Reserve fuel problem

[andrewwynn]

Measure the Ω reading I think it ranges from like 50 to 450 Ω. Higher more gas. If there is an open circuit it will read full all the time. Did you say your left sending unit is a replacement?

[talljames]

Yes, genuine bmw unit. Will check tomorrow. Does your Foxwell NT510 test this? If so, mine should do it too. But I will get the multimeter out.

[andrewwynn]

I don't think the foxwell will read the output of the fuel gauges but it might.

The dash test six reports based on the Ω reading from the level sensors so the first thing to check is reading at the sensor, then wiring and connectors.

[talljames]

I am getting D7 Fuel tank sensor 2 (without fuel pump) error code. Will check multimeter in the next few days. If that checks out ok then I am thinking it could be the cluster after all this.

[talljames]

Ok, so I took the back seat apart again and measured the ohms. I had filled the tank recently and had used some. The reading was 501 ohms. So, this seems ok. I decided to do another reset via rest 21. I took some before and after pictures (below). I noticed that the gauge needle has moved up to the full mark. Before the reset it was a little below. The numbers have also changed. This time when I did the reset the car wasn’t running.

[andrewwynn]

the numbers didn't change because of the reset, but the needle moving was because of the reset. watch the tank numbers as they drain, you won't see the numbers change until 10L is used. 501 seems a little high i thought it maxed at 450. if the left tank numbers don't drop along with the right, something is amis, get a new reading with the tank 2/3 full or so.

[talljames]

So the gauge is at 50 now and I measured the ohms. between 350-400. unfortunately I didn’t write it down after reading it and putting all back together. the test 6 display reads 41.6 / 10.5 / 52.2L.

[andrewwynn]

those numbers look pretty healthy; the 'key' is that the right should be about 014 when the left is about 275. I knew that my left gauge wasn't working properly when the right reads 014 and the left read over 300; that is impossible. the 'flood stage' is approximately 27.5L left and 1.4L right. everybody's case will be slightly different.

Check once in a while and it's especially important that the right hits a stable low number like 1.3 or 1.5 L and on level ground steady speed it should just stay there the whole time the left side goes all the way to 0.0L. if the right drops before the left is bone dry it means the siphon jet isn't working.

[talljames]

I’ve been checking the price of those siphon jets (a pipe contraption that goes from one side of the tank to the other) and they are quite expensive. Will keep monitoring and post up again.

[talljames]

Yes, happened again. So, siphon jests, left sucking jet pump (didn’t know there was one), etc...sigh.