Can u bypass fuel pump relay?

[jhonmagee]

I hav a question can I bypass the fuel pump relay ad run the fuel pump on a fuse tht turns on wen the key goes on to run the pump so the car wil start ad can i leave it like tht permenantly?

[strad]

Short answer is no. You cannot bypass a relay. Think of a relay as a big electrical switch. You can't run the circuit without the switch. And why would you want to do that?

[jhonmagee]

Short answer is no. You cannot bypass a relay. Think of a relay as a big electrical switch. You can't run the circuit without the switch. And why would you want to do that?

Because the car wont pass the power to the pump

[flyfishvt]

then fix the reason it wont send power to the pump. If you bypass it you will literally be playing with fire.

[Miguel93]

If you want to bypass the fuel pump relay because your fuel pump isnt getting power, then obviously it would be the fuel pump relay that has gone? Does it click when you turn the key? If not just get a new one, shouldn't be too much

[Avec]

Jesus. Second fuel pump relay issue that stares the owner in the face and they don't see the answer. If you need to jump the relay to make the fuel pump run - your damn relay is bad. How hard can that be to figure out?

Brains, people. Use them.

[jhonmagee]

Jesus. Second fuel pump relay issue that stares the owner in the face and they don't see the answer. If you need to jump the relay to make the fuel pump run - your damn relay is bad. How hard can that be to figure out?

Brains, people. Use them.

Ive changed the relay already many times it doesent click

[flyfishvt]

Checked fuses? Not just look at them but have you pulled them out and tested them?

What makes you think the fuel pump isn't working?

[strad]

Does the relay have power with ignition on? If it doesn't have power, the relay will not work, nor will anything else connected to it. If it doesn't have power, track that problem down.

[JDStrickland]

If you bypass the relay and the pump works, then the relay is bad OR there is no power to turn the relay on. It's not rocket science,

The relay takes a low current switching circuit to turn it on, and the contacts close to pass power to a high current load.

Bypassing the relay tells you the wiring is okay, and is a suitable test, but to redesign the car to go around a relay is nothing short of crazy.

[jhonmagee]

If you bypass the relay and the pump works, then the relay is bad OR there is no power to turn the relay on. It's not rocket science,

The relay takes a low current switching circuit to turn it on, and the contacts close to pass power to a high current load.

Bypassing the relay tells you the wiring is okay, and is a suitable test, but to redesign the car to go around a relay is nothing short of crazy.

It runs to rich wen bypassed now my question is I get power on pin 30 ingnition on ad off it wrks well the pin to the left of it I think 86 it gets 12 volts ad the other for the fuel pump I hav to jump it from pin 30 ad the other one on the bottum is tht a ground?

[jhonmagee]

Pin 30 ad 86 get power pin 86 turn power on ad off wit the key the other pin is for power to pump ad is the other ground?

[KevinMullins]

A bad DME (Main) relay will cause the fuel pump relay to not work as well.
Try swapping DME relay for a temporary test. (see pic)

DME (ECU / MAIN) Relay -
Pin 30 is the 12v input (always hot coming from battery)
Pin 86 is 12v to activate relay (always hot)
Pin 85 is a “switched” ground coming from the DME (only active when key is on)
Pin 87’s are the 12v output (only hot when relay is active and plugged in)

1. Middle Pin 87 goes to Fuel Pump Relay
2. Outside Pin 87 goes to fuel injectors, etc.

FUEL PUMP Relay –
Pin 30 is the 12v input (always hot coming from battery)
Pin 85 is a “switched” ground coming from the DME (only active when key is on)
Pin 86 is 12v to activate relay (only hot when DME relay is plugged in and good with ignition on)
Pin 87 is the 12v output to the fuel pump (only hot when relay is active and plugged in)

Voltage Tests –
Relays unplugged (out of socket)…
Ignition OFF - Pin 30 on both sockets should be 12v hot at all times. (use any ground point to check)
Ignition ON – DME relay should be 12v hot between Pin 85 and Pin 86 (this confirms good signal from DME)

With DME (MAIN) relay plugged in…
Ignition ON… Fuel Pump Relay socket should be 12v hot between Pin 85 and Pin 86 (this confirms DME-Main relay is good)

Jumper Tests –
With both relays (Main and Fuel Pump) out of their socket…
Insert jumper wire between Pin 30 and Pin 87 into the Fuel Pump Relay socket – you should have power at the fuel pump.
Insert jumper wire between Pin 30 and Pin 87 into both relay sockets (both 87’s on the main relay) - you should have power at the fuel pump AND car should start.

[pbonsalb]

It runs to rich wen bypassed now my question is I get power on pin 30 ingnition on ad off it wrks well the pin to the left of it I think 86 it gets 12 volts ad the other for the fuel pump I hav to jump it from pin 30 ad the other one on the bottum is tht a ground?

If you do try swapping relays, check the pin out or use a BMW relay. The pins are located differently on some BMW relays than on standard relays. Always worth checking to avoid frying wires.

Seems odd the motor ran too rich with a bypass, since the relay does not provide variable power. It should not run rich with a bypass or with a good relay.

[strad]

If you do try swapping relays, check the pin out or use a BMW relay. The pins are located differently on some BMW relays than on standard relays. Always worth checking to avoid frying wires.

Seems odd the motor ran too rich with a bypass, since the relay does not provide variable power. It should not run rich with a bypass or with a good relay.

The fuel pump only supplies fuel at a specified volume. If the car is running rich, it is running rich for a reason other than one involving the fuel pump.

[sjpgoalie]

The fuel pump only supplies fuel at a specified volume. If the car is running rich, it is running rich for a reason other than one involving the fuel pump.

This. The pump is on/off. Nothing about it modulates or regulates fuel flow. That's the purpose of the regulator, pressurized fuel rail, injectors and the signals going to them from the dme.

If you don't have power at the relay as you can't hear it click, it is time to see if you're getting power at the DME pin-out. The problem may be in the loom. If you're getting power at the pin-out, but not at the relay, it is obviously somewhere in between, which is the thick loom that runs across the fire wall and blower filter.

[KevinMullins]

Working backwards the next thing in line is the DME (Main) relay.

Ignition-> DME-> DME (Main) Relay-> Fuel Pump Relay-> Fuse-> Fuel Pump

[jhonmagee]

Working backwards the next thing in line is the DME (Main) relay.

Ignition-> DME-> DME (Main) Relay-> Fuel Pump Relay-> Fuse-> Fuel Pump

It gives error code 1261 it says incorrect fuel

[flyfishvt]

Pin 30 ad 86 get power pin 86 turn power on ad off wit the key the other pin is for power to pump ad is the other ground?

If i read this correctly then YES you are correct. Pin 30 should have 12 volts at all times. Pin 86 should have power with the key turned on. Pin 85 is ground Pin 87 goes to the fuel pump. If you are getting 12 volts on Pin 30 and Pin 86 with the key on AND since you can make the pump run with a jumper wire then you have a bad relay. Replace the relay with the correct one and you should be ok

[KevinMullins]

Needs to measure voltage between pin 85 & 86 on the fuel pump relay socket with the key on.

Pin 85 is ground coming from the DME.
Pin 86 is power coming from the DME (Main) relay.

[jhonmagee]

If i read this correctly then YES you are correct. Pin 30 should have 12 volts at all times. Pin 86 should have power with the key turned on. Pin 85 is ground Pin 87 goes to the fuel pump. If you are getting 12 volts on Pin 30 and Pin 86 with the key on AND since you can make the pump run with a jumper wire then you have a bad relay. Replace the relay with the correct one and you should be ok

Update Wen relay is pluged in al pins wit the key on get 12 volts except pin 87 the relay is pluged in but stil no.power to 87 ad yes if I put power to the pump it starts the car

[flyfishvt]

Bad relay

[jhonmagee]

A bad DME (Main) relay will cause the fuel pump relay to not work as well.
Try swapping DME relay for a temporary test. (see pic)

DME (ECU / MAIN) Relay -
Pin 30 is the 12v input (always hot coming from battery)
Pin 86 is 12v to activate relay (always hot)
Pin 85 is a “switched” ground coming from the DME (only active when key is on)
Pin 87’s are the 12v output (only hot when relay is active and plugged in)

[*]Middle Pin 87 goes to Fuel Pump Relay[*]Outside Pin 87 goes to fuel injectors, etc.


FUEL PUMP Relay –
Pin 30 is the 12v input (always hot coming from battery)
Pin 85 is a “switched” ground coming from the DME (only active when key is on)
Pin 86 is 12v to activate relay (only hot when DME relay is plugged in and good with ignition on)
Pin 87 is the 12v output to the fuel pump (only hot when relay is active and plugged in)

Voltage Tests –
Relays unplugged (out of socket)…
Ignition OFF - Pin 30 on both sockets should be 12v hot at all times. (use any ground point to check)
Ignition ON – DME relay should be 12v hot between Pin 85 and Pin 86 (this confirms good signal from DME)

With DME (MAIN) relay plugged in…
Ignition ON… Fuel Pump Relay socket should be 12v hot between Pin 85 and Pin 86 (this confirms DME-Main relay is good)

Jumper Tests –
With both relays (Main and Fuel Pump) out of their socket…
Insert jumper wire between Pin 30 and Pin 87 into the Fuel Pump Relay socket – you should have power at the fuel pump.
Insert jumper wire between Pin 30 and Pin 87 into both relay sockets (both 87’s on the main relay) - you should have power at the fuel pump AND car should start.

The dme main relay sends power from the middle prong for the pump relay on the fuel pump relay with key on evrrysingle pin gets power except pin 85 to thr fuel pump I hav no idea why!!!!

[KevinMullins]

The dme main relay sends power from the middle prong for the pump relay on the fuel pump relay with key on evrrysingle pin gets power except pin 85 to thr fuel pump I hav no idea why!!!!

Pin 85 is GROUND from the DME itself.
This is why I said measure voltage between pins 85 and 86 on the fuel pump relay socket with key on.
85 and 86 "activate" the relay, 30 supplies constant power which then transfers to pin 87 and on to the fuel pump fuse/fuel pump when the relay is active.

flyfishvt is most likely correct in saying it's just a bad fuel pump relay, but try "temporarily" swapping the relays like I showed in an earlier post pic, if the car starts fine then it's for sure a bad fuel pump relay....but get the correct replacement relay.

[E28Scott]

bad typing

ftfy