Fuel Leak around Injectors

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Fuel Leak around Injectors

Postby Turbo67 » Wed Aug 12, 2015 8:32 pm

My 93 IC Cummins is leaking fuel around the front injector, but only when I drive it. I cannot make it leak idling or reving the motor.
Wets the injector and a little down the head if I drive it.
This is making it very hard to find the source.

Seems to be worse with the installation of the "Hot Screw" in the pump. I suspect because it is definitely pushing more fuel through the injectors based on the power and smoke.

I pulled it out, was very hard to get out, the nut was "crusted" to the body of the injector.
Replaced the copper sealing washer at the bottom after cleaning the injector body and the hole in the head.
Replaced the horse-shoe sealing washer on the return line.

Did not stop the leak.

Pulled it out again, disassembled it, hand brass brush cleaned the nozzle and the nozzle exterior seat down in the cap. Lapped the flat surfaces where the fuel transfers from one piece to the other with 2000 grit paper wetted with wd-40 on flat glass. Put it all back together. Still leaks, but again: only when I drive it.

What am I missing here??
Turbo67
93 Cummins 5.9L, VE Pump, 300,000 miles
4200 RPM Spring, indexed stock fuel pin, Fuel Screw maxed, then replaced with longer "Hot Screw", aneroid screw tweaked
Turbo67
fuel pin?
 
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Location: North Alabama

Re: Fuel Leak around Injectors

Postby thrashingcows » Wed Aug 12, 2015 10:15 pm

Is it coming "up" from the injector bore, or perhaps it's the injector line running to the top of the injector? I have had very stubborn lines that would not stop leaking. I have had to loosen, shift, re-tighten the line fitting at the injector many many times before I finally stopped the leak(s).
1984/93 Dodge Crewcab, W350, 1 Ton SRW, long box, 330K Km's, M&H spacer, 366 spring, fuel pin to deep side, 14cm housing, Piston LP, PS IC, Isspro Boost, Pyro and tach, NV4500, 29 spline NP205, 3.54's.


Check out the build....http://www.dieseltruckresource.com/dev/ ... 05923.html
thrashingcows
14mm rotor
 
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Re: Fuel Leak around Injectors

Postby Turbo67 » Thu Aug 13, 2015 3:00 am

thrashingcows wrote:Is it coming "up" from the injector bore, or perhaps it's the injector line running to the top of the injector? I have had very stubborn lines that would not stop leaking. I have had to loosen, shift, re-tighten the line fitting at the injector many many times before I finally stopped the leak(s).


I've had the injector out probably 4 times so far, so the supply line and return line have been off and on as many times. I don't think it is coming up from below as there are no bubbles around the injector nut. I have seen bubbles in the past and a new copper washer on the end of the injector along with a good cleaning of the end and the bottom of the hole stopped that.

What confuses me is that it will only leak under load. Stays dry at idle and winging the throttle.

I will run my finger around the line where it goes into the injector to see if a burr is there.

Thanks for the suggestions.
Turbo67
93 Cummins 5.9L, VE Pump, 300,000 miles
4200 RPM Spring, indexed stock fuel pin, Fuel Screw maxed, then replaced with longer "Hot Screw", aneroid screw tweaked
Turbo67
fuel pin?
 
Posts: 24
Joined: Fri Jul 17, 2015 8:50 pm
Location: North Alabama
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Re: Fuel Leak around Injectors

Postby Turbo67 » Thu Aug 13, 2015 5:44 pm

Some progress. Dried everything with carb cleaner, took it out back in the "field" and tried 2nd and 3rd gear gunning it in the grass. Dry as a bone. Then lined it up in the driveway and floored it just long enough for the boost and smoke to come up. Stopped, got out and it is leaking, but not the fuel nut. It is coming from further down. Either the return or the injector body.

It takes a load on the engine / drivetrain to make it leak.

Guess I'm going to pull it out again and inspect the sealing surface for the return and maybe open the injector up and polish the interior sealing surfaces some more.

Anyone on here had similar issues when rebuilding injectors?
Turbo67
93 Cummins 5.9L, VE Pump, 300,000 miles
4200 RPM Spring, indexed stock fuel pin, Fuel Screw maxed, then replaced with longer "Hot Screw", aneroid screw tweaked
Turbo67
fuel pin?
 
Posts: 24
Joined: Fri Jul 17, 2015 8:50 pm
Location: North Alabama
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Re: Fuel Leak around Injectors-FIXED!

Postby Turbo67 » Thu Aug 13, 2015 9:00 pm

Worked on the leak again this evening.
Removed the injector and examined the sealing surface where the return goes and the corresponding surfaces of the horseshoe washer. The washer did not seem to have a consistent crushed surface all around it. The injector sealing surface had some un-even spots and needed stoning and in a couple of minutes and it was flat again. Use a machinist's fine flat stone. Did the same to the return line banjo fitting for this cylinder. That was a little more difficult as it was still attached to the other 5 injectors. So I just carefully took a few passed on it till it was lightly cleaned up.

I then examined the banjo bolt and screwed it into the injector on the bench. Bolt started, but then got tight after about 2-1/2 turns. Broke out the dial caliper and measured the distance between the sealing face of the bolt and the injector body. Then compared that number to the combined thickness of the return line fitting and horseshoe copper washer. Turns out the bolt was becoming tight before adequate crush was being achieved on the washer. I had been reluctant to just keep tightening the bolt as it felt plenty tight. It is only about an 8mm or so diameter and I did not want to break it off in the injector. I worked the bolt in and out of the injector deeper and deeper each time to learn just how many turns I could go before it actually bottomed out. I counted the turns to achieve a little less space between the face and the injector body as compared to the overall thickness of the banjo fitting and washer. Then re-assembled everything, taking careful note of how many turns I applied to the banjo bolt. Snugged it all up and all is now dry!

I guess I could have just tightened till the leak stopped, but at the time I did not know what was wrong.

Through this experience I became familiar with the internals of the injector, so if I ever decide to replace the nozzles or set the pop off pressure, I know how it all goes together.
I also learned that old injectors that have been in place for a long time, need liberal soaking in a suitable solvent to loosen the rust. My hold down nut was locked to the injector body. I was not aware that these injectors have a ball bearing that aligns them with a slot in the head. I thought the nut was welded / machined into the injector body, not so! Learn from my mistake, soak things good, maybe apply propane torch heat, soak more. I nearly damaged my cylinder head and did damage the ball bearing in the injector body removing the nut as the injector "screwed out" with the nut. Not a good thing to have happen.
Turbo67
93 Cummins 5.9L, VE Pump, 300,000 miles
4200 RPM Spring, indexed stock fuel pin, Fuel Screw maxed, then replaced with longer "Hot Screw", aneroid screw tweaked
Turbo67
fuel pin?
 
Posts: 24
Joined: Fri Jul 17, 2015 8:50 pm
Location: North Alabama
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Re: Fuel Leak around Injectors

Postby thrashingcows » Fri Aug 14, 2015 2:31 am

Glad you got it finally sorted out. And it is never a bad thing to increase ones knowledge base. Thanks for the descriptions of the work you did...and the lessons you learned! ;)
1984/93 Dodge Crewcab, W350, 1 Ton SRW, long box, 330K Km's, M&H spacer, 366 spring, fuel pin to deep side, 14cm housing, Piston LP, PS IC, Isspro Boost, Pyro and tach, NV4500, 29 spline NP205, 3.54's.


Check out the build....http://www.dieseltruckresource.com/dev/ ... 05923.html
thrashingcows
14mm rotor
 
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Re: Fuel Leak around Injectors

Postby PToombs » Fri Aug 14, 2015 5:30 pm

Did your injectors have the seals between the nut and the injector body? There should be a square o-ring seal that goes in that gap to help keep water and crap out so that you don't have to go thru what you did.
pete

Just enough power to break everything behind the crankshaft.
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Re: Fuel Leak around Injectors

Postby Turbo67 » Fri Aug 14, 2015 7:55 pm

Yes that square seal was there. It broke when I removed the nut. But I replaced it with a new one. I think this motor probably sat in a salvage yard before I owned the truck, it has yellow paint writing on the side of the block, and its a 93 motor in a 96 body. Probably got water in there and rusted everything together.

Thanks!
Turbo67
93 Cummins 5.9L, VE Pump, 300,000 miles
4200 RPM Spring, indexed stock fuel pin, Fuel Screw maxed, then replaced with longer "Hot Screw", aneroid screw tweaked
Turbo67
fuel pin?
 
Posts: 24
Joined: Fri Jul 17, 2015 8:50 pm
Location: North Alabama
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