[DeTomaso] Engine run anomalie

boyd casey boyd411 at gmail.com
Wed May 13 11:18:36 EDT 2009


 I have been having a recurring problem with my car. It is a 73 L that is
not completely stock, Edelbrock intake, holley 650 w/ manual choke ,
MSD 6AL, MSD low profile distributor, MSD "blaster "coil,  All the MSD stuff
is new including wires and new plugs. I have recently added a" Fram "racing
fuel filter, a small " inline" gas filter ( so I can actually see the gas),
a fuel pressure gauge. The problem is the car will start and run and seem
okay. If I only drive it around the block I never have a problem. If I drive
it a few miles I don't seem to have a problem ( Unless I turn it off) when I
turn it off it won't re start. I thought I had a fuel tank debris problem. I
have removed the fuel gauge sending unit, fuel out let twice
and completely drained and vacuumed the tank to pick up any debris. I didn't
find any evidence of any particulate mater and the brass screen at the end
of the fuel pick up is intact and did not show any signs of blockage. I have
noticed that when my engine won't start my fuel pressure gauge stays showing
4.5 lbs of pressure( even though the engine is not running) that made me
think I had picked up some debris and that it was blocking the fuel inlet
and that the debris was being held in place by the vacuum created by the
fuel pump. I installed a vent line using a "T " connection  from mu fuel
line between my fuel filter and the intake to the carb and another "t"
connection in the vent line. I put a small ball cock valve in this line so I
could release the vacuum and "drop" any debris being held by the vacuum.
This works but not immediately. The pressure on the fuel gauge drops to zero
but the car still won't start. usually after around 45 minutes the car will
start. It occurred to me today that perhaps the problem is not a clogged
fuel line but a blocked Vent line. If the gas tank is not vented won't that
create a problem as more and more gas is sucked out of the tank and the
vacuum build and since no air is entering the tank it becomes increasingly
difficult and eventually impossible for the stock mechanical fuel pump to
suck up any gas. Does this make sense? If this is the case is the remedy in
the gas cap or the vapor separator assembly Aside from the vent line that
terminates there the other connection on top of the gas tank? Also Since I
don't have the original air cleaner or any of the vacuum operated emissions
devices do I still need to keep the charcoal canister? The return from the
canister to the air cleaner no longer exists. My concern was that if the car
were to have the misfortune of winding up in an inverted position would the
vent line to the canister prevent fuel spillage. If not is there any reason
not to have the vent line open to the air instead of the cannister( which I
would like to remove it if is not serving a useful function.) If this is an
issue that can be remedy with a new gas cap do I have to buy a "pantera "gas
cap  ,or is  there a "normal " vented gas cap I can use?Thanks,
Boyd



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