Running a Flex-Fuel intank pump

[Lensch09]

Low pressure fuel regulation code is popping up pretty frequently when I'm hard into the car. Car is also bleeding boost and occasionally hitting fuel cut. Looks to be time to replace the stock pump (failing since stage 2 @ 11k miles).

Our in-tank low-pressure fuel pump/filter/sending unit on the B8.5 is listed as part number 8K0919051AJ. This fuel pump is used in basically everything (A4/S4/A5/S5/RS5). The fact that this is the same pump that is used in the 3.2L is less than impressive. Also used in the RS5...which seems strange.

https://parts.audiusa.com/p/Audi__/E...0919051AJ.html

It seems as though many of us that are Stage II plus are running into issues with the stock pump.

Some B8.5 A4 2.0T cars support E85/flex-fuel. My assumption is that the pump used in these flex-supporting vehicles may flow more than the non-flex version (for more headroom) and may also contain internals that are more corrosive resistant to alcohol-based fuels. The flex-fuel supporting pump is 8K0919051AN ; 8K0919051AM. I believe that one forum member has already successfully swapped in this pump. Has there been anyone else?

https://parts.audiusa.com/p/Audi_201...0919051AN.html

Audi won't officially state that this pump works in the B8.5 S4, although I don't see why it wouldn't. Does anyone in the know have specifics on the differences between our stock pump and this E85 supporting pump?

If this flows more, this could be a great OEM upgrade for us.

-DL

[infinkc]

There was another thread about this a few days ago. For the price of the oem pump you can just get an aftermarket pump that you know has a good flow rate.

The b8 e85 pump is 8k0919051AN

Edit, found the thread http://www.audizine.com/forum/showth...?highlight=e85

There is also the dual pump option that GIAC is releasing, but you would need a good stock pump still.

[Lensch09]

There was another thread about this a few days ago. For the price of the oem pump you can just get an aftermarket pump that you know has a good flow rate.

I don't think it works that way with the B8.5.

The B8.5 does not have the standard run of the mill in-tank/inline fuel pump. It's overly complex for what it is.

Almost makes me wish I had a B8 pump with a more conventional design.

I do know that GIAC sells their "booster" pump, which could be an option. But the fact that my OEM pump is failing out on me doesn't give me a good feeling.

-DL

[infinkc]

I don't think it works that way with the B8.5.

The B8.5 does not have the standard run of the mill in-tank/inline fuel pump. It's overly complex for what it is.

Almost makes me wish I had a B8 pump with a more conventional design.

I do know that GIAC sells their "booster" pump, which could be an option. But the fact that my OEM pump is failing out on me doesn't give me a good feeling.

-DL

found the info, look at my post above.

[Lensch09]

found the info, look at my post above.

Gotcha, thank you sir. Looks like I'm gonna buy the flex one, and if things still don't work (especially after the new GIAC file gets released), looks like I'll be buying a Walbro fuel pump as well.

-DL

[ntsantos]

I've been interested in running this version pump as an oem e85 solution as well. I think this flex fuel specific pump may only be a piece of the puzzle. Most flex fuel cars, if not all, use a sensor in the fuel system to read the amount of ethanol in the system and adjust fueling from that data. Upon more research I stumbled upon this page (read the 5th paragraph down):
http://www.greencarcongress.com/2009...-20090915.html


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[AudBoost]

Tomorrow my car is having an inline E85 pump installed. Very similar to what Loe and Mrmomo313 are running except the pump getting installed in my car will be a Walbro 450 versus a 250 like Loe's and Mrmomo313's.

[Loe]

good luck today! Evan@crown motorsports will install it perfectly! Careful with having it hooked up right away to trigger 100% if its not boost based without a supporting file, the 255lph when running 100% (like a true in-line vs. boost base) is enough to induce "rich" misfires...

[shadycrew31]

FYI, the intank just feeds fuel to the high pressure mechanical pump which is why the intank pump is used in multiple different cars, the intank pump is under something like 80PSI, the high pressure pump attached to the engine is closer to 1700 PSI.

Now I am not saying your intank one is not failing or failed, I am just saying that upgrading it is 100% pointless and might even damage the high pressure pump if the upgraded pump increases the PSI going to the high pressure pump. .

[AudBoost]

good luck today! Evan@crown motorsports will install it perfectly! Careful with having it hooked up right away to trigger 100% if its not boost based without a supporting file, the 255lph when running 100% (like a true in-line vs. boost base) is enough to induce "rich" misfires...

Evan is the man!
We are going to setup to be boosted based until I can work with EPL on tuning.

[AudBoost]

FYI, the intank just feeds fuel to the high pressure mechanical pump which is why the intank pump is used in multiple different cars, the intank pump is under something like 80PSI, the high pressure pump attached to the engine is closer to 1700 PSI.

Now I am not saying your intank one is not failing or failed, I am just saying that upgrading it is 100% pointless and might even damage the high pressure pump if the upgraded pump increases the PSI going to the high pressure pump. .

The last time I logged my STFTs I saw higher numbers that I would have liked which indicate that the LPFP is pushing hard to keep up. When I switched back to the 93 file STFTs looked much better. So I am confident my LPFP is working just fine it just needs a little help when running straight E85.

[Lensch09]

FYI, the intank just feeds fuel to the high pressure mechanical pump which is why the intank pump is used in multiple different cars, the intank pump is under something like 80PSI, the high pressure pump attached to the engine is closer to 1700 PSI.

Now I am not saying your intank one is not failing or failed, I am just saying that upgrading it is 100% pointless and might even damage the high pressure pump if the upgraded pump increases the PSI going to the high pressure pump. .

I'm not too worried. The in-tank pump is voltage variable, and is regulated by the low-pressure potentiometer located up in the HPFP. After a bit more research, the flex-fuel version in-tank pump is OEM Audi, and generates additional head-room on the low-pressure end. Less a few hardware changes, it functions EXACTLY like the stock non-flex pump. If the additional pressure isn't needed, the ECU won't "dial it up."

This is significantly different than running a supplemental in-line that runs balls out 100% of the time. Given that our cars do not have return lines, the balls-out supplemental is not the best solution, in my opinion.

-DL

[shadycrew31]

I'm not too worried. The in-tank pump is voltage variable, and is regulated by the low-pressure potentiometer located up in the HPFP. After a bit more research, the flex-fuel version in-tank pump is OEM Audi, and generates additional head-room on the low-pressure end. Less a few hardware changes, it functions EXACTLY like the stock non-flex pump. If the additional pressure isn't needed, the ECU won't "dial it up."

This is significantly different than running a supplemental in-line that runs balls out 100% of the time. Given that our cars do not have return lines, the balls-out supplemental is not the best solution, in my opinion.

-DL

Yeah that was mainly what I was referring to, changing out the fuel pump for an aftermarket inline or in tank with twice the flow seems like a bad idea to me. I like your approach, looking forward to the results!

[jprice]

FYI I logged Dozzer's car with 189mm dual pulley running e85, and the replacement oem flex fuel LPFP didn't appear to have any trouble keeping up, and his car isn't throwing any P310B codes anymore (with his stock LPFP pump, it was).

Next person to install one should measure flow between the stock pump when they remove it and the flex fuel pump before they put it in. That would be pretty interesting.

[AudBoost]

Given that our cars do not have return lines, the balls-out supplemental is not the best solution, in my opinion.

Our cars do have a return fuel line. As Loe stated earlier the in-line pump is boost activated at around 8 to 10lbs so it is not 100% all the time.

[Lensch09]

Our cars do have a return fuel line. As Loe stated earlier the in-line pump is boost activated at around 8 to 10lbs so it is not 100% all the time.

If the B8.5 has a return line, it is not routed through the pump. I just looked at it last night.

It must go directly back to the tank?

-DL

[jachien]

According to the self study program, there is a fuel return line. Although I haven't exactly seen the physical pump, I'm inclined to believe the return is built into the intank pump.


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[Q5OnTheMove]

FYI I logged Dozzer's car with 189mm dual pulley running e85, and the replacement oem flex fuel LPFP didn't appear to have any trouble keeping up, and his car isn't throwing any P310B codes anymore (with his stock LPFP pump, it was).

Next person to install one should measure flow between the stock pump when they remove it and the flex fuel pump before they put it in. That would be pretty interesting.

Do you or dozzer mind posting logs? I'm interested in going this route but wanted to see numbers before I make the jump. Thanks

[jprice]

Do you or dozzer mind posting logs? I'm interested in going this route but wanted to see numbers before I make the jump. Thanks

What exactly are you looking for? He had low pressure from the lpfp, and now he doesn't with the replacement pump. He has a high fuel demand setup with e85 and dual pulley with 189mm crank pulley.

The only thing that would be really nice is to flow test a stock b8.5 pump vs the flex fuel one.

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[Lensch09]

I'm gonna try to get the logs on my stock pump tonight, pending time. My new Flex pump shows up tomorrow. Going to SF this weekend and work all week so there will be delay. Give me "two weeks."


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[shadycrew31]

There is no return line in the B8's, I had the entire system apart over the past few weeks. There is a low pressure feed line to the HPFP, on the HPFP there is a high pressure hard line going to two fuel rails, which do not have a return fitting or return line.

The lines you are seeing in the diagram heading back to the fuel tank area are most likely going to the carbon canister which catches fuel vapors.

[Rex Wilkinson]

I'm gonna try to get the logs on my stock pump tonight, pending time. My new Flex pump shows up tomorrow. Going to SF this weekend and work all week so there will be delay. Give me "two weeks."


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I just ordered a new OEM low pressure fuel pump w/e85. Hope to have it installed in a week or two

[-leman-]

Do you guys know what is the difference between B8 and B8,5 units?

The flex-fuel pump seems to be available for B8,5 only, and non flex-fuel part number is different for B8 compared to B8,5 but I thought maybe B8,5 could still be fitted or at least the pump itself could be swapped from the B8,5 flex fuel unit.

[doug97gxe]

Do you guys know what is the difference between B8 and B8,5 units?

The flex-fuel pump seems to be available for B8,5 only, and non flex-fuel part number is different for B8 compared to B8,5 but I thought maybe B8,5 could still be fitted or at least the pump itself could be swapped from the B8,5 flex fuel unit.

i believe Audi started making the 2.0T Flex Fuel in 2014 ? that would be the B8.5

[AudBoost]

There is no return line in the B8's, I had the entire system apart over the past few weeks. There is a low pressure feed line to the HPFP, on the HPFP there is a high pressure hard line going to two fuel rails, which do not have a return fitting or return line.

The lines you are seeing in the diagram heading back to the fuel tank area are most likely going to the carbon canister which catches fuel vapors.

No doubting what you are saying but if that is the case than what line is my Flex Fuel sensor plugged into that comes off the HPFP? It measures ethanol content correctly, as I have verified the measurements manually, so the line that it is plugged into is seeing fuel.

[LittleDozer]

There is no return line in the B8's, I had the entire system apart over the past few weeks. There is a low pressure feed line to the HPFP, on the HPFP there is a high pressure hard line going to two fuel rails, which do not have a return fitting or return line.

The lines you are seeing in the diagram heading back to the fuel tank area are most likely going to the carbon canister which catches fuel vapors.

Yeah, any time I've taken apart either pump I can't see a return line.

[LittleDozer]

No doubting what you are saying but if that is the case than what line is my Flex Fuel sensor plugged into that comes off the HPFP? It measures ethanol content correctly, as I have verified the measurements manually, so the line that it is plugged into is seeing fuel.

Sure it's not hooked up to the feed line going IN to the HPFP?

[shadycrew31]

Facebook destroyed the image quality but I highlighted the HPFP lines, there is one hardline on the HPFP which goes under the Supercharger and splits into two hard lines connecting into two sealed fuel rails.

Comign into the HPFP is a low pressure line from the LPFP, its a single line from the pump, there is another line in the engine bay that looks similar to the fuel line but its for the carbon canister.

[Lensch09]

Just so everyone can see what we're talking about...

Here is the hardware that I would recommend replacing with the pump ("nut", washer/gasket, base unit)


Here is the new flex pump/filter assembly (for the B8.5)







There is a second inlet/outlet that is "plugged" from the factory. This is normal. I also opted for the "cap" that you can see in the ETKA exploded diagram

Said "plugged" inlet/outlet


And the cap from Audi that I installed for piece of mind (don't want fuel in the back seat)




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[jachien]

Considering there are no wires going to the 'top' unit, I think that should be the fuel filter and the 'lower' unit is the actual pump, where all the wires are going. Can you tell if those 2 metal bars holding the pump to the cap are solid bars or hollow? I mentioned earlier that the fuel return should be contained in the 'in-tank pump', so I'm assuming that the casting of the plastic top cap has galleys so the fuel return is integrated. I do believe since obd2 standard came into play, fuel return was removed from all cars, but the manufacturers, didnt necessarily remove it, but rather came up with more creative solutions for fuel return. For example, 350z/g35 fuel pumps have a fuel return, albeit integrated into the plastic, rather than the traditional fuel return with a second hardline tube going up and down the length of the car to the engine.

[jachien]

Thanks for the pictures by the way. There don't seem to be very many pictures on the internet of the actual pump. And just for clarification, this is the flex fuel version?

[Lensch09]

Considering there are no wires going to the 'top' unit, I think that should be the fuel filter and the 'lower' unit is the actual pump, where all the wires are going. Can you tell if those 2 metal bars holding the pump to the cap are solid bars or hollow? I mentioned earlier that the fuel return should be contained in the 'in-tank pump', so I'm assuming that the casting of the plastic top cap has galleys so the fuel return is integrated. I do believe since obd2 standard came into play, fuel return was removed from all cars, but the manufacturers, didnt necessarily remove it, but rather came up with more creative solutions for fuel return. For example, 350z/g35 fuel pumps have a fuel return, albeit integrated into the plastic, rather than the traditional fuel return with a second hardline tube going up and down the length of the car to the engine.

The pump is 100% in the lower portion/lower sub-assembly. To be honest, the actual pump mechanism is housed in plastic and looks VERY similar to your standard Walbro/Bosch/etc. To me, it looks like a Bosch unit (probably an 040 or something similar is my guess). I'm thinking a person could easily retrofit a higher flowing unit into the lower sub-assembly housing, run some wires/connections and have a pretty seamless seamless upgrade. One would have to verify voltage/etc. But, it definitely looks doable, most likely with minimal trimming to the housing that contains the actual pump mechanism

Thanks for the pictures by the way. There don't seem to be very many pictures on the internet of the actual pump. And just for clarification, this is the flex fuel version?

This is the flex fuel version (picture of the "AN" part number is in one of the pictures above).

I will try to get some more pictures tonight while I'm installing the new pump. I was running on my way out the door to work this morning. I definitely think that an in-tank retro fit of a larger pump into the OEM housing is doable.

Stay tuned.

-DL

[Lensch09]

Thinking about it again now, the 044 Bosch pump probably couldn't work as a retrofit in the sub-assembly (it's too large from what I remember).

There are other pump manufactures that make higher volume units in a smaller package than the Bosch 044. I'm sure one of those would work just fine.

More pictures later.

-DL

[RLB6]

I'm anxious to see the results of installing this pump to gauge if there are any improvements in flow. For this going DP I'm sure the extra headroom in fueling will be more than welcomed.

[jprice]

I'm anxious to see the results of installing this pump to gauge if there are any improvements in flow. For this going DP I'm sure the extra headroom in fueling will be more than welcomed.

It's already been done on a DP e85 car, and it took care of fueling issues.


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[RLB6]

It's already been done on a DP e85 car, and it took care of fueling issues.


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Sorry, ahven;t been keeping up....BUT, that is awesome to hear. Sounds like this took the air right out of the GIAC in-line pump solution (potentially)

[Rex Wilkinson]

I just ordered a new OEM low pressure fuel pump w/e85. Hope to have it installed in a week or two

Update, new OEM low pressure fuel pump w/flex is in. It will be installed next Wednesday. Fingers crossed that it fixes the limp mode my car goes in shifting 3-4

[LittleDozer]

Sorry, ahven;t been keeping up....BUT, that is awesome to hear. Sounds like this took the air right out of the GIAC in-line pump solution (potentially)

Yep, you're looking at him :)

No issues yet

[13ttaz]

Yep, you're looking at him :)

No issues yet

LD, you might have indicated this previously, but you are also running the upgraded HPFP, correct?

[RLB6]

Yep, you're looking at him :)

No issues yet

Nice.