Post by p5andrew on Mar 21, 2020 12:26:57 GMT
Hi All
I have a P5B with standard HS6 carburetors. I have rebuilt the engine from the bottom up and this included the carburetors which all new jets, needle valves etc. The float levels have been set as per the manual. A secondhand standard AC pump was rebuilt with new valves etc. I initially had problems because the (rebuilt) mechanical pump would not pull fuel through. I then tried fitting the mechanical pump which came with the car and which had been performing perfectly happily prior to the rebuild and which was a pattern one. Same result. All fuel lines were disconnected and blown through and the tank breather was checked - all clear. Spill return pipe was disconnected both ends and blown through. Short pipe to top of the tank to which the spill pipe connects was blown through. Having reached this stage I checked that I had in fact refitted the fuel pump cam and that it was mounted the correct way round - all present and correct. Reserve valve was dismantled, checked and fitted with a new seal which had been weeping slightly. Still no fuel whatsoever being pulled through by the pump. I then tried disconnecting the fuel feed pipe to the pump, siphoning fuel through and then reconnecting the pipe to the pump. Still no fuel appearing at the carburetors.
Having got this far, and notwithstanding the fact that there were no fueling issues prior to the engine rebuild, desperation began to set in and I wondered if the fuel pump cam was so badly worn that it was not operating the pump lever sufficiently for the pump to prime. The pump was removed and an inspection made as best I could through the side of the timing cover using a light and mirror. Difficult to be sure but all looked pretty good.
Having noted that many owners have fitted Facet pumps to their P5's I reluctantly decided to do the same and fitted a Facet Red Top, presuming that this would at least give the certainty of a reliable fuel supply. The pump is fitted in the corner of the boot immediately below the bottom nearside corner of the tank where there is just enough space. All plumbed into the main fuel line (not the reserve). Pump ran well and quickly primed correctly. A pressure regulator was included immediately after the pump outlet. Success! The engine started and ran, though very lumpy. Difficult to set up the mixtures correctly, especially the right carburetor, but thought nothing of it at the time. Took the car for a drive and all running pretty well. After a check over all fluids etc went for a longer drive. After about 10 miles, the engine began losing power very badly and eventually cut out and would not start. Pump could be heard running very fast which I presumed was due to it not priming for some reason - by this time it was dark. Left car overnight in a safe place and on return in the morning the pump immediately primed and the car ran perfectly with no intervention. Drove the car home - about 1/2 mile - and almost as soon as the car was on the drive it cut out again and the pump was running very fast. I managed to get the engine running again though very rough indeed, and immediately noticed that the right carburetor was flooding and fuel was pouring from the overflow. Float and needle valve were checked and all was fine. I then checked the spill return pipe again and it seemed to be clear when blown through with compressed air, though it was difficult to be sure because of the very small holes through the unions to each end of the pipe.
My question now is, is the delivery of fuel from the Facet pump too great for the small holes to the fuel spill return pipe unions? Do these need to be bored out a little to prevent flooding of the carburetors?
Anyone got any thoughts/suggestions/advice??!!
The one good thing is that with the car not running, the virtual rally planned for tomorrow looks very tempting!
Andrew
I have a P5B with standard HS6 carburetors. I have rebuilt the engine from the bottom up and this included the carburetors which all new jets, needle valves etc. The float levels have been set as per the manual. A secondhand standard AC pump was rebuilt with new valves etc. I initially had problems because the (rebuilt) mechanical pump would not pull fuel through. I then tried fitting the mechanical pump which came with the car and which had been performing perfectly happily prior to the rebuild and which was a pattern one. Same result. All fuel lines were disconnected and blown through and the tank breather was checked - all clear. Spill return pipe was disconnected both ends and blown through. Short pipe to top of the tank to which the spill pipe connects was blown through. Having reached this stage I checked that I had in fact refitted the fuel pump cam and that it was mounted the correct way round - all present and correct. Reserve valve was dismantled, checked and fitted with a new seal which had been weeping slightly. Still no fuel whatsoever being pulled through by the pump. I then tried disconnecting the fuel feed pipe to the pump, siphoning fuel through and then reconnecting the pipe to the pump. Still no fuel appearing at the carburetors.
Having got this far, and notwithstanding the fact that there were no fueling issues prior to the engine rebuild, desperation began to set in and I wondered if the fuel pump cam was so badly worn that it was not operating the pump lever sufficiently for the pump to prime. The pump was removed and an inspection made as best I could through the side of the timing cover using a light and mirror. Difficult to be sure but all looked pretty good.
Having noted that many owners have fitted Facet pumps to their P5's I reluctantly decided to do the same and fitted a Facet Red Top, presuming that this would at least give the certainty of a reliable fuel supply. The pump is fitted in the corner of the boot immediately below the bottom nearside corner of the tank where there is just enough space. All plumbed into the main fuel line (not the reserve). Pump ran well and quickly primed correctly. A pressure regulator was included immediately after the pump outlet. Success! The engine started and ran, though very lumpy. Difficult to set up the mixtures correctly, especially the right carburetor, but thought nothing of it at the time. Took the car for a drive and all running pretty well. After a check over all fluids etc went for a longer drive. After about 10 miles, the engine began losing power very badly and eventually cut out and would not start. Pump could be heard running very fast which I presumed was due to it not priming for some reason - by this time it was dark. Left car overnight in a safe place and on return in the morning the pump immediately primed and the car ran perfectly with no intervention. Drove the car home - about 1/2 mile - and almost as soon as the car was on the drive it cut out again and the pump was running very fast. I managed to get the engine running again though very rough indeed, and immediately noticed that the right carburetor was flooding and fuel was pouring from the overflow. Float and needle valve were checked and all was fine. I then checked the spill return pipe again and it seemed to be clear when blown through with compressed air, though it was difficult to be sure because of the very small holes through the unions to each end of the pipe.
My question now is, is the delivery of fuel from the Facet pump too great for the small holes to the fuel spill return pipe unions? Do these need to be bored out a little to prevent flooding of the carburetors?
Anyone got any thoughts/suggestions/advice??!!
The one good thing is that with the car not running, the virtual rally planned for tomorrow looks very tempting!
Andrew
