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Fuel filter location

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Griz

Griz

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OK guys, I've decided that my BJ7 needs a fuel filter. I understand that most people install them back by the fuel pump. Question is should it be on the suction or the discharge side of the pump, or does it make any difference? Anyone have a recommendation for a filter available from NAPA or O'Reilly?

Griz
 
On suction side you will filter the gas before it hits the pump, which is a good thing. But if car has a steel pipe leading from the tank to the pump you will have to cut the pipe, which some folks do not like doing. I have heard some folks claim that the filter on the suction side can cause the pump to damage itself if the filter gets clogged, but I have never seen that happen myself. If you put it on the pressure side, I see no reason to locate it under the car unless you are trying to hide it. I'd locate it somewhere under the hood where you can reach it easily for replacement and inspection.
 
Thanks for the response LB. I do want to keep it out of sight and I think it would be easier to reach, if need be, by removing the passenger side rear wheel than by locating it deep in the bowels of the engine bay.

Griz
 
I put mine next to the carbs. The amazon pic looks slightly different than what arrived.
 

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RestoreThemAll said:
I put mine next to the carbs. The amazon pic looks slightly different than what arrived.
Click to expand...

ME too:
I also used a clear filter so I can monitor the fuel passing through it and the filter's dirt build up.
Used this set up for years no problems..
 
Bob, because it's a fresh restoration, and even though I had the gas tank professionally checked out and cleaned I still seem to be getting grit in the float bowls.

Dale, that sure looks like a tiny filter. Is it more like a strainer than a filter? I just got back from O'Reillys and got a metal filter (thought it would be more durable than a plastic filter if mounted in the back and exposed to rocks etc) that is about 2" in diameter and about 2" long.

Griz
 
If I remember correctly the one that I used has a bronze 40 micron filter. The engine ran for many years with no filter. I'd think that particles smaller that 40 microns would pass right on through and out the tail pipe.
 
The diameter is 1 1/8th inch and about 1 1/2 inch long...and it looks pretty to.:cool-new:
 
Hi Griz,

As Legal Bill indicated, the metal pipe connecting the tank and fuel pump is used to provide the ground for the sending unit. Cutting the pipe will sever the ground and would require another to be installed for the gas gauge to perform properly.

An SU fuel pump uses fuel flow for cooling and a blocked fuel filter will cause it to overheat and fail. According to Dave Dubois (recognized SU fuel pump expert), the SU pump will be able to pass rocks and small birds without issue so tank debris should not cause a problem. However, In this case I would go with John and install the filter on the outlet side of an SU pump.

Use of a modern aftermarket pump is another story. In this case, and if you don't mind installing a new ground wire, installing the filter before the pump and after the fuel tank will provide the greatest protection against the penetration of dirt and debris into the fuel system.

I guess I have been lucky and depended, without issue, upon the original protection provided by the installed screens that are part of the SU pump and carburetors for protection in my Healey.

Hope this helps,
Ray(64BJ8P1)
 
Billet filters on both my cars right at the carbs , easy to clean and very accessible.....
But oh the humanity its not "correct"
 
RAC68 said:
... An SU fuel pump uses fuel flow for cooling and a blocked fuel filter will cause it to overheat and fail ...
Click to expand...

I don't believe that's the case (but I'm open to correction; esp. by DD). The only part of an SU pump subject to heating--from electric current--is the pump body; i.e. the solenoid. If fuel gets in there you have a potentially serious problem, esp. with a points-driven system (fuel + air + spark = problem). The only heating of an SU pump is from the current flowing through the pump body (solenoid), which is only momentary and proportional to the rapidity of the pumping. If the line is blocked--or when the engine isn't running--the pump only fires a few times a minute, and there is no 'hold open' time--like in an OD solenoid--that would cause the solenoid to heat up. If there's an output or intake leak the pump will pump rapidly, which can cause heat buildup in the pump body.
 
Ray, good comment on the grounding of the sending unit, however I had previously installed a separate ground wire for the sending unit so cutting the pump suction line will be no problem. On my car there is more room to add the filter on that side of the pump so that's were it will be. Good comments all...thanks.

Griz
 
Hi Bob,

I am glad you are open to the concept.

Take a look at Dave's document and you will see how the SU pumps will overheat and burn out if fuel is blocked. It is not the temperature of the gas but stopping the operation of the pump that causes the unit to overheat. The pump must be allowed to pump and a blocked input filter would cause it to stop with power on.

https://userwebs.donobi.net/sufuelpumps/Fuel_Pumps/SU_Fuel_Pumps_Facts_and_Myths.pdf

Enjoy,
Ray(64BJ8P1)
 
RAC68 said:
Hi Bob,

I am glad you are open to the concept.

Take a look at Dave's document and you will see how the SU pumps will overheat and burn out if fuel is blocked. It is not the temperature of the gas but stopping the operation of the pump that causes the unit to overheat. The pump must be allowed to pump and a blocked input filter would cause it to stop with power on.

https://userwebs.donobi.net/sufuelpumps/Fuel_Pumps/SU_Fuel_Pumps_Facts_and_Myths.pdf

Enjoy,
Ray(64BJ8P1)
Click to expand...

Ray,

Right you are, the pump will 'stall' on the intake cycle and overheat/burn resistor if the inlet side is blocked. For some reason--you didn't specify--I thought you were referring to blockage on the outlet side--where Dave 'recommends' (sort of) to put the filter--which is not a problem. On the output cycle as the points (or SS circuit) will be open and current will not be flowing (the pump will slowly bleed down, allowing plenty of time for the solenoid to cool).

I don't think Dave is a fan of filters in general, esp. as a 'bandaid:'

"The bottom line here is that if you are having a sediment and/or rust problem with the fuel tank that is severe enough to require a filter, then the tank should be removed, cleaned and sealed, or a new tank installed." - DD

If you're sure the tank is clean, it's time to look at the lines.

I don't believe SU pumps are cooled by fuel; the only part that gets warm is the pump body/solenoid--which is insulated by by both a gasket and the diaphragm--from the pump head, which is the only part of the pump that contacts fuel. According to Dave's doc, pumps fail when blocked on the inlet causing current to flow continuously through the solenoid, which causes the internal resistor to fail (not from lack of cooling from fuel flow).

re: "I guess I have been lucky and depended, without issue, upon the original protection provided by the installed screens that are part of the SU pump and carburetors for protection in my Healey."

I agree. Almost 140K miles on my BJ8 without any problem with debris in fuel.
 
Most su pumps I've had apart already have a filter in the inlet side . It's a cylindrical very fine mesh item. .
 
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