fuel flow problem

[SD1too]

Originally Posted by Matt_75

Regarding the fuel level sensors, the IPK diagnostic mode is capable of telling you what each sensor is reading.

That does appear to be the case Matt but in fact the two fuel senders are wired in series; pins 1 & 3 are joined together and there's only one output to the IPK from pin 4 so it isn't capable of distinguishing between the individual sender's readings.

The guide to which you linked deals with this if you read further.

Simon

[Matt_75]

Originally Posted by SD1too

The two fuel senders are wired in series Matt; pins 1 & 3 are joined together and there's only one output to the IPK from pin 4 so it isn't capable of distinguishing between the individual sender's readings.

The guide to which you linked deals with this if you read further.

Simon

Should've read the full post before linking it! Thank you for clarifying

[PetrolFeet]

Problem solved!! For now, at least.
So the original problem was this:
Drove home from work, 8 miles. No hesitation or any sign of a problem, but had always taken a second or two of the starter motor to get going.
Had about a gallon, maybe slightly less, in the tank when I got home. Red light had not been on for very long, a few miles, gauge was just above the red circle.
Parked the car on a slope, pointing up hill.
Next day, won't start. Code reader reported no codes, and I remember from other times that the fuel pump on the petrol isn't monitored by the ECU so started looking there.
Lifted back seat, couldn't hear the pump running. Took off panel, took voltage, 12v there, still couldn't hear the pump. Used a light hammer and drift (screwdriver) to remove lock ring. Checked it for loose spade connectors and anything else looking dodgy, no problem found.
Incidentally, pump and filter both had finger loops so not the clip. Also, this whole saga goes on for a few days, not all at once, I got a day job and my fingers were freezing!
Then, noticed the white tray was bereft of fuel (there is a cup the pump draws fuel from, not direct from the tank). Poured half a gallon in through the pump hole. Put the pump back on.
Went to "start" the car hoping to hear the pump this time, they are sometimes noisier and sometimes quieter, when they are dry.
Couldn't hear the pump over the noise of the engine running.
Baffled and pleased and baffled, all at once.
Got the missus to lean on the pump with a can of deodorant as I tightened the lockring, which stayed down this time.
Went for a drive, got a new plastic 5ltr petrol tank and filled it, as well as the tank in the car. The car started first time every time with less starter motor than previously.
Drove around some more, no problem.

Is the problem solved? Was there ever a problem beyond running out of fuel? Why is the pump so quiet? Should the tray have been as dry as it was? If the tank was empty, is the gauge faulty? What is the relationship, if any, between the starter motor and the work I did? Is there a fault with the tank interior fuel transfer system (getting the fuel over the saddle)? Was the fact I parked on a slope significant? What is the meaning of life and why am I here?

Any suggestions as to the above, greatly appreciated.

[trikey]

Has anyone mentioned orange (now white) clip?

Sent from my SM-G780G using Tapatalk

[SD1too]

Originally Posted by trikey

Has anyone mentioned orange (now white) clip?

Nick has Andy ....

Originally Posted by PetrolFeet

Incidentally, pump and filter both had finger loops so not the clip.

I think he's saying that he has the original filter design.

Simon

[PetrolFeet]

Correct, old filter and pump, no need to check the filter side.

[PetrolFeet]

T-Cut has done another blinder here I think my problem is related to all the pipages in the tank. Static pump failed, maybe?

[PetrolFeet]

To see T-Cut's original work, including a similar diagram for diesels, see his post marked
Revised HowTo's with Recovered Images

[SD1too]

Originally Posted by PetrolFeet

Static pump failed, maybe?

Nick, I thought you might be interested in the description given in RAVE. For T-Cut's "static pump" it uses the term "venturi".

"The RH side of the tank contains the swirl pot and electric fuel pump. Fuel is drawn from the swirl pot and delivered to the filter and pressure regulator housed in the LH side of the tank ... The pressure regulator relieves excess pressure by diverting fuel into a return line within the tank. The return line incorporates twin venturis; the LH venturi draws fuel from the left side of the tank and delivers it to the RH venturi which maintains the fuel level within the swirl pot."

If I understand this correctly it appears that there is only one source of pressure: the electric fuel pump, which provides more than is necessary for the injectors. The residual pressure is used to supply fuel via suction tubes (venturis) back to the RH side of the tank.

The RAVE illustration shows two small diameter tubes. The "filter inlet pipe" appears to be the high pressure flow from the electric fuel pump to the regulator. The second tube is the "return to swirl pot/feed to right side venturi".

There is also a larger diameter "scavenging pipe (left to right side)" shown as "S" on T-Cut's diagram and this clearly delivers fuel to the swirl pot beneath the electric pump. I'm guessing that this may work on the syphon principle otherwise fuel may never be drawn from the LH side of the tank.

Nick; upon withdrawing the electric pump you observed that the swirl pot was bone dry. Doesn't this suggest that you merely ran out of fuel or the level became too low for the car's position on an incline? If so, perhaps the gauge senders are the problem if you were under the impression that you had sufficient in the tank.

Simon

[PetrolFeet]

Originally Posted by SD1too

Nick; upon withdrawing the electric pump you observed that the swirl pot was bone dry. Doesn't this suggest that you merely ran out of fuel or the level became too low for the car's position on an incline? If so, perhaps the gauge senders are the problem if you were under the impression that you had sufficient in the tank.

Simon

Yes, in simplistic terms that is correct.
However, when I looked around the pump I saw I was not the first to open it. Reading on this site suggests the whole system is fairly fussy regards seals and pipes, any of which could easily become kinked by my own or someone else's carelessness.
Also, "running out of fuel" in the pure sense has certain symptoms. It is possible, though unlikely, that I parked up with just enough fuel to last until I turned the engine off, but not enough to restart.
Why was the cup bone dry? If it had been dry the engine would not have run to get me there.
So, thinking more deeply, I suspect that the fuel transfer system can fail under certain low fuel conditions like mine. With no fuel to pick up there is no fuel to syphon the fuel from outside of the cup. Perhaps the cup in my tank is slightly cracked, and so while the engine is running the syphon pumps keep it full, but when parked at the angle I was, the fuel had leaked out of the cup and with no flow, further syphoning could not occur.

Whether you want a simple or deep explanation for failure is up to you.
Whether you think this info is of use to others, or not, is also a matter you have every right to your own opinion of.

When I first looked upon your site, which seems to be a font of wisdom, knowledge and ignorance in equal proportion to any conglomeration of man ever, (that's a compliment if you believe in the overall wisdom of humanity, and an insult if you believe Humans are Fools. Up to you,) it was all about the Clip formerly known as Orange. So I looked there first. As I had the seat up I checked the pump (mine seems unusually quiet, or I'm going deaf in that frequency range) and on not hearing it, looked further. If the pump had been noisier I would have looked elsewhere, but then I wouldn't have seen a white plastic cup in a black plastic fuel tank, leading to me finding T-Cut's most useful picture.

So there are two morals of this story:
1 Don't run out of fuel and carry a gerry can of it securely in the boot
2 The car has an unusual low-fuel behaviour - there may be enough fuel to run the car but not enough to restart it. Bear this in mind in all future fuel-related problems. I would guess this related to petrols and diesels, having more to do with the tank shape than anything else. The gauge can indicate several litres of fuel, but on an incline this may not be enough.

Reading this through before posting, I may seem acerbic, so let me finish with a Thank You to SD1too, without whose replies I would know less about the fuel delivery system of my car than I do; T-Cut, who should work as an educator in this field if he doesn't already; Matt-75 who gave freely of his experience in this matter, and the many other people who have contributed - even if with middling advice, has sustained me at a time of no car - deeply, Thank You.