Fuel pressure problem - Mallory 140 electric pump

[David Womby]

Happy New Year!

New Year: new problem.

My electric fuel pump was installed upside-down when I got the car and very noisy. Also, the filter never seemed full of fuel despite the pump and filter being mounted below the level of the fuel tank bottom.

I remounted the pump in the correct position (upright) and it's very quiet now BUT the filter still never stays full. I attached a pressure gauge to check the fuel pressure and things are behaving oddly. With the engine idling, the gauge sits at 2-3psi most of the time and the filter looks practically empty but every so often the gauge will jump to about 7psi for a moment or two simultaneously with a surge of fuel appearing in the filter. You can see this in this video (sorry for the poor quality) - at 27secs it drops to 2psi, at 57secs it jumps to 7psi and fuel fills the filter then it immediately drops again and the next surge to 7psi comes along at about 1min 27secs. Fuel pressure video

Any ideas what's going on here? I would be expecting to see the filter full all the time and the pressure constant. Is the pump/regulator toast? Thanks

David

 

[Jerry Hall]

Your video is marked private.

 

[David Womby]

Your video is marked private.

Thanks for telling me. I am a Youtube newbie. I think it's available now.

David

 

[Jerry Hall]

I don't know if those pumps can be rebuilt or not, it may be time to replace. I was having to replace external pumps on my 67 Gen III conversion car about once a year. It would not hold 25 psi on the fuel rail and the engine would not rev more than 3500 rpms without running out of fuel. I went with a in tank pump and problem solved.

 

[dvw]

Is the picture shown upright? If so the pump is upside down. Pumps go quiet when they pull air. Motor should beat the top. Why is the regulator mounted right to the pump?
Doug

 

[David Womby]

Is the picture shown upright? If so the pump is upside down. Pumps go quiet when they pull air. Motor should beat the top. Why is the regulator mounted right to the pump?
Doug

The photo shows the pump as it was. Upside down. I turned it the right way up. The video is of the pump right way up - motor at top. Regulator was attached to pump when I got the car and I left it that way. Is that a problem?

David

 

[33 IMP]

I believe the 140 Mallory are gerotor pumps, and much more trouble free than a typical vane pump. I would definitely suspect the regulator. Are you checking fuel pressure before or after the regulator? Check before the regulator to see if pressure is good/constant. And like Doug says, put the regulator up front where it belongs.

 

[David Womby]

I believe the 140 Mallory are gerotor pumps, and much more trouble free than a typical vane pump. I would definitely suspect the regulator. Are you checking fuel pressure before or after the regulator? Check before the regulator to see if pressure is good/constant. And like Doug says, put the regulator up front where it belongs.

I am checking pressure at a port in the regulator that is designated 'fuel pressure port'.

I will separate the regulator from the pump and check pure unregulated pump pressure.

David

 

[TN Mopar]

I use the 140 Mallory fuel pump and like it
They are rebuildable you just have to find the kit
They can be a bit noisy but I found rubber washers on the mounting bolts eliminates most of it

as I look at your picture you are pulling fuel through the filter
I would suggest the filter is a restriction on the feed of the pump
its not staying full because the pump wants more fuel than the filter will allow
those filters are meant for the pressure side of the pump not the feed side
you can try removing the filter and see if that helps

Also I can't tell from your picture or your video but where is the pump drawing from? is the pump above the level of the fuel?
they need to be below the fuel and have gravity assist

also what size is the pick up in the tank? 5/16th or 3/8?
are you sure the sock in the tank is not clogged?

and lastly I would move the regulator to the engine compartment, let the high pressure fight the resistance in the lines and fittings as opposed to the low pressure

 

[David Womby]

I use the 140 Mallory fuel pump and like
They are rebuildable you just have to find the kit
They can be a bit noisy but I found rubber washers on the mounting bolts eliminates most of it

as I look at your picture you are pulling fuel through the filter
I would suggest the filter is a restriction on the feed of the pump
its not staying full because the pump wants more fuel than the filter will allow
those filters are meant for the pressure side of the pump not the feed side
you can try removing the filter and see if that helps

Also I can't tell from your picture or your video but where is the pump drawing from? is the pump above the level of the fuel?
they need to be below the fuel and have gravity assist

also what size is the pick up in the tank? 5/16th or 3/8?

and lastly I would move the regulator to the engine compartment, lket the high pressure fight the resistance in the lines and fittings as opposed to the low pressure

Thanks. yes, the filter is before the pump. It was that way when I got it and I assumed it was to protect the pump? I can easily move it. The pump is definitely below the level of the tank bottom but the feed from the tank is up a vertical pickup pipe inside the tank to the top (I haven't measured but the lift required is about 12"), then the fuel line runs down to the filter you see in the video. The fuel line and all pipe fittings (except the pressure gauge I am using) are all 5/16" I am guessing the pickup tube is the same.

David

 

[TN Mopar]

They make filters designed for the tank side of an electric pump
Holley has a 100 Micron filter for tank side and a 10 micron filter for engine side
The test is simple, remove the filter and see if it changes your pressure

The 5/16th pickup could be part of the problem as well especially since you are pulling fuel up over the tank
also your filter sock could be clogged
I would consider a 3/8ths pick up especially if you have a high HP engine

 

[33 IMP]

David, as an aside, I love your Bristol. I notice that you mention a 62 727. Is your car a push button shifter? If so, seriously cool!

 

[David Womby]

David, as an aside, I love your Bristol. I notice that you mention a 62 727. Is your car a push button shifter? If so, seriously cool!

Thank you. Yes it does. Reverse, Neutral, Drive, 2, 1. No Park back then!!!!

David

 

[David Womby]

They make filters designed for the tank side of an electric pump
Holley has a 100 Micron filter for tank side and a 10 micron filter for engine side
The test is simple, remove the filter and see if it changes your pressure

The 5/16th pickup could be part of the problem as well especially since you are pulling fuel up over the tank
also your filter sock could be clogged
I would consider a 3/8ths pick up especially if you have a high HP engine

Thank you.

David

 

[David Womby]

OK. Here's an update.

I removed the filter that was between the tank supply and the pump. No change - still mostly 2-3psi with 7psi 'surges' every 30 secs or so.

Then I removed the regulator and connected the output of the pump directly to my pressure gauge. The pressure started out pegged at 10psi (That's as high as my gauge goes. The pump probably started out working at spec of 14psi.) then quickly dropped to 2-3psi and never came up again.

So, it seems to me that it's either a duff pump or possibly some degree of blockage in the pickup tube. FWIW I did blow into the fuel line from the tank pickup and could hear the fuel bubbling in there.

Thoughts?

David

 

[TN Mopar]

if I recall correctly there is a screen on the inlet side
you might pull the fitting from the pump and check the filter screen

lacking anything in the filter screen I would say it is time for a rebuild kit

 

[David Womby]

if I recall correctly there is a screen on the inlet side
you might pull the fitting from the pump and check the filter screen

lacking anything in the filter screen I would say it is time for a rebuild kit

Thank you.

David

 

[David Womby]

if I recall correctly there is a screen on the inlet side
you might pull the fitting from the pump and check the filter screen

lacking anything in the filter screen I would say it is time for a rebuild kit

Here's the inlet screen.

Looks clear to me. I'm inclined to just buy a replacement pump - I only need 5psi and ~50gph so this pump/regulator setup seems overkill anyway and more complex and expensive than I need.

David

 

[David Womby]

Before ordering a new pump, I thought I should check that it's not a blocked pickup tube in the tank but I didn't fancy trying to chisel off the sealant and take the pickup tube out. So I ran the pump standalone on the bench drawing from a jerrycan. I still could only get <3psi output and it's rated at 14psi from the factory. So I think that I can assume the pickup isn't my problem and the pump is.

David

 

[TN Mopar]

Before ordering a new pump, I thought I should check that it's not a blocked pickup tube in the tank but I didn't fancy trying to chisel off the sealant and take the pickup tube out. So I ran the pump standalone on the bench drawing from a jerrycan. I still could only get <3psi output and it's rated at 14psi from the factory. So I think that I can assume the pickup isn't my problem and the pump is.
David

One other thing is to try and adjust the regulator in the pump

but most likely yes time for a rebuild or replacement
The Mallory is one of the quietest pumps when mounted correctly

if you step down to the Mallory 110 GPH you wont need the regulator, they are internally regulated