Diesel Doctor

[mrpyman]

I need some help. I have a Detroit 8.2(in a boat) that when you turn the key off and it is running it doesn't shutoff the solenoid, and it stays running. When the engine is not running the solenoids pulls in and drops off when the key is turned off. I have read the manual and it tells me the solenoid has 2 coils one to pull in and the other to hold it in. I have not had a chance to do the Ohm check yet.This coil is new because the other one burned up last year. So I am thinking it is possibly the relay that energizes the coil, or it is wired wrong. Oh sometimes it will shutoff when the key is turn off not too often but it has happen. Thanks for any Help.

[mrpyman]

I was able to find the problem. It was a bad Diode in the alternator. I installed an inline diode from Ebay and the key shuts off the fuel solinoid.

[mrpyman]

I have another problem with the same motor and hope to get some help? The motor lost 300 rpm and slowed the boat down about 4 knots. I spoke with the guy who rebuilt the motors a few years ago and he said that the problem is fuel supply. i plan to remove all the fuel lines and blow air thru back to the tanks.Iam going to replace the filters and housings this year. I did replace the sock filters(secondary) last year but not the primary which is like a an oil filter style. Am I on the right track? Can the problem be in the turbo? the other motor when running the turbo whine is noticeable but not so much on the problem motor? Thanks

[kirkt]

You're on the right track with checking out the fuel supply. It's kind of hard to watch for black smoke on something that is blowing exhaust where you can't see it. About the only way to check the turbo is to 1) plumb a boost gauge into the intake after the turbo, 2) plumb a manometer into the intake before the turbo (To check for air flow restriction) or 3) unhook everything from it and give the turbo a good visual and feel the thing out. If there's something very wrong with it, you'll be able to tell. Plus, you have something to compare it to right there with you. Don't overlook the air flow, although it is a marine app. stranger things have happened. On those particular Detroit Diesels, they have kind of an unusual injection set-up too. They are kind of like the old 2-stroke systems where one side can get of balance from the other side of the engine. That might be something to look at as well.