6BT5.9M not starting ..again

[Ex Sailor]

Got a pair of 6BT5.9M 1988 vintage @ 3200 hrs. ea.
Since getting the boat in 2014, port engine started having intermittent starting problems. At beginning of this season, we had the injectors overhauled, filled the tanks and the thing was fine all summer ( 100 hrs. ) . Prior to haul out recently and after oil changes, the port engine would not start again ! Had to crank quite a bit ( there was no sign of it trying to catch .. just dead crank ! ) and on the 3 rd. / 4 th. 30 sec. crank cycle, the thing would start. Once starts, it runs fine .... although it did quit " once " right after start at idle rpm.

Marina Tech thinks it could be the lift pump as a start ..... then maybe the fuel shut off & sol. ... ? and so on .... he's not sure at this time.
Of note: The fuel is @ 1/2 tanks, ( tanks are plumbed together ) filters are very clean too and are full of fuel.

As a side question and when priming by hand at the lift pump: should the ignition switch be in the ON position ???

Any comments, thoughts would be appreciated before we have the Tech dive into this this thing @ 125.00 / hr.

Tx in advance .... F

 

[sunchaser]

Yes, it does sound like fuel starvation, the "why" is the puzzle. Why are you priming by hand? Will it re-start ok after a short shutdown? If yes then check for loose connections in the fuel lines or filters allowing air into system. If original lift pump then maybe that is culprit.

Be careful on long start attempts. Water can enter engine through exhaust.

 

[gaston]

First thing I would do would be remover an injector place it in a tin connected to the rail pipe then turn the motor over and see if any fuel is getting to the injectors ???

 

[Ski in NC]

When engine cranks but not starts, go verify that the shutdown solenoid has voltage to it and connection is tight. Common for blade connector to vibrate, fret and wear and then have a poor connection. Unplug it and plug it back in, should hear a faint click.

I think the solenoid on this engine is powered up to run, power off to shut down.

If ok, you may have a weak lift pump or a source of air in fuel supply, somewhere. If racor is indeed staying full, a fresh lift pump may be the least costly next guess.

 

[Ex Sailor]

Yes, it does sound like fuel starvation, the "why" is the puzzle. Why are you priming by hand? Will it re-start ok after a short shutdown? If yes then check for loose connections in the fuel lines or filters allowing air into system. If original lift pump then maybe that is culprit.

Be careful on long start attempts. Water can enter engine through exhaust.

Tx ... I should have mentioned in OP, it will not re start after a shutdown, eg. after finally getting it going, we shut down at the pump out for 45 min. ( engine was hot, as we ran it for awhile prior ) and it would not re start.... then the cranking again to get into the lift area.

The priming by hand thing just came to me from when we re installed the injectors and had to prime the system ... so I was wondering what state the shut off sol. should be in or is it even related when priming by hand.

 

[Ex Sailor]

When engine cranks but not starts, go verify that the shutdown solenoid has voltage to it and connection is tight. Common for blade connector to vibrate, fret and wear and then have a poor connection. Unplug it and plug it back in, should hear a faint click.

I think the solenoid on this engine is powered up to run, power off to shut down.

If ok, you may have a weak lift pump or a source of air in fuel supply, somewhere. If racor is indeed staying full, a fresh lift pump may be the least costly next guess.

Tx. Ski, as luck would have it ... it's the engine with the worst possible access to the lift pump or the Sol. ....

 

[gaston]

Temporally fit a gravity tank to eliminate everything from before the injector pump

 

[Ex Sailor]

When engine cranks but not starts, go verify that the shutdown solenoid has voltage to it and connection is tight. Common for blade connector to vibrate, fret and wear and then have a poor connection. Unplug it and plug it back in, should hear a faint click.

I think the solenoid on this engine is powered up to run, power off to shut down.

If ok, you may have a weak lift pump or a source of air in fuel supply, somewhere. If racor is indeed staying full, a fresh lift pump may be the least costly next guess.

Ski, we will look into it ( the click ) but the boat is on the hard ...... on the other hand, is there a chance that the Sol. may click but the mechanical connection / or the shut off may be misaligned .. ? reason I'm saying, I had this happen when my Gen. would not start with a key. The linkage to the shut off got out of alignment and that Gen. Sol. would not bottom out.

 

[OldDan1943]

My best advice, get a factory approved tech out there and get the problem fixed once and for all.
That "let's replace this part and see what happens.", gets real old and expensive after about the 4th replacement part.

After 2 or 3 long starts, drain the mufflers.
Fuel starvation, hmmmm, lets rebuild the fuel pump.
Could be something as easy as the fuel is draining because of an air leak. Trace the fuel lines back, looking for signs of fuel leak.

 

[Sugardog]

When engine cranks but not starts, go verify that the shutdown solenoid has voltage to it and connection is tight. Common for blade connector to vibrate, fret and wear and then have a poor connection. Unplug it and plug it back in, should hear a faint click.

I think the solenoid on this engine is powered up to run, power off to shut down.

If ok, you may have a weak lift pump or a source of air in fuel supply, somewhere. If racor is indeed staying full, a fresh lift pump may be the least costly next guess.

I replaced my blade connectors with eye/screw. Sounds like fuel drain back. I've always had good luck with 5.9's.

 

[Ski in NC]

Ski, we will look into it ( the click ) but the boat is on the hard ...... on the other hand, is there a chance that the Sol. may click but the mechanical connection / or the shut off may be misaligned .. ? reason I'm saying, I had this happen when my Gen. would not start with a key. The linkage to the shut off got out of alignment and that Gen. Sol. would not bottom out.

Solenoid just moves a little plunger. I'm pretty sure that if you hear the click, it can be assumed to be working. I think when they stick, they do not click. But been a while since I have fiddled with one.

CAV pump also can be very sensitive to air getting in from somewhere or drainback. Can be a devil to reprime.

 

[Ex Sailor]

I replaced my blade connectors with eye/screw. Sounds like fuel drain back. I've always had good luck with 5.9's.

Thank you, I'm not a gear head that said, where / what is the cause of drain back ?

 

[Cigatoo]

“I'm not a gear head that said, where / what is the cause of drain back ?”

Air, which is usually caused by a loose connection, split hose, cracked fitting, Racor filter not sealed correctly, or the like.Has anyone changed a fuel filter lately and not reassembled the Racor correctly?

Follow the fuel!

 

[Sugardog]

Back in the day when we built boats for in import industry, all wiring was screws, no push on. Failure was not an option.

 

[Jetstream]

Ski some boats do need the ignition switch on to use the hand primer. We had 6BTA's in our boat and she had fuel shut off solenoids on the tank outlets wired to the ignition switches. Have to agree with Old Dan about the starting problem They are not a complicated engine but get someone who knows them to have a look and it might save you a lot of time and money in the long term.

 

[Xsbank]

“If you can’t fix it with a hammer it’s an electrical problem.”

Shut-off solenoid. There’s a reason that there are so many of them for sale. Should be really easy to test, disconnect the lever and manually open the shut-off. If the engine starts, that’s it. You will have to stop the engine manually.

 

[OldDan1943]

This is the 3rd or 4th time I have been told, I am correct.
Someone call my ex-wife and tell her.

 

[Chrisjs]

I second careful check of fuel solenoid. Had an issue once where the engine (same model as OP) would crank but not start. Turned out there was enough juice in the battery to crank but not enough to deal with the solenoid at the same time, so the solenoid stayed closed. Replaced the solenoid before I discovered the problem was the starter battery. Fortunately an inexpensive part from the Cummins truck store.

 

[Pgitug]

To replace the fuel solenoid is about $300+. Take the time to eliminate this by removing the solenoid, check the electric connections and BEFORE you put it back wire the shut down linkage open. You have now taken this part out of the equation with little effort.

 

[Chrisjs]

Agree with your comments, Pgitug, except for price. You can easily source a Cummins replacement for under $100. My recollection is my Cummins part cost around $75 a few years back from the truck parts store. Also, there are generic available for less than the Cummins price. Fitting is easy and does not require "marine mechanic".

 

[Ex Sailor]

Anyone know what the thing is that's sitting on the side of the Hi Press. pump .. ? is that the shut off solenoid ?

Tx FB

 

[Chrisjs]

Here it is:
https://www.sbmar.com/articles/cummins-marine-6bt-fuel-shutoff-solenoid-location/

 

[Ex Sailor]

Here it is:
https://www.sbmar.com/articles/cummins-marine-6bt-fuel-shutoff-solenoid-location/

Tx. Chris ...... duuhhh I'm dumb !

 

[Yobbo]

How did you go did you fix this?

I had a similar problem after doing a fuel filter change, I could get the engine running but it would starve for fuel and die, and I would have to reprime the fuel system again, I was scratching my head for a while after all these are pretty basic, i then realized the old filter I took off did not have a rubber O ring on it, I removed the new filter and found the old O ring was still on the fuel filter housing, I removed the old O ring replaced the filter, reprimed and have not had a problem since, but now I always double check with any filter change that the old O ring is off first.

 

[Mr. Blu]

Reading this thread I remembered a situation with our Cummins.We once had a problem with starting the engine which (after half a day searching) appeared to be caused by one of the push buttons to shutt off the engines. This button was mounted on the flybridge of our President 385 Sundeck. For some reason, moisture or dirt, the push button made a connection which therefor continuously deactivated the solenoid. No problems whatsoever before. If you have a shut off button on the engine check them by disconnecting it. Maybe this is the answer to your problem. Good luck. Cleaning the button with WD-40 did the trick.


You can also connect a wire directly from the + of the battery to the solenoid. If then the engine starts (or if you hear a click) you know that the solenoid does not get (enough) Volts.

 

[Xsbank]

This:

 

[Maerin]

This:

Sorry, that's not the solenoid for the CAV pump. It's this:

https://www.ebay.com/itm/CAV-DPA-12...id-Switch-Stud-type-single-conn-/390558387709

And you can see it's not in the hundreds of dollars as reported. If it's in fact in need of replacement, it's an easy job.

A reliable test to eliminate the solenoid as the problem is to unscrew it from the pump, remove the plunger and spring, and screw it back in. If the problem disappears, the solenoid is the culprit. You can run the engine that way until the replacement part arrives, but you'll need to shut it down at the injector pump. The shutoff lever is on the top of the pump throttle housing, it's in the upper left corner opposite the throttle cable, and is a short lever with a spring. Just rotate the lever and wah-lah: Shut down.

I had one go intermittent- how sweet, it would just shut down, no warning. Started right back up. Disconcerting.

Priming, as Ski indicated can be a bear. Put throttle wide open, hand on the ready while cranking. Be careful you don't load up the exhaust with water, you may want to close the thru-hull to prevent that until it fires.
There are two priming ports on the pump, on is on the side of the throttle housing, the other is on the circumference of the distributor section of the pump at about 10 o'clock looking at the fuel line end of the pump. It helps to purge them if the pump gets air.