Fuel errors change after adding fuel to tank

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Fuel errors change after adding fuel to tank

Unread postby ragtop50 » Sun Sep 02, 2018 7:55 pm

During my data logging today, I was getting consistent fuel errors of about .92 to .95. Two or three logs showed the same thing, and consistently in the same area of the MAF curve. Easy enough to fix.
I stopped and fueled up (same fuel as before, 89 non-ethanol) and did another couple of logs and now I get widespread 1.02 to 1.10 fuel errors.
Why would fueling up cause such a swing? Air bubbles from tank? Now I am not sure what to trust in these logs.
ragtop50
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Posts: 17
Joined: Fri Dec 15, 2017 1:55 pm
Name: Randy Langdon
Vehicle Information: 1990 Mustang LX Convertible, A9P QH with A9L2 - TunerPro RT
TW170 Heads
Lunati 20350711 Cam (221/229 @.050, .542/.565 lift, 112 LSA)
GT40 Tubular intake with TMOSS ported lower
Tremec 3550 5 speed
3.55 gears (31 spline setup)
9:1 Compression
SD 80 lb injectors
Stock MAF (for now)
Shorty headers (1-5/8), x-pipe with Spin Tech 9000 Mufflers (full exhaust)

Re: Fuel errors change after adding fuel to tank

Unread postby decipha » Mon Sep 03, 2018 11:01 am

thats perfectly normal fuel grades vary station to station

its always best to stay away from non-ethanol stations
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decipha
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Re: Fuel errors change after adding fuel to tank

Unread postby ragtop50 » Mon Sep 03, 2018 11:29 am

I always buy gas at the same station, they just offer a non-ethanol 89 octane that I use for lots of stuff that tends to sit a while without running. In fact the previous tank came from same pump about a week earlier. I have heard of the return fuel causing air bubbles to get sucked up by the pump, especially when fuel level is low and was wondering if my results may have been evidence that it is true. I know Pro M makes a hanger that supposedly eliminates this.
I am very interested why you say to avoid non-ethanol?
ragtop50
General Poster
 
Posts: 17
Joined: Fri Dec 15, 2017 1:55 pm
Name: Randy Langdon
Vehicle Information: 1990 Mustang LX Convertible, A9P QH with A9L2 - TunerPro RT
TW170 Heads
Lunati 20350711 Cam (221/229 @.050, .542/.565 lift, 112 LSA)
GT40 Tubular intake with TMOSS ported lower
Tremec 3550 5 speed
3.55 gears (31 spline setup)
9:1 Compression
SD 80 lb injectors
Stock MAF (for now)
Shorty headers (1-5/8), x-pipe with Spin Tech 9000 Mufflers (full exhaust)

Re: Fuel errors change after adding fuel to tank

Unread postby decipha » Mon Sep 03, 2018 11:57 am

most non-ethanol stations don't get fuel too often, that fuel usually sits for month the one up the street from me only gets fueled twice a year

any vehicle sold in the U.S. for the 1986 model year and newer is required by law to comply with ethanol standards of 10%, its pretty useless to avoid ethanol as its a great additive
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decipha
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Posts: 15331
Joined: Mon Jul 15, 2013 5:29 pm
Location: New Orleans, LA
Name: Michael Ponthieux
Vehicle Information: Supercoupin' x10
90 (4x 5spds) - Dante, Ruby, Daja, Ava
91 4r70w - Skarlett
92 (2x) 5spd & auto - Bianqa, Andrea
93 auto - Danika
94 5spd Rionda
95 auto Aisha
Vehicle 2 Information: Others:
00 Lincoln LS - Luanda
98 Camaro SS - Bounquisha
02 Harley F-150 - Sasasha
03 Marauder - DyShyKy
00 Explorer 5L - Bernyce


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