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Old 08-20-2019, 08:28 AM   #1
Junior Member
Join Date: Sep 2018
Location: North Little Rock, AR
Posts: 7
Onan 5500 Fuel Pump replacement ground

Onan 5500 Marquis fuel pump question. Does the control board dictate whether a newly replace fuel pump has the ground necessary to allow the fuel pump to run?

Background on problem. We have 20+ year old Fleetwood Pace Arrow Vision that is relatively new to us. Have been exercising the generator regularly while we took care of other issues with the unit. About a month ago my husband tried to do a regular start up. It would not start and made a grinding racket. Reg diagnosed this as most likely a starter issue. We decided to replace the starter ourselves. Ordered the proper starter from Onan and lowered the generator on a motorcycle jack so I could lean in to remove the starter. The fuel pump was in the way, so we decided to replace fuel pump and add fuel pump filter at the same time. Ordered Airtek fuel pump that cross referenced with the one we were removing and added Onan fuel filter at the threaded end. Replaced the starter, spark plugs and fuel pump, replaced fuel line from pump to carburetor and jacked the unit back up and secured. (This was all harder than it sounds).
When we started the generator is started and ran for about 40 seconds. Sounded like it was fuel starved. Loosened the fuel line at the carburetor and only a trickle of gas came out. Reg suctioned the line and gas would come through the line. Checked both the old fuel pump and the new fuel pump by hooking them directly to battery and they both run with power and ground from an auto battery. However, when power (from auto battery) is applied to the fuel pump that is mounted to the generator and grounded under the mounting bolt, nothing happens.
I have watched every You-Tube I can find, but not coming from an auto mechanic background I don't understand all the details of Onan generator. Called Flightsystems, Inc. but their RV technician is on vacation this week. Thought maybe some of you could give me some insight.


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Old 08-20-2019, 11:41 AM   #2
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Join Date: Apr 2013
Location: Tallahassee, Florida
Posts: 142
How are you applying power to the fuel pump directly? Where? Do you have a picture of your setup?

Do you have a volt meter to check for 12v power when you hold the stop button down (prime position)?

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Old 08-21-2019, 01:17 AM   #3
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I don't believe this vintage gen primes when the stop button is pressed. I had the gen stop running in hot weather and wouldn't restart for about a half an hour of cooling off. I wired in my own prime button and found out the pump wouldn't run when hot, common problem. This a new pump so I would think it is good so I would make sure you have a good ground on the pump because the gen supply's power to the pump when you press the start button.

There is a fuel filter delete for the carb fitting because they can leak from vibration which is bad. The remedy is to put the filter delete barb on the carb after place a filter after the pump.
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Old 08-21-2019, 01:42 PM   #4
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Location: North Little Rock, AR
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We did replace that old filter at the carborater with the fitting you displayed in the second picture. We did add a filter to the end of the new fuel pump. The old fuel pump did not have a filter attached and was mounted with only one bolt. We do think it is probably a grounding issue. We attached black automotive wire along with the new pump ground to see if we could find another place on the RV that would produce a ground when powering the pump with a power line from the auto battery. After touching every bolt within a two foot reach for grounding and not having any luck, we wondered if we had another problem. Going to check the power line to make sure it is hot (can't remember if we did that or not). As soon as the Arkansas heat wave breaks, I'll be back out there. Thanks for your input. I know the fuel pump gets power signal from control board, but we did not know if it gets any ground signal.
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Old 08-23-2019, 11:17 AM   #5
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Location: North Little Rock, AR
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Update. Generator running. Used 6mm serrated flange bolt to mount fuel pump and ground wire. This was a tight fitting bolt, but it is secure and I think the point of contact under the serrated nut is better as well. Also made sure the power contact was totally tight. Learned a lot in this experience!! Thanks to all the IRV2 forum discussions, photos and videos for giving us the confidence to tackle this.
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ace, fuel, fuel pump, onan, replace, replacement

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