Fuel Injector leak

I just installed new injectors in a 3 cylinder Ford 455 back hoe. Got it running, but have a leak at one of the injectors where the line from the fuel pump connects to the injector. Disconnected it, gave it as good a look as I could with the bad lighting I had. Reconnected it, and tried again. Does not leak as much but still does.

Ran out of time and had to switch to a more pressing job.

There is no seal in that connection .... is there?

Correct, there is no (replaceable) seal there. Next time you go back to it, try this. Put a wrench on the line nut, crack it loose and back it off just enough so it's not tight. Jam it down tight again. Loosen it again and jam it down tight again. Do this three times. You will see the wrench goes a little farther each time you do that. Then start it up and see if that helped.

Harry in Ky said:

Correct, there is no (replaceable) seal there. Next time you go back to it, try this. Put a wrench on the line nut, crack it loose and back it off just enough so it's not tight. Jam it down tight again. Loosen it again and jam it down tight again. Do this three times. You will see the wrench goes a little farther each time you do that. Then start it up and see if that helped.

Click to expand...

Hi,

I seem to be having a similar problem with my 1971 diesel MF135 -- a slow leak at the point indicated by the yellow arrow in my photo below. I tried your trick, and it helped, but didn't completely solve the fuel leak. I can see the logic, having to do with slightly deforming the nipple on the end of the aluminum fuel line, so that it forms a tight seal with the receptacle-end it plugs into on the injector. I tried your "3-times" method of loosening-tightening, and extended it to 5 times, but we're still leaking about 1 drop/minute -- just enough to threaten a fire, since this is the injector right over the exhaust pipe.

Could we possibly apply a thin coat of Form-A-Gasket to the nipple before insertion, and let it cure for 24 hr? That's more or less what Form-A-Gasket is designed to do, to seal up microscopic scratches and gaps on mating machined surfaces. The trick would be to place as little as possible, to make sure that no excess broke off and clogged up the injector.

What do folks think?

Oh -- note the handy special-purpose tool I made to tighten these injector nuts. It's a box-end wrench with a cut in it, just big enough to get past the fuel line. Works great. Use an angle grinder to make the cut.

Bill Knecht said:

Hi,

I seem to be having a similar problem with my 1971 diesel MF135 -- a slow leak at the point indicated by the yellow arrow in my photo below. I tried your trick, and it helped, but didn't completely solve the fuel leak. I can see the logic, having to do with slightly deforming the nipple on the end of the aluminum fuel line, so that it forms a tight seal with the receptacle-end it plugs into on the injector. I tried your "3-times" method of loosening-tightening, and extended it to 5 times, but we're still leaking about 1 drop/minute -- just enough to threaten a fire, since this is the injector right over the exhaust pipe.

Could we possibly apply a thin coat of Form-A-Gasket to the nipple before insertion, and let it cure for 24 hr? That's more or less what Form-A-Gasket is designed to do, to seal up microscopic scratches and gaps on mating machined surfaces. The trick would be to place as little as possible, to make sure that no excess broke off and clogged up the injector.

What do folks think?

Oh -- note the handy special-purpose tool I made to tighten these injector nuts. It's a box-end wrench with a cut in it, just big enough to get past the fuel line. Works great. Use an angle grinder to make the cut.

View attachment 65740

Click to expand...

So you made a flare nut wrench. Although, they are usually 6 point.
By the line on the back side of the flare, it looks like the line is not quite square with the injector. Can you bend the line around at all, enough to square it up better with the injector? Maybe should have left your wrench full length!

Bill Knecht said:

Hi,

I seem to be having a similar problem with my 1971 diesel MF135 -- a slow leak at the point indicated by the yellow arrow in my photo below. I tried your trick, and it helped, but didn't completely solve the fuel leak. I can see the logic, having to do with slightly deforming the nipple on the end of the aluminum fuel line, so that it forms a tight seal with the receptacle-end it plugs into on the injector. I tried your "3-times" method of loosening-tightening, and extended it to 5 times, but we're still leaking about 1 drop/minute -- just enough to threaten a fire, since this is the injector right over the exhaust pipe.

Could we possibly apply a thin coat of Form-A-Gasket to the nipple before insertion, and let it cure for 24 hr? That's more or less what Form-A-Gasket is designed to do, to seal up microscopic scratches and gaps on mating machined surfaces. The trick would be to place as little as possible, to make sure that no excess broke off and clogged up the injector.

What do folks think?

Oh -- note the handy special-purpose tool I made to tighten these injector nuts. It's a box-end wrench with a cut in it, just big enough to get past the fuel line. Works great. Use an angle grinder to make the cut.

View attachment 65740

Click to expand...

The ring on the bulge of the pipe is not supposed to be at an angle. I would bend the pipe tip upwrard just a fraction, then give it some tightening. I would not use goo on it. It is a metal to metal seal. Jim

Bob Bancroft said:

So you made a flare nut wrench. Although, they are usually 6 point.
By the line on the back side of the flare, it looks like the line is not quite square with the injector. Can you bend the line around at all, enough to square it up better with the injector? Maybe should have left your wrench full length!

Click to expand...

"Flare nut wrench" -- interesting! I'm just a shade-tree mechanic at best, and this is my first tractor. But, let me say this: I'm a retired psychology Ph.D., and yet, working on these machines is a really humbling experience. Doing it right takes intelligence, creativity, patience, and perseverance equal to just about anything I experienced getting my doctorate. I've come to have great, great respect for those here with high mechanical and electrical aptitude. I am drop-dead serious about that.

Janicholson said:

The ring on the bulge of the pipe is not supposed to be at an angle. I would bend the pipe tip upward just a fraction, then give it some tightening. I would not use goo on it. It is a metal to metal seal. Jim

Click to expand...

Makes sense. I'll give that a whirl & report back. My thanks to you and Bob.

Use NO sealer at that location or you risk sticking the injector tip valve. Lines are NOT aluminum either, but steel. The loosening/tightening trick USUALLY takes six or more tries if line is to seal. If the leak appears just back of the line nut the line MIGHT be cracked just inside the nut and leak will get worse when trying to wiggle the line back and forth. Only fix for a cracked line is replacement. CAV used to have the steel line end olives available to repair lines, but I haven't seen any for years.

On my Olivers, the injector lines are held tight with rubber lined clamps. I've had to loosen the clamps and nut at the injector to get lines started straight and then tighten nuts on injector and pump and then tighten clamps.

Dieseltech said:

Use NO sealer at that location or you risk sticking the injector tip valve. Lines are NOT aluminum either, but steel. The loosening/tightening trick USUALLY takes six or more tries if line is to seal. If the leak appears just back of the line nut the line MIGHT be cracked just inside the nut and leak will get worse when trying to wiggle the line back and forth. Only fix for a cracked line is replacement. CAV used to have the steel line end olives available to repair lines, but I haven't seen any for years.

Click to expand...

Yes, I noticed yesterday the lines were steel because they had some rust on them. That's what's making it hard to reposition the feed line. When I move it, it just springs back to its original position.

Question: If it turns out that nothing works, and it comes down to having to replace the injector and its feed line, can I replace just that one faulty set, or do I need to replace all 3 injectors and their feed lines?

Bill Knecht said:

Yes, I noticed yesterday the lines were steel because they had some rust on them. That's what's making it hard to reposition the feed line. When I move it, it just springs back to its original position.

Question: If it turns out that nothing works, and it comes down to having to replace the injector and its feed line, can I replace just that one faulty set, or do I need to replace all 3 injectors and their feed lines?

Click to expand...

You could try and swap some injectors around, I've done that before to try and stop line leaks.

Bill Knecht said:

Hi,

I seem to be having a similar problem with my 1971 diesel MF135 -- a slow leak at the point indicated by the yellow arrow in my photo below. I tried your trick, and it helped, but didn't completely solve the fuel leak. I can see the logic, having to do with slightly deforming the nipple on the end of the aluminum fuel line, so that it forms a tight seal with the receptacle-end it plugs into on the injector. I tried your "3-times" method of loosening-tightening, and extended it to 5 times, but we're still leaking about 1 drop/minute -- just enough to threaten a fire, since this is the injector right over the exhaust pipe.

Could we possibly apply a thin coat of Form-A-Gasket to the nipple before insertion, and let it cure for 24 hr? That's more or less what Form-A-Gasket is designed to do, to seal up microscopic scratches and gaps on mating machined surfaces. The trick would be to place as little as possible, to make sure that no excess broke off and clogged up the injector.

What do folks think?

Oh -- note the handy special-purpose tool I made to tighten these injector nuts. It's a box-end wrench with a cut in it, just big enough to get past the fuel line. Works great. Use an angle grinder to make the cut.

View attachment 65740

Click to expand...

inspect the line end that goes into the injector and the injector inlet. that line seals at the front and yes it is a bit cocked by looking at the sealing ring made by the nut but that is not where it seals the diesel. same deal as a JIC fitting. kinda looks like the sealing surface has some pitting on the line end.? so if you cant make it seal you need another line is what i would try.

Dieseltech said:

You could try and swap some injectors around, I've done that before to try and stop line leaks.

Click to expand...

That's an interesting idea. I'm adding it to my list of things to try.

Now that I think of it, I'm sure this leak originated back from the last time I had to bleed air from the fuel lines. I just hadn't noticed it till now.

On yet another note, p 112 of my Parts Book for the MF135 oddly shows TWO different, but similar-looking, fuel line assemblies for the Perkins engine's cylinder #1 fuel injector. The first line is part #738162M91, the second is #735678M91. The Parts Book lists #738162M91 as belonging to "Perkins 35354318", and #735678M91 as belonging to "Perkins 35355292". The lines for cylinders 2 and 3 have just one part number each. Moreover, I noticed yesterday that the flare nut for injector #1 (the one that's leaking) is a 5/8", whereas the other two nuts are slightly larger.

What's up w that? Two slightly different engine models? Could it be that a previous owner replaced the line with the wrong one?

Bill Knecht said:

On yet another note, p 112 of my Parts Book for the MF135 oddly shows TWO different, but similar-looking, fuel line assemblies for the Perkins engine's cylinder #1 fuel injector. The first line is part #738162M91, the second is #735678M91. The Parts Book lists #738162M91 as belonging to "Perkins 35354318", and #735678M91 as belonging to "Perkins 35355292". The lines for cylinders 2 and 3 have just one part number each. Moreover, I noticed yesterday that the flare nut for injector #1 (the one that's leaking) is a 5/8", whereas the other two nuts are slightly larger.

What's up w that? Two slightly different engine models? Could it be that a previous owner replaced the line with the wrong one?

Click to expand...

The original lines have 5/8 wrench nuts, I've seen some replacements with 11/16 nut size. Either will work, and MF MIGHT have superseded the original line with one from a different supplier.

The suggestions to have the line square or connecting straight on with its seat when held in position is probably the most important thing that can be done to assure proper seating for a good seal. Considering your background you may not be aware of the reaction of different metals under force. If you are, you will quickly find out those lines are not aluminum, that metal would be way to soft to withstand the vibration of the high pressure pulses within the lines. They are a steel alloy(meaning they have added elements in them to increase strength) and may also have a protective metallic coating on them. Another thing worth mentioning be careful not to get in the “line of fire” of a leaking injection line. When they are slowly forming a drip it is probably not an issue. If there is a spray or mist present be careful not to get to close the liquid is under a high enough pressure it can get injected into your skin. This requires immediate medical attention or it can lead to a required amputation. The same applies to hydraulic systems.

used red MN said:

The suggestions to have the line square or connecting straight on with its seat when held in position is probably the most important thing that can be done to assure proper seating for a good seal. Considering your background you may not be aware of the reaction of different metals under force. If you are, you will quickly find out those lines are not aluminum, that metal would be way to soft to withstand the vibration of the high pressure pulses within the lines. They are a steel alloy(meaning they have added elements in them to increase strength) and may also have a protective metallic coating on them. Another thing worth mentioning be careful not to get in the “line of fire” of a leaking injection line. When they are slowly forming a drip it is probably not an issue. If there is a spray or mist present be careful not to get to close the liquid is under a high enough pressure it can get injected into your skin. This requires immediate medical attention or it can lead to a required amputation. The same applies to hydraulic systems.

Click to expand...

Roger that about aluminum being too weak. I put in 20 for the FAA & know that commercial aircraft are basically big aluminum tubes, and that they have a limited number of duty cycles, expansion/contraction cycles due to changes in air pressure. An aluminum feed line would go through one duty cycle every time the engine was turned on, and possibly millions (I don't know) if the functioning of the fuel injector leads to pressure waves propagating through the feed lines (basically like the "water hammer effect" seen in household plumbing). An aluminum line would eventually rupture, is the end result.

Well... after considerable jockeying, the flange nut seems to be holding without leaking. Let me just thank all of you for the help. Y'all are super.

Now -- on to the next problem!

Bill Knecht said:

Well... after considerable jockeying, the flange nut seems to be holding without leaking. Let me just thank all of you for the help. Y'all are super.

Now -- on to the next problem!

Click to expand...

Yipee> Jim