BMW M5 Forum and M6 Forums banner

21 - 40 of 66 Posts

·
Registered
Joined
·
33 Posts
Discussion Starter #21
So I just did the ground wire test, 1 at the plug, and to a solid body ground in the trunk and the results are interesting. I got reading of 2.4ohm all the way down to .1ohm, and it actively fluctuated, it did not settle on any one reading, sometimes it would hover around .3-.5ohm but then continue fluctuating.

That doesn't seem right to me? But again this is my first real experience with an electrical issue so I don't really know just yet.
 

·
Registered
Joined
·
33 Posts
Discussion Starter #22
In reading about the path to ground joint, would that cause these pumps to burn out? Because each of these pumps have worked flawlessly when first installed, but after sitting for as little as a week, they are dead. I would like to think if the pump wasn't being powered properly it wouldn't matter if I just installed a new one or not correct?
 

·
Registered
Joined
·
33 Posts
Discussion Starter #23
941055


Attempting to post a picture, hopefully it works! I don't think what's going on with the ground here is correct.... The previous owner did have hella lights retrofitted. The ground wire going from the crimp to the relay plug feels really weak where the bend is at 12oclock (where brown crosses over the red/white power wire).

Is this a suspect? Would something like that cause this?
IMG_20200713_191733.jpg
 

·
Registered
Joined
·
10,038 Posts
Is this a suspect?
Might be but I have no idea what that is grounding. Your readings for the ground are suspect and are telling you that there is a problem. Your pumps were not burnt out that just had intermittent grounds, they are perfectly fine. It is to bad you did not come here when you had your first problem.
I suspect that is the ground wire for the pump, but you will have to decide. Clean that mess up and crimp or solder up the joint but don't cover that up. Once you are done fixing that we might need to wrap a wire around that and ground that, it just depends on the reading you have. It is clear someone has messed with this so it is hard to know what else might be messed up. Just fix that and test again, but you are getting closer.
 

·
Registered
Joined
·
10,038 Posts
I just got a helpful message. It appears that my question was answered the X13379 joint should be the ground to activate the fuel pump relay. So follow those three wires to where they go, you can guess the one going to the pump or maybe use your new volt meter skills to figure that out. One should run to the relay plug, then definitely follow that third to where it mounts to the body. Either something will be loose there or it will be corroded.
Also in the center of the picture there is a brown wire that goes past the red white wire and right at that point it looks like it might be damaged, so look close to make sure it is not.
 

·
Registered
Joined
·
33 Posts
Discussion Starter #26
Yeah that ground that passes over the red/white is from the relay plug to that slpice, it felt very weak when moving it in comparison to the other ground wirings.

Tonight I will trace those and see what I see!
 

·
Registered
Joined
·
33 Posts
Discussion Starter #27
I just got a helpful message. It appears that my question was answered the X13379 joint should be the ground to activate the fuel pump relay. So follow those three wires to where they go, you can guess the one going to the pump or maybe use your new volt meter skills to figure that out. One should run to the relay plug, then definitely follow that third to where it mounts to the body. Either something will be loose there or it will be corroded.
Also in the center of the picture there is a brown wire that goes past the red white wire and right at that point it looks like it might be damaged, so look close to make sure it is not.

I am having an issue finding that oem brown wire to replaced the damaged part with. I looked on FCP euro which is where I primarily order parts from and I can't seem to locate it.

I would prefer to fix this proper with factory equipment, and ideas where I could get my hands on some?
 

·
Registered
Joined
·
10,038 Posts
Depends were you are. But I would just go to the Parts Source or Canadian Tire and have it in my hand today, you won't get that color so if you want the OE wire go to the dealer, I suspect wire might have a large markup but will likely still be cheap enough.
I would just grab each wire at that joint and tug them. If they don't come out or wiggle then that joint is likely fine, might even be factory. Your readings suggest the big problem is after that joint if it is not loose. You tested from the pump to ground so the relay ground could only be adding to the funny readings if there was a messed up path to ground from that joint to ground. Cutting that wire to the relay would have no effect on your readings if you had a solid ground. Almost certainly the problem is from that joint to where it goes to the body so do that first.
If you hit a road block wrap a wire around that joint tightly then take it over to the battery neg and try the tests from that thread again. That will confirm that the problem is after that joint. Likely you will succeed with all the tests and if you do then that would say there is little wrong with the relay ground wire. Again you have to decide because you are the one with your hands on the car.
 

·
Registered
Joined
·
33 Posts
Discussion Starter #29
That joint isn't lose, I unwrapped the loom in the trunk area and nothing looks out of place.

I have yet to trace the the grounds past the splice...however for fun I decided to retest the pump on the 1 and 4 pin and got 2.0ohm, which is high I believe. I also tried to start the car and while cranking it sputtered. Which means you were right sailor, the pump isn't dead, but something is impeding power to it. Is it possible the 2.0ohm I got from testing the fuel level sensor pins would cause this?
941088
941089
 

·
Registered
Joined
·
33 Posts
Discussion Starter #30
I guess that wouldn't make sense actually...idk this is starting to make me brake my calm.

From another thread I read that a function pump should have 4ohm and that fella had 297ohm or something like that. I pulled my fuel pump out of the tank and found that I go 2.0ohm...im not quite sure what to make of that.

I retested the relay ground wire to body and got 3.4ohm (which should have tested the splice and everything else in line with it?) I'm not sure how significant 3.4ohm is... Is a bad ground anything above 1.0ohm?
 

·
Registered
Joined
·
10,038 Posts
I have yet to trace the the grounds past the splice...however for fun I decided to retest the pump on the 1 and 4 pin and got 2.0ohm, which is high I believe.
It does not matter what the ohms are and they will likely change a little as the pump armature is rotated, the temperature will also have an effect. More than I am going to try and explain to you, go get a college coarse on DC motors. When you had the pump out if you wanted to see if it worked all you had to do was apply 12V to it and it would have run. The bench test I told you about before. Your pump is not getting 12v that is why it is not running and you will likely find the problem at the ground or one of the other wires.
Don't read too much into the ohms tests we were just looking to see if the pump had ohms(if it read 0, that would have been a problem) to start, it does so move to the next step test the wires feeding it and leading out both should be zero. We know the ground is not so that is the next step finding out why not.
You are over complicating this. I could give this task to a first year apprentice and he would be done already.
The things you are testing might be relevant, but they are not now the only question that must be answered now is why does the ground wire have resistance when it should have none.
A bad ground is anything above 0, depending on how the meter is set.
If you wanted a side track to see if things are working plug everything back in except for the relay and put that wire on from the joint and run it too the - battery. Then run the tests from that thread. Had you done that you would have seen everything works, in all likelihood.
 

·
Registered
01 Carbon/Silverstone Exhaust: Jedders-HJS high flow cats-resonator delete-Xpipe-Eisenman cans
Joined
·
2,547 Posts
I'm assuming that at some point you have checked your fuses. There are two separate fuses, one for the pump and one for the relay as you can see in the diagram.
 

·
Registered
Joined
·
33 Posts
Discussion Starter #33
I'm assuming that at some point you have checked your fuses. There are two separate fuses, one for the pump and one for the relay as you can see in the diagram.
Yes I have, they were fine, I swapped them with new fuses respectively. Sailor is right, I'll bench test my pump that I pulled, follow my suspect grounds and see what I see.

Yesterday I way over complicated things for myself.
 

·
Registered
01 Carbon/Silverstone Exhaust: Jedders-HJS high flow cats-resonator delete-Xpipe-Eisenman cans
Joined
·
2,547 Posts
As I mentioned before, voltage drop testing is much more sensitive for finding a loose or corroded electrical connection. Here is a simplified way to test your entire circuit (link below). Test the ground side then if it's good test the power side. If you get more than 0.5V drop then you can start to narrow down the search. You will need a pump in place. Backprobe the pump connector. Put your multimeter on DC volts and use the max/min function if it has it. Once you are set up you can turn the key to energize the circuit.
 

·
Registered
Joined
·
33 Posts
Discussion Starter #35
Unfortunately I will be away from the car until the weekend, so my next post will be then.

The pump runs, as sailor said it would on a bench test, I followed the ground and it led me to the passenger taillight, the only weirdness was the splice, which upon closer inspection is the fuel pump relay/fuel pump grounds spliced into another leading to the ground mention earlier.

When I get back to the car I will replace the relay-splice ground and if no change continue with a voltage drop test.

Thank you everyone for all the helpful advice so for, and hanging in there with my inexperience.
 

·
Registered
Joined
·
10,038 Posts
led me to the passenger taillight
Take a picture so I don't have to ask a ton of questions. If it bolts to something unbolt it clean it and re bolt it. Also do an Ohms reading right there and see if it goes to 0 before you un bolt and clean. Voltage drop is not going to get you any closer you know the issue is in the ground wire, that is all a voltage drop test will tell you. Do an ohms test right at that joint if it is still not 0 then do the jumper wire to the battery and that will confirm the issue is from the joint to the body ground. You work down the wire and you started at the pump which gave you a funny reading so go to the joint if the reading is still funny it is closer to the body ground, move closer. If it drops to a solid 0 then the problem is between the joint and the pump, work backwards then, simple, well for me it is.
 

·
Registered
01 Carbon/Silverstone Exhaust: Jedders-HJS high flow cats-resonator delete-Xpipe-Eisenman cans
Joined
·
2,547 Posts
Voltage drop testing is more sensitive than looking at resistance if it's not a major break. This is from Rob Siegel who wrote a book on BMW electronics. The technique is otherwise the same. Start wide and then move in one connection at a time to pinpoint the bad one.
 

·
Registered
Joined
·
33 Posts
Discussion Starter #38
Voltage drop testing is more sensitive than looking at resistance if it's not a major break. This is from Rob Siegel who wrote a book on BMW electronics. The technique is otherwise the same. Start wide and then move in one connection at a time to pinpoint the bad one.

I will do a voltage drop test as soon as I get back to the car, I do think I found my issue though. I will get back to you on my findings though.
 

·
Registered
01 Carbon/Silverstone Exhaust: Jedders-HJS high flow cats-resonator delete-Xpipe-Eisenman cans
Joined
·
2,547 Posts
If you think you found the issue that's cool you can just repair it and skip the testing, she how she runs. Good luck!
 

·
Registered
Joined
·
33 Posts
Discussion Starter #40
This is a learning experience for me, as you can see. So it doesn't hurt to learn how to run a voltage test, even if it isn't necessary. We shall see come the weekend though! :)
 
21 - 40 of 66 Posts
Top