Malpassi fuel pressure regulator
#21 Re: Malpassi fuel pressure regulator
Thanks David, it was actually partly based on your original post that I had fitted mine. I also like the fact you have a port to attach a pressure gauge so you can actually check what pressure you are getting. This is especially useful on a freshly restored car where various components of a fuel system have been rebuilt or renewed in that it allows you to see things are working as they should.
Back to the original question , my gauge remains steady at all rpm. The pump is a new one purchased from Burlen with the electronic conversion. The pressure regulator is set at 2.6psi. 4.2 S2.
As far as I know the fuel is being consumed by the engine rather than "returning" to the fuel tank although that would be nice.
A pic of the installation for Geoff.
Simon
Simon
1969 S2 OTS
1969 S2 OTS
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#22 Re: Malpassi fuel pressure regulator
Evening chaps,
I’m going to play a little with this over Easter.
I will probably run a hose into a spare can and see if the pump drops pressure at all. This should eliminate any issues with the carbs. I will then also clamp this hose shut and see what that does.
Ho hum !
Tim
I’m going to play a little with this over Easter.
I will probably run a hose into a spare can and see if the pump drops pressure at all. This should eliminate any issues with the carbs. I will then also clamp this hose shut and see what that does.
Ho hum !
Tim
Series 1 FHC purchased 40 years ago. Courted my wife in it.
Series 1 2+2 when the kids were small now sold.
Series 1.5 OTS in opalescent maroon, Californian car. My retirement present.
Series 1 2+2 when the kids were small now sold.
Series 1.5 OTS in opalescent maroon, Californian car. My retirement present.
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#23 Re: Malpassi fuel pressure regulator
The SU pump works 'on demand' which is why you can hear it clicking when you turn on the ignition. The clicking stops when the carb floats get to the top of their travel and the bowls are full of fuel. As the engine consumes fuel the bowls empty and the floats fall, the pump clicks allowing more fuel in - basically you have three toilet cisterns under the hood!
If you see the pressure on the fuel meter drop to zero that is perfectly normal. It will register again as soon as the pump starts working which will be because the pressure in the fuel line has dropped because the engine is using its reserves and the floats are demanding re-supply. I would be worried if the pressure remained constant as it would indicate the pump is running continuously, which is not good.
If you see the pressure on the fuel meter drop to zero that is perfectly normal. It will register again as soon as the pump starts working which will be because the pressure in the fuel line has dropped because the engine is using its reserves and the floats are demanding re-supply. I would be worried if the pressure remained constant as it would indicate the pump is running continuously, which is not good.
David Jones
S1 OTS OSB; S1 FHC ODB
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#24 Re: Malpassi fuel pressure regulator
The pump stops delivering fuel when it senses the float chambers are full due to the pressure increase caused by the float valves closing. When the floats fall again pressure drops and so the pump status delivering fuel again. Therefore, pressure fluctuation is perfectly normal.
Like David said, the toilet cistern principle.
Regards
Stuart
If you can't make it work, make it complicated!
'62 FHC - Nearing completion
'69 Daimler 420 Sovereign
'78 Land Rover Series 3 109
If you can't make it work, make it complicated!
'62 FHC - Nearing completion
'69 Daimler 420 Sovereign
'78 Land Rover Series 3 109
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#25 Re: Malpassi fuel pressure regulator
Technically speaking the pressure should never drop to zero as long as the pump is on, ticking or not. Whether the bowls are full or partially or totally empty, you should still have a pressure reading.
Having an occasional zero pressure reading is illustrating an issue.
Of course, with all due respect to the wiser community, I stand to be corrected.
Having an occasional zero pressure reading is illustrating an issue.
Of course, with all due respect to the wiser community, I stand to be corrected.
Ralph
'69 OTS + '62 OTS - Belgium
'69 OTS + '62 OTS - Belgium
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#26 Re: Malpassi fuel pressure regulator
From the Hagen Poiseuille equation, flow is proportional to the pressure differential.ralphr1780 wrote: ↑Wed Apr 17, 2019 8:56 pm
Of course, with all due respect to the wiser community, I stand to be corrected.
If the pump is stopped there is no flow, and therefore no pressure.
Andrew.
881824, 1E21538. 889457. 1961 4.3l Mk2. 1975 XJS. 1962 MGB
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Adelaide, Australia
881824, 1E21538. 889457. 1961 4.3l Mk2. 1975 XJS. 1962 MGB
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#27 Re: Malpassi fuel pressure regulator
Andrew, stop the pump and disconnect a pipe, you will get a flow because of remaining pressure in the circuit. Once the pressure is zero flow will stop, precisely the well respected Poiseuille equation.
Ralph
'69 OTS + '62 OTS - Belgium
'69 OTS + '62 OTS - Belgium
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#28 Re: Malpassi fuel pressure regulator
Only if there is elastance in the circuit, because the liquid is incomprehensible. I suppose the pump diaphragm might provide some elastance but I would expect the pressure to drop to zero until the pump restarts.ralphr1780 wrote: ↑Thu Apr 18, 2019 5:11 amAndrew, stop the pump and disconnect a pipe, you will get a flow because of remaining pressure in the circuit. Once the pressure is zero flow will stop, precisely the well respected Poiseuille equation.
Andrew.
881824, 1E21538. 889457. 1961 4.3l Mk2. 1975 XJS. 1962 MGB
http://www.projectetype.com/index.php/the-blog.html
Adelaide, Australia
881824, 1E21538. 889457. 1961 4.3l Mk2. 1975 XJS. 1962 MGB
http://www.projectetype.com/index.php/the-blog.html
Adelaide, Australia
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#29 Re: Malpassi fuel pressure regulator
Easy check is to see if the fuel filter bowl empties. If it does then you have a problem.
David Jones
S1 OTS OSB; S1 FHC ODB
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#30 Re: Malpassi fuel pressure regulator
Hi All....I was thinking of a filter King for a new build im doing.......So just been speaking to Burlan re the 1308 pump and HD8 carbs......Their view is if the pump is working correct it will deliver pressure between 2.5-3.8 which will work perfectly well with our carbs so long as they are in good order and have good float valves.......adding a filter king could actually introduce problems becaus it could affect the flow rate.......the SU pump has built in valves so will hold up pressure....however it depends on the position on the floats when the pump is switched off...down then no pressure...up and you will see pressure......Steve
Steve
69 S2 2+2 (just sold) ..Realm C type replica, 1960 xk150fhc
69 S2 2+2 (just sold) ..Realm C type replica, 1960 xk150fhc
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#31 Re: Malpassi fuel pressure regulator
"adding a filter king could actually introduce problems because it could affect the flow rate"
After 45,000 miles with the Filter King I can testify there are no such problems. I would be interested to know how many miles of testing they did to come up with that statement.
After 45,000 miles with the Filter King I can testify there are no such problems. I would be interested to know how many miles of testing they did to come up with that statement.
David Jones
S1 OTS OSB; S1 FHC ODB
1997 Porsche 911 Guards Red
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#32 Re: Malpassi fuel pressure regulator
Some of the filter kings have brass fittings that can accept both 6mm and 8mm hose......so if you fit an 8mm hose the i/p and o/p from some of the filter kings will be restricted to 6mm......this photo has the dual size input....others just have larger 8mm so something to be aware of
Steve
69 S2 2+2 (just sold) ..Realm C type replica, 1960 xk150fhc
69 S2 2+2 (just sold) ..Realm C type replica, 1960 xk150fhc
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#33 Re: Malpassi fuel pressure regulator
Careful – the words ‘hoist’ and ‘petard’ are in floating in the ether .The above statement looks correct to me, but no, I won't duke it out on Saturday, especially as you're a gun expert as well.
The risk of introducing problems would be true if the F-King gadget were a no movable parts, sealed-for-life mechanism, on the basis that in at least one respect the more components there are in a system, the greater the cumulative probability of a failure occurring. In practice, the F-King thing does have movable parts and is not sealed for life. It therefore adds the twin potential failure modes of human error, like pressure maladjustment or failure to attend to a clogged filter (possibly invisible) - and materials failure: e.g. bowl gasket problems.
You could quite reasonably counter by saying you were assuming the F-King regulator would be in good working order and performing to spec, otherwise its use would not be expected to be up to par. But then this whole thread is predicated on the assumption that something was wrong or out of spec with your car that required a F-King fix. I think this is far from proven, although I totally accept your 2008 account (which I’ve seen for the first time here) as being an accurate record of what you observed with your car.
That is excellent news but irretrievably anecdotal in the big picture. To most of us the only car that matters is our own, but we must concede that absence of evidence in our tiny samples is not the same as evidence of absence overall.
Possibly more than the number of cars you have tested my good friend. I would expect the exclusive global source of SU pumps and carbs to hear enquiries occasionally from people having problems with non-standard fuel systems. I would not be at all surprised if, after taking a full history, those customers were advised to replace all non-standard parts, to at least achieve a baseline from which Burlens, as maker of all the bits involved, could then solve any mystery. I would anticipate that in many cases the mere act of returning to standard spec would clear up a proportion of the problems. Which brings us to the elephant in the front room of your beautiful Nottinghamshire home David – the issue of probabilities.
From your initial 2008 thread, and subsequent comments, you seem to be saying that there is an inherent risk/flaw in running as A-series SU fuel pump with SU carbs, unless an accessory fuel pressure regulator is interposed. I may have got that wrong.
The fact that no carburetor 6 Cyl Jag ever came with and FPR (as far as I know) and that millions of British cars left their factories also without external regulation cannot be ignored, surely? SU made the pumps and the carbs to work in unison, and they do that without any extra tech. The range of pump pressure produced and the range of pressures which the float valve is capable of sealing, overlap sufficiently to work as designed. The fact that your car responded to the mod doesn’t prove the SU pump and three toilet cisterns are mismatched, it suggests something else was wrong. The fact that 45,000 miles later everything is still working well also says nothing about pump and carb compatibility except the Malpassi is almost certainly not harmful.
Angus said he will hold our jackets...
1E75339 UberLynx D-Type; 1R27190 70 FHC; 1E78478; 2001 Vanden Plas
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#34 Re: Malpassi fuel pressure regulator
I will be selling tickets....
Jeremy
1967 S1 4.2 FHC
1967 S1 4.2 FHC
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#35 Re: Malpassi fuel pressure regulator
Crikey chaps !
Seems like a case of “ light the blue touch paper and stand well back “. Lots of contributions to this thread since I started it . Thanks to all and to some of you who replied off line.
Latest situation , I removed the pipe from the inlet to the regulator and let the pump run. Seemingly no issues.
Then I took the car for a bit of a thrash - again seemed ok. So maybe I was worrying about a problem that doesn’t exist.
Seems like a case of “ light the blue touch paper and stand well back “. Lots of contributions to this thread since I started it . Thanks to all and to some of you who replied off line.
Latest situation , I removed the pipe from the inlet to the regulator and let the pump run. Seemingly no issues.
Then I took the car for a bit of a thrash - again seemed ok. So maybe I was worrying about a problem that doesn’t exist.
Series 1 FHC purchased 40 years ago. Courted my wife in it.
Series 1 2+2 when the kids were small now sold.
Series 1.5 OTS in opalescent maroon, Californian car. My retirement present.
Series 1 2+2 when the kids were small now sold.
Series 1.5 OTS in opalescent maroon, Californian car. My retirement present.
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#36 Re: Malpassi fuel pressure regulator
This certainly is a solution looking for a problem.....
The irony is that the SU pump as standard on an E type has - effectively - a filter king pressure regulator already built into it
to Peter
The irony is that the SU pump as standard on an E type has - effectively - a filter king pressure regulator already built into it
to Peter
John
1969 Series 2 FHC
1969 Series 2 FHC
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#38 Re: Malpassi fuel pressure regulator
I'd take a contrary view and suggest that you want the fuel pressure to be as high as possible, subject to it not being so high that the float bowls are prevented from sealing the carburettor from the pump.
The reason for this is that I'd want to have my float bowls recharged as quickly as possible and thus keep the carburettor at its optimal working point at all times. This is the only purpose of the fuel pump - once the float bowls are full, the fuel pump simply drops out of the equation and any operating problems are carburettor problems, not fuel pressure problems.
SU have determined that this is up to about ~4psi, but no higher.
Since we have some design figures for this pump, lets stress test them and see what drops out.
79.5 litres per hour is 17.8 gallons per hour
60mph at 10mpg is 6 gallons per hour but we are driving a 150mph capable car, so....
120mph at 15mpg is 8 gallons per hour
If we assume the pump is old and knackered or by virtue of the voltage supplied through an old harness, only 70% of capacity is available, then we now need one spec'd to run at 11.4gallons per hour.
Since we are driving a fast road car and are stupid enough to pull away onto the German autobahn on a cold engine, with the choke on, we may be consuming 25% more fuel - we now need to supply 14.3 gallons per hour.
Now lets restrict the fuel flow with a timely upgrade that drops an average 4psi down to 2.5psi and assume that the aggregate flow drops by the same amount. (Just think about "the area under the graph".)
We may now need to have a pump capable of supplying 22.8 gallons per hour and so it may not be advisable to floor the accelerator on a cold engine when already running high rpm. You won't have a problem pottering about on UK roads, but Burlen do have a point here, as they've obviously done this calculation many years before us.
Interestingly, the v12 etype is a more thirsty beast than this and the solution Jaguar came up with was to install two SU pumps in parallel (and return the excess fuel to the tank).
It may be that as F-king filters have no idea what is going to be connected to their product, one might wonder whether the pressure restriction is there for the benefit of the filter maker.
Two other points:-
Firstly, no mention was made of whether this was an average pressure, a maximum pressure or a minimum working pressure.
Secondly, there was some doubt expressed about "pulsing". A lift pump has plenty of power to push fluid at the beginning of its stroke but does next to no pushing at the end of its stroke, so I'd expect the flow to be very uneven and pulse. What is observed and measured however is dependent on the gauge, so a gauge with a soft thin pliable rubber seal will respond and report "pulses" much more than a gauge with a thicker or less pliable seal which will dampen out the variation, even though it is measuring the same pump. Put another way, I'm relaxed about seeing what David has reported - it doesn't demonstrate anything is wrong.
In short, I'd come back to where I left this - the aftermarket regulator may be needed if a non standard pump is fitted, but it probably isn't of any material benefit nor detriment to normal driving conditions. (Running your car hard as per the worked example is not "normal driving conditions" for these purposes and that may not be the only "fail" scenario we can come up with.)
kind regards
Marek
The reason for this is that I'd want to have my float bowls recharged as quickly as possible and thus keep the carburettor at its optimal working point at all times. This is the only purpose of the fuel pump - once the float bowls are full, the fuel pump simply drops out of the equation and any operating problems are carburettor problems, not fuel pressure problems.
SU have determined that this is up to about ~4psi, but no higher.
Since we have some design figures for this pump, lets stress test them and see what drops out.
79.5 litres per hour is 17.8 gallons per hour
60mph at 10mpg is 6 gallons per hour but we are driving a 150mph capable car, so....
120mph at 15mpg is 8 gallons per hour
If we assume the pump is old and knackered or by virtue of the voltage supplied through an old harness, only 70% of capacity is available, then we now need one spec'd to run at 11.4gallons per hour.
Since we are driving a fast road car and are stupid enough to pull away onto the German autobahn on a cold engine, with the choke on, we may be consuming 25% more fuel - we now need to supply 14.3 gallons per hour.
Now lets restrict the fuel flow with a timely upgrade that drops an average 4psi down to 2.5psi and assume that the aggregate flow drops by the same amount. (Just think about "the area under the graph".)
We may now need to have a pump capable of supplying 22.8 gallons per hour and so it may not be advisable to floor the accelerator on a cold engine when already running high rpm. You won't have a problem pottering about on UK roads, but Burlen do have a point here, as they've obviously done this calculation many years before us.
Interestingly, the v12 etype is a more thirsty beast than this and the solution Jaguar came up with was to install two SU pumps in parallel (and return the excess fuel to the tank).
It may be that as F-king filters have no idea what is going to be connected to their product, one might wonder whether the pressure restriction is there for the benefit of the filter maker.
Two other points:-
Firstly, no mention was made of whether this was an average pressure, a maximum pressure or a minimum working pressure.
Secondly, there was some doubt expressed about "pulsing". A lift pump has plenty of power to push fluid at the beginning of its stroke but does next to no pushing at the end of its stroke, so I'd expect the flow to be very uneven and pulse. What is observed and measured however is dependent on the gauge, so a gauge with a soft thin pliable rubber seal will respond and report "pulses" much more than a gauge with a thicker or less pliable seal which will dampen out the variation, even though it is measuring the same pump. Put another way, I'm relaxed about seeing what David has reported - it doesn't demonstrate anything is wrong.
In short, I'd come back to where I left this - the aftermarket regulator may be needed if a non standard pump is fitted, but it probably isn't of any material benefit nor detriment to normal driving conditions. (Running your car hard as per the worked example is not "normal driving conditions" for these purposes and that may not be the only "fail" scenario we can come up with.)
kind regards
Marek
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#39 Re: Malpassi fuel pressure regulator
Hi Marek......are we sure that adjusting the pressure down reduces the flow rate on the filter king...Steve
Steve
69 S2 2+2 (just sold) ..Realm C type replica, 1960 xk150fhc
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#40 Re: Malpassi fuel pressure regulator
'Effectively' is right, rather than technically, since damping the pressure pulses isn't quite the same as imposing a pressure limit.
David, as far as I'm concerned, has almost single-handedly brought this site to be one of the world's best - if not THE best - E-type web resources, largely through his incredibly dogged research into matters historical and technical. His measurements in 2008 were valid, I'm sure. I just don't hold the view that they represent a problem needing fixing. His F-king fitment helped matters with that non-standard car at that time and thus some level of cause/effect may reasonably be inferred, although one would reverse/repeat several times to check for a consistent link.
For my part I learned that merely because I'd just got an early EFI V12 running properly (where any running fuel pressure below 30-ish is a fail and dead head pressure of 60 psi normal) that didn't mean David's description of E-type SU pumps as 'high pressure' was questionable. On that issue I'd have been better off keeping quiet instead of piping up when I did a few days ago.
Tomorrow should be fun.
1E75339 UberLynx D-Type; 1R27190 70 FHC; 1E78478; 2001 Vanden Plas
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