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Help needed!?!?! 

 

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 Post subject: Help needed!?!?!
Posted: Sat Sep 10, 2005 10:15 pm 
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Ride: EF Falcon XT-T

Location: Mornington Peninsula
VIC, Australia

Ok my cars got a weird issue.
my car is Dual fuel (GRA setup)
LPG runs perfectly fine, it did 15.9 @ 88mph while running on LPG
petrol on the other hand has a problem under ~2900rpm
petrol could only manage 16.4 @ 89mph.

while i know the car deffiantely has more power on petrol (once it clears 2900rpm)

the issue is, under 2900rpm the car has flat spots, hesitates and just feels real sluggish, this problem is not evident on LPG.

I've replaced leads/plugs
fuel filter
fuel pump is working 100%

the only thing i can now think of is the injectors, but the injectors arnt that old.

since its an EF i know it can't be timing related (also since LPG is fine)

so i'm after as many ideas as possible.

 

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FALCN6 - EF GLi Turbo, 20" Rims, Air Bag Suspension, Straight LPG, 225rwkw
DTHWGN - EA GL Wagon, LTD Interior, Satin Black, 5.0, Turbo
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Posted: Sat Sep 10, 2005 10:25 pm 
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do you run the gas on gas all the time, or do you alternate frequntly between the two fuels

 

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Posted: Sat Sep 10, 2005 10:30 pm 
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Ride: BF XR6, BF XT Wagon

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Location: Perth
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Its an EF so it could also be the coil pack. or maybe the oxygen sensor. Different amount of unburnt oxygen from using one fuel to another ie Petrol/Gas.

 

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Posted: Sat Sep 10, 2005 10:37 pm 
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Most dual fuel setups i've seen have a relay hooked up to the EGO sensor that disconnects its output from the ECU only when running on LPG. This is so the ECU can't write values to the adaptive table (since it can't "sniff" the mixture). If the relay isn't working properly, the lpg might be set at the wrong mixture, and the ecu is trying to adapt. The lpg only needs to be slightly out of tune for the ECU to think "Hmm... my EGO sensor is lean/rich - time to richen/lean up the mixture". If this is the prob, when you go back on petrol, it'll run like s**t.

Try running it on petrol for a week or so, and maybe also do a computer reset (battery disconnected for 30 mins). That will erase anything learnt, and you can start from there. But before you do that, be sure to grab any stored codes if you haven't already :P

Of course - this is just an idea - it might be totally unrelated ;-)

 

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Posted: Sat Sep 10, 2005 11:00 pm 
Getting Side Ways
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Ride: EF Falcon XT-T

Location: Mornington Peninsula
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LPG most of the time, but the injectors were changed not long ago.
doesnt the oxy sensor get ignored @ WOT?

 

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FALCN6 - EF GLi Turbo, 20" Rims, Air Bag Suspension, Straight LPG, 225rwkw
DTHWGN - EA GL Wagon, LTD Interior, Satin Black, 5.0, Turbo
RACER - EF Futura , 5.0, 5 Speed
PROJECT - 83 Thunderbird, Lowered, 18" Billet Wheels
DAILY - BA Fairmont Ghia 5.4 3V

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Posted: Sat Sep 10, 2005 11:16 pm 
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I think so - but it still uses the ACT to determine how rich the "preset richness" gets (according to a docco I read a while ago). If its great on gas, maybe its time to look at the sensors that are pointless on gas. TPS, ACT, Coolant temp sensor etc. Also, check to see that you actually ARE getting WOT - i've had a throttle cable melt on the manifold once, which lead to me getting just shy of WOT. Not noticable while driving (unless you have a 3 speed with kickdown), but might not be putting the ECU into WOT stradegy - eg Go to preset rich, 28-ish degrees timing etc. Test the voltage on the tps and see if you are getting to around 4.4 - 4.5 volts for WOT - but check by getting someone to press the throttle for you while you test.

 

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EF II Sedan
Ex Chaser, Dual Fuel (Impco LPG)
LSD High, 3.23, Black wheels, other shiny bits.

EB II Sedan <--- R.I.P. (Rest in pieces - gone to the wreckers for $50...... bargain!)

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Posted: Sun Sep 11, 2005 12:10 am 
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Do you run on LPG all the time?
Is your petrol tank below the quarter or on red all the time?

some times if running LPG it can cause sludge to form in the return line {petrol tank}. I think thats what it said in my wifes EF tickford LPG owners manual.

 

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Posted: Sun Sep 11, 2005 12:32 am 
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i'm just wondering how some of these would effect *only* under 2900rpm.
once it hits 3000rpm it pulls like a train

 

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FALCN6 - EF GLi Turbo, 20" Rims, Air Bag Suspension, Straight LPG, 225rwkw
DTHWGN - EA GL Wagon, LTD Interior, Satin Black, 5.0, Turbo
RACER - EF Futura , 5.0, 5 Speed
PROJECT - 83 Thunderbird, Lowered, 18" Billet Wheels
DAILY - BA Fairmont Ghia 5.4 3V

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Posted: Sun Sep 11, 2005 12:45 am 
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I'm not sure how this would relate to an EF but I use to have a dual fuel XF and I could only adjust the timing to burn really well on LPG or really well on petrol, never both at the same time. So I set the dizzy for LPG and left it at that. I know the EF uses coil packs but could it be a similar situation where the fuel burn is only optimal for one type of fuel and not both at the same time?

 

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Posted: Sun Sep 11, 2005 1:02 am 
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EFFalcon wrote:
i'm just wondering how some of these would effect *only* under 2900rpm.
once it hits 3000rpm it pulls like a train

My XR8 used to do the same thing exept its not on gas, but a mate showed me a trick to tell if it was just in need for an ecu reset.
use full throttle off the line, then back off the throttle by about 1/4, if it seems to have more go, reset all ur sensors to factory settings (or desired if you know what you are doing) then reset the ecu. as my car has a few mods i found the "normal" way of reseting the ecu to be no good ,so I start the car ,bring it to normal temp, unplug the battery for 10-15 min, then start it & let it idle for 5 mins, turn it off for 2 min, turn on the ign select D if auto ,hold the throttle full for 2 min (not running of a***!) let the throttle off ,put back in P then turn ign off.
when driven for first time use all gears manually for 5km.
DO NOT FLOG THE s**t OUT OF IT WHILE DOING THIS!
the car is now ready to abuse

 

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Posted: Sun Sep 11, 2005 1:55 am 
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I suppose logically it shouldn't be an ignition issue as it runs okay on LPG but s**t on petrol - if the ign system isn't up to scratch you'd think it would most likely show up on LPG operation. As far as Impco LPG systems go, the oxygen sensor is switched by relay over to the gas computer (CDP), and I would imagine all closed loop LPG systems would have the same principle - the mixture needs to be controlled somehow - the oxy sensor is the last component in the loop.
I would suspect the fuel delivery system as little petrol use points the problem in this direction:
1. Fuel Pump: Possibly, but since it just pumps, fuel starvation should be more likely in the higher RPM range.
2. Fuel Filter: If you don't use petrol very often, it could have a blockage, but same deal as the fuel pump. Since it's been changed, its eliminated.
3. Fuel Reg: Could have perforations in the diaphragm - pull the vaccy line while running, do the straw suck thing, if you taste traces of petrol, there is leakage.
4. Injectors: Could be likely culprit. Perhaps some good FM'er will let you substitute theirs for testing.
5. Stale fuel: If petrol doesn't get used, it goes stale, this could make your engine run crap, but again, probably most likely at higher RPM.
What to do:
1. Reset the ECU, but use the post by 1SLYEL (I think it's a sticky).
2. Run the car on petrol, pull and blank the vaccy line off the fuel reg - if the engine idles a bit smoother, most likely the injectors are dirty, if not, could be fuel reg. Your injectors should be slightly more noisy when you do this test. Maybe take the car for a run with the fuel reg vaccy line off and blanked, see if the car runs any different.
At least once a week, use petrol on a trip - 30 km's or so. This way your petrol system gets regular use - don't just rely on petrol starts for this purpose. Make sure you add some petrol every month - 15L or so, so your pump keeps immersed - seals harden if the pump dries out.

Anyway, just spitballing - hope this gives you some ideas . . . . .

 

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Posted: Sun Sep 11, 2005 2:10 am 
Getting Side Ways
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Ride: EF Falcon XT-T

Location: Mornington Peninsula
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i'm not overly fussed on the condition of the fuel system.
sooner or later the entire petrol system will be removed, the main issue i want to work out so i know the engines at 100%.
theres no point me going and doing stuff to it if theres a problem, all good if the problem is simply bad injectors or what ever, but if its something else i'd rather know now and fix it.
I'll reset the ECU on monday and see what eventuates.
its the 2nd set of injectors that have been in it, and the last set were blocked up etc, but wasnt having the same effect this is having.

 

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FALCN6 - EF GLi Turbo, 20" Rims, Air Bag Suspension, Straight LPG, 225rwkw
DTHWGN - EA GL Wagon, LTD Interior, Satin Black, 5.0, Turbo
RACER - EF Futura , 5.0, 5 Speed
PROJECT - 83 Thunderbird, Lowered, 18" Billet Wheels
DAILY - BA Fairmont Ghia 5.4 3V

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Posted: Sun Sep 11, 2005 2:41 am 
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Ride: 96 XH/97 EL

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Obviously it's up to you what you do - although you should mention what you've noted above in your initial post.
In this circumstance dual fuel is an advantage as far as fault finding goes - anything that LPG/petrol uses in common will most likely not be at fault, it's the components that are not commonly used by both that need to be looked at . . . .

 

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96 XH Longreach 'S': LPG, Alarm, 3.23:1 LSD, Cruise, Trip Comp, ABS, Power Windows, Mid Series Dome Lt, Climate Ctrl
97 EL Futura S/W: LPG, Alarm, LED int Lts, Trip Comp, F/Lane Dome Lt, Climate Ctrl, T5 Conversion

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Posted: Sun Sep 11, 2005 5:13 am 
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when running on gas, is the intake air temp sensor still being used? the reason I ask is that ,if it is n't it may be dirty and running quite rich. on the v8 the IAT heats up to cleanse itself after being turned off. or the map sesor could be at fault according to the book, meaning closed loop will give wot power but inaccurate metering down low rpm

 

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Posted: Sun Sep 11, 2005 10:23 am 
Getting Side Ways
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Age: 34

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Ride: EF Falcon XT-T

Location: Mornington Peninsula
VIC, Australia

even at WOT the car has problems.
it doesn't matter if its 5% throttle or 100% throttle, if its under 3000rpm it hardly moves.
even trying to hold a constant speed (80km/h or 100km/h for eg) is quite a task as the car hesitates.

 

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FALCN6 - EF GLi Turbo, 20" Rims, Air Bag Suspension, Straight LPG, 225rwkw
DTHWGN - EA GL Wagon, LTD Interior, Satin Black, 5.0, Turbo
RACER - EF Futura , 5.0, 5 Speed
PROJECT - 83 Thunderbird, Lowered, 18" Billet Wheels
DAILY - BA Fairmont Ghia 5.4 3V

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