1988 535is fuel guage inop

[90turbo1]

So this is not a typical fuel guage inop thread.

a little back story,

we had a partial old style cluster installed in this vehicle tach did not work, si board was screwed but the fuel guage worked. we then installed the new style instrument cluster (repaired gears on speedo) and like before fuel guage does not work.

we have checked the sending unit in tank and found it sweeps through the ohm readings from full to empty I think 70 ohms full, 5 empty.

low fuel light will come on dash when tank is almost empty so that circuit is working.

the guage works with the junk cluster we have so I believe the wiring from tank to guage is working.

i have checked the nut on back side of the fuel guage and it is clean and seated properly. the temp guage works as should and the tach and speedo work like should with exception of fuel milage guage moving all over the place it seems.

so when key is off the fuel guage goes to empty in a nice sweep, when key is turned to run the needle goes full in one sweep and doesnt move from there. I would assume the little motor that moves the guage is working. there must be something on board that is not or I am missing something. anyone experience this before?

[fuzz1]

Hi mate I've got a problem with my BMW x5 and I was searching through some forums and found a old one from back in 2013 and seen you are a level 1 BMW mechanic and thought if I could ask you for some help and I had no other way of contacting you and seen you are still active on here all the years later.
The issue is I brought the car a few months back and I came to start it one morning it ran fine and all of a sudden it just turned off on me and I tried to start it and it would just cut out so I thought id sort it out on the weekend and the battery when a bit down so I jumped started it and it started but when I went to move it out of the driveway I felt it was a bit Shakey and went to fill it up with some fuel as planned on going for a long drive it had just under a 1/2 tank and got onto the motorway/freeway and I gave it some gas and it started shaking like crazy and cut out I found a layby and rolled it over and then I tried restarting it and it started got a 100 ft down the road and it just cut out on me again eventually I got a flatbed home and called up the AA and they reconned it be the fuel pump so I got to replacing it with another one at it still did the same thing starts runs for 10 seconds and then cuts out I did a bit more digging and some folks said the EKP module could be bad so I changed that as well and still the same thing then I got told about the DDE sky blue relay and that may have blown so I just changed it a week ago and I still have the same issue I also changed the fuel filter, also I did replace the battery but it did not change anything. So now I am scratching my head trying to figure out what the problem is and trying to find some suggestions to what the problem could be. BMW E70 30D M57 engine I would really appreciate any help/ suggestions to what this problem could be.

[sixerguy]

Holy hijack fuzz1!

So the junk cluster's fuel gauge operates ok, but the other cluster's fuel gauge doesn't operate correctly?

Is it possible to swap over the working gauge to the cluster you want to use? I've only had my e24's cluster out once but it seemed like most of the gauge pods were removable and replaceable...

-Drew

[90turbo1]

yes that is correct but the cluster that does not work is a late cluster and the one that does is early one, they are different in the way they mount