Engine cranks but will not start!

[EcToCrUsHeR]

I've spent the last few weeks endlessly troubleshooting my 1999 3.0L mercruiser I/O without any luck. First off the ignition system is an "EST system". I'm getting fuel but do not have spark at the spark plugs or at the coil wire. So far I have replaced the battery, alternator, and coil with lock success. Also, I'm not getting any voltage to the + leads on the coil and was thinking this might have something to do with the Ignition Control Module (ICM). Any ideas as to what it may be?

 

[NetDoc]

Re: Engine cranks but will not start!

If the engine cranks, it's not your battery or alternator.

However, not getting voltage to your coil is a problem. Check your fuses and check your ignition switch circuits. Pay special attention to any possible cut offs like an oil cut off switch.

 

[EcToCrUsHeR]

Re: Engine cranks but will not start!

If the engine cranks, it's not your battery or alternator.

However, not getting voltage to your coil is a problem. Check your fuses and check your ignition switch circuits. Pay special attention to any possible cut offs like an oil cut off switch.

The old battery was bad and I wasn't getting any voltage at the purple excitation lead on the old alternator so i replaced it.

How exactly do i got about testing the ignition switch. The service manual has a 4 prong and mine is a 3 prong. I've removed the switch itself and without power checked the switch for continuity in the off, start, and run positions. The contacts on mine are labeled "s" "b" and "i"

 

[NetDoc]

Re: Engine cranks but will not start!

The contacts on mine are labeled "s" "b" and "i"

Start, Battery and Ignition.

You should have continuity between B and I when on and B, I and S when in the start position.

 

[Don S]

Re: Engine cranks but will not start!

Do you have the kill switch lanyard installed?
Check the B terminal on your ign. switch, you should have battery voltage on it, even with key off. Do you?
There is a 15 or 20A fuse on that red/purple wire going to the ign. switch, is it good?
Check the circuit breaker on the engine. It has the red purple wire feeding the ign. switch, is it ok? Check with a meter, they may be damaged and look good but not working inside.

 

[EcToCrUsHeR]

Re: Engine cranks but will not start!

Start, Battery and Ignition.

You should have continuity between B and I when on and B, I and S when in the start position.

just tried it. everything checks out just like you said... what should i check next?

 

[Don S]

Re: Engine cranks but will not start!

Did you see my post just before your last one? Looks like we were typing at the same time.

 

[EcToCrUsHeR]

Re: Engine cranks but will not start!

Did you see my post just before your last one? Looks like we were typing at the same time.

I missed it... checking out the lanyard and switch now. I don't have a lanyard installed but the boat ran fine with it like that since i bought it. Also, how do i go about checking for voltage at the the "B" terminal? where do i ground the voltmeter?

 

[Don S]

Re: Engine cranks but will not start!

where do i ground the voltmeter?

There is a ground terminal (black wire) on each of the instruments, pick one that's the easiest to get to.

 

[EcToCrUsHeR]

Re: Engine cranks but will not start!

Do you have the kill switch lanyard installed?
Check the B terminal on your ign. switch, you should have battery voltage on it, even with key off. Do you?
There is a 15 or 20A fuse on that red/purple wire going to the ign. switch, is it good?
Check the circuit breaker on the engine. It has the red purple wire feeding the ign. switch, is it ok? Check with a meter, they may be damaged and look good but not working inside.

I do not have the killswitch lanyand installed but it didn't effect the boat before. I checked the "B" terminal and got 12.5V, I also checked the fuse which was intact. I tested the red purple wire all the way back to the harness for continuity and it checked out alright. I did not see the circuit breaker in the engine and was not able to find it in the manual either. Are you sure the EST system came with one?

 

[Don S]

Re: Engine cranks but will not start!

If you have 12.5 volts at the B terminal, everything on the engine is fine.
Now turn the ignition switch to the run position. You should have 12.5 V on the I terminal (purple wire).
That purple wire also goes through the lanyard kill switch. It may be turned on, but it could be faulty. Does your instruments work when you turn the key on?

 

[EcToCrUsHeR]

Re: Engine cranks but will not start!

If you have 12.5 volts at the B terminal, everything on the engine is fine.
Now turn the ignition switch to the run position. You should have 12.5 V on the I terminal (purple wire).
That purple wire also goes through the lanyard kill switch. It may be turned on, but it could be faulty. Does your instruments work when you turn the key on?

When i checked the "I" terminal with the key on i got 12V. Is there a way to bypass the lanyard switch temporarily to check for spark again when cranking? My instrument lights come on but only a few of the clusters actually work. It's been like that since i got the boat.

 

[Don S]

Re: Engine cranks but will not start!

Normally, there should be two purple wires coming from the kill switch up to the helm area. Find those two wires under the dash and they should have connectors. Unplug the wires going to the kill switch and hook the wires from the wiring harness together under the dash.

 

[EcToCrUsHeR]

Re: Engine cranks but will not start!

Normally, there should be two purple wires coming from the kill switch up to the helm area. Find those two wires under the dash and they should have connectors. Unplug the wires going to the kill switch and hook the wires from the wiring harness together under the dash.

Ok, so i found what i think you were talking about. I have a little switch that has "OFF" annotated on the bottom part. It has two purple wires going through it. I'm going to clip them and connect them together to bypass the killswitch. I guess the other plug in front of the shifter is a 12V power outlet (kinda like a car cigarette lighter).

 

[Don S]

Re: Engine cranks but will not start!

Have no idea what you have. I can't see it. I'm just going by how most are wired.

 

[sschefer]

Re: Engine cranks but will not start!

Have no idea what you have. I can't see it. I'm just going by how most are wired.

Good job Don, he's almost there. 6ft of 12ga and 4 aligator clips and I'd have that thing running and gone in under 10 seconds. 5 seconds with a screwdriver and side cutters.

 

[EcToCrUsHeR]

Re: Engine cranks but will not start!

I'm getting around 10V at the coil now but still no spark...

 

[EcToCrUsHeR]

Re: Engine cranks but will not start!

Have no idea what you have. I can't see it. I'm just going by how most are wired.

Ok, thanks for the help though. After troubleshooting with the manual it points to the control module so i guess i'll buy that and see what happens.

 

[Don S]

Re: Engine cranks but will not start!

Is that 10 volts while cranking or just when the switch is in the run position?

 

[Don S]

Re: Engine cranks but will not start!

Don't go buying parts yet, I'm not sure at this point if it would cure your problem.
Still lots of things to check before ordering parts.