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Post by biffofo on Apr 8, 2022 7:43:26 GMT
morning all
i am going to fit a leccy this weekend to my P5B , was going to disconnect the old mechanical and just run on the leccy.
However I've been advised to simply leave it there to preserve originality and install the leccy upstream of it, basically in series.
Fit a switch in the car and start her up on leccy, the fuel will flow through both pumps then. Once started and warmed up i then have the choice of leaving the leccy on or switching it off.
Sounds Ok to me , i think any advice please ?
As an alternative is it also possible to install leccy down stream of mechanical, easier to pipe up and i guess same principal
fuel is drawn through mechanical by leccy pump
thanks
Brian
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Post by Phil Nottingham on Apr 8, 2022 8:43:57 GMT
Yes it will work and the pump can be installed downstream or up. I woild not advise leaving the existing oump as the diaphragm will leak fuel into the sump. There is loads on SEARCH
If you want originality but not over safety leave it in place and bypass it
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Post by enigmas on Apr 8, 2022 10:38:32 GMT
I agree with Phil, don't run the mechanical in series with the electric pump. If the diaphram splits you'll have a sump full of petrol! If you must, fit a lockoff switch/valve (LPG petrol lockoff) and bypass fuel connector to keep the mechanical pump out of the fuel circuit when the electric pump is functioning. But really, why bother? Deep six the mechanical pump and buy 2 cheap Facet pumps and keep the other as a spare if you're a worrier?
As an aside, modern fuels (for EFI engines) evaporate more readily than the product originally formulated for carburettors, so why stick with a mechanical pump (excessive cranking) unless the car is used regularly.
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Post by biffofo on Apr 8, 2022 14:59:39 GMT
hi
thanks for the info to both of you
are you highlighting the possibility of the diaphragm splitting due to the ethanol problem or due to overpressure ?
I run her on E5 with an ethanol inhibitor additive , and sad to say limited mileage
brian
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Post by Phil Nottingham on Apr 8, 2022 16:42:47 GMT
hi thanks for the info to both of you are you highlighting the possibility of the diaphragm splitting due to the ethanol problem or due to overpressure ? I run her on E5 with an ethanol inhibitor additive , and sad to say limited mileage brian The diaphragms split though old age and use whatever fuel or additive is used. It is probably past it already. Modern piston pumps afar more reliable and have no diaphragms. A worn oil seal in the cheap AC pump will also slowly extract engine oil and dump it on the road |
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percy
Rover Rookie
Posts: 72
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Post by percy on Apr 8, 2022 20:51:40 GMT
There's a vent hole in the upper section of the pump which will expel petrol before it drains into the sump. Any problems should be obvious by smell and a visual inspection. Diaphragms normally last about 40 years and rebuild kits are readily available. Any deterioration is slow and not sudden as with electric pumps. Many owners mount electric pumps in the wrong place anyway. The correct place is under the car on the crossmember next to the reserve tap.Tried & tested quality British made AC pumps more than up to the job and a lot of nonsense talked to the contrary IMO.
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Post by p5andrew on Apr 8, 2022 22:46:41 GMT
Facet pumps are pretty much the best available IMO. I have one fitted to myP5B and it has been faultless over the 10k miles covered since fitting. In my case I decided to fit the pump in the boot beside the bottom left corner of the tank rather than to the crossmember because I preferred to mount it in a more protected environment. The only downside is that the reserve will no longer be operational.I cannot urge too strongly that you include an inertia switch in the supply feed to the pump-an important safety device. The best place for the switch is on the bulkhead between the fuse box and the heater.
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Post by enigmas on Apr 8, 2022 23:18:23 GMT
There's a vent hole in the upper section of the pump which will expel petrol before it drains into the sump. Any problems should be obvious by smell and a visual inspection. Diaphragms normally last about 40 years and rebuild kits are readily available. Any deterioration is slow and not sudden as with electric pumps. Many owners mount electric pumps in the wrong place anyway. The correct place is under the car on the crossmember next to the reserve tap.Tried & tested quality British made AC pumps more than up to the job and a lot of nonsense talked to the contrary IMO. I don't believe so Percy. I've run low pressure Facet pumps for over 3 decades on several (classic British) cars and projects without issue or reliability problems. I've also got several original equipment SU fuel pumps on a shelf that I keep for nostalgic reasons (ornaments) but would never rely on them from past experiences. Facet pumps can be either pusher or puller types depending on specification and fitment location. Generally though, most are fitted below the fuel tank. I have one fitted to my SD1 powered 1958 MG Magnette high up on the firewall and it functions without issue. Needle and Seat Fuel pressure.Most low pressure Facet pumps put out about 4 PSI and cater for most carburettors fueling requirements. Some needle and seat configurations run even lower pressure requirements, for example Zenith Stromberg CD carbs (as found on Rover V8s) require about 2.5 - 3 psi as the needle and seat are very pressure sensitive. Fitting a cheap fuel pressure regulator ensures consistency. See image below. As for fuel types, its formulation and it's effect on classic carburettored fueling systems, look up the literature. The evidence is there in spades. With regard to Efi systems, they are designed to recirculate fuel fuel back to the tank, so fuel is constantly in motion in the lines negating heat percolation/vapour lock issues with current fuel formulation.    |
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percy
Rover Rookie
Posts: 72
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Post by percy on Apr 9, 2022 10:09:39 GMT
Fair comments re electric pumps & respect to your research. The AC mechanical fuel pumps have been happily pumping away in a wide variety of vehicles for 100 years.Simple, provan technology which usually gives plenty of warning of failure. Cleverly designed to cease pumping fuel when carbs aren't calling for petrol. It might come as a surprise that NOS AC pumps for the P5B are usually sold for in excess of £300 and they are getting rarer in new condition although any pump can be restored to new condition even to the extent of rebushing the arm & pin. My P5B has an AC type P pump and I have experienced no problems with vapourisation or insufficient supply under heavy demand. Each to their own but I do think the original type pump fitted comes in for a fair amount of unfair criticism when other factors might be at play.
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Post by enigmas on Apr 9, 2022 10:51:43 GMT
I didn't say I had anything against mechanically driven fuel pumps Percy...especially if the car is used regularly. Mechanical fuel pumps very well may have been around for 100 years, but "petrol" is formulated quite differently today than when carburation was the primary form of fuel metering for internal combustion engines. I'm assuming you live in the UK(?) where the petrol(?) incorporates a high percentage of ethanol. That chemical blend does marvellous things to the internals of mechanical fuel pump diaphrams and original factory fuel hoses if left unchecked.
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Post by Phil Nottingham on Apr 9, 2022 14:31:04 GMT
The AC pump was a cheap Leyland cost cutting exercise for the new P5B in place of the expensive Twin electric SU which could have been made double output if necessary to maintain adequate flow.
As it was, the AC pump was only just sufficient for the purpose but BLMC had to offer an electric conversion before the end of production to cover warranty issues particularly overseas
A failing of this pump apart from the diaphragm and oil seals is wear in the linkage and camshaft lobe which reduces the throw and the pressure. This leads to vaporisation in slow traffic and starvation at high speeds. The grinding over of starting the engine after a couple of weeks disappears and it demonstrated the weakness of a part worn AC which could not draw up petrol that is assisted by the siphon effect
Until I changed the AC pump to a compact foreign mechanical pump sold by the club I had this trouble regularly. I did not trust it long term durability so I converted to electric. The Facet piston pump has now been on over 20 years without trouble and a 100k miles mounted low down at the front so that Reserve is still operational.
Few AC pump repair kits included the oil seal which wears and allows oil drips from the vent hole which is not there to prevent petrol draining into the sump either as a worn oil seal will allow it flood in unnoticed.
I am all for originality if it serves eg points/CB over electronic ignition but electric fuel pumps are more reliable. Rover thought so with the P4 and P5! The earlier Rovers did have a mechanical AC (I have now converted our P to electric for the same reason as the P5B
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Post by 3litrekiwi on Apr 9, 2022 20:58:27 GMT
Facet pumps are pretty much the best available IMO. I have one fitted to myP5B and it has been faultless over the 10k miles covered since fitting. In my case I decided to fit the pump in the boot beside the bottom left corner of the tank rather than to the crossmember because I preferred to mount it in a more protected environment. The only downside is that the reserve will no longer be operational.I cannot urge too strongly that you include an inertia switch in the supply feed to the pump-an important safety device. The best place for the switch is on the bulkhead between the fuse box and the heater. My Mk III is still original with the double SU pump in the boot however I have noticed a petrol smell from time to time and think it is from the reserve end of the pump leaking slightly. I tend to keep the tank full so not switching to reserve is my current solution. I have a couple of spare pumps one of which is labelled as rebuilt by a previous owner. How long ago this was and how well the rebuild was done is unknown though. Having followed this thread, a solution that occurs is why not fit two Facet pumps in parallel, one to the main and one to reserve? It seems that this could also be a fix that retains the reserve on a P5b if the cable and valve were replaced with a switch. Everything could be reversed if originality was important however the pumps are pretty well hidden in the boot. Having a dual setup also provides a bit of redundancy should a pump fail. There would also not be the sound of the pump getting up to pressure at startup. It wouldn't be a difficult job to convert the cable to operate a microswitch that drives one pump or the other either directly or via a relay. This would also simplify the plumbing under the car and remove the two way valve that seems to be an issue with leakage. |
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Post by Phil Nottingham on Apr 9, 2022 21:20:59 GMT
The twin SU set up on P5s was excellent and ultra reliable. Our Coupe has it. 2 Facets in the boot would be expensive and unnecessary anyway. The Facets are noisy and I am part deaf but a front mounted pump is quieter and easier to plumb in. I only hear it at idle and when the ignition is off. I can hear the SUs ticking at idle but the the IOE6 is far quieter (almost silent) than the rough noisy V8s than than be heard for miles before it appears  |
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Post by johnwp5bcoupe on Apr 10, 2022 8:26:26 GMT
The twin SU set up on P5s was excellent and ultra reliable. Our Coupe has it. 2 Facets in the boot would be expensive and unnecessary anyway. The Facets are noisy and I am part deaf but a front mounted pump is quieter and easier to plumb in. I only hear it at idle and when the ignition is off. I can hear the SUs ticking at idle but the the IOE6 is far quieter (almost silent) than the rough noisy V8s than than be heard for miles before it appears Oooooo  |
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Post by Phil Nottingham on Apr 10, 2022 9:41:26 GMT
Nice article in Take 5 about your seat reupholstery  John |
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Post by johnwp5bcoupe on Apr 10, 2022 11:46:39 GMT
Nice article in Take 5 about your seat reupholstery John Thanks Phil my magazine hasn't arrived yet Busy doing a spare front seat as I had material leftover |
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John