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skysummit · 05-22-2016, 03:36 PM

Hello,

I have a 1986 older RV with a Onan Emerald1 GenSet. A few years back the generator was not operating and it took a new control board to fix it. It worked great for a year but recently it would crank but not fire-up and I noticed the fuel pump was not working. I purchased a brand new fuel pump and still no luck. I just realized the fuel pumps are fine. I believe the problem is that they are not getting enough voltage. I'm getting about 12.3 volts to the generator which makes it crank just fine, but the generator is only supplying about 8.3 volts to the furl pump while trying to start it which isn't enough voltage to get the pump working.

Any suggestions?

Thank you

RV_Tech · 05-22-2016, 07:46 PM

you say the voltage at the gen is 12.3, what is the voltage during cranking? if it drops excessively during cranking it is either a battery or grounding issue. if the voltage to the gen is good during cranking i hate to say it but it could again be the control board.

okcnewbie · 05-23-2016, 06:41 AM

You can get the service manual here;

Index of /~n0nas/manuals/onan

I think you need the 965-0528. There's a procedure for checking out the control board, etc.

skysummit · 05-23-2016, 08:43 AM

Quote:

Originally Posted by RV_Tech

you say the voltage at the gen is 12.3, what is the voltage during cranking? if it drops excessively during cranking it is either a battery or grounding issue. if the voltage to the gen is good during cranking i hate to say it but it could again be the control board.

Thank you for pointing that out. I tested the voltage to the generator while cranking and it also drops to about 8 or 9 volts while cranking and then back to 12+ when I stop cranking it. I'm taking apart all the ground connections I can find and cleaning/grinding them clean to see if that works.

RV_Tech · 05-23-2016, 01:36 PM

these are often grounded under the gen or behind it on the chassis and are left exposed and corrode easily. If not a corroded ground issue next step would be bad cells in the battery. let me know how it pans out

skysummit · 05-23-2016, 09:29 PM

Quote:

Originally Posted by RV_Tech

these are often grounded under the gen or behind it on the chassis and are left exposed and corrode easily. If not a corroded ground issue next step would be bad cells in the battery. let me know how it pans out

There is a metal platform which the generator sits in. That is bolted to some steel framing which is attached to the RV. There are two heavy gage ground cables which run from this steel framing to a nut & bolt that drives though one of the steel flooring frames below the generator. I took all of these apart, wire brushed through the grease & rust to the bare metal and put it all back together. I also checked my cables at the battery again.

I'm still getting voltage drop while the starter in cranking. I get about 12.3 dropping to about 8.3 while the RV motor is off. If I start the RV and let it idle I get about 13 to 14 volts at the generator which drops to about 9.5 - 10 volts while the starter is cranking. This is apparently still not enough voltage to activate the fuel pump.

I'm wondering if there is so much corrosion that I just cant get a good ground between where the car battery grounds to the car engine up front and 15-20 feet back where the generator is grounded to the frame.

What if I ran a long ground directly from the battery all the way back to where the generator sits in the metal frame? I have some long lengths of heavy gage wire.

twinboat · 05-23-2016, 09:58 PM

If you fill the carb. with the prime button before cranking, you don't need the fuel pump running for a minimum of 30 to 40 seconds.

I prime mine by holding the stop button down.

The carb bowl fills with gas during priming and can run the engine for quite a while without a fuel pump.

So, I don't think your fuel pump is the problem, unless you have an empty carb.

If you don't have a prime circuit, put a boat gas tank squeeze bulb in and pump it up.

You should only need to prime after running out of gas or after letting it sit with gas in the carb for weeks.

The voltage drop you are seeing is normal for that gauge wire and lenght.

Try jumper cables to the starter from your car. That takes the voltage loss out of the equation.

For you doubters, shut off your fuel pump or pull the line off the filter, before the pump, and see how long the generator runs.

I do this on my MH generator or my outboard motors before storage every 6 months.

okcnewbie · 05-24-2016, 05:41 AM

Have you tried with the MH running? Are you sure you have at least a half a tank of gas

RV_Tech · 05-24-2016, 08:38 AM

you can try running a heavy gauge wire straight to the battery and see if that helps. If NOT it would be wise to test the batteries under load. A dead cell in a battery can cause this as well. If you have access to a GOOD battery jump pack try that as well. It completely sounds more like a grounding or battery issue more than anything else. It is priming. but that much of a voltage drop as just not enough for the starter to quite kick over and get the compression needed to fire up the gen.

skysummit · 05-25-2016, 08:04 AM

Quote:

Originally Posted by RV_Tech

you can try running a heavy gauge wire straight to the battery and see if that helps. If NOT it would be wise to test the batteries under load. A dead cell in a battery can cause this as well. If you have access to a GOOD battery jump pack try that as well. It completely sounds more like a grounding or battery issue more than anything else. It is priming. but that much of a voltage drop as just not enough for the starter to quite kick over and get the compression needed to fire up the gen.

I got it to work!

I did a lot of different things so not sure which one was responsible for finally getting it to turn over. I went through and cleaned every ground I could find and even added an additional heavy grounding wire from frame to generator.

I always had a half tank of gas but there still could have been a priming problem as the electric fuel pump, the carburetor, and the line between them was completely dry. I filled the gas tank all the way up which might have given a bit more pressure on the gas supply line and who knows but that extra gas in the tank might have helped prime it.

My Battery was always fine & strong but originally the ground connection could have been compromised.

In any event, it finally started. It ran very rough & erratic at first (it has been sitting without running for close to a year) but it finally settled in so then I ran it under full load for 30 minutes yesterday, but it still sounds like it could run smoother. Any suggestions for that?

Thank you all for your advice. It obviously was helpful and successful.