No power to Fuel Pump Fuse

[Panici]

Jumped the fuel pump relay to see if I could get my pumps to work. No luck.

Did some testing, and it turns out, power from my fuel pump relay isn't getting to the fuel pump fuse.

According to the wiring diagram I have, the fuse and relay should be directly connected, right?

EDIT: Disregard above
I was jumping the wrong relay.

Here's some new information.
-Terminal 30 of my fuel pump relay (red wire) only has 0.7v on it when it should have 12v all the time.
-Terminal 87 which should go to the fuel pump fuse, rings out as grounded. (as does one side of the fuse)

-When I jump 12v directly to the fuel pump fuse, both pumps turn on, and I have fuel pressure.

[spdracrm3]

Hey guys,

Jumped the fuel pump relay to see if I could get my pumps to work. No luck.

Did some testing, and it turns out, power from my fuel pump relay isn't getting to the fuel pump fuse.


When I jump 12v directly to the fuel pump fuse, both pumps turn on, and I have fuel pressure.

According to the wiring diagram I have, the fuse and relay should be directly connected, right?

first be sure your jumpering correctly pin 30 to 87

as you can see in your diagram there is a connector between the relay and fuse "C101 " pin 13, that and the wiring between relay and fuse are most likely where your problem is (there is also a connector in the fuse box itself C214). last pages in ETM's show connector views and locations

[Panici]

first be sure your jumpering correctly pin 30 to 87

as you can see in your diagram there is a connector between the relay and fuse "C101 " pin 13, that and the wiring between relay and fuse are most likely where your problem is (there is also a connector in the fuse box itself C214). last pages in ETM's show connector views and locations

Yes, relay is jumpered correctly. ~0v at fuse.

When testing with ohmmeter, I get ~70ohms from relay to fusebox. No beep on continuity test.

I'll check both connectors tonight.
Wiring goes into main loom, hope I don't have to tear it all apart to troubleshoot.

[spdracrm3]

go after C101 first as its the easiest to get to and take apart , ohm test from relay to pin 13 C101 then (check both halves of connector as you wont know which half is which) then pin 13 to fuse. that will eliminate half the track and maybe even find the issue

70 ohms is not much resistance but there is no load on system and it really shouldnt have any

[Panici]

EDIT: Disregard above
I was jumping the wrong relay.

Here's some new information.(I checked the wiring colors, I'm testing the proper relay this time!)
-Terminal 30 of my fuel pump relay (red wire) only has 0.7v on it when it should have 12v all the time.
-Terminal 87 which should go to the fuel pump fuse, rings out as grounded. (as does one side of the fuse)
-Fuse has 0v to it.
-When I jump 12v directly to the fuel pump fuse, both pumps turn on, and I have fuel pressure.



My current theory is that I have a ground fault between the relay and the fuse. This toasted the power wiring to the relay, and now it only reads 0.7v. However, if this theory was correct when I jumped 12v to the fuse, I should have melted the jumper wire I was using, as it would be shorted to ground.



Edit:
Found this connector under the dash. Is it factory? Green/Violet should be for the fuel pump. Other side of the connector is a black wire.
Neither side tests as grounded though, so the problem is likely before this.

[spdracrm3]

the ground your seeing on pin 87 is thru the fuel pump windings and is correct to see that (notice the G300 on the other side of the fuel pumps? thats the ground you see when checking circuit) ,and since you jumpered to 12 and it didnt melt your wiring that side of the circuit is good (usually want to use a fused jumper for just this reason) . only having .7 V on pin 30 is your problem for sure ,you need to trace that (red wire) back to the battery junction block (shown in diagram) and find the voltage drop

whats the voltage on pin 30 of the main relay ? as you can see its shares the same feed and could lead to a idea as to where the problem is

[Panici]

the ground your seeing on pin 87 is thru the fuel pump windings and is correct to see that (notice the G300 on the other side of the fuel pumps? thats the ground you see when checking circuit) ,and since you jumpered to 12 and it didnt melt your wiring that side of the circuit is good (usually want to use a fused jumper for just this reason) . only having .7 V on pin 30 is your problem for sure ,you need to trace that (red wire) back to the battery junction block (shown in diagram) and find the voltage drop

whats the voltage on pin 30 of the main relay ? as you can see its shares the same feed and could lead to a idea as to where the problem is

-Yeah, I knew I was playing with fire without a fused jumper. I just bought the parts to put one together this week.

-Makes sense that the ground I'm seeing is through the motor windings.

-That red wire disappears into the main harness. I was hoping I wouldn't have to tear into it. Maybe I can trace back from the junction block?

-I'll check the voltage on the main relay tomorrow night, and post on here.

Thanks for your help!

[spdracrm3]

looks like you have a 86 325e right?

looks like the 325e is the same as a 325i with the battery junction block on the right engine compartment bulkhead (page 7000-3 in the 87 325e ETM ) shows a picture with cover removed ( that is where the red wire for your main/fuelpump relay comes from ) so check voltage there also ,if you have 12v there the problem is in harness between there and main/fuelpump relays , if you dont have 12v there problem is between there and battery or at battery itself

[Panici]

looks like the 325e is the same as a 325i with the battery junction block on the right engine compartment bulkhead (page 7000-3 in the 87 325e ETM ) shows a picture with cover removed ( that is where the red wire for your main/fuelpump relay comes from ) so check voltage there also ,if you have 12v there the problem is in harness between there and main/fuelpump relays , if you dont have 12v there problem is between there and battery or at battery itself

Right being passenger side?
If so, I did check there, and had +12v.

[spdracrm3]

yes right is passenger side , on my IX the junction block is behind the washer fluid bottle and a cover , on some models the battery sits here also (instead of in trunk) .

if you have 12V there then check the small wires for clean/tight connections as one of them is the power feed to relays (maybe the connection is just loose)

[Panici]

Car runs!
Thanks spdracrm3 for your help!

After looking at a few wiring diagrams, I realized that the large cable going into the junction block is also +12v. The block was so dirty that it previously measured at 0v, and I thought it was a ground.

I dug in my multimeter probe, and got +12.xx volts. I then measured the smaller wire, and had +11.8x volts.

I knew both of these should be directly connected to the battery, and should have the same voltage.

Tore apart the trunk and found the fusible link. Sure enough, it was corroded, and came apart in my hands.

Replaced it with some 16ga wire (for now) and checked relays for +12v. Check.
Tested for fuel at motor. Check.
Tested for spark. Check.

Put the plugs in and the motor came to life!

It was quite smoky (burning off the ATF and light oil I had sitting in the cyls). After a quick drive around the block, all the smoke disappeared, and the misfires are mostly gone!

https://www.youtube.com/watch?v=_Jc6dvslhPs

[spdracrm3]

great always glad to help bring em back to life, looks like you have a lot of work ahead of you there , but at least now you know it runs and is worth forging forward on it, and learned some in the process.

[Bulldog]

Well got about the same thing going as above ....
88 m20b25 with harness already had round plug came out of a early chassis ....just dropped it all into my 87 325e .....looks like everything is working but fuel pump can jump relay to make work and can jump power to pump fuse with also turn pumps on.....