Topic: Issues getting the 390 to run correctly

[Matt1968]

Sorry, I feel bad for even asking!     Just wanted to make sure everything was checked.

OH no prob.....I'll take all advice you can give!

[somethingspecial]

How old is the gas in the tank? Is it three years old? I have a trailer queen GT390 GT/CS which has been sitting for several years.  Last year I introduced contaminated fuel into the tank which made a mess of things. Had to drain the tank, refresh the carb and it started right up and ran for about one minute.  Sputtered and quit. I checked everything, very similar to what you described.  I did not want to change the plugs.  Finally I pulled and cleaned up the plugs (5 hours to do) and she fired right up and ran great.   The next morning, it tried to start and coughed and sputtered and would not start.  Decided to change the plugs, not just clean them up (another 5 hours down the drain) and she fired right up and has run great ever since.  Long story short, you may have fouled plugs.   Todays replacement plug for the GT390 is the Autolite 45.  Tip:  if you remove the valve covers, much easier to change plugs.  (mine also had the smog tubes which is why it took so long).

[Matt1968]

How old is the gas in the tank? Is it three years old? I have a trailer queen GT390 GT/CS which has been sitting for several years.  Last year I introduced contaminated fuel into the tank which made a mess of things. Had to drain the tank, refresh the carb and it started right up and ran for about one minute.  Sputtered and quit. I checked everything, very similar to what you described.  I did not want to change the plugs.  Finally I pulled and cleaned up the plugs (5 hours to do) and she fired right up and ran great.   The next morning, it tried to start and coughed and sputtered and would not start.  Decided to change the plugs, not just clean them up (another 5 hours down the drain) and she fired right up and has run great ever since.  Long story short, you may have fouled plugs.   Todays replacement plug for the GT390 is the Autolite 45.  Tip:  if you remove the valve covers, much easier to change plugs.  (mine also had the smog tubes which is why it took so long).

I bypassed the tank altogether,  I ran a 3/8 hose with a filter on the end from a gas can to the fuel pump.  All fresh gas with carb cleaner poured into the gas can.  Just out of curiosity,  if plugs get fouled,  will they defoul themselves with enough run time?

[Matt1968]

How old is the gas in the tank? Is it three years old? I have a trailer queen GT390 GT/CS which has been sitting for several years.  Last year I introduced contaminated fuel into the tank which made a mess of things. Had to drain the tank, refresh the carb and it started right up and ran for about one minute.  Sputtered and quit. I checked everything, very similar to what you described.  I did not want to change the plugs.  Finally I pulled and cleaned up the plugs (5 hours to do) and she fired right up and ran great.   The next morning, it tried to start and coughed and sputtered and would not start.  Decided to change the plugs, not just clean them up (another 5 hours down the drain) and she fired right up and has run great ever since.  Long story short, you may have fouled plugs.   Todays replacement plug for the GT390 is the Autolite 45.  Tip:  if you remove the valve covers, much easier to change plugs.  (mine also had the smog tubes which is why it took so long).

[/b]

Since owning this car since '88,  I would challenge anyone to find a more difficult engine to work on...plugs, exhaust manifolds, etc, etc, etc.  A big block in a 68.

[Bob Gaines]

[/b]

Since owning this car since '88,  I would challenge anyone to find a more difficult engine to work on...plugs, exhaust manifolds, etc, etc, etc.  A big block in a 68.

Maybe not more challenging but just as would be a 67(with thermactor) or 69 . All difficult .

[Matt1968]

Maybe not more challenging but just as would be a 67(with thermactor) or 69 . All difficult .

I'll agree !

[GT500KR]

 Changing plugs on my CobraJet car, I discovered by carefully raising the motor up with a floor jack helps a lot. I do it one side at a time, by jacking the motor up with only one motor mount through bolt removed. This way the motor "rocks" to one side, giving you a little more room. Watch your fan shroud, and loosen/remove if ness.  7 and 8 by the master is still a bit of a pain no matter what though....