Morris Major Forum
I962 Morris major elite
 Highton, Victoria, Australia
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Oct 28, 2016 11:06 PM
Top Contributor
 Joined 15 years ago
21 Posts
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Biddulph, Staffs, UK
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In reply to # 20308 by ozieagle
It doesn't matter. Ah, that will be why SU built psher and puller pumps
that operate at different pressure
then won't it
SU "puller" pumps, for fitting on the firewall are about 2.5 psi, whilst "pusher" pumps are 3.5 psi. Practically either one can be used in either situation. Both are less that 4 psi, which is the limit of pressure an SU carby can cope with.
Herb
that operate at different pressure
then won't it
SU "puller" pumps, for fitting on the firewall are about 2.5 psi, whilst "pusher" pumps are 3.5 psi. Practically either one can be used in either situation. Both are less that 4 psi, which is the limit of pressure an SU carby can cope with.
Herb
Less facetiosly,
a rear mounted puller pump
in worn condition
is likely to be unable
to push enough fuel
to the carburettor
to keep the engine
happy when it's pulling
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Biddulph, Staffs, UK
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Have you considered
fitting a double header banjo,
or T
and returning excess fuel
to the tank
via a pressure relief valve Gaffer?
That way,
fuel spends very little time
in the engine room.
which means it gets to you carb
while it's still relatively cool.
The simplest way to return to the fuel
is to T into the fuel line
close by the tank
Make sure you T in between
the pump and the tank
Edited 2 time(s). Last edit at 2016-10-30 03:09 AM by 0123.
fitting a double header banjo,
or T
and returning excess fuel
to the tank
via a pressure relief valve Gaffer?
That way,
fuel spends very little time
in the engine room.
which means it gets to you carb
while it's still relatively cool.
The simplest way to return to the fuel
is to T into the fuel line
close by the tank
Make sure you T in between
the pump and the tank
In reply to # 20312 by plumby
Yes, Herb, I am having exactly those fuel-flooding problems now on my 1275cc Minor, probably because I have fitted an electric pusher pump at the back. This was done to ensure the fuel was delivered even in very hot conditions.
I find the fuel being delivered is overwhelming the (checked) needle and seat in the 1.5" carby. So, I see there are marks where the excess fuel has been dripping past the hot extractors onto the 'floor' of the engine bay!
This afternoon means urgent work to either constrict the pipework to the carby, or else swap back to the standard SU arrangement.
I find the fuel being delivered is overwhelming the (checked) needle and seat in the 1.5" carby. So, I see there are marks where the excess fuel has been dripping past the hot extractors onto the 'floor' of the engine bay!
This afternoon means urgent work to either constrict the pipework to the carby, or else swap back to the standard SU arrangement.
Edited 2 time(s). Last edit at 2016-10-30 03:09 AM by 0123.
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Biddulph, Staffs, UK
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In reply to # 20314 by ozieagle
Hi Phil,
If you have an SU pump, you can fit it in the back, where you have the other pump. It may need some engineering modifications to fit. Whatever you do, don't get a pressure regulator, they fail and cause another round of grief. I went down this road with my MGB, the regulator was OK for a year or so, then I started having all sorts of issues. Bought a fuel pressure gauge and found that, despite the regulator, I was getting 6-7 psi at the carbs, even with it dialed back to 1 psi. By the time I had sorted it all it cost me more than a new SU pump.
What I did with my Wolseley HS2 carby is drill a hole in the float cover, under the fuel inlet, and inserted a small 1/8" brass tube, (from model shop) with a tube running out the hole for the shocker. This guarantees that fuel and hot exhaust bits don't come in contact.
Could be intersting
when you pull up
over a smoldering fag end Herb
Herb
edited to add
Don't constrict the plumbing, it won't make any difference to the pressure, but may adversely affect fuel delivery. Once the flow stops the pressure will increase to the pump pressure.
If you have an SU pump, you can fit it in the back, where you have the other pump. It may need some engineering modifications to fit. Whatever you do, don't get a pressure regulator, they fail and cause another round of grief. I went down this road with my MGB, the regulator was OK for a year or so, then I started having all sorts of issues. Bought a fuel pressure gauge and found that, despite the regulator, I was getting 6-7 psi at the carbs, even with it dialed back to 1 psi. By the time I had sorted it all it cost me more than a new SU pump.
What I did with my Wolseley HS2 carby is drill a hole in the float cover, under the fuel inlet, and inserted a small 1/8" brass tube, (from model shop) with a tube running out the hole for the shocker. This guarantees that fuel and hot exhaust bits don't come in contact.
Could be intersting
when you pull up
over a smoldering fag end Herb
Herb
edited to add
Don't constrict the plumbing, it won't make any difference to the pressure, but may adversely affect fuel delivery. Once the flow stops the pressure will increase to the pump pressure.
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Highton, Victoria, Australia
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Oct 29, 2016 03:13 PM
Top Contributor
Joined 15 years ago
21 Posts
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In reply to # 20317 by 0123
a rear mounted puller pump
in worn condition
is likely to be unable
to push enough fuel
to the carburettor
to keep the engine
happy when it's pulling
a rear mounted puller pump
in worn condition
is likely to be unable
to push enough fuel
to the carburettor
to keep the engine
happy when it's pulling
If you know how an SU pump works, you would realize that a "worn" puller pump at the front would be worse than the same pump at the back. The pump sucks on the power stroke and then squirts under spring pressure, so with a weak pump at the front it has to suck all the way through the fuel lines, which is harder than sucking through a short length of fuel line.
The main failure of an SU pump is that the points burn and need cleaning or replacing. Other failure modes are the diaphragm getting too stiff, the valves cracking or the coil burning out. Any of those conditions will make the pump non functioning, whether at the back or front.
One important thing is to not have a filter between the tank and the pump. Restricting or blocking fuel flow to the pump can cause the pump to stall in a power on condition, causing the coil to over heat or burn out.
Herb
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Biddulph, Staffs, UK
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Ah, that will be why SU built pusher and puller pumps
that operate at different pressures
then won't it smoking smiley
that operate at different pressures
then won't it smoking smiley
In reply to # 20327 by ozieagle
If you know how an SU pump works, you would realize that a "worn" puller pump at the front would be worse than the same pump at the back. The pump sucks on the power stroke and then squirts under spring pressure, so with a weak pump at the front it has to suck all the way through the fuel lines, which is harder than sucking through a short length of fuel line.
The main failure of an SU pump is that the points burn and need cleaning or replacing. Other failure modes are the diaphragm getting too stiff, the valves cracking or the coil burning out. Any of those conditions will make the pump non functioning, whether at the back or front.
One important thing is to not have a filter between the tank and the pump. Restricting or blocking fuel flow to the pump can cause the pump to stall in a power on condition, causing the coil to over heat or burn out.
Herb
In reply to # 20317 by 0123
a rear mounted puller pump
in worn condition
is likely to be unable
to push enough fuel
to the carburettor
to keep the engine
happy when it's pulling
a rear mounted puller pump
in worn condition
is likely to be unable
to push enough fuel
to the carburettor
to keep the engine
happy when it's pulling
If you know how an SU pump works, you would realize that a "worn" puller pump at the front would be worse than the same pump at the back. The pump sucks on the power stroke and then squirts under spring pressure, so with a weak pump at the front it has to suck all the way through the fuel lines, which is harder than sucking through a short length of fuel line.
The main failure of an SU pump is that the points burn and need cleaning or replacing. Other failure modes are the diaphragm getting too stiff, the valves cracking or the coil burning out. Any of those conditions will make the pump non functioning, whether at the back or front.
One important thing is to not have a filter between the tank and the pump. Restricting or blocking fuel flow to the pump can cause the pump to stall in a power on condition, causing the coil to over heat or burn out.
Herb
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Highton, Victoria, Australia
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Nov 11, 2016 01:03 AM
Top Contributor
Joined 15 years ago
21 Posts
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Tamworth, new south wales, Australia
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