Fuel hose help please !

[Jonny TR6]

Whilst the smell of petrol in the car confirms I have a Triumph, it’s time to let it go and move with the times.

I have a Bosch fuel pump installed which went in in approx 2008 and stripping things down, I traced the smell to a slight weep where the soft lines eventually go to the hard line that runs through to the front of the car.

I’ve therefore bitten the bullet and taken the alloy tank out and am going to replace all the rubber fuel hoses with Cohline 2240 R9 which can handle pretty much anything ethanol wise.

I do however have an issue in that one of the hard lines in the system in 8mm o/d, which the installer reduced to 6mm o/d and then a piece of rubber hose was used to connect the 6mm pipe to the 4.7mm hard line. No wonder there’s a slight whiff in the air !

What I’d be very grateful for is if someone can help me with the following questions..

1.) how do I go from either 8mm or 6mm o/d to 4.7mm o/d. I don’t want to use one piece of rubber hose for obvious reasons.

2.) is there such a thing as R9 hose with an I/d of approx 4.3 - 4.5mm ?

I don’t want to bodge this, so getting it right first time is important.

Many thanks in advance !

Jonny

 

 

Edited July 2, 2022 by Jonny TR6

[stuart]

If your talking about the whole front to rear feed pipe then it should be 5/16" or 8mm front to back regardless.

Stuart.

[Jonny TR6]

As ever Stuart and the 7th cavalry to the rescue !

Thanks Stuart - that means I need to replace the whole line, which isn’t a problem. Another thing sorted.

Edited July 2, 2022 by Jonny TR6

[Jonny TR6]

Next question and bear in mind any fuel injected system I’ve ever had has been on a modern car..

If I’m increasing the o/d from 4.7mm to 8mm surely I’m decreasing the pressure from the pump to the MU ? Bernoulli’s theorem is haunting me from the old days, so does that affect anything upstream, i.e MU PRV etc ?

It’s all a learning curve at the mo so very happy to be educated.

Cheers

Jonny

[Mk2 Chopper]

The best thing to do Jonny is once you have the set up how you want it, do a pressure test right at the metering unit and if necessary adjust the pressure by means of the PRV to obtain the correct reading of around 106 to 108psi. You'll need a pressure gauge and some means to connect it to the fuel line. 

Gareth

 

[Jonny TR6]

Thanks Gareth - every day’s a school day !

[Waldi]

Johny,

4.7 mm OD would ve very unusual for a fuel line on our cars (from prv to mu).

The return line however is 3/16”, are you not confusing both?

If it is a bit messy what you have you can order new sections of pipe from our suppliers.

Waldi

[Jonny TR6]

It’s 4.7mm all the way to the engine bay. Here’s the PRV which is in the boot. The rubber mounts had started to dissolve with the leak, so a new pair on order.

 

 

Also a pic of the feed to the MU. I think the PO put the connection in to allow a pressure gauge to be put into the line.

Theres been some knocking against the inner wing so will clamp it securely and once I replace the line.

 

Edited July 3, 2022 by Jonny TR6

[Waldi]

Jonny,

the black rubber line is the MU return line (MU to tank), very low pressure, basically. Is is 3/16” metal pipe with a couple of 3/16” rubber hose connection pieces. Use R9 spec for those with jubilee clips. Do not forget the section above the tank.

The other rubber line with the red ring is the high pressure feed which comes from the PRV. Use R14 spec with crimped connections here. I do not like jubilee clips on this line (PRV to MU) but others have relied on double jubilees. Not me.

 

[Jonny TR6]

Many thanks Waldi - really helpful. It’s all new to me, so this info is invaluable.

Need to get the car on axle stands during the week (BBQs and rels popping round today delayed things) and have a good look underneath and fully understand what’s what.

Are the crimp clips better than proper fuel line clips ? Wouldn’t use jubilee, but understand the equal pressure all round fuel clips are ok ?

Wasn’t aware of R14 - will do some research so I know what it is and get some ordered.

[Waldi]

Jonny,
R9/14 are grades of fuel hose according specification SAE J30, example SAE J30 R14 is “fuel injection hose, suitable for the high pressure in the line from Pump-PRV-MU.

Gates and Cohline have a range of suitable hoses.

My preferred method of connecting the high pressure hoses is with crimp-ferrules, as used on brake lines and hydraulic hoses.

I doubt the clips can hold the hose tight, they work on a narrow band, where the ferrule covers more of the ferrule ribbings. Have not looked at their specification.

Also read manufacturers datasheet for minimum bending radius and allowable temperature (at working pressure).

Waldi

 

[Mike C]

I've used pairs of SS jubilee clips with heads spaced 180 degrees apart on my HP fuel hose for the past 25 odd years with no problems. From memory back in those days there was a factor of safety of at least 2 on the Jubilee design safe WP tables for a single clip.

Conversely, over that time I've had numerous problems with the rubber fuel hose material itself until Gates Barricade came on the scene. That included importing SAEJ30 R9 hose from the UK which would last about a year handling the Australian high octane fuel blends of 10 years ago.

Edited July 4, 2022 by Mike C

[Jonny TR6]

I’m pleased to report all hard lines correctly installed as per spec. Which is nice.

Also, R9 and R14 on the way, as well as some me Sapphire Blue paint to tidy up in the boot where the paint had softened.

No need for a fancy PRV either as I’m not changing the fuelling, but will get a pressure gauge for the future.

Thanks all for the help so far - especially Waldi !

Edited July 4, 2022 by Jonny TR6

[astontr6]

On 7/3/2022 at 2:07 PM, Waldi said:

Jonny,

the black rubber line is the MU return line (MU to tank), very low pressure, basically. Is is 3/16” metal pipe with a couple of 3/16” rubber hose connection pieces. Use R9 spec for those with jubilee clips. Do not forget the section above the tank.

The other rubber line with the red ring is the high pressure feed which comes from the PRV. Use R14 spec with crimped connections here. I do not like jubilee clips on this line (PRV to MU) but others have relied on double jubilees. Not me.

 

That rubber hose from MU to return fuel termination is not correct? It s/b a piece of nylon 66 hose ( 5.5 I/D X 8mm O/D secured by 2 X O clips 'Double ear types'. Whilst nylon 66 is not a 100% ethanol proof it is far better than rubber. If you want the proper stuff that is 100% proof you have to go to nylon 12 sold by the Hose Shop. Can be difficult to obtain in the UK from other sources.

Bruce.

[Waldi]

Hi Bruce,

I was referring to the pieces under the car and in the boot (tank inlet).

I’m not sure about the ID of the first bit (with the bend) attached to the MU-return, I have a std rubber hose there as well.

Cheers,
Waldi

[RogerH]

On 7/2/2022 at 7:36 PM, Jonny TR6 said:

Next question and bear in mind any fuel injected system I’ve ever had has been on a modern car..

If I’m increasing the o/d from 4.7mm to 8mm surely I’m decreasing the pressure from the pump to the MU ? Bernoulli’s theorem is haunting me from the old days, so does that affect anything upstream, i.e MU PRV etc ?

It’s all a learning curve at the mo so very happy to be educated.

Cheers

Jonny

Hi Jonny,

Once the larger pipe is full of fuel it will produce the same pressure as the smaller pipe.  Leave Bernoulli to play with his Pizzas

 

Roger

[Jonny TR6]

Gone with Waldi's recommendation of using crimp connections. Had to order a special crimping tool, but it's funny how tools for one-off jobs end up coming in handy in the future.

[Waldi]

Hi Jonny,

can you share a link of the tool you bought? 
A good method to test the completed hose is to try to rotate the ferrule in the hose. If it turns (by hand), it is probably not tight enough.

Cheers,
Waldi

[Jonny TR6]

Here you go Waldi https://www.ebay.co.uk/itm/130639578599

I do still however have the issue of going from 4.7mm pipe (return from the MU) to 8mm (return to the fuel tank) if anyone can assist ? What do other people do ?

[Waldi]

Thanks Jonny,

This design looks better to me than worm-drive style clamps.

Did you check the allowable working pressure with the supplier?  I could not see it in the Oetiker information on the WWW.

Regarding the step in diameter in your MU return line: The diameter should be 3/16” from MU to tank. Are you not confusing the two elbow connections on the tank: MU-return with PRV-return? The PRV return is the bigger one, the MU return is 3/16”. Hope this clarifies your issue.

Cheers,
Waldi

[Jonny TR6]

1 hour ago, Waldi said:

Thanks Jonny,

This design looks better to me than worm-drive style clamps.

Did you check the allowable working pressure with the supplier?  I could not see it in the Oetiker information on the WWW.

Regarding the step in diameter in your MU return line: The diameter should be 3/16” from MU to tank. Are you not confusing the two elbow connections on the tank: MU-return with PRV-return? The PRV return is the bigger one, the MU return is 3/16”. Hope this clarifies your issue.

Cheers,
Waldi

Hi Waldi - I ordered Mikalor clips https://www.ebay.co.uk/itm/222278335919?var=521113983348 can't find the working pressure on their data sheet https://mikalorcompany.com/hose-clamps-and-clips/industry/two-ear-clip-2Will check out the tank this evening, it's slowly starting to fall into place with your help !

 

[Jonny TR6]

Going back to the 8mm to 4.7mm - the 4.7mm returns from the MU and then connects with rubber hose to an 8mm hard line. This goes into another rubber hose which finally connects to the inlet next to the filler.

I can understand why it’s been done this way, as getting the tank in is a tight squeeze and having the flexi hose aids installation.

Pics to aid description 

 

 

[Waldi]

A hdd a, you have a non-standard tank. But maybe you can still fit the 3/16” elbow as per the original, on the nozzle next to the filler neck. But a soldered connection from 5/16 to 3/16 could be a possibility too if you want to maintain the existing situation.

Have a look at the Moss catalogue, it helped me a lot during my restoration. In fact I had 2 paper copies, one in my garage, the other in the lazy chair.

Cheers,
Waldi

[Jonny TR6]

All sorted - I needed a 5/16 to 3/16 reducer and managed to find one for £2.99 delivered. That way I can use the correct hose diameters with the connector in the middle, rather than trying to cobble a single rubber hose onto 2 different diameter pipes.

Edited July 7, 2022 by Jonny TR6

[astontr6]

23 hours ago, Jonny TR6 said:

Here you go Waldi https://www.ebay.co.uk/itm/130639578599

I do still however have the issue of going from 4.7mm pipe (return from the MU) to 8mm (return to the fuel tank) if anyone can assist ? What do other people do ?

Hi Johnny,

There were some special fittings used by BL here to keep to one size of bore, My car is a 1973 car with a screw in adaptor on the M/U, not the push in interference fit brass tube, and another adaptor on the free running nut/pipe back to the fuel tank. Using a short piece of black nylon tube. Its all one size of I/D. As I have had the car from new, its all as OEM fitted.

Bruce.