Zel's Fleet Blog...Rover, Renault, Peugeot, Trabant, Invacar & Sinclair C5

[Atodini]

Zel,

I don't think I've ever come across a low-pressure carburettor (SU) set-up fitted with a return to tank pipe.... SU's in later years were often installed contrary to the companies recommendations.....

I have, somewhere, an SU "bible" from the 1960's where it states that the maximum float chamber delivery pressure should not exceed 1.5psi on HS2 and HS4 and 2psi on HS6 versions and that they should never be fitted with mechanical fuel delivery systems....

SU electric pumps were/are supplied in 2 versions, a 1.5psi "puller" pump for use where the pump is located in the engine bay (i.e. Morris Minor) and a 2.5psi "pusher" where the pump was located at the rear of the vehicle near the fuel tank. I've no experience of the Hardi pumps but would guess they are similar. All mechanical pumps tend to operate between 4psi and 8psi. I eventually binned the SU carb for a Weber though - got tired of regular fuel leaks!!!! Webers been on there for 25 years now - no issues whatsoever.

The SU "bible" also goes into great length about how to convert your Austin A30/35 or Standard 8/10 from the original Solex or Zenith to SU HS2....

A Reliant Rebel (Zenith carb) I owned back in the '70's, went up in flames (at a set of lights on the old A1 at Sandy in Beds), when the output pipe on the AC mechanical fuel pump popped out, showering the distributor with petrol!! Hence when I acquired my present Kitten, the first thing I did was remove the mechanical pump and fit an SU one.

Is it possible that the return pipe fitted to your car is maybe for the fuel injected version? Or is indeed actually necessary? If its as blocked as it seems to be maybe it has always been blanked off.....

John

[suffolkpete]

That may have been the case in the sixties, but I have owned four cars with DU carburettors since then, and all have had mechanical pumps from new. I have never come across a return feed with an SU carb/mechanical pump combination.

[Zelandeth]

The return line is definitely standard fitment on the V8 P6.

Part labelled as 39 in this diagram is the return line.



This was fitted I'm pretty sure specifically to deal with the issue of vapour lock. An issue that I'm sure is a hundred times worse today thanks to the volatility of modern fuels.

The factory routing of the fuel line around the engine bay doesn't do it any favours in this regard either.

Could run a bit of small bore copper tube as a return pipe, save a lot of hassle?

The bit which requires a bit of thought is how to get it back in to the tank. I've got an idea in mind, but need to investigate the arrangements currently in place in more detail before I can see if it will work or not. Hoping I might get a chance this afternoon, just waiting for a (now late) grocery delivery to turn up first.

[suffolkpete]

Almost certainly due to vapour lock, to which V8s were prone. Many owners have fitted electric pumps to combat this. My four pot P6 doesn't have a return, but my Matra does, and the return has a very small orifice, 0.7mm. I would imagine that if the Rover is similar it would get blocked very easily.

[Zelandeth]

...the return has a very small orifice, 0.7mm. I would imagine that if the Rover is similar it would get blocked very easily.

This is pretty much what I was afraid of. If Rover had put that at the engine end it wouldn't have been too hard to deal with, however with it being built into the return piping on the in-tank assembly it's going to likely be really difficult to clear if we're talking something that small.

Also, more than slight envy with regards to your Matra. They are very high on my list of "favourite cars I've never actually seen in person and know next to nothing about, but want anyway." A neighbour of ours in the early 90s had a Rancho in almost neon orange which obviously very much appealed to me as a youngster at the time. Would have loved to see what else they would have come out with in the following years if they'd stuck around in some alternate automotive universe. Slightly bonkers but brilliant seems to be my overwhelming memory of it. The Murena seems to me to have a similar tagline. Are those seats half as comfortable as they look?

-- -- --

A plan is forming.

Had a closer look at the breather on the tank today and it's a helpfully large diameter. I confirmed that it was pretty easy to feed a bit of copper brake line in there and it will easily slide round the corner right into the tank, so I can get the end well clear of the breather port itself.



Nice that they switched to a push on hose for the breather on the later cars - the early ones used threaded unions here like we've seen elsewhere on the fuel system which probably would kicked this idea to the kerb.

I just need to find where the other end of that large bore nylon line is, and feed the copper line in from there - that way the breather setup will not be compromised at all (albeit having its capacity reduced a bit), and we'll have something to which we can attach our return to tank in the meantime. Pretty easy to crimp the copper pipe a little to give us a restriction to emulate the function of the original orifice if we need to as well.

Yes it's a bit of a bodge, but I'd like to think it's a reasonably well thought out one and one which doesn't involve any modification to the car itself. Once the inevitable happens and we fit a replacement in-tank assembly (keeping in mind that the fuel gauge sender on there is also dead) so it is a matter of when rather than if, the additional copper line can just be removed and be chucked back in the "this will be useful one day" pile in the corner of the garage. Just need to make sure everything is properly secured in place and that we make sure there's a drip loop on the bottom of the line where it emerges from the breather in case any fuel gets forced out there during filling the tank (it shouldn't) so we can make sure it drips somewhere harmless rather than ending up dripping on the brakes, exhaust or anything else likely to get hot.

[suffolkpete]

Also, more than slight envy with regards to your Matra. They are very high on my list of "favourite cars I've never actually seen in person and know next to nothing about, but want anyway." A neighbour of ours in the early 90s had a Rancho in almost neon orange which obviously very much appealed to me as a youngster at the time. Would have loved to see what else they would have come out with in the following years if they'd stuck around in some alternate automotive universe. Slightly bonkers but brilliant seems to be my overwhelming memory of it. The Murena seems to me to have a similar tagline. Are those seats half as comfortable as they look?

Very comfortable, if you're not too tall, I've done some long journeys in mine and they're great fun to drive. It's not so well known that they built the Renault Espace series 1 to 3 and the Renault Avantime, but if you really want to see bonkers, visit the Musee Matra in Romorantin. Keep your eyes open, Murenas appear from time to time and they don't fetch huge amounts of money.

[gazza82]

The SU "bible" also goes into great length about how to convert your Austin A30/35 or Standard 8/10 from the original Solex or Zenith to SU HS2....

That's simple for the A30/35 .. get the manifolds and carb from another A-series like a Mini and bolt it on! The downdraft Zenith warps over the years.

There is a tweak on the A30/A35 to the throttle level but that's just to make the movement smoother. I converted my A35 to a 1 1/4" SU from a Riley Elf back in the 70s and swapped to the Elf's cable throttle and a custom throttle pedal.

[Zelandeth]

Very comfortable, if you're not too tall, I've done some long journeys in mine and they're great fun to drive. It's not so well known that they built the Renault Espace series 1 to 3 and the Renault Avantime, but if you really want to see bonkers, visit the Musee Matra in Romorantin. Keep your eyes open, Murenas appear from time to time and they don't fetch huge amounts of money.

Imagine they will handle really pretty well if they're as light as I seem to remember them being. Never know, maybe one will appear somewhere in the future, I'd resigned myself to never getting a P6, and a few years ago I stumbled into ownership of a V12 XJ-S which I swapped a Lada for...

-- -- --

A closer inspection revealed that there are two breather lines attached to the fuel tank in the P6, I'd not spotted the one to the left.



Some quality metal work by whoever put the speakers in evident there too - which I found when I stabbed myself with it.

Turns out that the breather line on the right is blocked somewhere. The tank fitting is fine, but I can neither blow through nor suck through the line which vanishes into the car behind the tank.

The one to the right on the other hand is properly open to both atmosphere and to the tank, so we do have a working tank breather. This arrangement is quite different to the setup shown in my manual, likely as this is a later car. I really need to find a diagram for the later setup as it would be nice to know where these things are actually going.

I think based on the fact that we clearly have one emphatically not working breather, I'm just going to make my life easier and steal the tank port from the clogged one entirely for my return line and to cap that breather line off in case they are connected together elsewhere behind the tank and I unexpectedly wind up with it dumping fuel into the boot.

There's obviously something amiss with the one line so that needs investigating - I think when I go in to change the sender I'll just budget some time to actually pull the tank so I can get to everything in behind there. Wouldn't be the worst idea anyway as I'd like to make sure there's no rust hiding in behind and under there and do what I can to make sure none gets started.

Found this line floating around in the back of my engine bay not attached to anything.



It used to be visible here in the engine bay behind the right hand cylinder head.



I'd originally thought this was a breather from the gearbox, but apparently not as it was just bundled in among the various pipes running down the side of the bell housing under the car. Answers on a postcard?

Elsewhere under the heading of Zel using ridiculously overkill hardware for mundane tasks, this old time clock has now been given the task of switching the light on my fish tank.



It's rated to 20kW...should be able to deal with the 4W we're dealing with here. I did have a closer look at the innards when I first got it, and looking at the contacts I'm pretty sure it's never been used to actually switch anything. Bit silly, but it pleases the engineer in me to see really nice quality kit getting a second chance at life. Plus I now don't need to remember to turn that light on in the morning - which I've a terrible record for remembering to do.

[Dick]

I like the fish tank control meter thing, what a great idea

[Zelandeth]

Had a chance to look into the lack of heating in the P4 today. Initially couldn't get any water through the heater core.

Poking a screwdriver into the feed immediately revealed the reason for this.



The valve itself was also well and truly gummed up. Eventually, after a good 15-20 minutes digging and generally faffing about with it I managed to get a decent flow through it.

Turned out that the linkages were also adjusted wrong, so the valve wasn't opening when the heat control was set to high.

I then faffed about for a while getting it bled - there's no proper provision for bleeding the system on these and the heater is the highest point on the system so it's a bit awkward.

We now have...some vague suggestion of warmth. I suspect I may need to bleed it a bit further or poke the linkages a bit more. Progress though. I also want to see if I can get hold of the cable and get the flaps for the windscreen demisted vents open. I'm not inclined to dismantle the whole control assembly to try to reconnect it, but if I could just get the demisters open and just leaving it that way would make sense at this time of year.

As Abby was in the office today so I didn't have the Peugeot on hand it drew the short straw for daily duty today.



Still enjoying this car. Hopefully I can get it equipped with more or less a fully working heater tomorrow.