Cummins 6BT not starting

[Lee Kellerman]

Hey guys I’m in need of some help from the crew of the sb community. I have just finished a repower of my 1981 topaz 28 with a pair of 2005 Cummins 6BT 5.9m motors, CPL 8206, Delphi Cav injection pumps, these are government reman engines so not Brand new. The issue I’m having with one of the motors is that she’s not firing unless with a gas soaked rag over the turbo. Here are the steps I’ve taken to make sure all routes were covered: -injectors cleaned and rebuilt -fuel shutoff solenoid spring and plunger removed -plenty of air flow -Plenty of good fuel to system -ive cleaned the top end of my injection pump to make sure mechanical shutoff wasn’t sticking -hooked up a fuel bulb  and primed system while cranking to make sure fuel is getting to injectors. -good got batteries so plenty of cranking power …I’ll update if I can think of anything else. So here’s my latest issue I’ve found, motor is at TDC, and markings on inspection plate read setting should be at letter D, but when I look at the injection pump it’s set at C. Could the timing be my issue? If so is there a way of me being able to adjust it myself or is a Cummins technician required? I am at my witts end with this motor that is holding up a boat I need for commercial use. Any help or guidance would be greatly appreciated. Boat is located in SE Florida. thanks fellas. Lee Kellerman Hold Fast Boatworks llc          

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[Tony Athens]

Glad you stuck it out–You did good..

I’d ask the seller to “participate” if he told you something other wise.. 

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Lee Kellerman

[Lee Kellerman]

Update to this thread, I was finally able to get this issue resolved, pulled the pump and injectors and sent them in for rebuilds. Apparently the injectors were off in their pressure settings as well as the pump all gummed up from what i would guess was old fuel. Fired right up after being reinstalled and she’s running like a top, thanks for the info from everybody on this site.  

[Francis Valerio]

CAV pumps do not like to sit for long term storage.  They can be very temperamental to corrosion that can build up inside of them.

WITH THAT SAID… Do NOT pull the CAV pump at this time you still need to verify if you are getting proper fuel to the injectors.

I will ask again…Are you getting any smoke out the exhaust when you are cranking???  (or do you smell  unburnt fuel)?  This may ascertain that you are getting fuel in one or more injectors and getting close to primed….

The injector lines when “cracked” do not need to be very loose….just cracked.  When you have proper fuel they should be dribbling pretty good or actually squirting

On a CAV pump there should be a timing mark on the engine (timing cover) and a mark on the CAV pump that line up…that is your timing mark… if they are lined up or pretty damn close then you should be good enough to fire up.

I may try a touch of starting fluid to see if she will fire up momentarily just to confirm that this is a lack of fuel issue…These engines do not have glow plugs so starting fluid will not do any damage…just saying tho and I would not do it often and ONLY for troubleshooting purposes.

There are at least 2 different bleed screws on the side of a CAV pump (I think they are 8mm) that you can loosen and prime the system until they squirt fuel to make sure the pump is FULL of fuel.  These usually look like a nut with a small bolt in the top of it.  You use 2 wrenches…one to hold the bottom nut and the other to loosen the actual bleeder bolt. (maybe a 10mm and 8mm??? I forget off the top of my head)

If it is full then you crack the injector line and crank like stated in the post above.

Even though the diesel Injector pump squirts fuel under extremely high pressure it will only show as a pathetic dribble from a completely open injector line.  When the line is only slightly cracked it will present itself as more of a powerful squirt.

These things sometimes can drive you crazy and just dont jump the gun and get ahead of yourself and start tearing things down…. there is a possibility that the most basic thing (like checking fuel at the injectors) is just not being checked correctly.  These are dirt simple engines and are very very reliable but they do NOT and will not run if there is air in the fuel system.

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Lee Kellerman

[Lee Kellerman]

Clark,

I have cracked the injectors while cranking, in several orders. One, then some, then all at once. Same results each time, fuel pushing through but not from what I can tell at a heavy spray rate. I’ve used the fuel from the boat, 5 gallon jugs over the motor, fuel bulb inline and dyed diesel and pump diesel so I could tell when the color changed and was flowing through. I pulled the injectors and inspected them as to find any debris or whatever might be causing an issue and nothing…I know I posted that these were sold as zero hour motors, from the sellers listing but I did notice discoloration inside the cover of the injection pump causing me to think they were ran at least once. It looked to me as old fuel sat in the pump and possibly??? Could have gummed up the fuel system??? Also the injectors looked as if they were brought up to a temperature as well. I cleaned as much of the parts as I could without interrupting any settings. The mechancal shutoff was pretty sticky and didn’t move freely in the beginning.

I’m pretty novice when it comes to mechanics of diesels but get the gist of their workings…I have been staring at the manuals for the cav pump for the past two weeks and know that I’d rather have a shop dive into the pump and definitely not me. I was just wondering if the timing could have been my issue since from what I’ve read via manuals that the motor inspection placard says for TDC setting to be on the letter D and my pump through the inspection plate is set on letter C. Once again I know very little about this topic and was just looking for some insight from the pros on here. I’ll try to think if I’ve left anything out and post back on here. Once again thanks to everyone for any help. This is one of my towing and salvage rigs that I run throughout the islands and the US and would take any lessons to learn about the engines with good faith. 

[Lee Kellerman]

Tony,

I purchased these motors from adelmans trucking, a company that Had a good reputation of engine resales from what I researched. They bought a large lot of these motors from a government auction and relisted them, as zero hour rebuilds in good running condition. I had them on pallets since may and had to convert the 24v to 12v systems, add heat exchangers, and raw water cooling pumps. Redesign motor mounts for my application and have exhaust elbows made up( sbmar showering bells of course). The motors were setup for the rib boats with outdrives I believe. I did run both motors before install but had the issue with one other than running on a fuel rag, yes I know pushing the install was foolish but I had run out of time and space where the engines were stored. Worst case scenario I can pull the engine and go from there, not an issue but hate to have to do it….

[Francis Valerio]

Just to add to this thread… 100% you MUST VERIFY FUEL AT THE INJECTORS!

(are you getting smoke out the exhaust when cranking?)  I do NOT think this is a timing issue but rather a FUEL issue…

 

You need to crack loose an injector line and crank the engine.  If you get no fuel there then you must dig deeper and verify there is no air in the system.

 

If this is a govt surplus engine that was stored then it prob has no fuel in the IP.  You can bleed the air out of the IP as well.  CAV pumps can be tricky sometimes BUT if they are full of fuel you should be good to go…

 

VERIFY and we will help you

2 users thanked author for this post.

Lee Kellerman, Tony Athens

[Tony Athens]

I am kinda being blind sided here as to this thread.. You bought a pair of engines from ??, and installed them without running them before the install , or actually “seeing” these exact engines run?   If so, may I ask who supplied them and what  the  ” supplier”  told you” . Why?  Because let’s warn others to be more diligent in used engine purchases from ???.  The internet and this site goes a long way to help in “both directions… yea  & ney

If you did “see” them run, then we’ll move past this and try and sort it out between me, you,  and the seller…………………. Tony

[Clark Leighs]

No one yet?

 

Are you positive the engine is getting fuel to the injectors?   Have you cracked , very loosely,  the nuts at the injectors and seen fuel spit out in a good squirt,  not just an anemic dribble?     DOne at least 3 injectors like that?

Tried a jug of CLEAN fuel above the engine for gravity feed to eliminate any likely hood of a failed lift pump?

Put it through the last filter just before the lift pump though as you do not  want dirt entering the injection pump or injectors.

 

With the gas from the rag getting it to fire there is life in it yet but if the timing is off  it won’t matter except to indicate there is life.    

As far as the timing I can’t help you.   

Try to get a shop  manual which is always a good idea to have.   Some owners manuals will also have this info.

Hopefully this provokes some interest about the timing issue.

 

[Lee Kellerman]

Here’s a few pics of the project 

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