Hard Drive · Jun 6, 2020

Hi everyone.
Having replaced my low pressure fuel pump filter twice, with the last one recently, and knowing it has to be fitted the correct way around I thought to do an exposure.
The correct way is indicated by an Arrow on the filter's body and also on the plastic holder.
I wondered what the filter's internals looked like, in that it should be fitted the correct way.
See the pictures.

The blue arrow indicates the fitted/flow direction.
I originally tried cutting the filter open with snips, hence the initial battleground appearance.
I used a hacksaw next, which worked.
When fitted the correct way, the maximum surface area for filtering is in use.
Filtered fuel then flows through to the inner chamber and out through the spout.
Reversed, the filtering is more limited as the level of exposed area is very small, especially when compared to the correct way.
I hope this helps some. It also says, to me, that if fitted incorrectly it will still pass enough fuel for running.

andyfreelandy · Jun 6, 2020

Useful, thanks.
I plan to do a similar ortopsy on a duff lp fuel pump at some point.

Hard Drive · Jun 6, 2020

andyfreelandy said:
Useful, thanks.
I plan to do a similar ortopsy on a duff lp fuel pump at some point.

And that's the kind of stuff I really like.
Getting into the guts of parts can give us a heads-up view of what lies ahead.
Forewarned-is-forearmed.
Nice one Andy.

andyfreelandy · Jun 6, 2020

Here we are.
Failure mode, after 5000 miles, was one brush worn right down and detached from braid so breaking electrical connection.

This was an All Makes pump. About £35.

I cut about 3mmoff the top rim and then unsoldered the power socket leads from the brush connections.
The remaining bit of brush is shown in photo 4.
The actual pump is held together with allen bolts. Will carefully disassemble and post photos.
The diesel encases the motor, brushes and commutator. Not sure oil is good for the internals but that is the way it works. Floods diesel all over the workings and out the end via a non return valve in the output port.
Could repair it but sealing would be tricky.
Now need to compare with a pierburg £200 job. Anyone???

paul99 · Jun 6, 2020

andyfreelandy said:
The diesel encases the motor, brushes and commutator. Not sure oil is good for the internals but that is the way it works. Floods diesel all over the workings...

The diesel is used as both a lubricant and a coolant for the pump. It's pretty standard nowadays, even the petrol pumps in the fuel tanks use the immersion in fuel as a coolant. Sounds dodgy as anything, but it seems to work.

andyfreelandy · Jun 6, 2020

Lubricating brushes needed electrical connections seems odd!

Sparking commutator in petrol tank seems risky, esp as fuel tank empties and fills with vapour.

I'd like an alternative pump with sealed electronics.

paul99 · Jun 6, 2020

I don't think the petrol ones are lubricated by the fuel, just cooled. The diesel ones are usually fuel lubricated, though. Which is one of the reasons why it is a bad thing to run a diesel tank dry.

Nodge68 · Jun 6, 2020

andyfreelandy said:
Sparking commutator in petrol tank seems risky, esp as fuel tank empties and fills with vapour.

It's totally safe to pass fuel, even petrol through the pump. There aren't any sparks, as they are quenched by the fuel. The vapour can't ignite, as there no oxygen in the tank, just fuel vapour, which requires oxygen to burn, so it's totally safe.

paul99 said:
I don't think the petrol ones are lubricated by the fuel, just cooled.

Petrol pumps are still lubricated by the fuel, same a diesel pumps.

andyfreelandy · Jun 6, 2020

Nodge68 said:
The vapour can't ignite, as there no oxygen in the tank, just fuel vapour, which requires oxygen to burn, so it's totally safe.

What about when you open the cap and then turn the ignition on??

Nodge68 · Jun 6, 2020

andyfreelandy said:
What about when you open the cap and then turn the ignition on??

The fuel vapour pressure is higher than the air pressure outside the tank, so there's always fuel vapour escaping, keeping air out. Also the fuel passes right through the pump motor, so there's never any oxygen for the vapour to burn in, so it doesn't.

kernowsvenski · Jun 6, 2020

Some Aircrash Investigation type analysis going on here. I like it!

kermit_rr · Jun 6, 2020

Never saw petrol as a good lubricant!

Nodge68 · Jun 6, 2020

kermit_rr said:
Never saw petrol as a good lubricant!

Anything that keeps metal from metal can be used as a lubricant, even water.

Hard Drive · Jun 7, 2020

Aircraft fuel pumps work in the same way. Their bearings are lubed with the fuel also. Thats AVTUR, and not AVGAS.

andyfreelandy · Jun 11, 2020

So having written twice to All Makes about the earlier failure. Having offered to send photos of failure to help them with product development, I have received no reply.

I have sourced a set of quality motor brushes 5mm x 8mm to replace the worn out brushes.

I am going to drill and fit retaining screws into the top section, which is sealed with an O ring, reassemble and see what a low price pump can do with the right brushes. A £3 upgrade!!

Also, can service the pump in the future. There doesn't seem much else to fail.
Will check armature and brush alignment when assembled as one brush had worn to nothing and other one seemed OK.

If A M decide to reply I will let you know. Didn't ask for a refund or replacement purely wanted to help them.

Hard Drive · Jun 11, 2020

andyfreelandy said:
So having written twice to All Makes about the earlier failure. Having offered to send photos of failure to help them with product development, I have received no reply.

I have sourced a set of quality motor brushes 5mm x 8mm to replace the worn out brushes.

I am going to drill and fit retaining screws into the top section, which is sealed with an O ring, reassemble and see what a low price pump can do with the right brushes. A £3 upgrade!!

Also, can service the pump in the future. There doesn't seem much else to fail.
Will check armature and brush alignment when assembled as one brush had worn to nothing and other one seemed OK.

If A M decide to reply I will let you know. Didn't ask for a refund or replacement purely wanted to help them.

When you stripped the pump, how did the commutator appear? Was it black with carbon and were the segments shorted? What I find troubling is that only one brush was worn beyond limits. Either the bush was faulty or there was uneven pressure being applied. I admire your plan to rebuild, even for experimental purposes, which I like to do, but will use the cliche, you get what you pay for.
However, it would certainly be interesting to see how it goes. Good luck.

andyfreelandy · Jun 11, 2020

Commutator like new. Either badly fitted brush, spring wrong tension or already worn when fitted.
Reasonably well made apart from this, hence my referral back to manufacturer but no interest from them..... Yet!!!

andyfreelandy · Jun 13, 2020

Fitted my £3 set of brushes today, had to file a couple of mm off the length.

Running sweetly. Will give extended bench test before casing up.

andyfreelandy · Jun 13, 2020

Anyone got a failed Pierburg to open and photograph for comparison??
What do you get for an extra £100 - apart from it working for more than 5,000 miles that is !!
Also - can HD update thread title to reflect the pump as well??

Thanks

andyfreelandy · Jul 8, 2021

Today had a bit of spare time !! So decided to answer my question above - what is in a Pierburg to warrant the extra cost??

Loads is the answer, compare the photos below to the ones of the cheap pump that I photographed above.
Proper sized brushes, more robust assembly, screw type pump gears, cast support structure rather than plastic.

Sadly the Pierburg still failed !! Brushes were far from worn, but one of the diecast pins had broken off holding the brush tensioning spring so it was intermittent. Hitting it got us home, nice to see the problem.

Pump in pieces, motor assembly, broken diecast spring pin, screw type pump, assembled less case.

Shame you can't service and refit case, couldn't reliably repair this one, but a brush change should be possible.
The difference in quality between the Pierburg and the All Makes is really shocking, look at the build and compare.

I'm never replacing with a cheap pump again !! Not, of course, that I would be that tight normally, the previous pump was bought in a hurry when I moved house as mine had started making noises and I didn't want it to fail !!!

Active Member

Well-Known Member

Active Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Very

Well-Known Member

Active Member

Well-Known Member

Active Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Similar threads