EST Ignition Advance

[maxumized]

Troubleshooting a possible ignition problem.

Using the jumpered EST timing procedure, I set the base timing to 1' BTDC, and then when removing the jumper, rather than going to the idle timing of 12'BTDC, it jumps to nearly 22'. I would think this is a problem with the module, but I tried another and it does the same exact thing. In fact, I've tried a different distributor and ignition coil as well.

Anyone know what might cause this?

 

[Don S]

Re: EST Ignition Advance

What are we working on?

 

[maxumized]

Re: EST Ignition Advance

Sorry.

A frankenstein.

It's a 97 Maxum, but the long block is a new (2009) GM Marine 3.0. The only thing original is the carb (rebuilt) and the intake/exhaust manifold.

So, in that respect, I'm not quite sure what base timing to use... is the timing more dependant on the carb, the long block, etc... In any case, both the new (came with the long block) and original distributor / coil set both advance nearly 20-22 degrees at idle from base timing, no matter what the base timing.

I'm at my wits end with this boat, I just can't seem to get it right.

 

[Don S]

Re: EST Ignition Advance

Give details on how you put it into base timing mode, and take it back out of base timing mode. Be very specific on when you put it into and out of base timing mode rather the engine was running or not. And specifics on what your "jumpered EST timing procedure" actually is. Also include what outdrive you have.
It all makes a very big difference

 

[maxumized]

Re: EST Ignition Advance

First, I crank the engine on the muffs and idle for a while.

After warmed up, I jumper the white leads on the distributor, and then bypass the shift interrupt. As soon as I bypass the shift interrupt, the idle drops significantly.

At this point, I consider this "base timing mode". This is where I've set to 1'BTDC. Once that's complete and the distributor is clamped down good, I turn off the engine.

Then I remote rewire the shift interrupt and unjumper the white leads.

When I start up again, I check the timing at idle, and this is where I expect the timing to be 12'BTDC +/- 2'. However, this is where I'm finding it to be about 20-22'BTDC.

This is an alpha one outdrive, standard rotation, 1.94 ratio I believe.

 

[Don S]

Re: EST Ignition Advance

After warmed up, I jumper the white leads on the distributor, and then bypass the shift interrupt. As soon as I bypass the shift interrupt, the idle drops significantly.

This should be done WHILE the engine is running.

At this point, I consider this "base timing mode". This is where I've set to 1'BTDC. Once that's complete and the distributor is clamped down good, I turn off the engine.

Remove your jumper between the white wires BEFORE you shut the engine off.
It's fine to do the shift interrupt wires after shutting off, but I am sure you need to remove the jumper wire from the 2 white wires while it's stll running.

 

[maxumized]

Re: EST Ignition Advance

Yes, I jumped the white leads and bypassed the shift interrupt while the engine was running as recommended. This is how I notice the idle dropping. I'm assuming it is normal for the idle to drop, once the shift interrupt is bypassed, as it is retarding the timing to base?

Secondly, I'm almost certain I've actually removed the jumpered white leads while running, as well. Either way, it always ends back at 20-22' BTDC at idle.

Don, the manual actually states to remove them prior to shutdown.

"8. Aim timing light at timing tab and recheck location of timing mark. Repeat Step 7 until timing is correct.
9. Stop the engine. Torque distributor hold down bolt to 20 lb-ft (27 Nm).
10. Reconnect the two wires to the shift interrupt switch."

Is this incorrect? Does shutting off the ignition with the white leads still jumpered, then disconnecting them, somehow "set" the timing in the module?

 

[Don S]

Re: EST Ignition Advance

9. Stop the engine. Torque distributor hold down bolt to 20 lb-ft (27 Nm).
10. Reconnect the two wires to the shift interrupt switch."

Step 10 does not address the white wires, only the shift interrupt switch.
Disconnect the white wires while the engine is running. The rpm's should increase and the advance should work.
Once it does, shut the engine off and hook up the shift interrupt switch.

 

[maxumized]

Re: EST Ignition Advance

Sorry, forgot the next steps in the manual:

11. Remove jumper wire at distributor white leads.
12. With timing light still connected, start the engine and run at IDLE. Verify that timing did advance to 12' BTDC +/- 2'.

The manual still notes shutting down before removing the jumper and shift bypass.

However, trust me when I say I appreciate your advice, and I will try again just as you said. But, I'm fairly certain I've tried both ways with no difference. The timing certainly is advancing upon leaving base timing mode, it's just advancing what appears to be about 10' too much.

 

[maxumized]

Re: EST Ignition Advance

Update: I've tried the steps Don outlined above with the same results.

The ignition advance at idle is 20-22'BTDC after setting the base timing to 1'BTDC.

This happens on two different distributor/coil sets. I've checked the voltage to the ignition to make sure it's getting a solid 12v, and it is. I can't figure why else it would be doing this.

 

[AnthonyY]

Re: EST Ignition Advance

I am by far not as experienced as Dons but just wondering if this could be caused by worn springs and wieghts in the dist(actually I don't even know if yours has them). My 90 4.3 omc has an issue with the timing advance. It advances about 8 deg short of what the manual says (@ 3200 rpm I think, no manual in front of me now, but I had it when I was checking it)so I am leaning towards the springs. I just thought I would chime in(maybe I'll learn something). Could those springs allow the timing to advance too much(which is your issue)?

 

[maxumized]

Re: EST Ignition Advance

Anthony, thanks for the info, however, I'm fairly certain the EST does not have the spring/weight assembly. As far as I know the timing map is electronic and relies on a sensor in the distributor rather than mechanical or vacuum advance as with other systems. It's also worth noting that I'm getting the same, exact results with my original 1997 EST and the EST that came on the new long block.

Still at a stand still here... one thing I'm going to try next is check EST input voltages while actually under way to make sure the ignition system is getting a solid 12v for reliable operation. I'm not sure what else to check.

 

[Don S]

Re: EST Ignition Advance

What's your RPM when you are seeing 22??

 

[maxumized]

Re: EST Ignition Advance

Anywhere around idle, 650-750 or so. The worst part is, what if the advance curve was applying to the idle timing of 20-22'... timing could have been advancing well into the 30's at higher RPMs...

 

[JustJason]

Re: EST Ignition Advance

hmmmm.... if your advance really was 20-22 I would think you'd be turning well over 750rpms......

So... Are you sure your on the #1 plug wire?

Have you tried a different timing light yet?

 

[maxumized]

Re: EST Ignition Advance

hmmmm.... if your advance really was 20-22 I would think you'd be turning well over 750rpms......

So... Are you sure your on the #1 plug wire?

Have you tried a different timing light yet?

Yes, on number one plug. And two timing lights have been tried; just because of this issue I bought an adjustable advance light as suggested on this board because the timing tab only goes to 12, I wasn't going to be able to confirm full advance. As it turns out, I had to use it just to determine I'm actually getting 20-22' at idle!