What Do These Relays Do?

[Alex]

1985 Mercruiser 7.4/454 carbuerated -- There are two electrical relays that sit right over the mechanical fuel pump. The relays open and close rapidly maybe 20-30 times after I shut the engine down. The wires connected to the relays are pretty heavy gage. One goes to the starter.

I will order a shop manual for the electrical schematic (I need one anyway). But, but my curiosity is going to kill me before it arrives? What do the relays control and why are they clicking?

Speaking of shop manuals, who outs out good ones. With cars, I recall the Clymer(?) manuals sucked and the Ford and GM shop manuals were the best. Is the same true with Mercruiser manuals?

Thanks in advance

Alex

[Rawleigh]

Alex: Get the Mercruiser manuals. My friend who runs Mercruisers asked if they are the ones with the red buttons on them. He says he thinks you may have a grounding issue with them. They always have 12 volts running through them until you cut off the switches. I'll check it out further and let you know.

[Alex]

Yes, Rawleigh, there is a reset button. Thanks for the help.

[Alex]

I looked for loose grounds, but didn't find any. That in no way rules anything out given my meager diagnostic skills. I can get the engine to start with difficulty (no apparent rhyme or reason when it will start and when it won't). When it starts, it will run for 15-30 seconds and quit abruptly. Then I hear rapid clicking from three places:

1) The two relays over the fuel pump that I mentioned earlier,
2) The Thunderbolt ignition module bolted to one of the risers, and
3) The distributor right where the wires from the Thunderbolt module connect.

Definite call-and-response going on between the three. A click from the Thunderbolt module will cause the relays to respond, and then the distributor will put in its two cents.

Sometimes I can get it started again and it will run fine for the rest of the day. Other times, I give up and start drinking early.

It's pretty obvious that I'm not a crackerjack diagnostician. I will get some professional help (for me AND the engine). Just wondered if this situation sounds familiar to anyone.

Alex

[Bruce]

If they have red buttons then they are circuit breakers not relays.

If they are chattering, look for loose connections on the back.

If not replace them because they are bad internal.

They are the main engine feed.

[Alex]

Thanks, Bruce. I appreciate the help. I have so far to go before I realize there IS a pebble to be plucked.

Rawleigh, how did the engine install go yesterday? Where did you do it?

[Rawleigh]

Got it in yesterday, and today learned all about alignment. We did it in my friend's overbuilt boathouse with a Ramsey 5000 lb winch. No problem. I trailered his Carolina Skiff to my place, loaded the engine with my excavator, then launched the Skiff and ran it up the creek to the boathouse. Those skiffs are handy brutes!! It will be interesting to see how my alignment job runs! I am going to recheck it after the Fourth.