Fuel tank pressure 97 GTX

[mikidymac]

As Popps said, the check valves will typically cause you to run lean not rich like your plugs show. If the inlet check valve doesn't work the tank will build a vacuum and starve the carbs for fuel. If the pressure relief is bad it can cause the carbs to dribble when sitting from the fuel pressure that can build up causing hard starting and flooding.

 

[JJinSC]

I think he has moved on from vent issues, though, I realize that is what the subject still states. One person has responded with question about the carb’s. I don’t think that has been answered yet. Other than that the OP is asking for other ideas like MPEM or rectifier.

 

[ghostntheshell]

Is there a hard start issue too?
Those plugs look to me like it’s running rich.

Could be the needle seat leaking fuel into the cylinder?

 

[CRei]

No hard start, I’ll change plugs, this is the second set of carbs on here doing same thing. Do MPEM go bad on these, rear electrical box would the coil be at fault? Thanks

 

[CRei]

Leaking needle and seat? Loading it up??

 

[POPPS]

One year,,,when my xp800 was stored outside,(partially to full sun ),,,,I had similar symptoms,,,luckily I got a good lead from a dealers mech,,,and he lead me to the check valve,,,I removed it,,,and ,problem solved,,,I went thru everything,,,with a fine toothed comb....spent many hours chasing this gremlin...That little black and white check valve,,,would not open,,,and forced the needle at the seat to open.

 

[ghostntheshell]

I have been having hard starts too. Very wet plugs. Flooded.

I had a boat mech friend rebuild my carbs (I was present, doing other things) and he pulled out what I can only describe as a piece of gasket material (very small) that said was interfering with the needle / seat and was likely causing my flooding issue.

AND the previous parts were not OEM.

AND I had to track down a fresh, new, OEM mikuni screw, as it appears the last guy didn’t use a JIS and stripped it to the point it wasn’t usable.

Lucky we got it out.


I also have a new fuel pressure relief valve I’m putting in (after I take it to the lake and do some testing).

 

[POPPS]

I have NEVER found a piece of anything in the seat,,,,it's carb'd right,,,if so...are the clear plastic fuel pump check valves,,,in tact,,,not cracked?,,,easy to miss.,,are the carb gaskets in the correct order?,,,are the pilots threaded in securly?

 

[CRei]

One year,,,when my xp800 was stored outside,(partially to full sun ),,,,I had similar symptoms,,,luckily I got a good lead from a dealers mech,,,and he lead me to the check valve,,,I removed it,,,and ,problem solved,,,I went thru everything,,,with a fine toothed comb....spent many hours chasing this gremlin...That little black and white check valve,,,would not open,,,and forced the needle at the seat to open.

I replaced the check valve in fact was not even one in there, put the line on the black end which lets nothing out only breath in, is that correct ?

 

[mikidymac]

Yes it should let air into the tank not out.