| Author |
Message |
Bob Vandawalker (Rav221)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, July 27, 2005 - 6:45 am: | |
I have a 3 cyl Izuzu diesel generator intsalled at the rear of the bus above the engine compartment, which is about 5 ft off the ground. The fuel is connected to the main fuel tank via a seperate feed and return line. The main tank is near the front half of the bus which makes for a long run. My problems is it usually takes two or three times before the generator will stay running for more than 10 seconds. The generator has an electric fuel pump at the engine. Once running everything is fine.
I think that the fuel is draining back to the tank. I tried installing a check valve near the tank, but then the generator had a problem pulling the fuel through the line ( distance and height). I removed the check valve.
I have now purchased an aux electric fuel pump which I plan to install along with the check valve.
Question: Should the aux fuel pump be installed between the check valve and tank, or between generator and check valve? Has any one else had this issue? Any better ideas?
PS, The generator fuel pump does run automatically for about 5 seconds before the starter circuit engages, but I think it's pressurizing from the fuel in the filters.
Bob V. |
Jack Conrad (Jackconrad)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, July 27, 2005 - 7:20 am: | |
My understanding is that electric fuel pumps work better when pushing than pulling. I would install the pump near the tank and perhaps a separate switch to "pre-fill" the the fuel line. Hope this helps, Jack |
Marc Bourget
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, July 27, 2005 - 7:49 am: | |
Ditto, Jack's comment by the tank.
If it's draining back, and no check valve seals perfectly, permanently. Consider placing the pump in a bypass loop, like the "primer" system pictured on the CCC site.
The genset may be able to pull against the "head" once the prime is restored. |
Pete/RTS Daytona (Pete_rtsdaytona)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, July 27, 2005 - 8:14 am: | |
How about adding a "primer button" circuit to energize the fuel pump "prior" to starting the generator - |
Jim Bob
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, July 27, 2005 - 8:24 am: | |
Most small engine fuel pumps can lift about 1 meter. We see this problem often in marine applications if the genset is significantly higher than the tank. Your genset needs an aux pump mounted near the tank because pumps push better than they pull. The pump will have check valves in it too so that will help.
Use an aux relay so you don't draw too much current from the energizing circuit on the genset (one of those cube relays is perfect) & a breaker for the power going to the pump. I'd include a momentary switch at this point for priming/filter changing.
Your fuel supply line should also be no larger in diameter than the genset mfg suggests. It would be about 1/4" ID for your set. The larger the ID, the harder the engine mounted pump has to pull to lift the column of fuel (a 1/2" column weighs a lot more than a 1/4" column)
Also, most fuel returns just empty into the top of the tank, allowing the fuel to fall freely. I suggest that you change that & extend the return so that the tube is always submerged. Sometimes the engine's fuel system "breaks the siphon" by sucking air back through the return, allowing the supply fuel to drain back to the tank.
If the above doesn't solve the problem completely, consider installing a solenoid valve in the fuel supply line (at the tank) to shut off the supply when the engine stops, thereby keeping the fuel from draining back. But this is not the best solution. |
John MC9
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, July 27, 2005 - 8:27 am: | |
I dunno, Pete... He said:
"I tried installing a check valve near the tank, but then the
generator had a problem pulling the fuel through the line "
I doubt it'd pull thru a pump that's off..?
How about a second 1-2gal tank located at the genset and
use the auxiliary pump at the bus tank to keep the small one
filled? Awww...... why not just move the original genset pump
to where the fuel tank is? They do push better than they pull. |
Pete/RTS Daytona (Pete_rtsdaytona)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, July 27, 2005 - 9:52 am: | |
John
I meant adding a "prime button" to energize the existing fuel pump "prior" to starting the generator - at least you'll have a little head start getting the fuel back to the generator prior to starting it - did this When I had a GMC classic M/H with the old onan in a drawer - before the mod it would take a long time to start the onan - but if I held the "prime" button" for 30 seconds - It would start instantaneously - It helped that I had the full 12 volts to the fuel pump - without any voltage loss from the starter draw - worked great for me
Pete |
Tom Caffrey (Pvcces)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, July 29, 2005 - 1:46 am: | |
Bob, another possibility is to run the return line from the main engine to a small generator fuel tank near the generator. When the tank fills up, an overflow line from near the top to the main tank will keep the tank from overfilling.
If the supply for the generator is taken from near the bottom of the generator tank and the return line from the generator goes to the top of the tank, you will have a simple day tank setup.
Anytime the main engine runs, it will automatically refill the day tank. If a small lift pump is added to prime the main engine, it can be rigged to also serve as a way to refill the day tank without running the main engine.
This type of system is used on boats, and it works really well. The day tank on our boat is 15 or 20 gallons, but it only needs to be big enough to carry you between refillings.
Ours is for a stove and will carry us two to four weeks before needing refilled. In six years, we've only run ours empty one time.
If you play your cards right, it can even serve as a reserve for the main in case you ever get caught short of fuel.
I just put this out as food for thought.
Tom Caffrey PD4106-2576
Suncatcher |