94 3.0L EST ignition

[HT32BSX115]

Howdy all,

got a 3.0L EST ignited engine.

Timed to 1* BTDC with the "timing" wires shorted

When I remove the "short" the engine dies.

The module is also pretty warm when the engine is running ("short" connected)

What sort of failure modes do these things exhibit?


Thanks,

Rick

 

[Don S]

Re: 94 3.0L EST ignition

Merc or Volvo?

 

[HT32BSX115]

Re: 94 3.0L EST ignition

It was obvious to me


It's a 94 Merc 3.0L LX Alpha. (don't have the ser) but the service manual gives a pretty specific procedure for setting the timing with an EST dist.

when I first tried to set the timing, after setting it at 1* removing the wire did not change the timing to 12BTDC like the manual indicates.

I pulled the connectors and looked for corrosion in the pins etc and reconnected , now it dies when I remove the short. I did all the Merc tests for resistance in the coil, pickup coil etc. (but it runs..... if the coil or pick up was bad it wouldn't run)


I am thinking module. (the only thing left) I just made the assumption that when it fails the engine quits. I suppose the electronic timing advance could fail and it keep running......

 

[Don S]

Re: 94 3.0L EST ignition

Not sure what you mean by "Shorting the wires". Are you referring to the jumper between the 2 white wires on the distributor, or hooking the harness wires together to bypass the shift interrupt switch?

 

[HT32BSX115]

Re: 94 3.0L EST ignition

Yes. The 2 white wires on the dist that are shorted together when setting the timing. (after bypassing the interrupt)

I short those 2 together and set the timing to 1*. disconnect and the engine dies.


The timing should go to 12BTDC when disconnecting the short.

 

[HT32BSX115]

Re: 94 3.0L EST ignition

OK...(I was inadvertently withholding info)

I just bolted a rebuilt long block engine into the boat and this is the first startup.....

 

[Don S]

Re: 94 3.0L EST ignition

Have you tried to restart it with all the wiring back in normal position? Does it haave spark?

 

[HT32BSX115]

Re: 94 3.0L EST ignition

Well there's the problem.

We start it with the jumper in place.

It will only run with the "shorting" wire (dist white wires) in place. If I remove the jumper while it's running, expecting a timing change from 1* to 12*, it just quits.


The first time we tried it with the jumper in place nothing (no timing change) happened when we removed it.

I pulled all the connectors from the coil and dist looking for corroded plugs etc and reconnected them. After that it quit when removing the jumper.

 

[Don S]

Re: 94 3.0L EST ignition

We start it with the jumper in place.

There's your problem, you need to install the jumper while the engine is running, or you WILL damage the module.

 

[HT32BSX115]

Re: 94 3.0L EST ignition

I'm reading the service manual as we speak and it does not say connecting the jumper before starting will damage it but I suppose it could happen.
I am pretty sure I DID start it with the jumper in place the first time. (shame on me)

I'll go back out and try to start it with the jumper disconnected. I'll reconnect and remove it after it's running....(if it will run) It sure have been nice if the manual had indicated that shorting the "advance" wires prior to starting could damage something.....

I am skeptical that they would design it that way since someone trying to set the timing could kill it and easily restart it with the jumper in place by accident.


The manual I'm referring to is #16 Page 4B-21 to 4B-25

On page 4b-25 it only says

IMPORTANT: Be sure to remove jumper before returning engine to service, otherwise timing will not advance.

 

[HT32BSX115]

Re: 94 3.0L EST ignition

Well......figured it out.

1. There was a hole in the Sierra manifold that must be plugged that causes a serious vacuum leak. Makes the thing run on 3 cyls. (the hole was about even with #3) the other cyls seemed to run ok. pulling each plug wire (one at a time) made it run on 2 cyls (except when I pulled #3) putting a bolt in the hole sealed up the vacuum leak and it ran well on all 4.

2. Once I got it running good enough to get it below about 1200 rpm I could see the module change the timing.

3. The interrupt switch actually applies 12v to the module to activate the interrupt.
(so bypassing the switch is like activating it)

4. connecting the 2 white wires will then allow the engine to run (once the interrupt is activated by bypassing the switch)

5. If you have a big vacuum leak it's very hard to set the timing (or anything else for that matter!!)

Whew!

Thanks Don, for reminding me about the shift interrupt switch. I think the first time I tried it I didn't actually bypass the switch which is why the engine dies when you pull the white-wire jumper.

I think I am finally starting to learn something about this stuff!! I'll actually be able to find a job doing it when my wonderful union brothers decide to strike......I may still be able to make the house payment!!