Merc 5.0 starts and dies.

[bryceheinz]

Re powered my 86 sea ray that had a rim bolt 5.0 with a center bolt 5.0 thunderbolt iv engine. The engine will fire right up and run perfect for a couple seconds then die and backfire through carb if you try and throttle it. I don't believe I have a fuel issue. The manifold is grounded separately and I am providing a jumper to the purple wire at coil so I can rule out my harness. Any ideas?

 

[Bondo]

Ayuh,.... The backfire when throttlin' it, says it's a fuel delivery issue,.....

 

[alldodge]

Don't understand the "rim bolt" or "center bolt" terms.
Is this a mechanical or electric fuel pump? If electric check the wiring to the fuel pump

 

[bryceheinz]

Center bolt valve cover. Rim bolt valve cover. Mechanical fuel pump. Thunderbolt iv. 2bbl carb

 

[alldodge]

Thanks

will fire right up and run perfect for a couple seconds then die and backfire through carb ---------------- if you try and throttle it

Running great for a couple seconds isn't long, but then it dies and backfires.

So does it back fire on its own without any throttle, or does it only back fire when throttled in the couple seconds?

Will it idle for longer then 2 seconds IF it is not throttled?