From: John De Armond
Subject: Re: 1980 Dodge Transvan
Date: Fri, 03 Oct 2008 15:58:18 -0400
On Fri, 3 Oct 2008 11:58:35 -0700 (PDT), email@example.com wrote:
>Had rats make nest on manifold, caught on fire. Need desperately to
>replace vacuum lines. Can't find where some of them go to!
>I believe this is the problem with the van no longer running right,
>but would welcome any other ideas. Van runs, but seems to not get
>enough gas to continue running. Must stop and pump gas, as restart
>it! Any ideas welcome. Three lines were burned up, and were
>plugged, this doesn't work. Suggestions on finding a schematic on
>carb would help, can't find make or size of carb. however!!!! It's a
>It is a 360 v-8 1980 22ft. Dodge Transvan.
With an engine that old, the carb is probably a Slobberjet, er, Quadrajet.
Does it have a bakelite (black) center section? If it does and if the fire
got near enough to the carb to blacken it or show any signs of heat then
figure on a replacement. That bakelite section is very easily damaged by
heat. I'd go with one of the quality non-Holly aftermarket carbs.
Next question. Does your vehicle have to be smog inspected?
Assuming it does not, there is only one line that is absolutely essential.
That is the line from the ported vacuum on the carb to the vacuum advance on
the distributor. Everything else is smog control and is not essential.
To find the ported vacuum port, crank the engine and either feel each port on
the carb with your finger or hook up a vacuum gauge. Plug any ports that are
sucking at idle. Those are manifold vacuum. The ported vacuum will have no
vacuum at idle but will quickly develop vacuum as the throttle is cracked. By
the time the throttle blade is a quarter inch open, the vacuum will mostly
have decayed again. This port is usually located down low on the carb toward
the rear approximately on the plane of the throttle shaft.
Run a vacuum line from that port to the port on the vacuum advance diaphragm
on the distributor. yer done
There are two other applications that may need engine vacuum. The warm air
carb heat if you have it, and the vacuum controls in your dash, again if you
The dash is easy. There will be a hose penetrating the firewall. On most
Mopars of that vintage it comes through near where the throttle cable does.
Simply connect that line to a source of engine vacuum (something that sucks it
idle. Optionally, a check valve and vacuum reservoir (junk yard or car parts
store) will store vacuum so that your HVAC won't change modes going up hills.
If you have a carb heat system, there will be a vacuum diaphragm on the intake
to the air cleaner. There will also be a smaller diameter (~2.5") running
from under the air intake to a shroud on an exhaust manifold. This is
designed to feed warm air into the carb when the engine is cold and then
divert to ambient air when it warms up.
If you have this apparatus and you want the engine to run smoothly shortly
after cold crank then it should be connected. Somewhere in the intake
manifold's water jacket, usually near the thermostat housing, will be a
temperature operated valve. A pneumatic thermostat. It screws into the
manifold with pipe threads and has a vertical (usually) black plastic body. It
will have two or three ports.
If it has two ports then it is easy. Simply run a tube from a source of
engine vacuum to one port. Run another tube from the other port to the port
on the diaphragm on the air cleaner.
If it has three ports then it's like a SPDT switch. There is a common port
and one port that is open when the engine is cold and another when it is hot.
It's easy to figure out which is what by finding out which two ports conduct
air when cold and which two conduct air when hot. The port in common is the
common port. Again, connect the two ports that are CLOSED when hot as above
and plug the third port.
There is a remote possibility that Mopar had converted to the air
cleaner-mounted thermostat by then. If there is one then it is mounted on the
underside of the air cleaner housing outside the diameter of the air filter
element. It sticks through the bottom of the housing. It has two ports and
connects as above.
If your vehicle has to be smogged then I can't help you. You'll need to
consult one of the on-line manuals that has photos of where all the hoses go.
The smog inspector looks for the proper hose routing as part of the visual. I
try not to work on pre-EFI smogged cars :-)
Have you looked carefully under the hoodlet, particularly on the underside of
the hood itself? Usually somewhere in the engine compartment is a diagram of
smog hose routing.