Chinook RV

I've heard of people doing this with the steel floor in vans, not sure if anyone's done it on a chinook?

I'm at a point now where cutting one more hole in the floor wouldn't really change much...

It looks like it might be more of a hassle than it's worth. The fiberglass will likely splinter, and then make it more of a pain to loosen the fuel pump bolts that are under the steel cross member hat-channel.

And with that hole cut, would you be able to lift out/put in the old & new fuel pumps?

First pic showing the area, and channel. 2nd pic showing the side view.

I wouldn't think it is that hard to drop the fuel tank to replace it. I wouldn't want to drill a hole in my chinook although it is not that hard to reglass the section back in.

I wouldn't have a huge problem making a hole, if there were a really good reason. Depending on the year (at least from my era forward; not sure about 18+ etc.), it's either plywood with a fiberglass layer on the underside, or I believe a fiberglass/foam/fiberglass sandwich. Either can be cut fairly easily. Depending on where it comes out inside, you could use a round boat deckplate (if under furniture or carpet); if in the open area you'd likely want to get more fancy (or go for a nautical look ).

But that said, would I? Probably not. My buddy with an E-450 other-brand Class C had the fuel tank dropped (to repair/replace a generator fuel line) and also had the fuel pump done just because they were in there. It wasn't cheap, but it also wasn't ridiculous. I guess I'd classify it as an "ouchy" maintenance bill but I'd only expect to do it once if at all.

OTOH, if I were driving to Panama... maybe? But maybe not as from what I've seen auto repair folks in out-of-the-way places can pretty much do it all. I'd likely have it done the "regular way" before leaving and then see how it goes.

On the (this must be the fifth) other hand, since your rig is completely gutted anyway, maybe make a hole, change the pump, and then permanently repair it. That would be much easier than making a concealed access plate to use over and over. Just a bit of core and some fiberglass (cheapish), patch, fair and go on.

Good point on the crossmember though. That might mess up the whole plan anyway. Maybe someone who has done the job will let us know on that.

It's been on my mind as it's accessible right now. I was standing in the generator hole, and just looking around at things. My pump sure looks like it hasn't been changed in awhile, likely never, and I'm right at 100k and reading how it's sort of just a matter of time at this age/mileage.

I think if the crossmember wasn't in the way I might be inclined to cut the hole and see how it goes. Might just be easier in the long run (but not easier on the wallet) to have a shop do the job the normal way. I think most of the pains shops have are reconnecting things with all the RV tanks & plumbing in place. Not so much of a problem here for me...

Blue, my floor is the fiberglass-1/2" ply, foam, ply sandwich. I put a pic in my build thread of cutting a hole out to repair another hole. Got me thinking...

You may need to have a set of laparoscopic tools to attach the tubes and nut when you access it thru a small opening.

Out of curiosity, I see three nipples out of the fuel pump assembly. One probably goes to the fuel filter, but what about the other two? Anyone know where the generator get the fuel from? I there a separate and dedicated hole for the generator?

I believe the tubes are Supply/Return/Aux (goes to a hose that goes to the generator.) I believe the generator pickup tube only lets you draw the tank down to ~1/4 full. My gen. hose has a bolt in the hose, and a hose clamp around it.

A note on the floor construction: Your plywood/foam is one I haven't seen before (not that I've cut into everyone's floor ). Mine in my '99 is two layers of plywood with a fiberglass layer on the underside (so the plywood is the strength; the fiberglass protects the underside). There are some solid fiberglass areas such as the wheelwells and around the fuel fill, etc.

Later models I believe went to a sandwich construction. What this typically means is two fiberglass skins bonded to a foam core (not white expanded polystyrene but a core type foam such as nidacore, divynicell, corecell or etc.). In the sandwich construction the three layers have to be firmly bonded for their planned strength. Essentially it's kind of like an I-beam with the fiberglass skins being the top and bottom and the foam being the web (if I have that term right). In other words it holds the two fiberglass layers at a set distance apart which makes the whole thing strong. This is often used in fiberglass boatbuilding.

From what I have read Chinook went to this method because the Destiny was quite close to it's GVWR (and then used it in other models as well). Foam core generally is a bit lighter. (Although my Concourse with plywood floor seems like it's often lighter than later models, but then maybe that's because they have more options like tile floor, etc.) I like how Chinook kept on trying newer techniques as time went by even though they kept the models similar (especially the 21-footer).

I just had my fuel pump replaced by mechanics. Dropping the tank allows best access to replace the pump, but the tank needs to be in-place to reattach the fuel lines. As you can see there is little clearance. In our case it took many attempts over several hours. We weren't sure they would be able to do it. One reason for an access hole is to reconnect the fuel supply tubes.

Ah, good point on the reconnecting with the tank raised. I’d think Ford would’ve left some slack in the fuel hoses for that. Maybe it’s harder with the generator line and other Chinook stuff in the way? I’ve read up on some other RV makers that make an access hole from the factory.

The previous owner of my rig had attempted floor repair from a leaky fridge. In addition to "cleaning up" his work during my remodel, I cut an access hole for the fuel pump. It's a 10" square and simulates a manhole cover in the design. Meaning the top ply rests on the edges of the smaller hole of the lower ply. Held in place with screws. An easy mod at the time, and you never know.