Prado 120 sub tank in a GX470 - has anyone done it? Well I’m gonna try! (1 Viewer)

[Genuine Stone]

@Toyoland66

Thank you so much for spending the time to document this, I'm in Australia and own a GRJ120 and in the early 2000's it was very popular to do LPG conversions and the early non injection LPG systems have not aged well, which means I have been treating the car as it only has an 80L capacity as I never turn on the LPG (it likes to blow up airboxes)

The main part of these conversions was removing the rear sub tank (which painfully were scrapped) by cutting and shutting everything else, I have found myself a donor car of the exact model and will be picking up the sub tank assembly this weekend, your photos have been a great resource as I've not yet removed the cylinder to see where everything should be but can see where lines were removed and capped off.

I'm glad I only really have to worry about connecting old parts that were taken out instead of building it from the ground up but am looking forward to see how you progress in your build.

 

[Toyoland66]

it’s happening next week over the thanksgiving break y’all.

again, apologies for the timeline and everyone waiting for me to break the ice for this upgrade. I have a lot going on and other responsibilities, but I did post the info and parts list, so nothing stopping someone else from running with it (I’m kidding but only a little).

plan is as follows:
-remove existing spare tire crossmember and spare tire mounting parts
-temporarily remove charcoal canister
-test fit subtank and confirm mounting for tank straps
-install rear subtank mounts
-drop main tank, install new fuel pump, siphon line to subtank, remove 3/4" evap line and replace with 3/4" rubber line
-splice fuel level sender(s) electrical and tie into 6 conductor wire to switch
-remove existing and install new fuel filler
-reinstall main tank
-relocate charcoal canister and build new mounts
-plumb evap lines to charcoal canister that run above subtank
-hang subtank
-plumb remainder of vent, evap, supply lines
-profit?
-other things that I am forgetting
-test and fire up

I have all the OEM, electrical, mounting, and plumbing parts in hand to get this done. Knock on wood that I don’t have the snags with installing the new filler that @grinchy had, or other issues that I’m not anticipating. I don’t expect to get this done in one day but hope for less than 4. We will soon find out, more to come.

 

[grinchy]

I’m pretty sure you won’t need to botch a body lift to get you new filler in!
Have fun! I found a nutsert /rivnut setter and a variety of sizes of rivnuts helpful for making the brackets, along with a rivet tool and rivets. 1/8” aluminum bar in 2” wide and some 1/8” channel to make 90s out of.
Can’t think of anything else, it’ll probably bolt together in four hours. . .

 

[Toyoland66]

@grinchy good call on a nutsert tool, I was planning on getting one. Any recommendations?

 

[grinchy]

@grinchy good call on a nutsert tool, I was planning on getting one. Any recommendations?

I got a generic one off Amazon. I have also made a few of the wrench / bolt manual variety too, though I keep breaking the bolts on those in the very small sizes (m3, m4). Sometimes the long handled ones don't fit so good in the available space under cars besides engines next to frames etc. Sometimes they do.

 

[Toyoland66]

Step 1, . So much more room for activities.

Cleaned up with some paint. Remember kids, safety first

Also removed this tab on the rear crossmember, this supports the spare and is no longer needed and I’m pretty sure will be in the way.

 

[Toyoland66]

On to the mounts.

The front mounts bolt to factory threaded holes, easy enough.

There are no accommodations for the rear mount on the GX. I started out assuming that the rear mounts went through the f-r crossmembers. From reviewing the Russian thread that is where they located their rear mount:

Notice however the tank appears to be too far forward, and they had to trim the tab on the frame crossmember in front of the tank.

I then found a photo of the mounting on a factory Aussie Prado and discovered that the mounting is on the L-R crossmember.

It’s tough to see in the screenshot but there are raised dimples on the crossmember that locate the mount. As luck would have it these dimples are also present on the GX. This simplifies things…

 

[Toyoland66]

Knowing that these dimples locate the mount it’s as simple as putting the strap in place and marking where the hole should be.

This puts the hole 25mm/ 1 inch forward of the rear edge of the crossmember. As transferred the marks were slightly off center of the centerline of the F-R crossmembers so I adjusted them to centerline.

The factory crossmember would have threaded holes in this location. The crossmember is enclosed and I couldn’t think of a good way to add a female threaded insert. I decided to install a threaded stud from the top similar to how the Russian build did it.

Transferring the marks to the top side places them at the corner of these pressed indentations for these wire clips.

I figured that losing two of these mounting clips isn’t critical. The studs are m10 bolts with the head cut off and a heavy duty washer welded in its place. I thought it should be low profile so the trim piece can still bolt down over the top without interference. I did a bit of work with a hammer and punch to get the washers to sit as flat as possible and welded them in place.

 

[Toyoland66]

Here’s what it looks like from underneath.

You can see here I removed the wire loom clips that conflict with the bolts.

trim reinstalled like nothing ever happened.

 

[grinchy]

Nice find on the dimples. The 200 had these as well. This would have been a good place to drop in a couple rivnuts, but through bolts certainly work too.

 

[Toyoland66]

I considered that but have concerns about the load, the full tank weighs about 150 lbs, and while I’m sure the rivnut can handle that load I am not sure the crossmember can. It’s a single layer of 16(?)ga sheetmetal.

 

[Toyoland66]

I messed around with the charcoal canister a bit yesterday afternoon. It only takes about 5 minutes to disconnect the lines and drop it out of the way

I was able to confirm that the sub tank fits without interference, I wasn’t sure if the fittings would hit the mounting clips for the canister but appears to clear

Bad news is that the charcoal canister isn’t as pliable as my cardboard mock-up and I’m having a tough time getting it into this space

It needs to fit above the framerail and slide in far enough to clear the body crossmember and rotate up. This wiring and grommet is part of the problem so when I revisit this I will pull the wires and grommet out to see if that gets the required clearance. This harness feeds the trailer plug and the charcoal canister. Another potential option is to pull some body mount bolts and raise the body. Plan B is relocate the canister to the engine compartment so I ordered a few more fittings in case I have to do that.

 

[racwerx]

thanks for pioneering this, following along as I really want to do something similar.

 

[grinchy]

It needs to fit above the framerail and slide in far enough to clear the body crossmember and rotate up.

body lift that corner to provide room to get the canister in? I assume once it is up there it would have the clearance between body and frame to allow for appropriate body movement?

 

[Toyoland66]

body lift that corner to provide room to get the canister in? I assume once it is up there it would have the clearance between body and frame to allow for appropriate body movement?

I measure 5.25" between the framerail and body, the canister is 4.375" thick at the thickest which is the rear rear which has a small flange running around it. If I can get it past the body crossmember it should be good. Body mount is right there so should be easy to raise it a bit if needed

 

[grinchy]

An inch sounds like enough clearance

 

[ArBrnSnpr]

As I watched my gas needle drop closer to "E" while I passed the "Next services 124 miles" sign at midnight, I thought of you. I'm pulling for you! If this pans out, I'll likely be putting this on my to-do list.

 

[Toyoland66]

The evap system is making things difficult.

I pulled the wiring harness back up into the interior and that provided enough clearance to get the charcoal canister in place

Issue is the sensor apparatus on the canister hangs past the canister body enough to conflict with the subtank.

Next course of action is to remove the offending assembly from the canister and recheck the fit

This physically fits but now have to figure out fittings to fool the system into thinking these items are still attached.

 

[Toyoland66]

I went ahead and ordered a Prado charcoal canister, mounting bracket, and vent plumbing. In order to get the swap complete and back on the road I will temporarily place the existing canister in the interior and run the hoses to it through the hole in the floor. I then need to figure out one of two options;
-use the existing charcoal canister in the location shown above and figure out fittings to remote attach the controls portion to it
-use the prado charcoal canister which mounts in the engine bay, and figure out how to attach the controls portion to it so it doesn’t throw codes

the existing charcoal canister is too big to mount in the engine compartment.

 

[Toyoland66]

For reference: