Fuel filter location

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shadango

shadango

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I currently have the fuel filter (a fram see thru type) installed right before my mechanical fuel pump (318 engine).......

I have been having issues with the engine dying and have replaced the fuel pump as part of the attempt to get things right.

wondering if the fuel filter should be after the pump instead......or if it matters. someone has suggested that having the fuel filter before the pump can actually kill the pump over time....

My issue is I have installed the holley fuel regulator right off of the steel fuel line...so no place before the regulator to install the filter like the directions say.....

Here is my current setup....

DCP_0158.jpg
 
The earlier models had the fuel filter cut into the vertical line from the pump.
Kinda beside and paralell to the dipstick tube. Those were metal can filters though. I dont know if the plastic type can withstand the heat that would be in this area.
 
I had installed a fuel pressure gauge when I started having issues to see what the pressure is. The edlebrock tech I spoke to said it needs to be no higher than 6-6.5 psi. I was running 7 and 8 psi so I got the regulator.

I was thinking maybe the filter location was an issue but I am not so sure now...

Still the car wants to die once fully warmed up.hot.

I've replaced the rubber fuel lines......back by the tank, just a short piece, and then at the front, to the fuel pump.

I just got back a while ago from a ride....drove around just fine for a good 20 miles or so.....ran great...then as I got closer to home, it wanted to die when stopped, in drive..........as I got closer to home, same as yesterday, it got uglier.

Have been messing with it in the garage now for a good couple hours.....tried different variables:

Swapped in a new ignition module
Swapped in a new ballast
Checked coil readings....16k or so between either terminal and the center, low ohms across the two terminals
Voltage at the coil is around 6.8 or so when not running.....higher , like 8.9 , while running
Tried different rod springs
Tried different settings of the IMS screws, a half turn at a time, either way
Tried bumping up the throttle screw a bit, by 1/4 turn...idled faster but still no good.
Tried adjusting fuel pressure from 5 to 6, then to 4

In all cases, the engine idles, starts running poorly at some point and then dies out on its own unless I gas it.

Fuel filter still looks like it doesnt have much gas in it, but the carb is getting fuel, cause when I work the throttle I get gas there.....

Watched the venturi nozzles a idle and I cant see any gas dripping....

I am at wits end. :banghead:
 
My quarter placed on temperature related problem. Either your temp gauge is wrong and the engine is running too hot or the carb spacer is wrong and the carb is getting too hot.
And by the way, the air bubble is not a problem but would go out with a vertically positioned filter.
 
The temp gauge reads about 160-180....now it could be a little higher due to the way the sensor is in a fitting that rises a bit out of the manifold....but the stock temp gauge also reads at the low end of the scale/range.

The carb body is hot when I touch it..I already have the special heat isolating carb gasket from edelbrock..........
 
Coils and wires break down when overheated too.
As for that vacuum question, any engine that doesn't idle smoothly will make erratic vacuum.
 
The fuel filter needs to be after the mechanical pump.The pump is designed to push fuel,not pull it.
No need for the regulator with the mechanical pump.
Get rid of the clear filter,its dangerous.Get a metal one.

faucet pics 827.jpg
 
Tested the coil...had 13,600 ohms or so from terminal to the center....going to let it cool down completely and see if that changes.....

Had run different wires and had three of them come apart (seem to have melted).....If the wires were bad, would they act fine when cold and then act poorly when heated up?

I have the regulator becaise edelbrock told me that their carbs should see no more than 6.5 psi...my pump was pumping at 7 and 8 so thought I would give it a try.

I really dont think that fuel getting to the carb is the issue at this point.....but I guess I could give it a try.......

I have noticed some crud in the newest filter, so maybe I do have some stuff in teh lines or something, but the filter is catching it....and again, the car is only dying when totally hot. Up to that point it runs pretty well aside from the idle being lumpy....

re: the clear filter.....this is a fram filter, the number they say is for this car....

Why is it dangerous?
 
Johnny Dart said:
The fuel filter needs to be after the mechanical pump.The pump is designed to push fuel,not pull it.
No need for the regulator with the mechanical pump.
Get rid of the clear filter,its dangerous.Get a metal one.
Click to expand...

How does a mechanical fuel pump work then if it doesn't PULL fuel from the tank?
 
I would remove anything fuel/wise away from the motor,as far as posible away from heat.You can also use insulation on fuel line to keep from getting hot.I use that tube stuff you put on water pipes in your basement.
 
Fuel pumps (and most other pumps) are much more efficient at pushing rather than pulling. If there is any restriction in a line between the pump and tank you have to worry about vaporization due to the lower suction pressure in the line. Seen multi-million dollar plants brought to their knees by that occurrence. The pressure regulator is needed in this case because Edelbrock carbs are not setup to handle the fuel pressure put out by most fuel pumps. Stock pumps can have pressure of over 7 psi which will cause an Eddelbrock to flood and push fuel out the bowl vents. Loose fuel on top of hot engine is not a very good thing...
 
dustertogo said:
How does a mechanical fuel pump work then if it doesn't PULL fuel from the tank?
Click to expand...

Let me rephrase what I said.
It pulls from the tank,but there shouldnt be any restriction.
As far as I know,every chrysler car from our era, had the filter after the mech pump.They did it this way for a reason.

I have a hi-flow Carter mech fuel pump/Edelbrock carb on my car with absolutely no issues.
 
pettybludart said:
I would remove anything fuel/wise away from the motor,as far as posible away from heat.You can also use insulation on fuel line to keep from getting hot.I use that tube stuff you put on water pipes in your basement.
Click to expand...

RE: movingb stuff away from motor...Pretty much right now, that is the case.....the fuel line is running up thru the stock location.....any other routing would put stuff closer to heat sources.....

The hose going from the regulator to the carb feels hot at some point, but have pulled the line from the c arb when it is doing this and the gas that comes out feels cool......the rest of the lines etc dont feel too hot at all.
 
Steve68 said:
Fuel pumps (and most other pumps) are much more efficient at pushing rather than pulling. If there is any restriction in a line between the pump and tank you have to worry about vaporization due to the lower suction pressure in the line. .
Click to expand...

How could I test to see if there is in fact vaporization going on (ie vapor lock)?

when the problem occurs, there is still gas at the carb because I can work the throttle and gas shoots out just fine...when I remove the fuel feed hose from the carb, gas comes out......I would think that if here was vapor lock, the carb would be dry....wouldnt it?
 
learned something new. to the top with this vintage thread.
 
It's a non issue for filter location. Some vehicles had filter brackets right on the frame rail a foot away from the fuel pump in the tank side right from the factory. Almost every older Dodge truck I've worked on had the filter in that location.
 
The pump creates a a low pressure area in a tiny cavity inside of it, and ATMOSPHERIC pressure pushes the fuel that is in the tank, towards the low pressure area. Once the fuel is in the pump, it pushes it towards the carb. The float valve is the restriction that backs the pressure up. Of course the atmosphere has to have access to the tank, to make this happen, and that is the number one reason that the tank has to be vented. If the tank is not vented, eventually the fuel will stop moving forward. AND, don't forget that the float bowl also has to be vented, else the atmosphere cannot push fuel up the fuel wells.
IMO, for most streeters, it makes absolutely no difference where the filter is located. Mine is just ahead of the right rear spring mount in the area that a torque box would be mounted. Mine is a big metal can, designed for an EFI car. It has over 120,000 miles on it.
IMO, just don't put a thin-walled plastic-bodied filter on the suction side of a 5/16 line; the walls of the filter will flex on every pump stroke, and if the pump is too weak, the filter will act like a pulse dampener, and very little fuel will actually move thru it.
IMO, you should prove the tank and float-bowl are vented.
 
Johnny Dart said:
As far as I know,every chrysler car from our era, had the filter after the mech pump.
Click to expand...

Every 1970 Dart with a 318 had the original fuel filter between the end of the fuel line from the tank and the fuel pump.

I wonder if the OP's car has headers that put one of the pipes too close to the filter or the metal fuel line...
 
str12-340 said:
Every 1970 Dart with a 318 had the original fuel filter between the end of the fuel line from the tank and the fuel pump.

I wonder if the OP's car has headers that put one of the pipes too close to the filter or the metal fuel line...
Click to expand...

If it were me , I`d find a diff. coil to compare w/ the existing one , switching them out for a try would be easy . Coils have been pnown to break down after getting hot ------------jmo
 
Coils get real hot without a ballast resistor.
 
Fuel should be sucked through a screen and pressurized through a paper filter. Most all fuel pumps on the suction side uses just small spring under the pump diaphragm for drawing fuel from the gas tank. Now for the pressure side of the pumping action, its uses a fulcrum and cam lobe to achieve pressure needed to push through a paper filter and amble fuel supply to the carb.

Screenshot (32).png
 
Not a good idea to use a paper filter on the inlet side of a suction pump.......which is probably why the factories put them on the outlet side.
 
str12-340 said:
Every 1970 Dart with a 318 had the original fuel filter between the end of the fuel line from the tank and the fuel pump.

I wonder if the OP's car has headers that put one of the pipes too close to the filter or the metal fuel line...
Click to expand...

So you are saying the fuel filter was under the car somewhere between the tank and fuel pump ?
 
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