5.0L Starting issue

[Frozen]

I'm having a hard time with my carb on my 1988 OMC 5.0L.Some times it starts right up no problem. Other times it just cranks and cranks. Fuel delivery is not a issue, always getting fuel pressure at the carb and the small carb filter is clear. It just like the carb is not squirting fuel. If I go to the carb and push the little pin that the linkage pushes fuel squirts. And eventually after cranking enough the engine does start. What could be wrong? Where do I start to look? Once the engine is started it runs great. Also it seems to only happen after having been run then sitting for a few hours then trying to restart I get the issue. If I restart 5mins after it's been running no issues. Or if it sits overnight no issues. Any ideas before I buy a new carb?

 

[Silvertip]

Re: 5.0L Starting issue

After sitting for a few hours the engine is cold. Is the choke closed at that point. Are you giving the carb a couple strokes with the throttle only? Are you also providing a little throttle when warm or after stitting for a few hours. In other words, what are your starting procedures (hot, cold, and warm). Is the engine properly tuned? Many folks have never owned a carbureted car so they have no idea how those systems work. Two identical carbureted engines may require different starting techniques. You should not have to crank the engine more than a few seconds for it to fire.

 

[Frozen]

Re: 5.0L Starting issue

If the boat has sat overnight or longer I pump the throttle a few times in neutral then give it just a little throttle and it starts right up.

If the boat has been run and I turn it off and restart within a short amount of time I pump the throttle a few times in neutral then give it just a little throttle and it starts right up.

If the boat has been run and then has been sitting for a fews hours I I pump the throttle a few times in neutral then give it just a little throttle, but it does not start. At this point I open the engine hatch take the spark arrestor off and hit the little pin and make sure I see fuel squirting and give all the linkages a little wiggle. I do this a few time and crank long enough it finally starts and runs as normal.

I know fuel is getting to the carb at 3psi. Any ideas?

 

[RogersJetboat454]

Re: 5.0L Starting issue

Sounds like it's time for a thorough carb rebuild. Fuel pressure sounds a bit low to me too, perhaps the pump is getting tired.

Has the ignition system been checked over? May not be the causing the main concern, but something out of time/tune may be contributing to your difficulties.

My 2?...

 

[Frozen]

Re: 5.0L Starting issue

Sounds like it's time for a thorough carb rebuild. Fuel pressure sounds a bit low to me too, perhaps the pump is getting tired.

Has the ignition system been checked over? May not be the causing the main concern, but something out of time/tune may be contributing to your difficulties.

My 2?...

I ordered a carb rebuild kit yesterday, that's next weeks project. I believe the ignition system to working properly but not 100% sure. I really need someone else to be on the boat and work the throttle so I can see what the carb is actual doing or not doing. Also my boat has a electric fuel pump thats output is 7psi. I have a regulator mounted at the carb set to 3pis, should it be higher? I can adjust the regulator.

 

[RogersJetboat454]

Re: 5.0L Starting issue

I ordered a carb rebuild kit yesterday, that's next weeks project. I believe the ignition system to working properly but not 100% sure. I really need someone else to be on the boat and work the throttle so I can see what the carb is actual doing or not doing. Also my boat has a electric fuel pump thats output is 7psi. I have a regulator mounted at the carb set to 3pis, should it be higher? I can adjust the regulator.

Is the fuel pump a marine grade unit? If it's located in the bilge, it needs to be. What kind of carb are you using? 3 psi should be fine for idle to midrange. May even work for WOT (especially W/ a 2bbl), as long as there is enough volume of fuel going into the carb. I would rebuild the carb, and see where you stand on the upper end of the throttle. If it feels like it's running out of fuel, and/or the spark plugs read that the engine is going lean, try raising it up to 4-5 psi.

Again, just my 2?...
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