View Full Version : I just tried to start my 3gm30f after it has sat for 2 yearss

12-21-2007, 09:06 PM
I hooked up a garden hose to the water pump....and the started the engine...started and ran well...then noticed that the fuel pump pully was not moving so freed it up and and heard the hose surge...almost like it was filling up the engine!///then water started to flow out the air intake...this can't be good...guessing I will pull the head tomorrow which i have never done...loooking for thoughts and tricks / procedures on pulling the head.

Thanks in advance. Dave

12-21-2007, 09:19 PM
"If you want to start and run a engine, fill a pail with water and allow the sea water pump to take what it needs. By placing the water hose direct you have filled the exhaust line and it has backed up into the engine. Remover the injectors and remove the precups, turn the engine over and blow the water out of the cylinders. Use some WD 40. When you are sure the water is out. Install the precups with new packings and insulators. Run the engine and hope you have not bent a con rod. Good luck, and get a service manual. It has all the instructions and pictures for you to go by.
Good luck and enjoy, Ron"

12-21-2007, 11:57 PM
"if you haven't run it, or tried to start it full of water you should have no problem. get the water out of there, get it going, and run til warm. you will need to change the oil. (maybe a couple of times) there is bound to be some water in the oil. I wouldn't pull the head just yet."

12-22-2007, 07:16 PM
"Wow...thanks for the help. Will does as you say...in moments... what are "Precups"?

I do have a service manual and it is less than straight forward. Thanks,



12-22-2007, 07:24 PM
The precups are 2 parts one has a 10 mm center hole and the other next to the piston has a protrusion and has 4 small holes in it. they slide out towards the injector. Use penitrating oil and a crocked pick

12-22-2007, 09:38 PM
I am on the boat...injectors out...blew out one "cup shaped" item from the center injector port...guessing this is the "Precup" can' get the other out...cranking and shop vac lots of moisture

12-22-2007, 09:40 PM
found the cup...looking for a piece with 4 holes in it...

12-22-2007, 09:58 PM
looking deep into the hole I see a concave item that has holes in it....not sure how I would get it out....pondering putting it all back together and seeing if I can get it to fire...dip stick still looking black...What do you think about running it for 10 minutes and then changing out oil (assuming I can get it started).?

Also can you recommend your favorite parts source?

Thanks a million.


12-22-2007, 10:23 PM
The concave part with the 4 holes is the second part of the precup. There is a copper ring then concave precup another copper ring then the second precup with the hole in the center then an insulator that goes between the precup and injector. It is a fiberous washe shape that makes that seal. Get all these out and clean them up. It may be ok to start and run you engine but remember to replace them all afterwards. Find a dealer that sells parts and get them. They are common repacement parts. Give them model and s.n

12-23-2007, 12:06 AM
"Sorry to be so new to this...and your information is really helping me a lot.

I have been looking through the manual without much luck identifying the 2nd pre-cup (or even the 1st, actually)....what I have is a copper disc that is the mating surface between the injector and anther flat surfaced item that fits down in the hole that has a small hole in the center and is cupped on the back side.
as I look at the other ones (that are stuck...will file a paint can opener to make a hook tomorrow to pull them out) it does not appear that there is anything below that "cup" that looks removable...
hmmm. ( I am hoping to be successful in removing a cup tomorrow so that I can compare what I am looking at...everything soaking in wd-40 tonight.

All the best,


12-25-2007, 01:26 PM
Thanks... I have the engine back together and will start it next time I'm at the boat (I Hope).


12-25-2007, 02:47 PM
"one word of caution, Dave. DO NOT use ether or any other sort of starting fluid on your engine. have seen several with broken piston ring lands due to this. its a good engine, but will not stand up to abuse. good luck with it. P.S. if it doesn't start within 20 - 30 seconds, turn off the seacock to prevent filling it with water again."

12-28-2007, 07:37 PM
Thanks everyone...Got it running and just ordering replacement packings and the like...aprreciate very much the help. Dave