Cummins QSB 5.9 No start

[tpires919]

Hi, I was wondering if anyone can point me where to look into my issue. This engine is in a boat. When I turn on my ignition switch I have the alarm and fuel pump noise coming on, but when I hit my start switch it is complete silence. I had this issue happen about 3 weeks ago and I removed all battery cables and cleaned them up and it fixed the issue until today, it started all over again. I am able to start the engine by jumping it at the starter or running a wire directly to the battery. I am unsure of where to look next. I plan on looking at the batteries again tomorrow night.

Topic

[Terry McDonald]

Hi. Have you found out the problem as to why it won’t start. I have the same motor and the same issue. My mechanic is pretty certain it’s the starter relay. And he has seen them go before ?

[tpires919]

Yep the fire suppression system isn’t rigged properly. During the repower it looks like they bipassed the entire thing. I had the bottle certified after I bought it. At the time they tested and it wouldn’t shut down engines, blower or generator.

Going to have that wiring fixed over the winter

[Dave Carlson]

Did you check the fire suppression system lockout?

[tpires919]

Also I did check and bypass the neutral safety prior to running the multimeter

[tpires919]

So it didn’t start again when I just went down to fill it up. I checked the relay, there’s volts going to it. I ran the whole circuit with a multi meter, I have 12 volts going everywhere until it gets to the harness. Talked to the mechanic at the marina this was the “box” he mentioned before, after talking with my Cummins mechanic, he told me it’s definitely the harness or a connection in that harness that is intermittently failing. He recommended replacing the harness.

[Fireisland1]

Look just next to the starter for a relay that goes to the starter solenoid.

[tpires919]

So went down there today, load tested the battery it checked out. Also engine fired up every time. So the interment issue continues.

[tpires919]

ty fireisland1, I will try a load tester on the battery tomorrow.

I cleaned up all the connections I could find and they seemed good. I voltage tested the mag switch and the starter today. They both showed constant 13 volts when battery was on, ignition on both showed 13 volts, hitting the start button did nothing so amps stood the same, both these volts are higher than my smart craft gauges show.

A mechanic from the marina took a look at it after I left, he said he found a “box” that has 12 volts going in but nothing coming out. I have no idea what “box” he is talking about, so I will have to have them show me unfortunately I can’t get down there while they are there until Monday.

[Fireisland1]

Do the basics.
Test batteries[ with a load tester ]
Clean All connections . This includes grounds all the way to the engine.
Key on, you should not see any voltage drop. >.2v
Check relay and solenoid connections.
Test key switch or jump out to test.
After all is complete if no start exists , test starter solenoid.

[tpires919]

wanted to add to this, when this first happened the relay switch was replaced as we thought that was the culprit boat worked for a few days and issue reappeared. Then I cleaned connections and it was fine for a few weeks. Also a multimeter to the battery shows 13.6 volts, yet when my ignition is on and gauges turn on, it only shows 11-12 volts.

[Author]

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