Fuel Pressure drop when e85 put into gas tank
11-03-18, 08:31 PM
#1
Full Member
Thread Starter
Fuel Pressure drop when e85 put into gas tank
Hi guys, this seems weird and hope you can help. My FD has been running perfectly on pump 98 gasoline for the past year.
Finally got around to organising a tune on e85 and so got my gas tank low, and then added some e85. My Adaptronic Modular was showing an ethanol content of e43, so decided to drive it around more to empty the tank and fill up again to get the ratio up to e85. It drove perfectly for 2 hours just cruising around. I put a few more litres in the tank and ratio went up to e48. Figured ill just empty my jerry can of e85 into it the next day before the tune and it should be close to e85.
Next morning I try to start it, and it won't idle, keeps dying. I noticed the base fuel pressure had dropped from the 40psi it had been at for the past year, to only 34 psi. And when the engine was trying to idle the fuel pressure was in the 20s.
I changed nothing other than the fuel. I checked the speedflow fuel filter, exact same psi with and without filter in place. Pump is a walbro 460, hardwired to 12v constant. FPR is a Turbosmart FPR2000. Injectors are oem 850s in primary and Bosch 2200 secondaries. FP sensor is TI. GM flex sensor. Fuel lines are raceworks ethanol rated rubber lines. Intank hose is an Earl's submersible hose. All these parts are about 5000kms/1year old.
Now today, I drained the ethanol out of the tank, put pump 98 gas back in, and the base fuel pressure has automatically gone back up to 40psi and the car drives perfectly again...
Does anyone have any idea what is going on? Why would ethanol be making my fuel pressure drop?
Thanks in advance.
Finally got around to organising a tune on e85 and so got my gas tank low, and then added some e85. My Adaptronic Modular was showing an ethanol content of e43, so decided to drive it around more to empty the tank and fill up again to get the ratio up to e85. It drove perfectly for 2 hours just cruising around. I put a few more litres in the tank and ratio went up to e48. Figured ill just empty my jerry can of e85 into it the next day before the tune and it should be close to e85.
Next morning I try to start it, and it won't idle, keeps dying. I noticed the base fuel pressure had dropped from the 40psi it had been at for the past year, to only 34 psi. And when the engine was trying to idle the fuel pressure was in the 20s.
I changed nothing other than the fuel. I checked the speedflow fuel filter, exact same psi with and without filter in place. Pump is a walbro 460, hardwired to 12v constant. FPR is a Turbosmart FPR2000. Injectors are oem 850s in primary and Bosch 2200 secondaries. FP sensor is TI. GM flex sensor. Fuel lines are raceworks ethanol rated rubber lines. Intank hose is an Earl's submersible hose. All these parts are about 5000kms/1year old.
Now today, I drained the ethanol out of the tank, put pump 98 gas back in, and the base fuel pressure has automatically gone back up to 40psi and the car drives perfectly again...
Does anyone have any idea what is going on? Why would ethanol be making my fuel pressure drop?
Thanks in advance.
Last edited by mikey13b; 11-04-18 at 08:47 AM.
11-05-18, 04:24 AM
#2
Arrogant Wankeler
That is very odd, you would possibly expect ethanol to drag dirt through the filters but if it goes back to normal on pump I would only imagine that happening if your fuel pump was very finely PMW mapped and the extra volume demand on ethanol mean you needed high pump duty.
11-07-18, 06:17 PM
#3
Full Member
Thread Starter
It's very weird. The pressure actually seems correlated to the amount of ethanol in the mix.
As I added more pump fuel and the ratio went from e48 to e20 for example, the pressure increased a few psi. Then I added more pump fuel and the ratio went to e10 and the pressure went up another couple of psi, and now at about e4 the pressure is back up to 40 psi... What could be causing this?
As I added more pump fuel and the ratio went from e48 to e20 for example, the pressure increased a few psi. Then I added more pump fuel and the ratio went to e10 and the pressure went up another couple of psi, and now at about e4 the pressure is back up to 40 psi... What could be causing this?
11-11-18, 04:02 AM
#4
Arrogant Wankeler
Are you reading pressure from the electronic sensor or an analog gauge on the regulator?
Was the ecu set up with custom compensations or the baseflex fuel compensation?
It is unlikely a mechanical problem with the pump/reg, especially if it goes back to normal with regular fuel.
Are you running idle air bypass control?
Are the injector dead times correct for the primary injectors?
The only thing i can think of is a combination of fixed idle air and possibly a touch more electrical load with poor dead time compensation resulting in more manifold vacuum from the evaporation of the ethanol pulling more manifold vacuum and pushing to different cells in the fuel table/ignition table which aren't tuned well enough. Or the pressure sensor is being effected by the ethanol and skewing the fuel model, but I imagine it should all be alcohol compatible?
Was the ecu set up with custom compensations or the baseflex fuel compensation?
It is unlikely a mechanical problem with the pump/reg, especially if it goes back to normal with regular fuel.
Are you running idle air bypass control?
Are the injector dead times correct for the primary injectors?
The only thing i can think of is a combination of fixed idle air and possibly a touch more electrical load with poor dead time compensation resulting in more manifold vacuum from the evaporation of the ethanol pulling more manifold vacuum and pushing to different cells in the fuel table/ignition table which aren't tuned well enough. Or the pressure sensor is being effected by the ethanol and skewing the fuel model, but I imagine it should all be alcohol compatible?
Last edited by Slides; 11-11-18 at 04:08 AM.
11-11-18, 08:07 PM
#5
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Thread Starter
Thanks for your reply Slides. Yes I agree I don't feel it can be a mechanical problem, and suspected maybe the ecu is doing something especially seeing the pressure changes specifically in proportion to ethanol content, but didn't know how it could affect the base pressure with the engine off...
The fuel pressure is being read from an electric TI sensor connected to the port on the FPR. This should be ethanol resistant.
Regarding the compensation in the ECU I am not sure how it is setup. I did not change anything and my tuner only tuned it on pump 98 previously so I don't think he would have touched any settings related to ethanol yet. I'll have to have a search where to find this setting.
I am not sure about the idle air bypass control. I'll have to have a search.
I selected the 850cc primary injectors from the adaptronic drop down selection, should this already include the correct dead times?
The fuel pressure is being read from an electric TI sensor connected to the port on the FPR. This should be ethanol resistant.
Regarding the compensation in the ECU I am not sure how it is setup. I did not change anything and my tuner only tuned it on pump 98 previously so I don't think he would have touched any settings related to ethanol yet. I'll have to have a search where to find this setting.
I am not sure about the idle air bypass control. I'll have to have a search.
I selected the 850cc primary injectors from the adaptronic drop down selection, should this already include the correct dead times?
11-12-18, 06:33 AM
#6
Arrogant Wankeler
If you are running fd secondaries as primary injectors, yes.
other thought was if there is a blanket +5/10 degrees ignition timing or something weird with ethanol it will pull more vacuum at idle too.
other thought was if there is a blanket +5/10 degrees ignition timing or something weird with ethanol it will pull more vacuum at idle too.
11-21-18, 06:38 AM
#7
Full Member
Thread Starter
Well it seems the Haltech TI sensor was faulty. I hooked up a mechanical gauge and it read 40psi base pressure with e50 in the tank, whereas the sensor was reading 31psi.
Have now connected up a bosch sensor and getting 40psi base pressure also.
Have now connected up a bosch sensor and getting 40psi base pressure also.
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11-28-18, 01:47 AM
#11
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Thread Starter
I didnt notice any smell. But the only way to get it to fire at all is to spray wd40 in the inlet manifold and then crank it with WOT. So that would mean its flooded wouldnt it?
11-28-18, 03:10 AM
#12
Arrogant Wankeler
If its flooding the exhaust should stink or blow a bit of a cloud of fuel when it does kick otherwise i would be looking for water consumption or poor compression if it was starting ok before.
04-09-21, 08:11 AM
#13
Full Member
Old revival but I'm actually having this exact same issue. The reading seems to drop about 7-8psi on e60~ vs pump 93. Fast forward 4 months to now, I'm back on pump 93 and the first tank that ended up being around E30 or so didn't seem to change much, maybe 1-2psi, but as soon as I filled up with the second tank of pump 93 that brought me closer to E15, it instantly shot up another 6-7psi which would line up with the roughly 7-8psi total drop I had when I first went to e85(e60~ first tank).
Backstory: I know it's truly dropping though because it actually caused my old fuel pump(6 month old DW400) to lock up, I assume too much backpressure from the regulation going below 40psi. Thought it was a fluke when I first switched over to e85, maybe that the regulator nut had loosened (somehow coincidentally while I was at the station adding e85 for the first time). After the first pull, the car shut off and the pump would not run again until I took it out of the car and ran it free-air, this happened a couple more times until I limped it home cruising at like 30-32~ psi fuel pressure at -8 PSI vacuum. Regulator is an Aeromotive A1000 with a 40psi minimum. I changed out the filter and cranked up the pressure by 8 psi to set it where I wanted it and the problem went away after changing fuel pumps for peace of mind (to a Bosch 044). I'm still on the 044 now going back down to the Pump 93 (currently around E15 blend). So this is now 2 separate pumps with similar behavior. The only other change was the first tank of e85 I still had a little TCW3 in the gas from the pump gas, and have since been using e85 safe premix at 2oz/gal - but that should not be enough to change viscosity on a noticeable amount.
Backstory: I know it's truly dropping though because it actually caused my old fuel pump(6 month old DW400) to lock up, I assume too much backpressure from the regulation going below 40psi. Thought it was a fluke when I first switched over to e85, maybe that the regulator nut had loosened (somehow coincidentally while I was at the station adding e85 for the first time). After the first pull, the car shut off and the pump would not run again until I took it out of the car and ran it free-air, this happened a couple more times until I limped it home cruising at like 30-32~ psi fuel pressure at -8 PSI vacuum. Regulator is an Aeromotive A1000 with a 40psi minimum. I changed out the filter and cranked up the pressure by 8 psi to set it where I wanted it and the problem went away after changing fuel pumps for peace of mind (to a Bosch 044). I'm still on the 044 now going back down to the Pump 93 (currently around E15 blend). So this is now 2 separate pumps with similar behavior. The only other change was the first tank of e85 I still had a little TCW3 in the gas from the pump gas, and have since been using e85 safe premix at 2oz/gal - but that should not be enough to change viscosity on a noticeable amount.
05-22-21, 05:46 AM
#14
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Reviving an old thread again! Im also seeing the same behaviour. I have an FPR2000 and have tried both a TI sensor and a generic stainless steel sensor. I get a 7psi drop when going from e85 to 98.
Looks like the OP sorted it with a bosch sensor (I have one to try now). Did the last poster get it sorted too?
Looks like the OP sorted it with a bosch sensor (I have one to try now). Did the last poster get it sorted too?
05-29-21, 07:10 PM
#15
Full Member
I haven't spent any more time diagnosing it, I don't know if it's a sensor issue or some kind of viscosity issue. I generally switch premix from Klotz SuperTechniplate with e85 to Pennzoil Marine Plus TCW3 when I'm fully on pump gas. I don't think that plays a difference but it is very odd. I have the Haltech 150psi fuel/oil pressure sensor installed in an Aeromotive A1000 Regulator(same model # as their fuel pump, why, I have no clue).
All I do know is that manually adjusting the pressure to the previous base when switch fuels clears it right up.
All I do know is that manually adjusting the pressure to the previous base when switch fuels clears it right up.
05-29-21, 08:02 PM
#16
it’s likely being influenced by the specific gravity difference
E85 is approx. 0.80
pump gas is approx. 0.74
they can both obviously vary based on their actual contents; ethanol is heavier than gasoline, higher octane gasoline tends to weigh less, but that obviously depends on what’s being used for the octane change
fluid density will impact pump flow/pressure/power consumption, orifice flow/delta-pressure, etc.
.
E85 is approx. 0.80
pump gas is approx. 0.74
they can both obviously vary based on their actual contents; ethanol is heavier than gasoline, higher octane gasoline tends to weigh less, but that obviously depends on what’s being used for the octane change
fluid density will impact pump flow/pressure/power consumption, orifice flow/delta-pressure, etc.
.
09-16-21, 06:32 AM
#17
it’s likely being influenced by the specific gravity difference
E85 is approx. 0.80
pump gas is approx. 0.74
they can both obviously vary based on their actual contents; ethanol is heavier than gasoline, higher octane gasoline tends to weigh less, but that obviously depends on what’s being used for the octane change
fluid density will impact pump flow/pressure/power consumption, orifice flow/delta-pressure, etc.
.
E85 is approx. 0.80
pump gas is approx. 0.74
they can both obviously vary based on their actual contents; ethanol is heavier than gasoline, higher octane gasoline tends to weigh less, but that obviously depends on what’s being used for the octane change
fluid density will impact pump flow/pressure/power consumption, orifice flow/delta-pressure, etc.
.
just bumping to confirm; went from E37 to E50 and fuel pressure at idle decreased several psi, pretty sure it’s per my copied post above … completely aftermarket fuel system, external surge tank; dual staged external pumps, aftermarket filter, lines, FPR, rails, injectors; the works. Running premix with the addition of an ethanol specific top end lube to add lubricity and counter the ethanol dryness effect.
so that’s something to consider and account for imo if you intend to run different E% levels.
.
09-17-21, 12:44 PM
#18
Check the gauge on the FPR next time it happens to rule out a bad electronic gauge/sender. I suspect its the Prosport gauge doing Prosport things. I've replaced both the Fuelab FPR gauge and Prosport sender at least once before due to funny readings. I don't think either time it was an actual fuel pressure issue. It might just be ethanol gumming things up.
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