Re: Question on loosing fuel pressure going down track.
 

Here in the Southeast. it's not unexpected to find mud-dauber plugs in things like a fuel cell vent.

Re: Question on loosing fuel pressure going down track.
 

A lean miss-fire will show a rich condition due the un-burned fuel leaving the combustion chamber.

Re: Question on loosing fuel pressure going down track.
 

A wideband sensor will show a lean miss-fire as a lot of excess oxygen in the system, fooling you into thinking the engine is running lean.

A severely rich mixture will also show as a lean condition on a wideband sensor.

Spark plugs and header tubes don't lie.................. But the widebands can.

Re: Question on loosing fuel pressure going down track.
 

Been doing this many years, (not just my race car) I have never encountered that.
Misfires do look lean.

Re: Question on loosing fuel pressure going down track.
 

YES, a mis-fire will show lean on a wideband sensor. All that sensor reads is oxygen, when there's a mis-fire, oxygen isn't getting used on that cycle so it passes through the engine un-used. A wideband sensor in a collector is seeing the average of 4 cylinders. If say theres a distribution problem in an intake manifold, the average of the 4 could show close to perfect, but with the bad intake it may have a severely lean hole. The better way to check would be to weld 8 bungs into the primary tubes of the headers and either install 8 sensors or rotate 1 sensor over 8 passes down the track.

Re: Question on loosing fuel pressure going down track.
 

Have had very little spider plug fuel cap vents over winter.

Re: Question on loosing fuel pressure going down track.
 

Pull a plug wire off sometime and watch the wideband sensor. You will see the same thing happen as if you unplugged a fuel injector instead of pulling the plug wire.

The too rich showing lean though, that can be tricky to diagnose. A N/A engine will typically be falling on it's face though, but on a forced induction it can be misleading, therefore plugs and collectors are the best thing to determine the root cause.

Re: Question on loosing fuel pressure going down track.
 

On my other car I use a 2 step and car goes rich staging with trans brake and 2 step. Takes about 1.5 seconds to clear up when released.

Maybe 2 types of misfires. One with plug not firing and car goes rich , the other if injected and injector does open then car goes lean? IDK

Re: Question on loosing fuel pressure going down track.
 

Yes, the wideband can fool us if we don't use other methods to determine what is really happening inside the combustion chambers!

Just remember, a wideband sensor only measures oxygen inside the exhaust system, it knows nothing about fuel inside the pipe.

Re: Question on loosing fuel pressure going down track.
 

Ok here is the fix. I bypassed summit inline filter and changed vent line on fuel cell. 1 gallon in about 40 seconds and today's pass with leaner secondary rods im at 5psi in high and went 12.1 afr. May night be perfect but improved .3 mph
I want to thank everyone for the suggestions as they were helpful in chasing problem.