Auxiliary Petrol Tank

[enigmas]

As it's been quiet on the forum, I thought I'd post the next project for my coupe. Briefly, my P76 V8 powered Mk3 has been running on LPG virtually exclusively for the last 30 years since I re-engined and recommissioned the car.

LPG is still widely available in OZ or at least my home State of Victoria. With the price of petrol being heavily affected by the conflagration currently underway in the Ukraine, LPG is still fortunately 50% of the cost per litre of petrol prices in Victoria.

My primary rationale for fabricating the auxilliary petrol tank is essentially to act as a backup to LPG, especially if I'm ever in a situation or place where it's unavailable.

As an aside, my coupe runs a fully programmable ignition system with the option of 2 fuel maps. This literally allows at the flick of a switch to change the ignition map from LPG to Petrol or visa-versa. Each ignition map is designed for its specific fuel.

I'll also need to add an additional fuel filler to the DS of the car mirroring the PS filler.

Here are a few images of a cardboard mockup of the proposed tank in situ. The body of the tank will be fabricated from 1.2mm mild steel sheet.

[enigmas]

Auxilliary Tank Update

I managed to get in a couple hours this arvo assembling, welding, cutting out the end pieces and two internal baffles. I have the original petrol tank tucked safely away and was going to use the factory sender, but a local auto parts company "Speco" sell an adjustable fuel sender and gauge for $80. So rather than modifying the factory P5 sender to fit this tank (and possibly damaging it) it's a no brainer fitting an adjustable unit to the tank.

I still need to sort out a few technical issues. These include: Baffle location and shape, filler and fuel pickup position, an air vent tube to prevent fuel purging whilst filling, a drain plug and a suitable location to mount and access to the fuel sender. I'll also incorporate a return fuel line for any possible later fueling options.

A couple of questions

1. I have a Facet solid state electric petrol pump in hand but am still in two minds as to where it would be best installed, either within the boot or under the car.

2. The SU fuel pump on the MK3 P5 pulls fuel from the top of the tank, is this the same for P5Bs or was the fuel feed for the pump altered to the base or bottom of the tank?

Please feel free to chime in with your experiences guys.

Here area few more progress pix.







The top panel is currently just resting in place, as there's more internal work required before buttoning the tank up permanently.

[enigmas]

I managed to get in a bit more welding today. Three quarters of the tank is now fully seam welded and the internal baffles are permanently fixed. I'm waiting on the fuel tank sender, so until it arrives, the top can't be welded down permanently but other components including: air vents, fuel pickup, fuel return, filler neck drain plug and securing mounts can be done.



Baffles in place.

[enigmas]

I spent this afternoon adding and fabricating the petrol filling air purge line (5/8"), the return line (1/4") and the fuel line (3/8"). All in copper (as I had these various diameter copper pipes aside). I still need to add the filler neck and cut an opening into the top to accept the tank petrol gauge sender. Until that component arrives the top cannot be welded in place.

There are also several bracing tabs to be added to the air vent line and the internal fuel.

Here are a few pix.

[enigmas]

A bit more work on the auxilliary tank today adding 4 securing tabs at the base, a securing tab for the large copper vent and also redid the fuel return pipe incorporating a larger loop in its design. I still may yet add a (petrol) vapour vent and plumb it to a charcoal cannister I have aside from a 240K Datsun sedan. During hot days any fuel that vapourizes within the tank will be absorbed by the charcoal cannister and then be drawn into the intake stream when the engine is started. There's obviously a bit more plumbing involved adding this system, so we'll see. 😉

PS. For anyone viewing this post, the writing in yellow on the auxilliary tank below should say, "Faces LPG tank".





The image below is the boot outlay I'm aiming for when everything is in place. I've decided to mount the Facet fuel pump and filter under the car in a vacant corner space on the DS rear near the spare wheel carrier. Located in this position the pump and filter will be easy to access.

[dmaxwell]

Amazing work, I wish I had your skills in metalworking! What will the capacity of the tank be (British gallons, US gallons, litres, grams, pounds, etc.)?

David
California

[enigmas]

Thanks for the thumbs-up on the tank fabrication Phil, John, Mike & David. My calculations work out to approximately 30 litres (6.6 gallons) of petrol. That's more than enough as a reserve or backup fuel system for my needs. 😎

[enigmas]

Fuel Tank Sender & Gauge
The fuel tank sender and gauge arrived a couple of days ago or half the kit did. Due to covid and substitute temporary fill-in staff, I only received half the kit ie, the gauge. A call to the company, Engine Parts Australia on one of their contact lines quickly sorted the matter with a very helpful individual priority posting a complete gauge and fuel assembly kit to me. So I now have 2 gauges and the matching sender. Very good value for less than $80.





Note that the sender is fully adjustable. The adjustments for my specific tank are highlighted in green for the table directly below.


Speco the manufacturer of the kit also provide a comprehensive instruction sheet for all of their gauges. Only one page of their 2 page instruction sheet is shown below.

[enigmas]

Fitting the Petrol Tank Sender
Now that I have all the parts and instruction sheets for the sender and gauge, I was able to fit the assembly today. A couple of hours and it was done. The longest part of task was making the hole for the sender. As I don't have a suitable hole saw to cut through 1.2mm mild steel plate, my method is to scribe the hole size required and drill around the inner perimeter with an 1/8" drill bit. This is followed up using a small cold chisel then a half round file. It's tedious but it gets the job done. Still to be added is an air vent port for the charcoal canister (that will be added to the fuel system) and a drain plug at the base. I'm also going to fit one of the fuel gauges I was supplied with directly on top of the tank surface.

The pix below are self explanatory.

[johnwp5bcoupe]

Super job as usual Vince great welding skills :-)

[enigmas]

Thanks John, fingers crossed that it doesn't leak when it's all done and in place. I'll cap all the openings and pressure test it though before finally fitting it.

I trial fitted the tank today, primarily to sort out the exact through locations of the securing studs. This meant removing the spare wheel carrier as I didn't want drill into any critical components. As the Facet fuel pump and filter will reside near the spare wheel carrier (DS rear corner) several additional fuel & return lines will also need to be plumbed through the boot floor near the fuel tank outlets.

Interestingly, now that the spare wheel carrier is out of the way (I've never removed it before) I can see some other unrelated jobs that need attending to.

With a bit of luck I should have some more pix to post tomorrow.

[enigmas]

Tank Testing Time
After a few days of respite (the flu, not covid kicked-in and slowed progress down on my auxilliary tank project). Fortunately I managed to get quite a bit done today. As the plans for this project reside purely in my head, it's paramount that the various feed and vent pipes are correctly positioned and also remain serviceable when the need arises. These considerations do slow down the work.

Below is a pictorial record of today's work.

Adding the fuel tank drain plug and surround.




Positioning and cutting the hole for the fuel tank drain surround.


Access hole in boot floor covering.


The boot floor as viewed from underneath showing the location of the fuel tank drain.


Driver side rear shows the various pipes exiting the tank on the RHS. Look carefully below the tubes exiting on the side and 2 drilled openings (1/2" holes) can be just seen. The fuel feeds, lines to the pump and any wiring will pass through these openings.
Note the copper line running up seemingly vertically. It actually follows the contour of the LPG tank and is the tank vent line when the fuel cap is closed.



The 3/8" copper pipe seen here is the fuel feed line to the pump.


The tank temporarily in situ. Note that I still need to add a filler neck. Oops! I was so focused on the vents and feed pipes that I didn't notice that the filler pipe was absent. Fortunately my wife came out and inspected my work stating, "how do you plan on filling it?" One of those senior moments where I couldn't see the wood for the trees! 😉


This final image illustrates a test using water (as the liquid medium) to check if the tank has any welding seams or areas that may leak or weep. Note the red plastic top floating in the tank.
After draining the water I dried the interior and poured in some ATF that I swished around.

[enigmas]

Buttoning it up and adding the Filler Neck
I managed to finish most of the work on the tank today. The work took about 4.5 hours. After 4pm the light diminishes and it gets progressively darker. The winter solstice in OZ peaked 4 days ago.
Today's effort on the tank entailed fitting the petrol filler tube and welding the entire top panel in place. On this of work I tack the panel every 40 - 50mm and then weld a continuous bead between each tack weld, overlapping the tacks before stopping. I move to different sections of the panel to spread the heat load. Beads longer than 50mm tend to eventually bake the thumb of my left hand as I use it as a guide close to the nozzle to control the bead I'm laying down. I wear industrial leather gloves but the heat does have a way of pentrating through if I continue too long. Anyway, this method works for me and does provide good penetration and a leak free join.

The following images outline the work.







I had to add 2 more tack welds to the drain plug surround.

[enigmas]

Finalizing Details.
The construction of the auxiliary petrol tank was completed today. Nothing large, just small details, a couple of support braces for the petrol feed and return pipes, a small fixture for mounting the fuel gauge on the tank and a tab to hold the petrol gauge signal wire in place. There's one more addition that I'd forgotten...a metal protective surround for the fuel gauge. I aim to get a coat of etch primer on the tank tomorrow.

It's 6°C in cheery Victoria tonight with a high of 13°C tomorrow...Brrr!
The twin fuel fillers arrived today. Pix below.

Note the bracket transversing the 2 lower pipes.


The fuel gauge in situ.




The twin fuel filler caps.

[enigmas]

Ready to Fit.
Today I added a "brass" surround for the fuel gauge, (as it's what I had available and I like the contrast of metals.) Just a small measure of protection so that it doesn't get inadvertently knocked and broken. After that, the tank surface was lightly sanded, wiped down with thinners, then etch primed and painted satin black.

The tank is now ready to be fitted to the coupe after I reposition a couple of wires that were poorly located for the LPG system years ago. Being a bit OCD with detail at times slows the process down.

Stage 2 in getting this backup fuel system operational, entails mounting the fuel pump, fuel filter and plumbing the components together.

Stage 3, virtually the last part of the project, is to mount the fuel filler plumbing and fit one of the quick release caps to the DS rear, mirroring the location of the factory fitted cap.

[Mike’S-a-loon]

Beautiful job, Vince!

[enigmas]

Thanks Mike. Is Winston still garaged in Melbourne or has he been shipped OS?

[Mike’S-a-loon]

He's still there, but hopefully will be on a boat soon(ish)... These are difficult times for shipping, but there's no immediate urgency.

[johnwp5bcoupe]

Great Shed Engineering Vince I like the BMC sticker

[enigmas]

Thanks John, it's one of our club (BMC Leyland Car Club) stickers...just thought it would add interest and a bit of colour. 😉

[enigmas]

Grand kids, Garage door fettling, & Bolting the Tank in place
With 4 grandchildren storming through the house for the last couple of days, it provided the perfect opportunity to go outside and brave the elements. My work area is fully sheltered but it can still be chilly outside. It also provided the impetus to fettle the garage door as it had shifted slightly and was catching our pattern paved concrete driveway.

Here's a few progress pix.
The tank permanently in place, but not yet plumbed or electrically wired.


The 4 securing studs and the central tank drain as viewed from underneath. The hose hanging down on the RHS is the petrol feed forward to the engine.


Below is the new Facet low pressure pump, a small filter and 2 brass nozzles that comes with the kit. There are also 2 Efi high pressure but low resistance filters. One of the Efi filters will be plumbed to the outlet side of the pump.

[enigmas]

Rome wasn't built in a day.
Whenever I start a fresh task or project I never like to think about how long it may take to complete. If I did, I don't think I'd ever start.

Today I fitted the fuel pump, 2 fuel filters, the pipe work and hoses. I also connected the earth/ground wire to the chassis and lengthen then ran the power wire into the boot interior. It doesn't sound like much, but each piece/item has to be fettled, fabricated and secured in some manner so that it fits and doesn't interfere with other mechanical or electrical fittings.

Here are a few pix.

The Facet Fuel Pump and filter assembly.


The 5/16" copper tube that connects the tank fuel outlet to the pump inlet. There's also a filter attached directly to the fuel outlet to protect the pump. As the fuel tank is virtually new and the interior pristine there shouldn't be any issues with contamination or internal debris.


The fuel pump assembly and efi filter mounted in place.


The tank fuel outlet to the fuel pump plumbing exiting beside the DS rear wheel well. The tube in front of the plastic petrol filter is a fuel return line, currently blocked off.


This final picture, (has nothing to do with the fuel system) but shows the modified differential housing (Borgwarner 2.92:1 ratio) and the factory handbrake mechanism hooked up to the Jaguar MK2 disc brake calipers.

[enigmas]

Fitting the Filler Caps
Another cold day in Melbourne. Today's task, (actually the last couple of days) was to fabricate mounting plates for the alloy quick release filler caps. To clarify, both caps are alloy but the filler tubes which screw into the caps are machined mild steel. The PS filler is for LPG and the DS for petrol. The PS cap is really there purely as a cosmetic cover sitting over the LPG filler valve. The petrol side is more complex due to the physical nature of the plumbing. It has to allow fuel entry to the tank, as well as allowing air to escape, otherwise a purge situation can/will occur at the filler point. I also need them to be removeable should a technical need arise.

Keeping things British, I used the panel steel from a (1950s) MG Magnette front door skin that I had aside from a previous project. As the door skin had a nice radius to it this reduced the amount of metal fettling needed to match the curve of the rear section of a P5 where the fuel filler resides.

Like most things I do, the second version is always easier to fabricate, as the first one is generally about problem solving. For the moment they'll be held in situ with self tapping screws, but once I'm satisfied with their function they'll be pop riveted in place and then painted body colour, this obviously excludes the alloy caps.

Most of the auxiliary petrol tank plumbing and wiring is done but the physical pipe connections to the fuel filler of the tank is yet to be fabricated and connected. I've used the petrol main/reserve switch of my MK3 coupe to activate the petrol pump, obviously in the reserve position when it's required. "Main" position is off or dead (as the car primarily runs on LPG), switching to "Reserve" turns on the Facet petrol pump.

The pix that follow illustrate most of the processes required to complete this project.

[Phil Nottingham]

All very neat indeed!

[enigmas]

Thanks Phil, there's still some work ahead of me before it's all done and functional.