28Eliminator

Mine was on the wrong side from the factory, Actually I'm not sure which is the old or new style, and I'm not sure when they switched them.
Here is diagrams of the two.
http://www.mercruiserparts.com/Show_...SEPARATOR+TANK

http://www.mercruiserparts.com/Show_...SEPARATOR+TANK

ckentling

Do you have part numbers for the screen and o-ring kits so i cna try it on mine as well. I have experienced the same issue intermittently and would like to swpa the sceeen out to see if ti make a difference

THANKS

28Eliminator

ckentling, click on the links that I attached above.

ckentling

I saw that, but was hopeing to replace the screen and o-rings would not be a 1000 job

bsirk

I know I'm jumping in here late, but I've been keepin up with this thread, and I'm pretty sure I'm having the same problem. Just replaced a '96 502 with a brand new Gen VI 502 longblock using all the same accessories from the old motor (including the VST tank). It's got about 12 hours on it, so I'm still babying her. On Sunday I ran the boat for about 30 minutes crossing the lake and the outside temp was in the mid 90's. Met my buddy and just killed the engines w/o idling for more than maybe 20 seconds. When I went to go start it back up, it would fire initially, then putter out after maybe 2-3 seconds. This kept up until I finally bit the bullet and got towed in. When I got to the marina (maybe 30 minutes later) we tried purging the fuel lines (small purge valve under plenum) and just got straight fuel. Changed the fuel/water sep. and then tried to crank it again......same story. I initially thought the pump went out, or maybe an injector, but it has no problem starting, just won't stay running. So it's delivering that initial shot of fuel. From all the posts in here, it sounds to me like I'm having the same vapor lock issues, but this is a new issue to me. If I take the cover off the VST tank to clean the screen do I have to replace the o-rings, or is there anyway to do this and re-use the existing o-rings? Any other suggestions? Does this sound exactly like what you guys have experienced, or does this sound like something different??

mats

I opened and closed the VST tank on my 1996 502 MPI some 10 times without replacing the o-ring. I did not create any problems.

mats

I would check the fuel pressure. I would guess that a vapor lock or whatever that prevents fuel delivery would show

cloudmaster_321

I've never been not able to start back up. It may take a couple of tries, maybe a bit of throttle, but never had to be towed in because of it. It's just an annoyance every so often. I was told running ethonol gas could greatly contribute to this problem. So if possible, run straight gas.

28Eliminator

bsirk, I think your problem is different. Maybe the screen though. Does yours startup after it cools down. All of the vapor lock problems are not a problem when the motor and compartment are cool. It might be vapor locking though. The diaphram might be bad, or it may have a vacuum leak on the hose venting it.
When it happens again you can try and pull the plug off the top of the VST tank to relieve the pressure and then try to start it. If it starts and runs ok, then it is a vapor lock problem. This same procedure would be the first thing that any of you should try if you have a poroblem with vapor locking. I still every once in a while I still have the same issue that cloudmaster has. If the VST tank is not venting then it will start and run until the VST tank is empty, and then it will not start back up until it cools down and the pressure drops in the vst tank.

bsirk

Well, got mine figured out, and I can't believe we didn't try this earlier. The small plastic vacuum hose that runs from the first fuel pump to the VST was clogged as hell!!! I had the boat in the water Friday for a test run, since it started fine on the hose (I was still figuring vapor lock). Decided to go for a ride to see if it would happen again, and sure enough after our 30 minute ride, came back in the break wall and it died after about 1 min of idling. After sitting there for a while scratching our heads, we decided to pull that vacuum hose off and check its flow (again, can't believe we didn't do this earlier). Turns out the thing was clogged bigger than chit!! With the hose pulled off both ends I turned the key, and she started no problem and ran fine. So, the next morning got a new piece of hose, attached it, and made it to the KY Lake Poker Run by 10 am!!!! Figured it out just in the nick of time, and no problems through the rest of the weekend. So, you might want to pull all of you vacuum hoses off and check for clogs. Simple fix.