Fuel pump installation question

[fr€$h&m1nt¥]

Hi all

I’m installing a new fuel pump in the Acty and after some advice.

I planned to install as follows...

<<<< photos not uploading so imagine a straight line from tank outlet to pump to carb >>>>>>>


But instructions to say to install at 45 degrees like so...


<<<< imagine a photo with the pump pointing 45 degrees up away from the tank and then the hose angled back down towards the carb >>>>>

Anyone know if there’s a reason for this? Is it to limit return flow?

The instructions diagram suggests you can install horizontal but 45 degrees up is preferable and text only suggests 45 degree angle.

Cheers
Phil

[Deleted]

I could be wrong but I think it's because electric pumps work better when theres a bit of gravity-feeding involved. So the 45° ensures the input hose is downhill of the tank. It probably also makes sure fuel doesnt sit somewhere it shouldnt sit when not in use.

Also, like you say, flowback is less likely to get uphill back to the pump.

[crockpot]

Is it one of the Facet "cube" ones? If it is it's to stop them trapping air and hammering like a woodpecker on speed.

[Phil H]

The majority of electric pumps like to push but aren't so good at sucking - normally they specify a maximum head height which generally means mounting the pump no higher than the tank (because of the lowest tank level normally being below the pump, plus their "max head"). Angling it may also help with self bleeding I guess, but it's probably to keep the inlet of the pump as low as possible.

The exception to the rule is usually an SU pump - they can pull fuel from a good foot or two below them.

I'm also assuming a low pressure (carb) pump here - injection (roller) pumps can just about cope with being at the same level as the bottom of the tank!

[fr€$h&m1nt¥]

Feb 27, 2020 18:22:04 GMT crockpot said:

Is it one of the Facet "cube" ones? If it is it's to stop them trapping air and hammering like a woodpecker on speed.

Yes sorry I missed that bit.

Facet posi-flow 60104.

[fr€$h&m1nt¥]

Feb 27, 2020 18:27:03 GMT Phil H said:

The majority of electric pumps like to push but aren't so good at sucking - normally they specify a maximum head height which generally means mounting the pump no higher than the tank (because of the lowest tank level normally being below the pump, plus their "max head"). Angling it may also help with self bleeding I guess, but it's probably to keep the inlet of the pump as low as possible.

The exception to the rule is usually an SU pump - they can pull fuel from a good foot or two below them.

I'm also assuming a low pressure (carb) pump here - injection (roller) pumps can just about cope with being at the same level as the bottom of the tank!

Feb 27, 2020 18:07:13 GMT @thousandwords said:

I could be wrong but I think it's because electric pumps work better when theres a bit of gravity-feeding involved. So the 45° ensures the input hose is downhill of the tank. It probably also makes sure fuel doesnt sit somewhere it shouldnt sit when not in use.

Also, like you say, flowback is less likely to get uphill back to the pump.

Ah so this is different again to my thoughts - so the hose should drop down from the top of the tank where the outlets are to the pump and then angle the pump back up at 45 degrees?

[Deleted]

Feb 27, 2020 19:30:38 GMT fr€$h&m1nt¥ said:

Feb 27, 2020 18:27:03 GMT Phil H said:

The majority of electric pumps like to push but aren't so good at sucking - normally they specify a maximum head height which generally means mounting the pump no higher than the tank (because of the lowest tank level normally being below the pump, plus their "max head"). Angling it may also help with self bleeding I guess, but it's probably to keep the inlet of the pump as low as possible.

The exception to the rule is usually an SU pump - they can pull fuel from a good foot or two below them.

I'm also assuming a low pressure (carb) pump here - injection (roller) pumps can just about cope with being at the same level as the bottom of the tank!

Feb 27, 2020 18:07:13 GMT @thousandwords said:

I could be wrong but I think it's because electric pumps work better when theres a bit of gravity-feeding involved. So the 45° ensures the input hose is downhill of the tank. It probably also makes sure fuel doesnt sit somewhere it shouldnt sit when not in use.

Also, like you say, flowback is less likely to get uphill back to the pump.

Ah so this is different again to my thoughts - so the hose should drop down from the top of the tank where the outlets are to the pump and then angle the pump back up at 45 degrees?

Oh erm... yes that's what I thought. It's probably better to let Phil answer this though. I've not ever used one of those tick pumps so I really don't know.

[Phil H]

I think the picture uploaded is up the spout at the moment - but page 2 of this: mossmotors.com/media/instructions/377-420.pdf

First page of google results says:
As stated in the review (and the Facet installation instructions), pump should be mounted at a 45 degree angle. However, for best self-priming, the flow should be UP HILL.

[fr€$h&m1nt¥]

Feb 27, 2020 19:39:15 GMT Phil H said:

I think the picture uploaded is up the spout at the moment - but page 2 of this: mossmotors.com/media/instructions/377-420.pdf

First page of google results says:
As stated in the review (and the Facet installation instructions), pump should be mounted at a 45 degree angle. However, for best self-priming, the flow should be UP HILL.

Thanks, that link helps. I’m all for the 45 degrees angle bit I think the issue now is to run it 45 degrees up from the top of the tank or run hose down to bottom of tank and then mount pump down there, at 45 degree angle pointing back up to the the carb.

This diagram will probably fail...

Tank outlet=]\......... /——- carb
...................\......../
................... \_[//]pump

[Deleted]

[fr€$h&m1nt¥]

Feb 27, 2020 20:29:25 GMT @thousandwords said:

Appreciate that - the thing is though that the outlets are at the top of the tank so the fuel line would have to go down to the bottom to the pump and then right back up again.

After a night of tossing and turning and thinking I’ve decided to mount the pump on a bracket halfway down the tank so the line will drop 5” to the pump at 45 degrees and 5” above the bottom of the tank and then rise back up 5” to the carb.

That should be happy medium that meets all of the minimum requirements and I don’t think any restrictions from that setup is going to affect the overall thirst for a 550cc engine.

[melle]

This is how the one in my Saab 96 sits:



Don't forget to isolate the pump from the car body with some rubber spacers or exhaust bobbins or the noise will make you lose the will to live. Unrelated to mounting the pump, but I also installed a Jaguar inertia switch for safety and a Saab 900 fuel pump relay so the pump isn't constantly humming when the ignition is on but the motor not running.

[fr€$h&m1nt¥]

Mar 1, 2020 18:40:27 GMT melle said:

This is how the one in my Saab 96 sits:



Don't forget to isolate the pump from the car body with some rubber spacers or exhaust bobbins or the noise will make you lose the will to live. Unrelated to mounting the pump, but I also installed a Jaguar inertia switch for safety and a Saab 900 fuel pump relay so the pump isn't constantly humming when the ignition is on but the motor not running.

Thanks, I fitted mine today although not done the final plumbing switch over on the carb or the wiring yet.

My pump is prebuilt into a nylon casing which means rubber washers aren’t required.

[melle]

Ah, you got a posh one then!

[Rich]

Mar 1, 2020 21:37:45 GMT fr€$h&m1nt¥ said:

Mar 1, 2020 18:40:27 GMT melle said:

This is how the one in my Saab 96 sits:



Don't forget to isolate the pump from the car body with some rubber spacers or exhaust bobbins or the noise will make you lose the will to live. Unrelated to mounting the pump, but I also installed a Jaguar inertia switch for safety and a Saab 900 fuel pump relay so the pump isn't constantly humming when the ignition is on but the motor not running.

Thanks, I fitted mine today although not done the final plumbing switch over on the carb or the wiring yet.

My pump is prebuilt into a nylon casing which means rubber washers aren’t required.

They are still noisy. They kinda tick. Unless they are dry and then they sound like a hammer being shook in a tin box. I had a black case facet on the MGB because someone (not me) had fitted the wiring to the OE pump backwards, the rubber strap in the bracket fell out and the pump body (which was live because of the wiring discrepancy) burned the pump and loom. I fitted the new pump in the defunct second 6V battery bin and it wasn’t quiet but it wasn’t loud. I think you’ll be ok considering the fact it’s a pickup

[fr€$h&m1nt¥]

Mar 1, 2020 22:21:48 GMT Rich said:

Mar 1, 2020 21:37:45 GMT fr€$h&m1nt¥ said:

Thanks, I fitted mine today although not done the final plumbing switch over on the carb or the wiring yet.

My pump is prebuilt into a nylon casing which means rubber washers aren’t required.

They are still noisy. They kinda tick. Unless they are dry and then they sound like a hammer being shook in a tin box. I had a black case facet on the MGB because someone (not me) had fitted the wiring to the OE pump backwards, the rubber strap in the bracket fell out and the pump body (which was live because of the wiring discrepancy) burned the pump and loom. I fitted the new pump in the defunct second 6V battery bin and it wasn’t quiet but it wasn’t loud. I think you’ll be ok considering the fact it’s a pickup

Ah ok cheers. That sounds like it went in an explosive way!

It’s no drama for me to squeeze a pair of isolating rubber washers at the fixing points if it does end up being over noisy.

[Rich]

Mar 1, 2020 22:28:30 GMT fr€$h&m1nt¥ said:

Mar 1, 2020 22:21:48 GMT Rich said:

They are still noisy. They kinda tick. Unless they are dry and then they sound like a hammer being shook in a tin box. I had a black case facet on the MGB because someone (not me) had fitted the wiring to the OE pump backwards, the rubber strap in the bracket fell out and the pump body (which was live because of the wiring discrepancy) burned the pump and loom. I fitted the new pump in the defunct second 6V battery bin and it wasn’t quiet but it wasn’t loud. I think you’ll be ok considering the fact it’s a pickup

Ah ok cheers. That sounds like it went in an explosive way!

It’s no drama for me to squeeze a pair of isolating rubber washers at the fixing points if it does end up being over noisy.

Thankfully just broke down. Being a BL car, no fuse for the pump either. The rewire incorporated one. In your instance the bracket you’ve mounted it on may provide enough ‘spring’ to dampen the noise anyway. Just do regular spot checks on that for fatigue.

[fr€$h&m1nt¥]

Mar 2, 2020 7:57:21 GMT Rich said:

Mar 1, 2020 22:28:30 GMT fr€$h&m1nt¥ said:

Ah ok cheers. That sounds like it went in an explosive way!

It’s no drama for me to squeeze a pair of isolating rubber washers at the fixing points if it does end up being over noisy.

Thankfully just broke down. Being a BL car, no fuse for the pump either. The rewire incorporated one. In your instance the bracket you’ve mounted it on may provide enough ‘spring’ to dampen the noise anyway. Just do regular spot checks on that for fatigue.

Thanks, a bit like a springboard effect, something I'd thought about and I probably spend longer under the truck than driving it doing one thing or another so I'll check as I do other stuff.