[cv70chall]

I took my Challenger out last week for a short drive- about 1.5 miles. I parked the car on a very slight grade and when I tried to start it after 10 minutes, I could not get it to start. After several attempts, it would start and quickly die.
I managed to get her started and pulled out onto the street where it died again- this time on a level street surface. After more attempts- it fired up and got me nearly home before it died again as I was slowing down to turn into my development. We had to push it into the garage!
I was puzzled- as there was gas in the tank and visible gas in the clear glass gas filter.
I let her sit for a while, went into the garage and she fired right up and ran perfectly! What the hell?
Could this be a fuel pump issue? Gas tank issue? I've put nearly 50 miles on her since bringing her home.
What should I be checking for?
One additional question. I have the vent line running from the tank up the filler neck to a nipple on the filler neck. I also have a cap that has a small hole drilled into it for venting. I am replacing this cap with a regular non-vented type cap- seeing as the filler neck is already vented. (See the pic with the gas cap- and the small hole drilled into the cap- maybe this combined with the main vent line could be causing the fuel to come upward?

[dave-r]

You cannot vent the tank to the tank otherwise it is not vented at all. The vent on the filler neck just runs down into the chassis.

This is probably not your problem though. It sounds either like the fuel boiling in the fuel line, filter, or carb fuel bowls. In which case you need to look at keeping the fuel line and carb cool.

Or it is an electrical issue on the ignition with either a bad live connection somewhere or a bad ground connection.

[cv70chall]

If I remember correctly, the vent tube ran down the filler neck (see pic). The weird part was that the car behaved the way it did- even after I drove it a good amount- and behaved normally on a level surface in the garage.
What would cause the fuel to boil? I'm using the OEM fuel line, so it's not near anything hot (exhaust or headers)
What about the carb? How would I cool that?

[dave-r]

If I remember correctly, the vent tube ran down the filler neck (see pic).

That is not the stock 1970 set up. Although I think the California set-up might have been different.

It should be a steel line going vertically down through the floor from the top of the filler neck and just a short bit of rubber to join it.

What would cause the fuel to boil? I'm using the OEM fuel line, so it's not near anything hot (exhaust or headers)
What about the carb? How would I cool that?

As we are now getting into warmer weather the temp under the hood will increase. Fuel lines running along near the exhaust or headers need insulating. If there is any exhaust blowing from the system it can blow on the fuel lines. The carb can get hot if the heat cross-over on teh intake manifold has not been closed off. You can use a thick insulating spacer under the carb.
In fact if the fuel is boiling in the carb you will probably hear it if you listen closely.

The list of possibles is so long I can't list them all here.

It may be an electrical fault anyway.

Welcome to the world of the recently rebuilt 40 year old car. They always have teething problems like this.

[cv70chall]

Thanks for some starting points.
A few questions:

. On the Intake, where is the heat crossover? Maybe I can see it and if it is not closed off, what do I have to do?
You mentioned insulation for the fuel line. What type do I use?
What kind of gasket do I use fort he carb to further insulate it?
I understand the tank is not 70 but it still sounds like I have it hooked up correctly- with a line running from the top of the filler neck to the tank, right?
Lastly, since I have this line in place already- I still should get rid of the cap that has a hole drilled in it right? I assume that will prevent fuel from coming out that way.

[dave-r]

Thanks for some starting points.
A few questions:

. On the Intake, where is the heat crossover? Maybe I can see it and if it is not closed off, what do I have to do?

OK first of all you have to find out if fuel or electrics is your problem. Don't go changing things on the offchance. There are so many things it could be and you need to find the source of the problem first.

But to answer your questions. The heat cross over runs through the middle of the intake manifold. From the exhaust port on one head to one on the other head. On a stock exhaust system you have a butterfly in one exhaust manifold that closes off when the engine is cold so exhaust is forced through the intake manifold to heat it on cold mornings. This is something you do not want on a performance car. You can block off this passage in the intake simply by fixing a bit of tin plate in there with strong epoxy.

You mentioned insulation for the fuel line. What type do I use?

You can all all kinds of insulating wrap. Some are silvered to reflect the heat. Check out places like Summit Racing.

What kind of gasket do I use fort he carb to further insulate it?

Look up "carb spacers". Anything made from an insulating material. Wood plastic. Obviously not aluminium.

I understand the tank is not 70 but it still sounds like I have it hooked up correctly- with a line running from the top of the filler neck to the tank, right?

No. Wrong. A vent line from the tank to the tank is not a vent!! You have to vent to the atmosphere so that as fuel level in the tank drops, air can fill the space. Otherwise you will create a vacuum as the fuel is pumped out. The car will either stop because teh pump cannot pull any more fuel or the tank will collapse due to atmospheric pressure.

So either that rubber line you have there vents to the air or you have to have a cap with a hole in it.

[Adrian Worman]

When this fault happens Chuck just feel the large flat electrical connector at the base of the steering column. If the large red power wire in the centre of that bock feels hot then it's electrical. The culprit is nearly always that shit bulkhead connector assembly, no matter how good it looks it's absolute crap and always a weak link.
As Daveman sez........one thing at a time
Oh and the insulation for the fuel line will be the same as you get from any aircon spares supplier

[cv70chall]

Dave-
That vent tube (rubber line) runs from the tank up the filler neck and terminates at the nipple behind the neck to fender, so I',m correct in having an airway. I'll eliminate the cap with the hols as I don't need 2 sources.
I'll get on summit for that insulation too.

As far as it being electrical- this car fires up completely normal on a level surface so I can rule out electrical I think.

[dave-r]

Dave-
That vent tube (rubber line) runs from the tank up the filler neck and terminates at the nipple behind the neck to fender, so I',m correct in having an airway. I'll eliminate the cap with the hols as I don't need 2 sources.

I know you have that rubber hose going to the nipple on the filler neck. The problem is where the other end is going. It is supposed to go into the chassis leg so the filler neck and tank are exposed to atmosphere and any fuel from over-filling will run down into the chassis and out a drain hole rather than down your paint.

It the bottom end of that hose is going into the tank you have a problem.
The filler neck is part of the tank. So you are running the rubber hose from the tank to the tank. If you fit a cap with no hole in it you are sealing the tank from the air and the tank will collapse.

[cv70chall]

Understood. So given the tank set up I have, what should I do about that second connection? plug it or route a line from it where?

[cv70chall]

I'm going to have a non-vented cap.

[cv70chall]

Dave/ Adrian-

Just to be ABSOLUTELY clear..


My tank has TWO fittings. I can assume that the larger one is for the fuel line. I understand it is not a correct 70 tank.
My filler neck as a fitting near the top collar on the side. I assume that's a vent.
That being said, if I don't run a line from the second tank fitting to the fitting on the filler neck, where do I run the line?
Do I seal off the second fitting on the tank?
Do I simply run the line from the filler neck down into the chassis cavity for drainage?

I want to be clear about this. sorry for seeming ignorant...

[Pat]

First of al the rubber booth on the outer crome cap if for locking gas cap only so you should
peal of that clip and booth if you dont intend to use that original cap ! The pic show you a original locking
cap for the 1970 Challenger ONLY cap and the booth is there to seal the key hole in the cap to avoid water to come inside the cap ! Secondly you have a fuel sending unit for cars that have a return line
for fuel that 440 and 426 engine have from factory so the fuel vent back to the tank from the so caled vapor separator so my qestion is do you have the return line on the car and a vapor separator ?

[Adrian Worman]

The line that goes from the tank to the top of the filler neck may be a vent but only for ease of filling
As Daveman says, there must be a tank vent that normally goes up into the upper part of the rear qtr panel to form a loop and then drops down to the floorpan and lays inside the chassis box section.
On the 72 on cars like mine there is a bundle of tank vent lines that include a return ftmrom the charcoal cannister, I think there's 5 altogether. They go up the rear qtr in the same way but terminate into a pressed steel tube with a loose cap.

[cv70chall]

No I don't. I have a small block. Do I plug this feed off and not use it then?

[Pat]

Yes then you need to plugg the smalest line on the fuel sending unit and only use the big line that is to the fuel pump !

[cv70chall]

PERFECT.
And the line I have coming from the top of the filler neck simply needs to be routed somewhere inside the fender near the chassis right?

Thanks so much!

[Pat]

PERFECT.
And the line I have coming from the top of the filler neck simply needs to be routed somewhere inside the fender near the chassis right?

Thanks so much!

Yes thats corekt ! Hope it work now

[cv70chall]

the smaller fitting (see pic above) would probably be 5/16" right? I will need to locate a plug for that.

[Pat]

the smaller fitting (see pic above) would probably be 5/16" right? I will need to locate a plug for that.

Yes that sounds corekt ! That smaller fitting is above fuel level inside the tank but it can ofcorse leak out
gas if you dont put a plug on that fitting.

[cv70chall]

OK.
What type of plug would I use?