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3406b fuel in oil

40K views 30 replies 16 participants last post by  AaronF 
#1 ·
Hi, I have a 3406b 400 cat 7fb serial. The engine is pushing major fuel into oil, i'm talking 4-5 gallons in 100 miles. No smoking,rattling, or missing. Took valve covers off for about an hour watched lines, adapters, and nozzle retainers for leaks. Nothing. I was expecting to see fuel spraying everywhere. So could the problem be a nozzle under the retainer, transfer pump, or injection pump? Is there a simple way to test without disassembling everything? P.S. I had an o-ring under a bonnet on top of injection pump go bad, Caterpillar replaced o-ring.
 
#2 ·
The transfer pump would be my first guess since the MAJOR leak was not obvious with the VCs off.

But, you can take a syringe and needle (from the Farm-Fleet store etc) and pull some "oil" from around each injector and look to see if any one has an obviously different color indicating fuel. If that is inconclusive, take a CLEAN WHITE rag (towel) and place a drop or two of "oil" from the syringe on it and wait a couple minutes. If you see a ring of golden fluid around the black oil spot, you have fuel.

Obviously with that much fuel in the oil you would be looking for one "spot" to have a much more pronounced golden ring than the others.

Good luck!
 
#8 ·
Yeah Tony it is true and due I am electrician by trade and diesel mechanic second part however let me warn all readers anytime you open up the valve cover on any I say any electronic diesel engine expect pretty high voltage system in there I know I did work on one industrail engine that do run on about 315 volts or so AC and it have warning label near the electronic control panel.

I useally don't like to tell too many peoples a secrect how I do the testing on the Lucas electronic injector all I just used a common neon test light* and watch the flashing light when it blink on you know it working if steady on you have a bad controller or if not lit up either you have open connection or shorted connection somewhere in the system if you did get a short it will affect the next firing order.

Now get back to the OP situation my first guess will be injector transfer pump I know some of the them have O-ring in there and go bad over the time.

To troble shooting that unit follow Ynot's details he have right answer there.

Merci,Marc


* for test light make sure you get one it can read high as 240 volts and the other thing that if you getting DC instead of AC one side of neon light will be lit not both side of electrode.
^^^

This is a cool thread, and gettin better :happymugs

BTW Marc, all the motors here have the same warning sticker on em that shows the little stick guy gettin fried and falling. Kinda funny. And here they're all purdy set at 120vlts, but it's A/C, so you don't have the ground thing to save you if you get shocked. You just get blasted!! Cummins are the only ones sealed... Good job up there too man ^^ :thumbsup
 
#9 ·
^^^

This is a cool thread, and gettin better :happymugs

BTW Marc, all the motors here have the same warning sticker on em that shows the little stick guy gettin fried and falling. Kinda funny. And here they're all purdy set at 120vlts, but it's A/C, so you don't have the ground thing to save you if you get shocked. You just get blasted!! Cummins are the only ones sealed... Good job up there too man ^^ :thumbsup

Merci, Ynot.,

However ., let me pass a detail or two more along the way here.

Most of the electronic injector are " floating " power system which it mean that the system is not grounded at all not like the spark ingited engines the power source go to the electronic injector and go back to the controller aka ECM or Injector driver module one of the two.

Just want to remind all readers anytime you get near the wiring harness for electronic injector be extra carefull if you have to wiggle or check the connection make sure the engine is off and key is off postion { most ECM or injector driver do have some storta of setting that you need X of RPM to order to get them on }

Ynot let me chime in a trick here if you did verified that you get voltage to one of the electronic injector but the injector not firing properly a trick is get the clamp on anlog ampmeter and watch the neddle on the scale jump if not jumping then you have open coil in the injector if jump way too high then you got shorted coil.

( you should able get the factory spec for current drawage )

Merci,Marc
 
#5 ·
Good job John!! Very “Cattish” of you!! :thumbsup

Question. Does it miss? Was someone in the pump VERY recently? There are three places to look. The most common is what John said, tho you should see fuel just running out the spanner wrench holes for the nozzle adapters. It’s obvious what it is when you see it. If that is the case, replace the screws for the bleeds along with the washers. The screws crack at the head. $65 with nozzle dam seals for re-installation.

Second is the seat between the spacer and the barrel and plunger in the injection pump. Won’t happen unless someone was just in there and FUBAR’d.

Third is a broken tappet in the transfer pump. Just drop it down and wiggle the tappet plunger (steel thing stickin out the top).

If it’s a nozzle and it’s runnin down a liner wall, you wouldn’t be driven it. Good luck!!
 
#15 ·
Billy just curious. Did you ever solve your problem with fuel in Oil? I have the same problem. 3406C. opened the top, had it running, no visible leaks. also checked the Transfer pump. seems to be in good condition. Engine runs really good.
95% of fuel dilution in a B/C is the nozzle bleed screw. I'd put dye in it and pop the top again... :)

(sorry, i know this wasn't meant for me)
 
#18 · (Edited)
I remove the valve covers and take a rag over the cap nut and blow air into the other hole. If it comes out black it is good, if it comes out clear it is fuel and the injector is leaking, I have had them leak at not only the bleed screw but the top nut into the body.
 
#21 ·
I tried testing electronic injectors a few times and I watched the graph, pulse. It did allow me to confirm an open in the wiring.
 
#24 ·
The Autobots and Decepticons faught a deathmatch inside the engine.

Due to a badly cracked internal fuel line, the bottom end was flooded with fuel, drained axprox 18 gallons of oil/fuel mix out of the pan, and in the bottom of the pan there was the graveyard for the deadly battle. :swear

Damned thing (once oil/fuel was drained and fresh oil was put in) starts and runs like a top, just raps like a SOB! :swear

Time for plan E!
 
#27 ·
I do not ever remember seeing an internal fuel line crack, worn on the Jake head, but never cracked. One more thing to look for I guess.
 
#28 ·
A hard lesson learned for sure. From now on EVERY time I start an engine that I have done injector work to, the covers will be off for awhile so I can watch for any fuel leak. The line cracked right at the end of the line where the line goes into the compression fitting on the end near the intake.


theakerstwo, Ya I supose they are like republicans and democrats. They are the robots from the Transformers movies.
 
#30 · (Edited)
DIRECTED AT AaronF

I know Im digging up an old thread, but I am new to the site, and was wondering what the outcome was here. Did it trash the bearings? did you have to rebuild the motor? You said it was rapping pretty hard, so I would like to know what the rap was from?

Im looking at an 87 359 that has a broken number 5 injector line and a rap in the motor. I took a line with me when I looked the truck over. After putting a line on it and starting it, I heard the rap.With the rocker covers off I found a push rod with about an eighth of an inch of free travel, but could not see any obvious things that would cause the rap. The motor didnt have much blow by,and the rap sounds like its in the top of the motor.
The guy who has the truck said that there had been fuel in the oil about 500 miles after the rebuild, and the truck has been sitting ever since.
 
#31 ·
Long story short, all six of the rod bearings were in very small slivers/peices and looked like metalic sand in the bottom of the oil pan.

I don't know why the truck you looked at has fuel in the oil, but if there is 1/8" play in the valve adjustment, it sounds like one of the lifters broke/wore to me. Or a pushrod bent.
 
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