Generator issue

[Adamgre]

I'm sure this has been asked and explained 100 times but I can't seem to find an answer for my problem.I've got an 86 Minnie Winnie with a Onan Emerald I Genset. Rv was recently purchased and I've had the generator running and seemed to be perfect. The fuel level may have gotten too low to run the generator but I've since filled it up. I've had the fuel pump out and checked it on a good battery and it ran like it should then. When I take fuel line off of pump and try to start it no fuel is coming out, I'm gonna get a meter and check to see if I'm getting power to the pump but if I'm not then where would my problem lie? Also should fuel run out of the line to the generator? I don't have any coming out so I tried to trace the line, it seems to run to the carb? Is that correct? I figured it would go to tank but doesn't seem to. Thanks for any help In advance

[4x4van]

An '86 motorhome won't have the prime feature on the gen start switch. I changed out a failed fuel pump on my Onan 4.0 generator a few years back ('88 model MH) and added a toggle switch to prime it. BTW, I just used an automotive low-pressure fuel pump; much cheaper than an Onan unit. While running, the generator should trigger a relay that will provide 12v to the pump.

The 20v concerns me; that shouldn't be possible from a battery bank that's providing 12v.

[Adamgre]

I did check across battery and showed 12.5 volts when sitting and same when starting generator. I tried the prime feature but I guess mine doesn't do this because nothing happened. I'm assuming the fuel pump is ran by the generator so would that mean a bad regulator?

[westend]

He is using an analog meter, maybe reading off the wrong scale?

My suggestion would be to buy a half-way decent digital meter and see what voltage you have at the pump when depressing the prime button. With adequate voltage the pump should sound about the same as when you powered it straight from the battery. If it is about the same and you have no fuel from the line, there is probably a bad fuel line to the pump from the source. If it doesn't sound the same, you may have a bad electrical connection to the pump.

Good luck, I hope it's an easy fix.

[opnspaces]

Adamgre wrote:
Ok here's what I got. When trying to start I'm showing 20v to the fuel pump. If I take a hose and put in a can of gas it still doesn't pump anything, also if I suck on fuel line to pump gas flows freely. Why would I have 20v to the pump and why wouldn't pump still work

You probably don't have 20v to the pump. As suggested put the meter across the battery and see what the voltage reading is.

If you get 12v at the battery and still get 20 at the pump then you have a second battery with 2 dead cells somewhere that is wired in series with the first battery making 20 volts.

[Jerrybo66]

LittleBill wrote:
the HF meters work just fine, they are within .5 of a volt of my fluke

I totally agree but what are the odds that all HF meters are good compared to Flukes. My Fluke was around $200.00 and HF are given away free. How much quality control was involved between the two? Maybe out of the tens of thousands of HF meters, you got lucky with one that works. Congratulations. I'm not here to argue a American/chinese tool debate, I'm just trying to find a reason for his unreasonable voltage readings. His problem is the main topic here..
BTW, for a guy who knows quality equipment, what the heck are you doing with a free Chinese meter?? They're not heavy enough to be used as a boat anchor.. :B

[LittleBill]

the HF meters work just fine, they are within .5 of a volt of my fluke

[Jerrybo66]

I think maybe you have two problems. Either it's a HF volt meter or the battery in it needs replaced. I get radical readings in my American Made Fluke multi-meter when the internal battery gets low.

If you have unrestricted fuel to the pump and it doesn't pump, even though it runs, under "working resistance" to the motor it doesn't move fuel you may need a new fuel pump. Have you tried a pressure gauge at the outlet of the pump??. They're fairly reasonably priced at your parts store. They are a low pressure/vacuum gauge.. .Just some rambling thoughts....Maybe don't mean much....
Be sure to let us know your fix...

PS.. What I don't understand is how you can get 20-35V out of a 12V system. If that is possible then I should expect a 24 pk of Bud the next time I buy an eighteen pak. How do I 'splain that to the check-out gal?? 🙂

[Adamgre]

Ok here's what I got. When trying to start I'm showing 20v to the fuel pump. If I take a hose and put in a can of gas it still doesn't pump anything, also if I suck on fuel line to pump gas flows freely. Why would I have 20v to the pump and why wouldn't pump still work

[Matt_Colie]

If the unit is 12V DC based and you are getting 35V at the fuel pump, then check the meter across the battery. Was there a decimal point somewhere? You may have a bad meter or you may be reading a ghost.

Can you feel the pump run?

Most motorhomes have a separate fuel pick-up in the tank for the generator (APU). This pick-up is typically short so the APU can't run you out of fuel. The other unfortunate issue is that the old fuel lines may have been replaced and the person that did the job missed the APU lines completely.

Silly but cheap diagnostic trick...
Take the line off the fuel pump and try to suck fuel up. (Yes, if you suck with you mouth there is a chance of getting a mouthful of gasoline, but hey, its 20 proof - better than beer.) Just be cautious . I have pumps and jars I use for this test, but as a one-off you don't need to invest in those.
Oh, if you don't get fuel up there fast, you now know where the problem is....

Matt

[darsben]

HERE is a troubleshooting guide

[Adamgre]

There is a inline filter but it between tank and vehicle carb, I replaced it shortly after buying the rv. I'm still trying to figure out where the fuel line to the generator comes from. I've read when the tank gets around 1/4 full the generator will shut off. I was assuming the line was just higher on the tank and wouldn't pick up fuel but as far as I've gotten on the line it looks like it goes to vehicle carb. Hard to track it because it disappears under the firewall and I can't see much under hood. Will probably take dog house off tomorrow and try it that way and will try a hose in a can of gas to see if that will run the generator.

[Water-Bug]

If there is a fuel filter anywhere in the line, it should be replaced.

[Jerrybo66]

When I needed to give my generator a shot of carb cleaner I didn't want to dilute it with all the gas in the tank. I put gas in a gallon can then added the cleaner. Ran a hose from the can to the intake of the pump. It sounds like your problem may be a bad hose, cracked, making the pump suck air instead of fuel. If you try this application and the genny runs, that would pretty much show the problem is from the tank to the pump... Just a thought.... Good luck..

[Adamgre]

It is looking like a fuel line problem. I do agree about these fuels nowadays! I put an ethanol treatment in everything I own that's carbureted but this one is a new purchase. So if I do have a line problem does anyone know if this line does go to the vehicle carburetor or to the tank? From what I could see it looked like it went to the carburetor