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Old 09-15-2018, 11:37 AM   #1
kraftee
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Predator 3500 with Extended Run kit

So, after successfully using my excellent Predator 3500 Inverter Generator on several trips, I realized that it would be REALLY nice not to have to refuel the unit every 5-6 hours. So I bought the extended run fuel tank kit advertised on ebay with hose, filter, squeeze ball, fittings and billet fuel cap (I already had my own brand new 6 1/2 gallon "outboard" tank.) The company I bought the kit from is MRI-Denver and they included fairly detailed instructions with the kit.

However, there is a side note on the instructions that says, "In the Predator 3500, there is a vent at the top of the tank that goes to the charcoal canister that then goes to the intake. When the internal tank tops off it dumps fuel into the canister and it chokes out the generator. Disconnect the tank vent from the canister and cap it off." But there is NO mention as to where this hose might be found or how to "...cap it off."

After doing some quick internet research, I heard horror stories about generator cases filling with fuel and causing massive cleanup and run problems - not to mention fire hazards. Interestingly, NO ONE seemed to be able to supply any good info or pictures as to where this hose was that needed to capped off! There are a LOT of people asking for that specific info - including me. When queried about how to find the hose, the response was always this nebulous, "You'll find it, it's very obvious." Well it's not to me.

So, armed with my trusty LED flashlight, I decided to dive into the inner workings of the Predator. First thing was to pull off the side cover of the unit. This is the big red cover that also contains the oil fill door. After loosening the two caged phillips screws, you lift the little rubber fuel overflow flap at the top of the panel and then pull the panel towards you. There are some snaps that come undone, and the cover is loose. THIS is where I got confused last time. Because it is CROWDED in there - and nothing is labeled. No tag reading, "This is the vent hose you are looking for."

Eventually I figured it out. If anyone else is interested, here's how to find the vent hose: Looking into the left hand side, you will see the large, rectangular, silver valve cover for the engine. It's very easy to identify since it has the letters "OHV" embossed right on to it - bigger than life. Just above the top right hand corner of the valve cover, you will see the spark plug cap. It's the black plastic round thing that goes through a rubber grommet. Just above the spark plug and slightly to the right you will see two black rubber hoses with silver "squeeze" clamps that are plugged into the side of a black plastic box. This box is the elusive charcoal canister.

Now, the BOTTOM, SMALLER of the two hoses plugged into this box is your vent hose! To test this, use pliers to squeeze the clamp and slide it back along the hose. Then wiggle the hose free. Now, open your fuel tank cap. Blow strongly through the hose. You should easily hear the air whooshing out of the vent pipe inside the tank.

You must cap off, or clamp off this hose in order to use the extended run tank kit. The vent on the extended run tank now becomes the fuel tank system vent - since the internal generator tank will stay full all the time. It is worth noting, that if you wish to use the generator without the extended run tank, you will need to unclamp or uncap the vent hose again. Another option is to vent the standard Predator fuel cap. This is the route I am taking. I have posted a couple pics to help find the vent hose. You can see, in the second photo, that I have successfully capped the hose. I'll try to post a couple more of my modified fuel cap.
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Old 09-16-2018, 08:38 AM   #2
Willie & Bev
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Thanks for sharing that information. We will be buying a generator before next spring and I will keep this in mind.

Willie
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Old 09-28-2018, 05:40 AM   #3
kraftee
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In addition to capping or shutting off the tank vent on the Predator when using the extended run fuel tank kit, the instructions also make it plain that you must have the big tank higher than the the generator due to the fuel flow being strictly gravity/siphon. I initially thought it would easiest to simply leave the tank on the back rack of our Outback 324CG. However, the relatively short connecting hose meant that the generator was too close to our rear bedroom. Then there's the issue of rain. Predator recommends that some sort of cover be used over the generator in pouring rain (common sense, I guess.)

I initially looked into the available little pop-up style generator tents - but they're ridiculously expensive - and do nothing for helping get the ER tank up higher than the genset. I then decided to try to find a table of some sort. No luck finding the right size. So I decided to build a PVC pipe cover/tank support.

Used 3/4" schedule 40 pipe and connectors along with a sheet of 1/4-inch birch plywood and some zip ties. It's exactly the right size, plenty sturdy, and weighs practically nothing. In addition, I did not glue the legs in place so the unit comes apart for easy storage. Cost about $35 to build and if anyone is interested in the measurements, I am happy to post them.
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Old 09-28-2018, 06:27 AM   #4
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Nice little exoskeleton and fuel table. You could probably outfit the pvc structure with a tarp to shield the genny from the elements too. Niffy project. Thanks for sharing.
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Old 09-28-2018, 06:36 AM   #5
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Thanks. Yes, although this should keep the heavy water off the genny's most sensitive parts, I also thought about having a white tarp made. I would want it to form fit to cover the gas tank (reducing heat expansion) and drape down about halfway on three sides (obviously can't cover the exhaust outlet!) to help protect the genset even further - but still allowing it to have enough air to breathe and cool properly.
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Old 01-23-2019, 04:50 PM   #6
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Question

Could I ask you what you capped the line off with? Or what is the inner diameter size of that line? Thanks in advance, I’m following your footsteps with the cover as well.
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Old 01-25-2019, 04:27 AM   #7
kraftee
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Hi S22. Sorry for the delay. I just saw the post/question. The plug is about 3/8" diameter and plugs the line just fine. Hope that helps! Eric
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Old 01-25-2019, 07:43 PM   #8
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Kraftee,

I'm bringing my Champion 3100 generator on our month long trip to AZ and UT in April. We plan on boondocking many of the nights. Just curious how that extended run fuel kit has worked out for your Predator generator? The same ebay seller (MRI-Denver) has a kit for my Champion. To me, it a bit expensive for a specialized gas cap, primer bulb, gas line and fuel tank. But, to save me the hassle of refueling the internal tank every 5-6 hours and trial and error of building my own setup, I'm considering the purchase.

I haven't' found any reviews or youtube videos on how these gravity tanks behave. My biggest reluctance is obviously a gas leak.

Was it worth the purchase price? The other option is an extended run kit that requires some significant modifications and installation of an axillary fuel pump. It can be found here: http://www.pinellaspowerproducts.com/view/cfuelkit3400/

Btw, I'm going to emulate the design of your fuel tank platform if I buy this extended run kit. I like it because it's collapsable and lightweight. Thanks again.
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Old 01-26-2019, 06:30 AM   #9
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Well, interestingly, I have only had one chance to try out the extended run kit. At first it seemed to be working perfectly. After a few pumps of the primer bulb, I could see the fuel flowing through the glass filter as it filled the tank and gravity siphoning began. However, 4 hours later, the generator quit running. I checked and sure enough, somehow, the siphon had been broken. I tightened all the connections, manually filled the tank to the top, and tried again. Still no siphon. So, every 4 hours, all night, I got up and pumped the damn primer bulb until it filled the main tank.

At every race since, I have had access to hook-ups. So, that was the last time I used the generator. Not really sure what to think. I emailed the company, but no answer. I will be looking into the issue and trying to figure it out, but at this point, my honest advice to you is to go with the better, fuel pump-equipped kit.

As soon as I have the chance to look into the issue a bit, I'll post my findings.
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Old 01-26-2019, 02:00 PM   #10
Jrandywms
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I am trying to use a 6 gallon tank above my 3500 predator and have followed your instructions. When using a hose with a primer bulb on it I couldn't get the gas to flow from tank, even when pumping the bulb. I used a clear hose with attwood quick release fittings on each end. The tank on the generator was about half full. When I started the generator gas would not flow. I made a pvc pipe so I could blow into the vent on top of the filler cap on 6 gal tank. When the gas started to flow within 15 seconds the generator flooded out. I plugged the line that goes to the charcoal canister like you showed in your post. The 6 gal tank is about 5 inches above the generator. Any suggestions?
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Old 01-26-2019, 02:51 PM   #11
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I just came across a very good deal on Amazon for a Westinghouse 4500/3700 inverter generator. It has a remote start, a 3.4 gallon tank (verses 1.6 on my current 3100 Champion) and nearly 1000 more available watts. Reviews are good...noise levels are similar...and it's only $670. Can't find it under $1000 anywhere else. I may just sell my Champion now and hold off on the extended fuel tank purchase. The large capacity internal tank is what I've been looking for. No need to lug around fuel hoses and an external tank. Plus, I came across some starting issues with the gravity fed extended fuel tanks and different brand inverter generators, including the Predators and Champions. Now, how to tell the wife??
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Old 05-07-2019, 05:24 AM   #12
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Were you successful in getting this extended tank to work? I have been trying to get mine to work for some time. Would you please contact me, planning a coast to coast trip and really need to get this to work.
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Old 05-07-2019, 10:23 PM   #13
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Quote:
Originally Posted by Jrandywms View Post
Were you successful in getting this extended tank to work? I have been trying to get mine to work for some time. Would you please contact me, planning a coast to coast trip and really need to get this to work.
I've not read many confident reviews with these extended run tanks. There is a similar gravity fed kit for the Champion line of inverter generators. More than a few folks has issues on a "restart". I think "carb flooding" is an issue.

I have since sold my Champion and kept my 3.4 gallon Westinghouse. It worked perfect on our trip out west last month where we camped on BLM land much of time. Only needed to fill up the tank every few days.
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Old 05-08-2019, 02:09 PM   #14
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I already have a predator 3500 generator and not looking to replace it. Anyone who reads this please contact me if you have a answer. Problems I have noted, the gas tank on the generator has two lines from it, one to the carburetor the other to the carbon canister. The canister is used to get rid of the vapors that are created when the gas in the generator tank gets hot and make fumes. If these fumes are not relieved pressure will build in the tank. If a extended tank is used the pressure created in the generator tank will stop the gas from flowing from the aux tank. The generator gas tank has to be vent in some way. If anyone has made this work please contact me. Planning a cross country trip and need to get this working. Thank you in advance for you help, any advice about other generators or other extended generators is not requested, I own a Harbor Freight predator 3500 inverter generator and am only interested in this extended run procedure for this generator.
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Old 11-10-2019, 09:22 AM   #15
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CARB Breather Hose for extended Run Time

This may seem like a silly question but let me try anyway. If a CARB generator's fuel system is sealed, and the breather tube hooks into the cannister...they why can't we just remove the hose from the Canister, and put it into a gas can?



Make a hole in the gas can cap to route the hose through and maybe and extended hose. Besides making the generator no longer CARB compiant.....would the running generator suck fuel into the main tank from the extra gas can.



Just a thought....any comments?
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Old 05-05-2021, 04:59 AM   #16
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Thoughts please

Why not plumb out a line with a cutoff that runs directly from a tank to the carb. Put a 3 way behind the run start knob, seems like it should work. My tank rusted and my generator is apart. I’ll be trying this once I gather all the parts. Understanding the problems everyone else’s is having, I think a direct gravity fed line that bypasses the stock tank should work. No siphon either. A tank with an outlet at its bottom.
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Old 05-07-2021, 05:15 AM   #17
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Extending the tank

I’ve ordered the parts. A 3 way valve the I will mount to the side of my generator. Fuel goes from the OEM tank to the dial knob for run/ start. I will cut that fuel line between the knob and the carb and plumb to my 3 way valve. One line goes to the Carb the other goes to my new inlet mounted to the side plastic of the generator. External tank has a flared bulkhead nipple at the bottom of the tank. This is then connected to the new inlet mounted to the side of the generator. The 3 way can now provide fuel from either the internal tank or the external. There is no backfill into the OEM tank that risks flooding the carb. I plan to build a table as shown on this thread. Gravity fed- not siphoned - external tank on top- generator underneath. Yes - there is a line that will have to be connected and there will be 10 minutes of setup time- but I’m using this setup when I’m parked for days. Otherwise the valve is switched to internal tank.
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Old 05-03-2022, 04:08 PM   #18
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Anybody have an update on how you are getting the extended run aux gas to flow? Thank you.
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Old 07-31-2023, 12:40 PM   #19
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Awesome Exoskeleton set up! Could you provide the measurements? I plan on doing this with my Predator 3500...with the same set-up.....Predator 3500 with reserve tank. with a tent-type cover which will drape 3/4s of the genny...1.5ft clearance on all sides....of course open on the exhaust side. I was thinking of using an extended exhaust pipe with insulated coupler where it goes through the tent. Has been attempted by anyone to your knowledge?...or is it just an all around bad idea?...LOL! Let me know your thoughts! Thanks!
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Old 07-31-2023, 02:27 PM   #20
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The person who posted the pics of the "exo-skeleton" hasn't been on the site since 2021 so perhaps you will have to get your tape measure out and take measurements.
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