Community Forums

YC1 · 02-24-2016, 10:06 AM

Quote:

Originally Posted by wch1940

To clarify a few things; The starter will spin when I apply 12v directly to it, and the Bendix will pull in when I apply 12v to it (separately). There is no voltage present
on either one when the ign key is turned to start pos.

This is a new clue. If I understand correctly you can actually turn the engine over but it does not start, correct? I am assuming you put the ignition switch into the run position when doing this?

YC1 · 02-24-2016, 10:13 AM

You stated you tested the ignition switch. How did you test it? And why was it changed before?

I have a hunch a voltage is missing that feeds the ignition switch. This same voltage could be a run voltage too.

You should see a voltage come out of one of the ignition wires when you turn it on and also likely see a switched voltage when turning the key to the start position. It is possible your ignition key sends a ground but that would be easy to check as well.

You may have a fusible link open as a previous posted suggested.

Have you contacted the factory to see if you can get a schematic?

twinboat · 02-24-2016, 10:18 AM

Quote:

Originally Posted by wch1940

To clarify a few things; The starter will spin when I apply 12v directly to it, and the Bendix will pull in when I apply 12v to it (separately). There is no voltage present
on either one when the ign key is turned to start pos.

You put 12 volts from where ?

Are you saying there is NO 12 volts at the starter ?

There should be 1 big cable with 12 volts, right from the batteries, unless there is a control in between. ( disconnect, solenoid, switch )

wch1940 · 02-25-2016, 04:51 AM

I have not, I have to wait until weather and my son's work schedule permit another
trip under the coach.

wch1940 · 02-25-2016, 04:57 AM

There is a solenoid between the battery and the starter (which I have not located).
The Bendix only is wired directly to the battery, a small solenoid I mentioned in earlier posts supplies a signal to the Bendix. To test the starter I just momentarily
jumped it from the battery using a jumper cable.

twinboat · 02-25-2016, 05:20 AM

Quote:

Originally Posted by wch1940

There is a solenoid between the battery and the starter (which I have not located).
The Bendix only is wired directly to the battery, a small solenoid I mentioned in earlier posts supplies a signal to the Bendix. To test the starter I just momentarily
jumped it from the battery using a jumper cable.

I am just trying to confirm that there is battery power to the starter mounted solenoid ( I think you are calling it a bendix ).

One big post should have battery power at all times. One small screw post gets power from chassis mounted solenoid.

If you cross the 2 big posts the starter motor spins.

If you cross the big post with the correct small one, the engine should crank.

Vanwill · 02-25-2016, 08:09 PM

What Twinboat (and others) have told you is the definitive way to determine whether it is the STARTER itself at fault, or the control circuitry that operates it. If you momentarily touch a small jumper (piece of #10 wire) from the very large terminal on the solenoid (that is connected directly to the battery) to the small terminal on the solenoid, one of three things will happen.

1) The starter engages and starts turning the engine over. In this case, BOTH the solenoid (which I think you are calling the Bendix) and the starter are good. Your problem is in the circuitry operating the starter.

2) You hear an audible "clunk" as the solenoid engages, but nothing else. In this case, your solenoid is faulty--it is engaging the starter gear, but its internal contacts are not connecting the starter motor.

3) You hear nothing, see no sparks. In this case, the solenoid is also faulty--it's windings are not connecting.

Only in case #1 do you need to keep looking--the next step is what Myron (and others) have suggested--trace the small wire from the starter's solenoid back to the next component, which is likely a relay/contactor of some sort. Then you perform the same kind of test on that next component--if its output terminals are connected together, does the starter engage and turn the engine? If so, something is causing THAT component not to operate.

The whole process can be tedious, but it is not complicated. Verify the starter works, then trace backwards toward the ignition switch. SOMETHING in that trace will be failing to supply power.

NHRA225 · 02-26-2016, 04:40 AM

Quote:

Originally Posted by Vanwill

What Twinboat (and others) have told you is the definitive way to determine whether it is the STARTER itself at fault, or the control circuitry that operates it. If you momentarily touch a small jumper (piece of #10 wire) from the very large terminal on the solenoid (that is connected directly to the battery) to the small terminal on the solenoid, one of three things will happen.

1) The starter engages and starts turning the engine over. In this case, BOTH the solenoid (which I think you are calling the Bendix) and the starter are good. Your problem is in the circuitry operating the starter.

2) You hear an audible "clunk" as the solenoid engages, but nothing else. In this case, your solenoid is faulty--it is engaging the starter gear, but its internal contacts are not connecting the starter motor.

3) You hear nothing, see no sparks. In this case, the solenoid is also faulty--it's windings are not connecting.

Only in case #1 do you need to keep looking--the next step is what Myron (and others) have suggested--trace the small wire from the starter's solenoid back to the next component, which is likely a relay/contactor of some sort. Then you perform the same kind of test on that next component--if its output terminals are connected together, does the starter engage and turn the engine? If so, something is causing THAT component not to operate.

The whole process can be tedious, but it is not complicated. Verify the starter works, then trace backwards toward the ignition switch. SOMETHING in that trace will be failing to supply power.

Excellent !

wch1940 · 02-26-2016, 05:45 AM

I thank everyone for their suggestions.
To clarify several things: The starter solenoid does not power the starter, There is no
electrical connection between the solenoid and the starter and no internal power contacts.
The "Bendix"solenoid is connected directly to the battery and is engaged by a signal from the small contactor I located on the roof of the house battery compartment.
The starter has 2 large gauge wires on it, one is from the boost solenoid and the other must come from the remotely located "in frame rail" solenoid. I have not tried cranking the engine I merely verified that both the starter motor and the starter solenoid function

barmcd · 02-26-2016, 06:40 AM

The way I have heard the term bendix used is the part of the starter that engages the pinion gear with the flywheel of the engine when the starter is needed to turn the motor. It also disengages the pinion gear from the flywheel when the motor catches and the starter is no longer needed. It is not the part that send cranking voltage to the starter when the key is turned.

twinboat · 02-26-2016, 06:44 AM

The "Bendix" solenoid is piggyback mounted to the starter motor. It has 2 funtions.

When power is applied to one of the small terminals it creates an electromagnet field that pulls a plunger back towards the large contacts.

When it moves the plunger back an internal lever pushs the "bendix gear" into the flywheel gear.

At the last moment of movement, it bridges the 2 large contacts.

1 contact (1/2 inch diameter bolt, 3/4 wrench) needs and should have positive battery voltage from a large cable from the battery.

The second large contact has a short, bent, metal link to the actual starter motor positive post. ( I have seen the links burn up)

On the back of the starter motor is a large (1/2 inch diameter) post. It is the negative post of the starter motor and must have a large ground cable that should go back to the battery negative post. If not it will be bolted to the chassis.

There should also be a small (10 gauge) ground wire that loops up from the ground post, to the second small terminal on the "Bendix" solenoid. That completes the circuit.

Some Bendix solenoids have over crank, temperature sensors, that break the electromagnetic circuit if the starter gets hot.

Probably not a factor here, but something to look for.

I don't know if this helps at all but I am just trying to lay out the system.

Good luck.

Vanwill · 02-26-2016, 07:21 AM

Perhaps many of us trying to help are visualizing a Delco-Remy type starter with a solenoid mounted on the starter that both engages the starter gear into the flywheel gear AND supplies power to the starter. Does this gentlemen have something like the old Ford starters which did not have a solenoid, per se? Those starters shifted the entire armature (which had a fixed gear on it) forward when power was applied? I'm having trouble visualizing what he is describing as a starter with no solenoid.

Mike Canter · 02-26-2016, 07:31 AM

Here are some pictures of the starter used on that model CAT diesels. They are a little different because they have another solenoid/relay mounted on the starter and that maybe what is confusing to people.