Ford Muscle Cars Tech Forum banner

1 - 8 of 8 Posts

·
Registered
Joined
·
4 Posts
Discussion Starter #1
65 Mercury Marauder 390 4 barrel Edelbrock 1406

A couple months ago I noticed fuel leaking at my gas cap after I parked. I replaced the gas cap (a vented one) and shortly thereafter have been experiencing rough low idle and stalling issues when driving, but the gas cap is no longer leaking.

Since I purchased the vehicle about a year ago, I've always had starting issues after I parked when the vehicle was warm, but it had never had issues once it was running or upon initial start-up (even after sitting sometimes for a couple weeks). I thought this was due to vapor lock, but now I'm not so sure.

Not sure if these issues are related or perhaps I'm experiencing both vapor lock and gas tank venting issues. Any advice is much appreciated!
 

·
Registered
Joined
·
306 Posts
Next time you have the idle/stalling problem, try removing the gas cap and see if there is any difference. Also see if you hear a hiss when you remove the cap. If there's no difference in idle and no hiss or indication of tank pressure/vacuum then you can look elsewhere.

Pat
 

·
Premium Member
Joined
·
5,726 Posts

·
Registered
Joined
·
51 Posts
It could be that you had a leaking problem, which you fixed, but never had a venting problem. The real issue could be in the lines on the suction side of the fuel pump.

My buddy had a 390 monterey that sucked the fuel hose flat when he stomped on it. The rubber hose between the tank and the hardline was old and soft and did not have the wall strength any more. My merc had the pick up tube almost completely clogged and it would run the stock 6 cylinder OK but starved out the V8 when I swapped it.

I would declare victory on the venting and leaking and check the supply side to the fuel pump to make sure you have good flow there.
 

·
Registered
Joined
·
4 Posts
Discussion Starter #5
Thanks for the input. All the fuel rubber hoses do look a bit past their prime (and the filter), so I'll change those out. I was able to start it this evening and it idled ok, but it failed to restart when I shut it down after only running a few minutes. Noticed a decent size black puddle from the driver's side exhaust...
 

·
Registered
Joined
·
51 Posts
A friend once told me his trouble shooting method was to do everything he should have done 6 months ago and see if he still had the problem. 😁


a weak hose could also let some air in on the suction side. some of the old 390s also had a return line from the carb to the fuel tank to prevent vapor lock. not sure if yours does
 

·
Registered
Joined
·
30 Posts
You might actually be dealing with percolation in the fuel bowls on the carburetor. The Edelbrock design puts the bowls close to the exhaust transfer ports on the intake manifold. This gets the fuel hot, and when heat-soak happens after shutting down, modern fuels tend to boil, and hot starting issues happen. A phenolic or aluminum spacer between the intake and carb is often the solution. The stock Autolite/Motorcraft carbs had them and also had the fuel bowls on the front and back rather than the sides, so they are less prone to having this problem.
 
1 - 8 of 8 Posts
Top