Diesel injector fuel lines

[Steve PaveyParticipant @stevepavey65865]

[Steve PaveyParticipant @stevepavey65865]

slightly off topic as it's a 1:1 scale engine, but here goes anyway. My boat engine is a Perkins, and the fuel lines are all badly corroded due to the salty environment. The price for getting new ones made up is very high, so I was thinking I could make some up myself. These are all the high pressure lines from the injector pump to the cylinders. 3 questions:

Where to source the tube (I think it has to be steel or some sort of steel alloy, copper won't stand the pressure pulsing as it work hardens)?

Is silver soldering adequate to join the tube to the banjo fittings, or should they be brazed?

What sort of torch? – I don't have anything more than a plumbers gas torch at the moment.

[Brian OldfordParticipant @brianoldford70365]

May I suggest you investigate the use of CuNiFe tube. It is/was used for replacement brake lines on road vehicles and once fitted, to replace OEM steel, would outlast the vehicle.

[DDTParticipant @ddt]

Hi Steve,

Buy the correct fuel injection pipes, the fuel pressure thats involved here can be as high as 15,000psi this is why the pipe has a thick wall, brake pipe just isn't up to job, a couple of other points if you look the length of the injection pipes they are all the same, this is for correct injection timing the other thing is, going back to the pressure of the system when a pipe fractures this will atomise, as it is sprayed around the hot engine bay sparks from the alternator or other ignition source and you will have a fire! so please use the correct fuel pipe for the job from a quality supplier…….DDT

[Neil WyattModerator @neilwyatt]

I looked into this when I had a fuel leak on my Mondeo. In the end I cringed and bought a new pipe from Ford, I couldn't wait for an affordable one to be posted and they were 2/3rds of the price of one made up by a local diesel specialist so shop around.

Neil

[EmgeeParticipant @emgee]

Steve, DDT has given a positive answer to your question, sounds like good advice to me.

Emgee

[Gordon WParticipant @gordonw]

You can get pipes made up to suit. Agricultural engineers etc. do them. Usually much cheaper than OE, You provide the old end fittings. DDT is right, big fire hazard esp. on a boat.

[John PParticipant @johnp77052]

Hi Steve ,
As DDT has said the best and safest policy is to buy the proper
pipework,it is important when you change these to inspect the pipe
fittings on the pump delivery valves and also the injector inlet fitting for
signs of erosion ,sometimes even a very small leakage can eventually
form what appears to be a worm channel across the face of the pipe
fittings and is a common form of leakage.

"Is silver soldering adequate to join the tube to the banjo fittings, or should they be brazed?"

Are you now talking about the same pipework when you refer to banjo fittings
as injector pipe has the nipple ends swaged directly on to the pipe,see
You tube video
**LINK**

As these sort of fittings would normally be seen on the low pressure delivery to the
fuel pump.

John

[Steve PaveyParticipant @stevepavey65865]

I wasn't clear in my first post – the pipe in question with the banjo fittings is the spill pipe for excess fuel, which I think operates at a much lower pressure than the injector lines. As,far as I can tell under the flaking paint and rust this has brazed or silver soldered fittings but I'm not certain as I have yet to dismantle it. I imagine the injector lines have formed ends and matching fittings to give a joint similar to a compression fitting.

I'm aware that the system operates at high pressures, which is why I asked specifically for advice on the material the pipes are made from. I'm also aware that pipes are often made up by agricultural engineers, so it really can't be that difficult. Unfortunately the boat and I are not close to an outfit that can make them up for me, hence the questions.

[Chris SheltonParticipant @chrisshelton11794]

If they are the spill pipes, then very little pressure involved, most modern diesel engines use plastic or synthetic rubber pipework normally just held with a small spring clip.

It might be possible to cut out the rusting bits of pipe leaving stubs that you could put the rubber type pipe onto.

Vauxhall dealers used to sell a length of pipe suitable for replacing spill pipes on the early Vectra diesels

HTH

[Neil WyattModerator @neilwyatt]

Ah – game changer!

As Chris says spill pipes are very low pressure and not critical in the same way as the delivery pipes.

Neil

[Mark BarronParticipant @markbarron78673]

As a designer of diesel engine fuel systems I strongly recommend you do not make these fuel lines yourself.

Either buy the OEM part or visit a professional outfit who'll make up the hose to your requirement.

Mark.

[Steve PaveyParticipant @stevepavey65865]

Managed to dodge the showers this afternoon and do a proper inspection – the spill pipe definitely has brazed connections to the banjos so that's no problem to replace – thanks for all the advice that it does in fact operate at low pressure. I also found a long-forgotten box of parts while looking for tools, which included a set of proper Perkins injector pipes – flakey paintwork but no rust, and a real bonus. Perhaps I should have done a bit more work before posting, but it's all useful information for the future.

[Howard LewisParticipant @howardlewis46836]

Before fitting the pipes found in the box, do flush them through to clean them. The holes in the injector nozzles vary in diameter between 0.013 inch to 0.021 inch, so can be blocked VERY easily, and that could mean a new Nozzle, which will be expensive. (If you can get genuine ones for an older engine)

And check that the pipes are all the same bore as the originals

The Injector pipes used on older Perkins engines (pre Emissions controls) will be Bundy (Which is actually thin steel sheet wrapped into a pipe form.) The ends will be formed, not fitted olives.

Those pipes have to withstand pressures of upto 600 bar. So don't force the pipes into place, and do use the proper clips, in the original position, to hold them. Ignore this, and you could have pipes break, usually when least convenient or safe!

Only replace high pressure pipes with ones of the same length and bore. (At Perkins, we used three different bores, depending on the output and application). Some may have the bore printed on them, under the paint

Fuel Injection pumps, especially rotary ones, are VERY sensitive to pipe length and bore.

As an ex CAV, and Perkins, Development Engineer, believe me that a vast amount of time and effort has been devoted to matching the Injector pump, high pressure pipes and Injectors to achieve the required performance.

And this includes the spec for the Governor, The DPA injection pump has about 30 different governor springs available, which can be fitted in nine different ways, to control a variety of metering valves. So the possible combinations of pump specs runs into hundreds, if not thousands.

Use any part, not intended for that particular combination and the starting / performance / fuel consumption WILL be adversely affected. You could even damage the engine in the short, or longer, term

If you need new H P pipes, buy the proper ones. The above will explain why they are expensive.

Beware of "spurious" Fuel Injection spares. I have checked out some of the "Afterrmarket" parts, and a lot is rubbish. Can you imagine a universal "one suits all four cylinder engines" pump? These have been offered, .and the chances of getting one that exactly suits the engine are pretty remote.

Howard

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