Fuel pump replacement and questions.
#1
06-15-2016 | 10:16 AM
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From: Dayton, Ohio
Fuel pump replacement and questions.
I am in the process of replacing fuel pump in my 1993 XJ6.
After re-assembling the fuel pump unit, I connected the power to see if it's working (inside the tank with lines off). For the first 5-6 seconds, I am getting a strong solid stream of fuel, and after that it becomes "frothy" but still pumps.
Question I am having is: Is this normal? I can only assume once it empties the reservoir pump its sitting in, it's starting to get fuel from the bottom through the filter, but is this enough to run the car? Fuel pump enclosure has holes on top of it, maybe I should drill a few more holes on the bottom to assist with fuel intake? Or does the pump have a "variable power" so it pumps less volume when the engine is running?
Thanks for any info.
After re-assembling the fuel pump unit, I connected the power to see if it's working (inside the tank with lines off). For the first 5-6 seconds, I am getting a strong solid stream of fuel, and after that it becomes "frothy" but still pumps.
Question I am having is: Is this normal? I can only assume once it empties the reservoir pump its sitting in, it's starting to get fuel from the bottom through the filter, but is this enough to run the car? Fuel pump enclosure has holes on top of it, maybe I should drill a few more holes on the bottom to assist with fuel intake? Or does the pump have a "variable power" so it pumps less volume when the engine is running?
Thanks for any info.
#2
06-15-2016 | 11:15 AM
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Joined: Sep 2012
Posts: 2,646
Likes: 1,872
From: Victoria BC Canada
Hi - I did the replacement on my 94 last year and found the whole system of the fuel canister intake/flow etc to be puzzling but was assured it was a good system even though I couldn't totally get my head around the way it actually worked!
Jaguarpete, over on Jaglover's explained:
and in case you didn't know what an eductor was (like me)
and a few pics
Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page
good luck
Larry
Jaguarpete, over on Jaglover's explained:
There should be a sock filter on the pump suction inside the
canister and another sock filter on the bottom of the
canister. Inside the canister, there's a plastic tube that
goes to an eductor at the bottom of the canister over the
hole to the outside sock filter. When the pump runs, it
pumps about 225 liters per hour and about half of that flow
is diverted to the eductor for the sole purpose of keeping
the canister full, even at very low tank levels. The other
half of the flow goes to the fuel rail at the engine and any
fuel not needed is routed back to the canister. If you're
missing the sock filter on the pump, you can probably get
away without it.
canister and another sock filter on the bottom of the
canister. Inside the canister, there's a plastic tube that
goes to an eductor at the bottom of the canister over the
hole to the outside sock filter. When the pump runs, it
pumps about 225 liters per hour and about half of that flow
is diverted to the eductor for the sole purpose of keeping
the canister full, even at very low tank levels. The other
half of the flow goes to the fuel rail at the engine and any
fuel not needed is routed back to the canister. If you're
missing the sock filter on the pump, you can probably get
away without it.
We called eductors ''jet pumps'' in the Navy. They use a jet
of liquid, in our case gasoline at 35 psi pressure to suck
in (entrain) a larger flow of gasoline from the tank to keep
the canister full. It's a nice feature to prevent losing
fuel pressure when the tank is nearly empty and fuel is
sloshing back and forth. If the tank had a small sump
instead of a flat bottom, you wouldn't need the canister or
eductor.
And, if you keep no less than an eighth of a tank, you
probably could get away with simply attaching the pump to
the floor of the tank. I know Subaru, Tahoes and other
vehicles don't have such an elaborate system. In many
cases, the fuel pump and fuel gauge are together as a single
unit.
And you're right, the rubber sleeve on the pump suction
serves to dampen noise, I guess. Another great example of
over-engineering from Jaguar.
of liquid, in our case gasoline at 35 psi pressure to suck
in (entrain) a larger flow of gasoline from the tank to keep
the canister full. It's a nice feature to prevent losing
fuel pressure when the tank is nearly empty and fuel is
sloshing back and forth. If the tank had a small sump
instead of a flat bottom, you wouldn't need the canister or
eductor.
And, if you keep no less than an eighth of a tank, you
probably could get away with simply attaching the pump to
the floor of the tank. I know Subaru, Tahoes and other
vehicles don't have such an elaborate system. In many
cases, the fuel pump and fuel gauge are together as a single
unit.
And you're right, the rubber sleeve on the pump suction
serves to dampen noise, I guess. Another great example of
over-engineering from Jaguar.
Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page
good luck
Larry
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