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pressure in the fuel tank.
noticed difference between my car and my parts car on the weekend.
On my car i remove the fuel pump relay then crank car, pressure i undo is removed. I un do the fuel line at the fuel rail and only small amount comes out then stops.
on my parts car i remove relay, try to start car, un do fuel line and then fuel is constantly running out.
I go to open the fuel cap, whooooosh the tank depressurised. Return to fuel line fuel is no longer pouring out.
why is one car storing lots of pressure?
seems like it should not be keeping lines so pressureised.
On removing the fuel tank cap on the parts car was it pushing out ?, the fuel flowing out the fuel line is also a clue of positive pressure
This has to do with the EVAP ( vapor ) system
On the parts car do you have 1 only rectangle box ( vapar canister) on the left car side fwd of the rear wheel or 2 as 1 on each side of the car ?
See page 60 as there are 2 slightly different systems , 1 and 2 vapor canisters , 1 canister has the Rochester valve , and the 2 canister has the extra electrical valve ( canister close valve ) and no Rochestor valve
This threw me for a loop as I put a meter testing the whole engine wiring loom as the canister close valve ( if installed ) is wired into
On removing the fuel tank cap on the parts car was it pushing out ?, the fuel flowing out the fuel line is also a clue of positive pressure
This has to do with the EVAP ( vapor ) system
On the parts car do you have 1 only rectangle box ( vapar canister) on the left car side fwd of the rear wheel or 2 as 1 on each side of the car ?
See page 60 as there are 2 slightly different systems , 1 and 2 vapor canisters , 1 canister has the Rochester valve , and the 2 canister has the extra electrical valve ( canister close valve ) and no Rochestor valve
This threw me for a loop as I put a meter testing the whole engine wiring loom as the canister close valve ( if installed ) is wired into
no idea about the vapor canister. but yes if i had of unlocked the fuel cap and then let it go it would have launched upward a little bit. there was definite pressure build up.
on the weekend i will try to get a chance to look,
This guy made a good video explaining his problem.
I will tell you that I also had issues. I’d start by eliminating the Rochester valve. Just plumb the hose directly to the charcoal canister. See if that solves the problem with pressurization.
If it doesn’t, you’ll have to spend some time reaming tubing or simply replacing it….which is what I would recommend. Oddly enough, my gunked up hard pipe was the section under the car, not the section the guy in the YouTube video replaced.
That problem is on my parts car so not going to spend time fixing it.
whilst i aim to keep the parts car running and moving as much as possible i am not spending time making it perfect.
good to know if i ever suffer this on my driver tho
Did you ever eliminate injectors from the equation?
Worn injectors would allow too much fuel during open loop , which would be trimmed back during closed loop…
Negative fuel trims are a good clue.
Manifold cracks result in positive fuel trims as the car erroneously adds fuel because the lambda sensor detects the oxygen which has been sucked in through the crack and the ECU concludes that the mixture is weak.
The fuel pressure regulator was another interesting shout, as if it was stuck shut, the pressure would be too high, but the car could compensate during closed loop operation.
Did you ever eliminate injectors from the equation?
Worn injectors would allow too much fuel during open loop , which would be trimmed back during closed loop…
Negative fuel trims are a good clue.
Manifold cracks result in positive fuel trims as the car erroneously adds fuel because the lambda sensor detects the oxygen which has been sucked in through the crack and the ECU concludes that the mixture is weak.
The fuel pressure regulator was another interesting shout, as if it was stuck shut, the pressure would be too high, but the car could compensate during closed loop operation.
have not got a chance to do injectors yet.
had shipping issues.
i am currently waiting on a fuel pressure gauge and attachment to arrive.
and also new injector o-rings and electronic injector cleaner so i can do rebuild the injectors.
so installed a fuel gauge…..
adapter threads perfect.
chamfer on inside of adapter is a little smaller so it doesnt go on the rail as snug as i would like but all good.
but fuel pressure seems low when running
only about 36psi.
when car is off fuel pressure is ok. About 42psi
Not sure regulator, pump or injectors or all.
Last edited by Spud Maat; Oct 21, 2024 at 02:51 AM.
got it from a place online here. automotive superstore.
here are the links.
not sure where you could find the adapter over where you are.
the only thing that could be better is if the chamfer opening was a little larger on the adapter it could sit on a bit deeper and allow a couple more turns on the nut.
i am going to get some PTFE tape and put that on the threads just to be 100% safe and secure.
i had to cut a little off the plastic fuel rail cover and that rear bolt no longer goes in the plastic cover.
but that really does not matter.
The gauge does clear the bonnet.
i wanted it a little lower than it is but all good.
i think maybe it hits on the bonnet lining.
here is a video.
there is 2 clips in one.
the first 5 seconds is on initial startup today.
was 38psi on idle and then up to 42 or so on throttle.
second clip is after my drive when i parked at work.
was 36 initially, then you can see it behaving correctly climbing on throttle, dropping on release, etc.
it does then rest a little low.
on throttle it is getting to 44-45psi which my understanding is correct as these injectors are 43.5.
The theory about the fuel pressure regulator being the cause of the running rich problem was based on it making the pressure at the rail too high. Sounds like you have now eliminated that one Spud.
so i took the injectors from the parts car,
ultrasonic cleaned them, replaced the micro filters and o rings
put them in.
cleaned the fuel rail while i was there…..
and now. Fuel trims look much better.
will keep an eye on it.
if anything bank 1 is now running leaner than bank 2 which shows me the ecu was trying to compensate for a leak.
I hope my problem is now sorted.
will bench test the old injectors and see.
it should now sort itself out. Very happy!!!!
then old injectors look as tho they may never have been cleaned.
ok so i have been keeping an eye on my stft and they have kept looking good.
however, i noticed today bank one was giving me a 0 reding.
i checked it in both OBD fusion and Torque and both apps were giving me a 0 reading on bank 1 even after a reset.
i assume this means that there is likely a bad connection.
however i am not seeing a code.
i would have assumed if one of the o2 sensors is not giving any reading there would be a code.
As a new type of engine regulation technology design ECU way back when , the ECU ( and whole engine system ) has it's design faults as best engineering try at the time , only so much engineering manpower budgeted and must move on to other projects
Kinda like Honey Do list
Hi Andy
Your swapping around the O2 sensors and connector positions may have confused the ECU until it relearns the sensor parameters ( they are all different fine readings even new sensors out of box ) and will then " accept " them and not rejected for STFT calculation , the reader device ( design shortfalls ) also plays a role in the information displayed
Your final fully functioning O2 sensor / fuel trim determination is Hiway milage if in reasonable range
So we come back around to the ECU orientation that includes TPS and O2 sensors done at the factory to get it going " Premo " out the factory door
So in my opinion you are looking at cost to get the orientation done again after parts swap around or time / patients to let the ECU relearn
****** pebble from hand Grasshopper ( Kung Foo Master with a wink from blind eyes and flute music ) , My eyes recovered , but the song is still in my head
Ok so it seems a loose connection as thought was causing the 0 reading.
My next question is can we reset the LTFT?
or how long will it take to reset?
my LTFT is showing 9.4 on both banks, indicating lean running so the engine will bias overfueling.
as can be seen from all my videos, my STFT does jump around a lot going -5 -10 -20, always bouncing back to around 0.
Mostly the big - numbers are seen on throttle off.
i an thinking this is maybe caused by a bias set due to LTFT.
whereby it overfuels based on a lean LTFT but then the STFT reding causes it to balance and set back causing the STFT to jump around more than what it should be
Good reasoning , but LTFT may be a long average of the STFT and the difference may be available from reading the Jaguar 801s doc or other reading on the internet
