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Old 07-15-2019, 10:17 PM   #1
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Running an inline fuel pump

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For those of you that don't know me. I have been on this forum for quite some time. I have a 1990 Ford Fleetwood Flair Class A with about 39,000 miles on it and it's a fairly clean coach for the age, only lightly used. The motor runs most excellent but the fuel pump has given me a little trouble at least 3 times. I'm considering pulling the factory fuel pump from the tank and replacing it with an defiant inline fuel pump so it will be easier to replace if it goes out. The fuel tank is fairly easily to get off once I have all the gas safely removed. This is the big block Ford 460 motor on the F-53 chassis. Any suggestions on what would be an appropriate inline pump. Plus while I am a very experienced mechanic I do not know if the 460 motor needs a high pressure or a low pressure pump. I plan to leave the sending unit and strainer module in place and just reroute the 12 volt wiring to the new inline pump. Just going to use the existing steel fuel line to make the installation easy so it will be done correctly. I think it's a low pressure pump it needs but I am not sure. Please feel free to pile on the suggestions. I could use all the help I can get. Thanks in advance
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Old 07-15-2019, 10:23 PM   #2
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Old 07-15-2019, 11:39 PM   #3
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The most common reason for repeat fuel pump failures is dirt in the tank.
Drop the tank, clean and inspect and put a quality pump in.
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Old 07-16-2019, 07:02 AM   #4
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You didn't say what the trouble with the pump exactly was. If you have had multiple pumps go bad are you installing aftermarket pumps?
I was a Shop Foreman for the City of Phoenix and from our experience I would not install an aftermarket pump in my motorhome, or any of my vehicles.

If you go with an external pump get one with the highest flow rate. The small pumps sold by most local auto parts stores won't flow enough fuel. Look up the pressure of the oem pump to determine what pressure you need. You also need to determine where the pressure regulator for the pump is to see if you need to add one.

Not sure on you mh but most have a tie in to the oil pressure switch so the pump won't run if the engine stalls. Could this be your problem?
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Old 07-16-2019, 07:15 AM   #5
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I do not know if the 460 motor needs a high pressure or a low pressure pump.
If you are carburated, you'll need low pressure. If you're fuel injected, including a throttle body injector, you'll need high pressure.
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Old 07-16-2019, 07:55 AM   #6
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Before I dropped the tank I would install an inline pressure gauge and monitor the fuel pressure under normal driving conditions. The in tank pump will have a strainer attached which may have debris trapped in it which could restrict fuel flow. Check this before condemming the pump.
Ford vehicles are known for fuel pressure regulator problems. Install the pressure gauge down stream of the regulator to get a true pressure reading.
If the pump is bad I would replace it with an in tank pump like was installed originally. The in tank pumps run in fuel which helps to cool the pump. Electric pumps are designed to push fuel not to draw fuel. The closer to the fuel the more efficient the pump will be. I don't like to see a vehicle with an in tank pump run with less than 1/4 tank of fuel. Running the tank down to near empty often will shorten pump life from running too hot.
I don't have the pressure spec. for the F 53 chassis but an F 350 1990 pick up with a 460 delivers 45 GPH at 45 PSI. This pressure will be slightly lower beyond the pressure regulator. Usually about 5 PSI. lower.
Find and check the ground wire connection to the vehicle's frame. Take it apart and clean the connector and the frame to assure you have a good ground connection. Check the ground wire where it enters the connector for corrosion, rust and possibly broken wire strands. Poor grounds will cause the pump to overheat and sometimes shut down or slow down which will drop the fuel pressure.
If you do elect to replace the existing pump with an in line pump you should remove the in tank pump and make up a fuel tube which connects to the fuel pump hanger and install a filter on the bottom of the tube. The in tank pump will restrict the flow if left in the tank and you try to draw fuel through it. Keep the filter just off the bottom of the tank.
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Old 07-16-2019, 09:44 AM   #7
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vapor lock

I have had 2 F-53 chassis with the 460 engine. Both had the same problem with vapor lock on a hot day even with a new fuel pump. I would let the engine cool down a bit and she would start up and go until it got hot again maybe 25 miles. this was on hot days 90 plus deg F. Maybe a inline fuel filter would have helped with the problem.
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Old 07-16-2019, 10:14 AM   #8
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Running an inline fuel pump

Our 97 was a 460 EFI , the pump failures were a known issue due to hot vapor returning to the tank and overheating the pump. The fix was a ) keep the tank more than 1/2 full as the fuel will keep the pump cool, or b) replace with an upgraded o.e. Fuel pump and jumper harness. Not sure if itís still available. I think a 1990 may be carbureted though.
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fuel, fuel pump

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