Engine start problem - starter circuit?

[Streetcar]

I went to start up Volve Penta TMD31B after cyclone season.

First go I got a solenoid click only. Second go I got nothing - apart from a chattering sound from the relay in the starter circuit.

This relay is activated by the low current (primary) starter circuit and in turn completes the medium current (secondary) circuit to activate the solenoid (which then in turn completes the high current tertiary circuit to the starter motor).

I dont get any losses in the high current tertiary circuit and the batteries are good. However when the relay is chattering I dont get any voltage to the solenoid. The contacts in the secondary circuit seem fine and its a very short length of wire.

My best guess is that there is a low voltage in the primary starter circuit so that the relay does not activate properly and chatters on and off. In my guess, this then means there is no proper completion of the secondary curcuit and so the solenoid never gets a full load.

Does this sound reasonable, or could here be another explaination? If so what kind of faults should I be looking for in the primary starter circuit? Could it be the starter switch (keyed switch) itself? Any suggestions appreciated...

[DougR]

Your description/evaluation of the circuit is correct, and so it should be a fairly simple matter of following the circuits and finding the problem. A couple of things to check:

- voltage level at the red B+ wire on the back of the key switch. This needs to be full battery voltage. This receives its voltage from the black connection box on the engine after feeding thru the circuit breaker in that box.
- voltage level on the red/yellow wire coming out of the key switch when the key is turned to "start". This red/yellow feeds the low current start relay on the engine.
- the red/yellow wire coming out of the key switch on VP panels immediately goes to a connector in the wire which is put there to provide a connection for a neutral safety switch. Could there be a problem with the neutral safety switch?
- corrosion issue where the low current relay sits in its connector socket?
- low current relay grounds into the engine wiring harness which finds ground at the neg. pole of the alternator......problems with the ground there?
- bad low current relay?
- corrosion in either end of the engine/panel wiring harness?

Hope this helps.
DougR

[barnakiel]

Try:

1) contacts (some humidity? some corrosion? etc)

2) if a spare relay available, swap one by one,

3) and make sure the battery is full and sound ......

BTW I have seen relays fail in unexpected ways.

b.

[sailorboy1]

In my experience the problems are normally bad wiring in the start circuit or a bad start switch. Jump the supply to the relay directly off the starter primary, if the engine starts it is in the start circuit.

[Xlantic]

If you have battery jumper cables you can jump from the + of the battery directly to the starter to help diagnose the problem.

You can also jump from the - terminal of the battery to a good ground on the engine to check that the problem is not a faulty ground connection.

[seabreez]

Originally Posted by Streetcar

I went to start up Volve Penta TMD31B after cyclone season.

First go I got a solenoid click only. Second go I got nothing - apart from a chattering sound from the relay in the starter circuit.

Definitely a problem with the positive or ground cables. Check for corrosion or bad connections at cable ends. Check for voltage drop at the connection to post at the battery and connection to stud on the starter. Anything more than .2 of a volt drop is too much. Bypass the cables with booster cables to test. Then if the problem corrects itself then check that cable. Then use a screw driver and go to the starter and touch the small connection to the large connection where the cable is connected. if it wants to turn over then check the voltage at that small wire with the key switch in the start position. If you get the solenoid to click (loud click) and it does not turn over, reply and give some more info and I will lead you in another direction.

[Ndavies]

I have a very similar intermittent problem on a Yanmar 4JH2-TE. It usually starts with a few clicks of the key, but occasionally does not. I have changed the starter (including solenoid), and the starter relay and cleaned everything I can see, but I still have the same issue. I can only put it down to possibly an undersized wire from the key switch or a faulty key switch. Mine will start 95% of the time with a couple of clicks of the key, but as a temporary back-up, I have push switch rigged on the starter solenoid. So if you find the culprit - please share!

[Cadence]

You may want to check the ground to the coil circuit to the primary relay for corrosion.

[gbowen]

I have had many engine start problems over the years. You seem to know what you are doing but here are some simple items to check: the connections, are they all clean, tight and no corrosion. Battery voltage drop through the electric cable to the starter. For years I had a problem and usually started my motor by hand until the existing electrical cable split because of heat. I moved the batteries closer to the engine and put a huge electrical cable in. I had a faulty ignition switch too. They are cheap to replace. I do not think it is a faulty ring gear or the starter would just spin. Faulty solenoid or starter motor? These can be checked out fairly easily by a shop.

Best of luck!

gbowen

[Cadence]

Originally Posted by Cadence

You may want to check the ground to the coil circuit to the primary relay for corrosion.

People tend to stick the negative meter lead to a neg. that is handy. It takes both sides to get to the device.

JMHO

[Philsboat]

Could be a bad solenoid contact.The large washer in the solenoid that connects battery voltage to the starter cable gets pitted on one side and and leaves spikes on the other side.If the washer turns you get a poor contact and little current flows.Take the solenoid appart and clean the contacts with a file or replace the solenoid.

[Barney21]

Another suggestion, . If you check both battery terminals at the battery end. Visually they will appear perfect , however I have struck what is called a "dry terminal".
This happens when the wire inside the terminal corrodes / calcifies, You cannot see the problem until you remove the terminal from the wire. Buy 2 new terminals cut the old ones off and fit the new ones. I have had the problem on a tractor!

[Captain Bill]

I once had a similar problem with my 3jh3ce. I checked the voltage between the starter solenoid the battery and everything looked fine. I kept checking and could not find the problem. I talked to a local starter shop and told him the symptoms and he said I had a voltage problem, but the meter said I didn't. He was right. I was measuring the voltage between the solenoid post and the battery post or the ground wire bolt. I always had 12.6 and almost no drop when engaging the starter. I then checked the voltage between the solenoid and the engine block. When I engaged the started I only had about 3 volts, but from the grounding bolt I had 12.6. The problem was a bad connection between the block and the grounding bolt. I took it apart, sanded off all of the corrosion on the block, bolt and lug. When I put it back together it started the first time and every time since. When checking for a voltage drop you have to check it across every connection, not just the ends of the circuit.

[tinkrman69]

it sounds like either the switch or the relay. But I would jump power to the battery terminal on the key switch and try to start.if it works change that wire and clean the connections. if there is no change check ground to the relay with a meter. if you get 12+ volts attach a ground jumper and start. if it works then repair the socket for the relay ground. if not replace the relay. from your post, the problem sounds like it's in the low current part of the circuit. I've run into lots of these problems and replacing components have seemed to solve the problem only to return some time latter....thinking bad manufacture of component....but really it was a weak wire that caused the component to go bad. so checking the voltage drop on the individual wires..end to end...can save you.

[Streetcar]

An update on this:

Lots of good suggestions - especially DougR and tinkrman. Thanks but I am still wrestling with this when I get time to get to the boat.

Basically, I am convinced that the probem is in the low voltage start switch/panel circuit. Here is what I've found:

- when the main engine cricuit breaker is on and the start switch is not on, there is 12.6v between the battery -ve and the +ve input at the start switch. So all good there

- however when I turn the ignition on to position 1 (not to start the engine) the voltage drops to 11.6v. This is when the +ve input on the start switch is connected through all the instruments etc. So there is a ground leak somewhere and not enough voltage to activate the relay properly when starter turned

- next I disconnected the wiring harness (from engine to starter panel) at both ends and put an ohmeter across pairs of contacts at one end. Several combinations of contact pairs had some leakage between the wires. So there was a breakdown in insulation in the wiring harness.

- I lucked out finding another wiring harness (1993 engine) and installed that. Turned ignition on and still 11.6 volts.

- Since then I have been going through all the connections on the back of the starter panel and checking everything. No apparent wiring damage

I am about to go back and have another go at it, but would appreciate any suggestions for where to look next. A niggling thought is that this could be lightning damage...