1993 Detroit 12V71TA goes from starting perfectly to starter not working at all after

[Dune]

the shore power was disconnected. So figure maybe batteries getting weak, reconnect shore power and it's starter still does nothing. Something similar happened years ago to the same engine (port) and the problem was major corrosion at the crimped fitting of the big red positive wire that connects to the solenoid. But this time (on the new wire) the fitting seems ok.

So the first question is, out of 12 batteries, some of which are "house" and some are engine start.... is it typical for each engine to use it's own set of batteries, or do both engines work off the same set of "engine start" batteries ? I ask, since if they each use specific batteries I could swap connections and see if the port engine batteries are iffy. I suspect in the end however I'll find yet another corrosion issue somewhere along the positive wire to the solenoid.

The nightmare would be if it's the solenoid itself gone bad...they aren't that expensive but removal and installation will require first removing much water piping and other stuff in the way....and still be a PITA even after than due to the weight of the solenoid and the tight space.

 

[MYTraveler]

In at least some circumstances (maybe most), when a DC motor (like your starter motor) is supplied less than specified voltage, it will pull more than specified current, and the excess current may flow a fuse / pop a breaker. Perhaps that is what happened?

 

[caltexflanc]

the shore power was disconnected. So figure maybe batteries getting weak, reconnect shore power and it's starter still does nothing. Something similar happened years ago to the same engine (port) and the problem was major corrosion at the crimped fitting of the big red positive wire that connects to the solenoid. But this time (on the new wire) the fitting seems ok.

So the first question is, out of 12 batteries, some of which are "house" and some are engine start.... is it typical for each engine to use it's own set of batteries, or do both engines work off the same set of "engine start" batteries ? I ask, since if they each use specific batteries I could swap connections and see if the port engine batteries are iffy. I suspect in the end however I'll find yet another corrosion issue somewhere along the positive wire to the solenoid.

.

Depends on the boat. Most will have individual start banks for each engine, and many will have a switchable parallel solenoid to mate them together when one side is weak. But that doesn't mean yours is that way. You'll have to get in there and start tracing cables. A multimeter set to continuity and a long wire clipped to one lead is handy for that.

 

[Ski in NC]

Is your system 12v or 24v? Most 12-71's are 24v start or above, I don't think any are 12v starters. Are your banks 12v or 24v? May have a series/parallel solenoid for 12v batts to crank a 24v engine.

In any case, need a helper to push the button and you walk through the start circuit with a portable meter. Find where volts are and where they are not.

Starter and solenoid should not be that hard to remove for service. Heavy, like 50-60lb, but I don't think any plumbing needs to be removed. Still a PITA.

 

[crashley]

connect a multimeter to the starter terminal and negative and push the starter button if you are getting 24 volts at the starter the problem is with the starter or solenoid but if no volts there the problem is between there and the batteries

 

[hmason]

Be sure to clean the ground terminal. Clean the positive as well even if it looks good.

 

[Lepke]

Included is a pdf for Delco-Remy HD starter motors. It has a standard wiring diagram and trouble shooting. It explains how the starter is energized and the various circuits.

 

[Dune]

Included is a pdf for Delco-Remy HD starter motors. It has a standard wiring diagram and trouble shooting. It explains how the starter is energized and the various circuits.

Nice, thanks everyone. Will let you know what I find out eventually.

 

[Baker]

Be sure to clean the ground terminal. Clean the positive as well even if it looks good.

Yep!! I had this issue, although on a smaller scale, I took a look at my battery connections and they looked fine. My neighbor came over to help he jumped down there and took the connections off and wire brushed them anyway and VOILA, that was the problem. I never would have gone down that route. I would have gone to the next rabbit hole(since the terminals appeared to be in good shape)...and that likely would not have turned out well.

 

[bayview]

Any clicking?

 

[Dune]

Any clicking?

No....dead as a doornail when I press the start button in the engine room....even the voltmeter stays exactly on 13.5 volts, but curiously when attempting start via toggle switch at the helm, the voltmeter needle actually moves *up* a little (like to 14 volts)...probably meaningless....but the only other reaction is the oil pressure warning buzzer goes silent and the oil pressure warning light goes out.

Probably meaningless as to what the problem is, except it tells me the "engine run" toggle is probably working at least.

Bottom line is today's testing reveals the problem is mostly likely somewhere between the engine start toggle or engine room "engine run' button and the electrical box that houses the two huge "can relays" between the two engines.

In other words, when I press the starboard "engine run" button there is aprox 26 volts at the main positive terminal in that box that runs to it's starter solenoid (with or without the wire actually connected to the terminal), but when I press the port "engine run" button there is zero volts at the same terminal (port and starboard starter solenoid positive wires are connected together at that terminal)

Until today I didn't realize that when one presses the starboard engine run button, 26 volts must flow to *both* starter solenoids (and vice versa when the port system is working properly), but somewhere there must be a relay that only allows that voltage to complete the circuit to the starter solenoid and then the starter of the engine one wants to start. I hope that makes some sense...might be clear as mud.

Otherwise..
1. Batteries and battery terminals are good (besides voltages, checked batteries with SnapOn load meter)

2. Continuity of the main positive cable to the start solenoid is excellent end to end.... zero ohms resistance.

3. The two large "can" relays (part J9844, if curious.. http://www.texasindustrialelectric.com/T_114_12_series_parallel_switch.asp) in the electrical box between the engines seem to work fine... I can feel them both engaging and the voltages match at all terminals when the starboard engine is in start mode.

 

[Ski in NC]

You have a series/parallel relay to get 12v batts to do a 24v start. Will take a bit of pecking around with the meter to find the fault.

 

[Dune]

Forgot to mention in last post that there are a couple of fuses involved in the system but they are both good and their receptacles are showing continuity at the wires as well.

A wiring diagram of the start system from Viking would be nice but probably hopeless. The start system wiring not involves the lower helm and the engine room box, but the toggles on the flybridge as well !

 

[koliver]

Nice, thanks everyone. Will let you know what I find out eventually.

Is there a long run of the engine harness, going from the engine up to the instruments at the lower helm? If so, is there a connector between two pieces of this long run? Is that harness running along the stringer that supports the engine, with the connector in a location that could at some time before you owned the boat, experienced flooding of the bilge? Pulling that connector apart may explain where the bad connection is.
Trace the harness, find all connectors. Pull them apart, clean, apply dielectric grease or at least spray with WD40. Re-assemble.
Good luck!

 

[Xsbank]

Do you have a transmission neutral switch? Check that too.

 

[Ski in NC]

Second that about checking neutral.

Do solenoids clunk when you hit start?

 

[Dune]

Do you have a transmission neutral switch? Check that too.

OMG....Yes...I'll bet that's all it is... that would make perfect sense as I was making sure the tranny engagements worked right before I shut it down and turned off the shore power.... and now that I think about it I do have a vague memory of the port transmission lever being way out of adjustment compared to the starboard lever position... will report back later today. One huge dope slap to me if that is it.

 

[Dune]

That was it folks. Been so long since that happened I forgot it was even possible. Now I wonder if I should just loosen the one screw on the port engine handle and line it up with the starboard handle or make the neutral adjustment at the transmission ?