65 Mustang, fuel hose leak at clamp; where it meets pump.

[StephenSLR]

I keep getting leaks at my fuel pump inlet and outlet hoses. The fuel pump has the same size inlet/outlet pipe diameters but previously I had 2 sizes of hose on the pump, 1 x 10mm hose at the outlet and a smaller hose at the inlet, I'm assuming 8mm.

I replaced both hoses with new 3/8" fuel injection hose, it fitted snugly with a bit of a push to get it on. The line to the carb is same size as fuel pump inlet/outlet and same size as the fuel filter inlet/outlet however I notice the fuel line where it exits the chassis is smaller OD. I've also replaced the old clamps with stainless steel clamps.

The leaks stop when I tighten the clamps so it's not the fuel pump; I don't think.

I drove my car down to sisters (over an hour away), it sat for over a month and when I started it up it was leaking again. I tightened it up with screwdriver and drove to Picton for Cars N Coffee. Just before leaving I started it and checked underneath; no leaks.

I drove to Sydney and later that evening I headed out to the Mystery Cruise. It leaked again as I left my garage, this time I tightened it with ratchet spanner and there was considerable slack, it needed a few quarter turns. Drove from Parramatta to Newport for the cruise, drove back home no problems.

I started it up this morning and it was leaking again; I tightened it up again with the ratchet and there was considerable slack in the clamps; again a few quarter turns to tighten them up again. This morning only the outlet was leaking, usually it's both but both clamps needed a few turns and I don't over-tighten.

I have a feeling that when the car gets hot it expands the inlet and outlet pipes thus expanding or loosening the clamps and/or the hoses; when it cools down again the inlet/outlet pipes shrink but the hose and or clamps do not.

Here's a picture of my set up.



I guess my next course of action will be to attach a brass fitting and pipe going up to meet the carby pipe and have hose connector joining the two. However, it would still leak at the inlet pipe; unless this can be changed so the pipe is longer?

s

[boofhead]

Does the pipe have the barb or is it just tube? I ask because the clamp keeps the pipe there while the barb acts as the seal point(s).

[StephenSLR]

Does the pipe have the barb or is it just tube? I ask because the clamp keeps the pipe there while the barb acts as the seal point(s).

Barbs on both inlet and outlet, not sure if it's visible in the photo but you can make out an oversized lump just after the clamps.

s

[hybrid]

Are you sure some of the hard line is not cracked?

What you describe is really strange - barb or no barb.
Tightening that clamp with a spanner should be more than enough to seal it and keep it that way. You're talking less than 10lbs pressure generally.

Which line is leaking? Suction side or pressure side?

[StephenSLR]

Which line is leaking? Suction side or pressure side?

Both inlet and outlet leak; the leaks stop when I tighten the clamps; each time it leaks the clamps are somewhat loose, it's as if either the clamps unravel or expand or the hoses are shrinking.

It doesn't leak from anywhere else; I'm also thinking perhaps to ditch the pump altogether for a new one with attached filter with the pipe up to carb and see if it's any better.

s

[hybrid]

If you think the clamps are coming undone or the pipe is shrinking slightly (mind you, I've never heard of either happening), you could try one of the old school clamps that you expand with pliers to get on and then let go.

They should automatically take up any slack.

[StephenSLR]

If you think the clamps are coming undone or the pipe is shrinking slightly

Metal expands with heat and contracts when cold; I'm thinking the hose being rubber, expands when hot with the pipe but the hose doesn't shrink back to its previous state as rubber is not truly elastic whereas metal is.

It seems to happen after cooling off after a long drive; where the engine would be much hotter than short drives.

It's the only thing I can think of; of course I could be wrong.

s

[hybrid]

Yeah it's just that every engine would go through that same process and they don't leak. The hose can only expand as far as the clamp allows.

[mert]

Is it properly sized fuel rated hose? As OEM only used a simple spring clamp (I've never had one leak there) to me it points to faulty hose...

[65muzzy]

It could be the pump leaking and dripping onto the lines?

[hybrid]

Is it properly sized fuel rated hose? As OEM only used a simple spring clamp (I've never had one leak there) to me it points to faulty hose...

Right, so spring clamp is the right name

[ponyride]

I replaced both hoses with new 3/8" fuel injection hose, it fitted snugly with a bit of a push to get it on. The line to the carb is s

I'm pretty sure the flexible fuel line in the earlier cars is 5/16". It shouldn't take just a bit of a push to get on, they should be hard to get on and a real bugger to get off. I'm positive a smaller diameter hose will fix the problem.

The clamp shouldn't really be doing all the work to prevent leaks, which it sounds like it's doing when you tighten it up. If you replace the hose it might be worth getting some top notch clamps as well (they do vary in quality), or the original spring type as mert mentioned.

[StephenSLR]

I'm pretty sure the flexible fuel line in the earlier cars is 5/16".

The line poking out of the chassis is smaller; the fuel filter, pump and line to the double pumper is larger. I'm assuming it's 5/16 and 3/18 respectively.

I previously had 5/16 from filter to pump and that would leak too.

It could very well be an issue with the pump but it has me baffled.

s

[mert]

Right, so spring clamp is the right name

Umm... yes. But you can call it a bendy-fuely-leaky-stopper if you want... :rotfl:

Its a circular compression spring... more correctly a "flat wound spring clamp". The common after market worm type were not used very often by FoMoCo, and are not really that great IMO. I avoid them completely for OEM style, as cheap and available most go right for them...

http://www.amkproducts.com/bulk3.asp?part=B%2D10055

+1 on

they should be hard to get on and a real bugger to get off. I'm positive a smaller diameter hose will fix the problem.

[StephenSLR]

I have spring clamps on my Torana; haven't had a leak in 30 years.

The Mustang OEM is this style isn't it?



s