daily driver. A phenolic spacer and high octane (actually a 91/100oct mix) and i never had any issues. Spacer helped out a good amount.
 
Something needs to be mentioned. Vapor lock happens on the suction side of the pump not on the pressure side. So isolating the carb or pressurized fuel lines does nothing to help against vapor lock. Changing fuels can help against vapor lock or to get rid of it completely you would have to put the pump in the tank. Isolating the carb from heat can and will help against perculation or evaporization in the carb but this is a total different problem than vapor lock.

Chuck
 
Sorry, your right on that one. Well whatever i had! lol it would drive...decently around town. Try and run through a gear and it'd fall on its face and sound like a diesel engine braking :D
 
Headers? heat on the suction side of the pump will cause vapor lock, been there. I had a set duals put on a motorhome I had years ago, the fuel line was 1" from the headpipe. Freeway driving it was boiling the fuel to vapor right in the line. It was fine around town but the added heat from the freeway cruising with 4.10 gears it would start stumbling and slow way down.

Changing your fuel is probably what fixed your car. Fuel grade or brand can make a big difference sometimes. Different brands have different levels of additives that help against vapor lock.


Chuck
 
All very good and precise info, i thank you all. Once i get my gremlins solved, i will start answering questions instead of asking. Just have to clear the questions out of my head first. I guess i get ideas of what is wrong, but i feel like i want more ideas, so thats why i ask. My father has taught me everything i know about Mopars, but i cant always get the time to talk to him. Thats part of being young, i guess. Anyways, i may try an MSD coil, as i have heard good things about them, and more bad than good about Accel and their reliability. Thanks again.
 
I agree with Chuck that it sounds ign. related. I had an Accel coil do the same thing to me once. Ran good cold but not good hot. Then one day it died all together. Put an MSD coil on and it ran great all the time. Also on the part of not seeing a full filter all the time, if it's on the suction side I doubt it will be full because it's not pressurized. I'd leave it there so the fuel is filtered before it enters the pump.
 
When I had vapor lock, I just wrapped the fuel line as it passed the header with heat wrap. Problem solved.
 
You must log in or register to reply here.
-

Back
Top