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MG MGB Technical - Bloody Hellfire (Almost)

As a proud owner of my recently purchased GT, I'm now working my way through all the basic servicing.

After running about 100 miles since purchase, I went for a spin and my son had a drive. After a few miles we could smell fuel, so headed back home, where I have an extinguisher in the garage!
On inspection, while there was obviously fuel leaking somewhere we couldn't see where from.

A quick poke around revealed the carb interconnecting line, when flexed, was producing high pressure microjets of fuel everywhere! This was changed but even under close examination it was hard to see any holes or cracks.

I renewed this and looked at the other under bonnet hoses carefully and they looked in very good order. But thought it best to renew all just in case, so added it to the list.

While working on her over the weekend, I had just replaced the rocker and side cover gaskets. I took the car out for a good 10 mile hard blast and pulled up on my drive over a sheet of cardboard, so I could spot any drips.

With the engine still running and hot, bonnet up, I was looking underneath for oil spots, when a torrent of fuel suddenly showered down !!
Jumping up, I could immediately see the rubber pipe from hard line to the front carb had split wide open with fuel pouring out.

Incredibly lucky it didn't happen driving, as the sheer quantity was seriously alarming and I think that before I would have realised, with all that fuel and air rushing in, I'd have been driving a fireball.

Two points to the post

1 - It would seem from what I'm reading that higher Ethanol levels in fuel are causing many such problems.
The pipe I sourced from a local motor factor has the date stamped on it and says unleaded proof. I was assured this is resistant to the new fuel additives.

2 - The old pipes looked in really good order. But my GT shows all the signs of light use and lack of maintenance over the last few years. Those new to these old classics need to have a good long look at their lines.

I'm sure most of you know your own cars pretty well and are aware of these problems. But next time you have the bonnet open, it would be well worth a good tug and inspection on all the rubber fuel lines. Or for the cost of 1M of new line and 30 minutes work , just change them.(
R owen

Rob,
its much more likely p*ss poor quality rubber products not ethanol

do not believe all you read about ethanol from the traditionalists - we had this decades ago when lead was taken out of petrol all kinds of scare mongering - same with when I used Mobil 1 in my classics engine, I was told it would do bad things including rot me teeth and steal my good looks - luckily I'm not a Daily Mail reader so I ignored it all

it's usually people who never use their classics that come out with with the scariest stories - I use my present midget as an every day car, it is my only car that sits outside 24/7, 365/6, it's not a garage ornament so if there are problems with petrols and oil I'm likely to find them

I've done a couple of post on PH for a newish BGT owner with the same problem as you, I'll post them up next
Nigel Atkins

sorry, forgot to put thanks for posting a warning and sharing information

below are my quotes from a different thread put up yesterday - note I'm not saying that the ethanol might not effect the older rubber but its role might be overplayed by the scaremongers, as I actually use my car and have used my various classics as dailies for nearly 25 years I think I can have some confidence in my experience

if you do an Archive search on here you'll find posts on p*ss poor quality modern made rubber parts (and other parts)

"you'll get more practice if you put on the wrong type of rubber fuel hose - and probably from here (PistonHeads) warnings and scare stories about E5 and E10 from those that don't use their MGBs enough (not forgetting the need for ZDDP in engine oil or you'll lose your looks and teeth and and the price of beer will increase)

no doubt the rubber hoses for the brakes are checked and fine, and the clutch hose, and the hydraulic seals, and the suspension bushes, ect."


"from more than one experience of duff fuel hose, I'd not use the modern made 1/4" rubber stuff but I would use use modern made 6mm (I found fits better than 1/4" on the carbs too) I used, from Halfords, G4509 Goodyear Fuel/Emission - DIN 73379-1 - 6.0 mm X 3 mm - 2B >NBR/PET/CSM<

if the rubber just split then the following might not apply - but if any rubber fuel line has deteriorated from the inside then hopefully up to the filter the filter will have caught the bits, the fuel filter should also have been changed at the service, after the fuel filter [i]IF[/i] the rubber hose has deteriorated from the inside after the fuel filter then some bits [i]might[/i] get into the float bowls or needles and seats in which case you might notice fuel delivery problems whilst driving, [i]IF[/i] this happened you'd be able to look at some JT vids that will help you see where everything is to clean out your fuel bowls and needles and seats"

"many modern made rubber parts for classics have been very poorly made for a few years now, I've had fuel hose that wouldn't hold petrol going back 2-8 years, at least four different examples from four suppliers including general motor factors and one mg specialist part supplier, the hoses has lasted anything from a week or two and then splitting to nearly two years before deep cracks appeared on a bend of the hose to the carbs"
Nigel Atkins

1. Do buy an MG!
2. Do change the rubber for good quality stuff. Cooling, fuel and brakes. AND check the tyre age!!
Allan Reeling

A couple of things that I have done to minimize any fuel leaks in the future. First, I got rid of all the metal braided fuel lines - impossible to see deterioration under the braid. Second and perhaps a better precaution, I replaced all of the flexible lines with hose rated for fuel injection -it is a better grade hose and designed for high pressure (much higher pressure than our SU pumps will ever put out. Cheers - Dave
D W DuBois

good point about rubber braided covered hoses especially modern ones and you need to extend it to modern made oil cooler hoses

btw if you have an oil cooler fitted you want to add an oil thermostat if not already fitted otherwise your oil could often be overcooled even perhaps during some English summer weather, during colder weather, regardless of time of year, the oil cooler should be blanked off if an oil thermostat isn't fitted
Nigel Atkins

What year is your car? 74 and later used very thin-walled rubber tubing for the carbs, and once you get one of those fail you really need to replace the lot.

Unless you buy fuel from a pump that is labelled '95 E10', which can have up to 10% ethanol which is known to cause problems, it won't contain more than 5% ethanol which won't cause these problems.
Paul Hunt

Good info there guys, thanks.

Paul - Mine is a 78 model. Pipe wasn't thin walled but pretty sure it wasn't original. Car had a rebuild some 10 years ago and guess it was changed then.

I've changed all rubber sections under the bonnet. Are there any more rubber sections? Haven't had chance to look that up yet or check the car over.

Too pleased with the way its running now and enjoying it everyday at the moment :>)
Rob owen

There are probably two at the pump.
Paul Hunt

that's the fuel line considered

if any rubber items, or items with rubber in them have been fitted in the last few years they're the ones to keep an eye on

flexi-brake hoses, braided oil cooler hoses, coolant hoses, suspension bushes, drop links, steering rack gaiters, tre boots, axle straps, door/window seals and wiper blade elements

well those are the ones that come to my mind at the moment, many are p*ss poor from new and that's without them seeing an E10, if the car has been parked near one of those pumps then deterioration will be even quicker
Nigel Atkins

All rubbers eventually harden with age as I've found out when buying my cars.
! got my 1980 GT in 2003 from an owner who'd pampered the car but due to illness, only driven the car about 200 miles/year in the previous 5 years. Test drive was fine, after purchase ; drove the 15 miles home and found the link hose between the carbs was split and fuel boiling off the exhaust manifold..
In 2010 I exchanged the GT for a V8 roadster that had spent most of the previous 10 years in a garage. In this case I'd covered nearly 200 miles before the pipe connecting the fuel pump to the metal supply pipe split. In both cases the pipe had lost all flexibility and snapped when flexed.. Once all the flexible fuel pipes with fuel injection rated hose were replaced - no further problems.

The late RB cars do have 2 flexible hose connections, 1st between the tank and the pump, 2nd from pump to metal pipe that runs beneath car to bulkhead.
V Todman

This thread was discussed between 23/06/2014 and 28/06/2014

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