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V-8 Engine Tech

Intermittent “Lean Spikes” on Air/Fuel Ratio Gauge...

Mopar Big Block Talk

by RockyUSA » Sun Mar 17, 2019 5:54 am

Fuel delivery problem solved:

* New Carter M6903 Fuel Pump (Mancini Racing)
* New fuel pump pushrod (probably my primary problem)
* Metal 3/8" Stainless Steel Supply line all the way to the tank
- Insulated as it passes behind the exhaust, all the way to the carb
* Metal 5/16" SS return line all the way to the tank

Lots more clean-up and "fettling".

I am certain I am getting at least 15 more horsepower from my engine! 8) (Or at least I hope so, because this project was a LOT more work than I was planning on!)

Rocky
'72 Interceptor III - 133/5597
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'74 Toyota Land Cruiser FJ-40
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by Moparguy » Tue Mar 19, 2019 12:42 pm

a carb is NOT fuel injection , dont expect to see one behave as such
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by RockyUSA » Tue Mar 19, 2019 1:05 pm

The little smiley faces are indications of a things called "jokes"....

:)

Rocky
'72 Interceptor III - 133/5597
'73 DeTomaso Pantera
'74 Toyota Land Cruiser FJ-40
'95 Jaguar XJS Convertible
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by Joe Schiavone » Fri Oct 11, 2019 1:31 am

If you go with an Elec pump going through the mechanical pump you may want to replace the mechanical pump at a designated time in years. The downside of both is the diaphragm in the mechanical pump rupturing and allowing the gas from the elec pump diluting the oil. Do not know the appearance on the dip stick probably not likely. Just something to think about. RacerJoe
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by RockyUSA » Tue Apr 07, 2020 2:39 am

Mystery Solved:

I learned that the way an Air / Fuel (A/F) Meter works - the system is ONLY looking at the oxygen levels for the determination of a Lean / Rich condition. So if you have intermittent ignition (which actually puts out pulses of exhaust that are too rich, as the fuel is not burned) - the sensor reports it as too lean (because there's a lot more uncombined O2 in the gas stream. This is because the sensor can't assess how much hydrocarbons are passing the sensor.

So my "intermittent lean spikes" were being caused by an intermittent ignition issue - since corrected.

Rocky
'72 Interceptor III - 133/5597
'73 DeTomaso Pantera
'74 Toyota Land Cruiser FJ-40
'95 Jaguar XJS Convertible
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