Uh Oh. New Engine won't Crank...

[GilligansIsland]

Ok, I'll do my best to explain without pictures, and hopefully the symptoms will mean something to someon.

I just go a new Volvo 7.4 from Michigan Motorz which was run, timed and tested before it was shipped back to me. All I needed to do was drop her in, hook up my batteries and wire harness and start it up - that was the plan, anyway.

When I turn the key switch On, all wiring powers up as it should. When I turn the key switch to Start, I get nothing. As if the neutral safety switch is engaged. So, here's what I've done so far:

By passed the neutral safety switch - just in case
Cut out old wiring harness since it was a little loose, and directly spliced wires properly
Installed new relay mounted near the 50amp resettable breakers

Now here is where it gets weird...

I light tested all wiring from the helm harness with key in the On and Start position and everything seems good, EXCEPT when I test the Yellow/Red starter wire going into the relay. Going into the relay, I get power on the lighter guage wire. When I pierce the insulation on the heavier gauge Yellow/Red wire coming out of the relay the light lights and the engine starts kicking over!


I'll try to attach a pic of the relay.


Thanks.



I hope this makes sense to someone.

 

[Don S]

Re: Uh Oh. New Engine won't Crank...

See if this helps any.

View attachment Troubleshooting a Volvo Starting system.pdf

 

[GilligansIsland]

Re: Uh Oh. New Engine won't Crank...

Awesome link. That's getting printed and saved. I ran through each step and everything checked out.

Ok, followed the instructions and using that diagram, here is what's happening. When I connect my TL to ground and touch the wire connected to terminal 87, with the key in the start position, the engine cranks.

What's up with that?

 

[Don S]

Re: Uh Oh. New Engine won't Crank...

Pull the relay out of it's socket and do the tests and see what happens. Don't check the wires, check the socket connections themselves.

 

[Don S]

Re: Uh Oh. New Engine won't Crank...

Just an FYI, poking holes in the wires is the worst thing you could do. They really need to be sealed completely before corrosion starts.
Those little holes are just killers on marine engines.

 

[GilligansIsland]

Re: Uh Oh. New Engine won't Crank...

I checked as you said. LT on block and key in start:

85 lit
87 did not (but it shouldn't I guess)
86 (ready for this?) lit! Ground to ground lit!?

So I put the relay back together and probed the 86 terminal and the engine kicked. WTF!?


Note taken on probing wires. Thanks.

 

[Don S]

Re: Uh Oh. New Engine won't Crank...

86, is not grounded. Probably hooked to a hot wire somewhere on the engine.
Might disconnect the main round harness plug, then hook your TL clip to the positive battery terminal and see if the test light lights or not on the 86 terminal. It should if it actually goes to ground.

 

[GilligansIsland]

Re: Uh Oh. New Engine won't Crank...

Thanks. I just left the boat so I'll finish tomorrow.

I didn't think to check 86 with the key NOT in the start position. Would checking 86 in both the Start and off position narrow down what direction it might be getting power from? Is it possible that it's being powered from inside the harness?

Do those ends of the harness ever go bad or do they las forever?

 

[Don S]

Re: Uh Oh. New Engine won't Crank...

86 doesn't care if the key is in start or not. it's a ground. Should go from the relay socket to ground. That is why I said hook the test lead of your test light to the POSITIVE battery cable, then touch the tip of the TL to the 86 terminal of the relay socket.
That is how you test a ground connection with a test light. Any ground.

 

[GilligansIsland]

Re: Uh Oh. New Engine won't Crank...

I understand that, but since 86 lit the TL with the TL connected to the block, it is showing as powered. I'm wondering if 86 could be powered via 85 from inside the harness because of a fault of some sort.

I was thinking that testing 86 with the key switch on an off would show if if was being powered from 85.

Does that rationale make sense?

 

[Don S]

Re: Uh Oh. New Engine won't Crank...

Up in reply #7 I suggested you disconnect the main harness. That will isolate the problem to the engine and not the rest of the boat.

If it is only in the engine, then something is wired wrong or shorted, and that is just a guessing game as to where. But tracing the wires is how I do it, even if I have to open up the harness to see.

 

[GilligansIsland]

Re: Uh Oh. New Engine won't Crank...

I got ya. I already left the boat at that point, but I'll start there when I go back tomorrow.

Thanks.

 

[GilligansIsland]

Re: Uh Oh. New Engine won't Crank...

Test results:

LT Clipped on positive
Engine harness unplugged

85 no light
86 no light
87 light

Same as above except harness plugged in

85 light-little dimmer
86 no light
87 light

LT on Engine Block
Engine harness plugged in

No terminals lit.

 

[GilligansIsland]

Re: Uh Oh. New Engine won't Crank...

Some more results:


LT on Engine Block
Key in Start position

85 light
86 light - relay makes buzzing noise
87 no light (relay Is off)

LT on Positive
Key in Start

85 no light
86 no light
87 light

 

[Don S]

Re: Uh Oh. New Engine won't Crank...

Everything is backwards. You have a positive and negative reversed somewhere.


I would look at the circled area in this picture.

 

[Don S]

Re: Uh Oh. New Engine won't Crank...

With the TL hooked to the positive battery terminal, what do you get on the 30 terminal of the relay socket?

 

[GilligansIsland]

Re: Uh Oh. New Engine won't Crank...

Hooked to positive, the 30 term does not light

It lights when I convection to the block.

The area you circled is the main engine harness. I have cut that out because it was sloppy and resided correctly.
The odd thing is, before the motor was shipped it was ran and timed. I called to verify that they went through my harness which they confirmed. They said it started easily on several attempts.

 

[Don S]

Re: Uh Oh. New Engine won't Crank...

Hooked to positive, the 30 term does not light

Something is backwards for sure.

It lights when I convection to the block.

Have no clue what that means.

The area you circled is the main engine harness. I have cut that out because it was sloppy and required correctly.

There is where I would start looking.

Un-plug the engine harness going to the instrument panel and redo the tests on terminals 30 and 86 and see what happens.

 

[GilligansIsland]

Re: Uh Oh. New Engine won't Crank...

Damn spell check.

With the test light connected to Positive:
30 no light
85 no light
86 light
87 light

Test light connected to engine block:
30 light
85 no light
86 no light
87 no light

I think 30 is responding correctly, no?

 

[Don S]

Re: Uh Oh. New Engine won't Crank...

With the test light connected to Positive:
30 no light
85 no light
86 light
------------87 light ------------ ????

Test light connected to engine block:
30 light
85 no light
86 no light
87 no light

I think 30 is responding correctly, no?

Was that test with the harness disconnected?

Those look normal except the 87 light. It does not go to ground, it should go to the small terminal on the starter solenoid closest to the block. See the picture in the troubleshooting chart.