No power to Fuel pump

[Gk-89E30]

I have been trying to diagnose this problem and have hit a wall.
I have 89 E30 w/t M20 engine that was running fine. 2 days ago I replace the rubber hose that had been leaking (simple enough) and now when I attempt to turn on car I get crank no start.

The procedure that I took to replace the fuel line was I turned on car and while it was running I pulled Fuse #11 to the fuel pump. I then replaced the leaking hose. When I put everything back together the car wouldn't start.

To diagnose I have checked the following:

• Main relay - 12V from Terminal # 30 & 86
• Fuel pump relay - I am getting 0V from terminal #30 when ignition is off; But when turn on ignition switch I get 12V from Terminal #86 (which make sense since its connected to Mail relay) and Less from Terminal #30
• Fuse 11 - 0V even tried to short Terminal # 30 & 87 on Fuel pump relay; I swapped Fuse 11 and even used a test light to see if there is any power, still nothing
• Coil (for spark plugs)- 12V while ignition in on switch

My next step is:
- To check resistance to the crank position sensor
- To perform continuity test across the different parts of the circuity.

My questions:
Why I am not getting any power to the fuel pump?

From the circuit diagrams shouldn't I get constant 12V at Terminal #30 of the Fuel pump relay? I only get power when I engage the Main relay by putting ignition to position 2. Is this normal?

Did I mess something up by pulling out Fuse 11 while the car was running?

Am I missing something?


Here is the circuit diagram I am using:

[e30austin]

sounds like you have a dead fuel pump.

[Gk-89E30]

e30austin I just tested the fuel pump by Jury-rigging 12V battery directly to the fuel pump and the pump was pushing fuel

[Gk-89E30]

Update:
I did more diagnostics:

• Fuel pump: - Plugged 12V battery directly to fuel pump and it works. After started car it ran for several seconds then died. (see photo)
• Continuity test:
  • Battery - Terminal #30 (fuel pump) GOOD
  • Battery - Terminal #30 (mail relay) GOOD
  • Mail relay #87 - Fuel pump relay #86 GOOD
  • Fuel pump relay #87 - Fuse 11 GOOD
• Crank position sensor - 522 ohms (normal 540 ohms +/- 10%.) (see photo)

Anyone have an idea as to what else I can do to find the problem?

[McGyver]

I have been trying to diagnose this problem and have hit a wall.
I have 89 E30 w/t M20 engine that was running fine. 2 days ago I replace the rubber hose that had been leaking (simple enough) and now when I attempt to turn on car I get crank no start.

The procedure that I took to replace the fuel line was I turned on car and while it was running I pulled Fuse #11 to the fuel pump. I then replaced the leaking hose. When I put everything back together the car wouldn't start.

To diagnose I have checked the following:

• Main relay - 12V from Terminal # 30 & 86

You should always have 12V to 30, 85, and 86. The ECU will provide a ground on Pin 36 when the key is in run. The powers the electromagnet, closing the relay and providing you 12V at 87.

• Fuel pump relay - I am getting 0V from terminal #30 when ignition is off; But when turn on ignition switch I get 12V from Terminal #86 (which make sense since its connected to Mail relay) and Less from Terminal #30

You should always have 12V on 30. When you turn the key, this closes the Main Relay, providing power to 86 and 85. It should also provide a ground on ECU pin 3, powering the electromagnet, which closes the relay and gives you 12V at 87.

• Fuse 11 - 0V even tried to short Terminal # 30 & 87 on Fuel pump relay; I swapped Fuse 11 and even used a test light to see if there is any power, still nothing

The 12V on Pin 87 of the Fuel Pump Relay (requires the key at run) provides 12V to Fuse 11. Make sure the fuse isn't blown. 12V on Fuse 11 should provide power to the fuel pump on the Green/Violet wire. You should have a ground on the Brown wire.

Once you have good power to the fuel pump, the next issue could be a bad pump. When they start to go bad, they may work for a few minutes before overheating and seizing. You'll also be able to idle for a while, but might not have enough pressure to run the engine under load.

[Caperix]

The dme won't ground the fuel pump relay if it does not see a crank signal. Resistance checks are not the most reliable checks on these sensors, can you see the tac moving any when cranking? Do you have a scan tool that can read the rpm signal?

[Gk-89E30]

McGyver when I ran the first test on voltage I was using a pretty crappy multimeter, I now have a digital one which arrived from Amazon this evening. I am going to run the Voltage tests again to see if it works as above mentioned. I check using continuity test to see if fuse 11 was blown and seems to be working fine. I also swapped fuse just incase. As for fuel pump, If I was able to connect the fuel pump directly to a power source and had it turn on and even pump some fuels for me to get several second start, doesn't that mean that pump "should" be in good condition??

Caperix what do you mean by "tac"? Is this a poor man's test to see if the engine is turning or is it some way of telling if the crank position sensor is functioning? I am starting to think now that the crank position sensor might be at fault since everything else seems to be okay and from what I have read, as you mentioned the resistance test is not the most reliable to diagnose CPS problems. Unfortunately I don't have a scan tool, it would be very helpful right about now (seeing I have spent the better part of 2 days trouble shooting this).

Is there anything else that I should check before reaching to exchange the CPS. I am not looking forward to unbuttoning up front of Engine again, I just did timing belt change change just 2wks ago.

Also if I must change CPS is there an easy way of doing it w/o having to undo the radiator pipes? I just put brand new coolant.

Also I am still very puzzled by how the problem started in the first place. Removing fuse to fuel pump.

[Gk-89E30]

Any advise on whether it's better to buy OEM Crankshaft position sensor or after market. The price difference is huge!! $170 OEM vs $50s-60s aftermarket. I would prefer not to drop that much $$ Is there a good quality aftermarket CPS

[McGyver]

I feel like you're probably overlooking something really simple. There's no point in buying parts until you verify what's broken. It could be as simple as a broken relay.

McGyver when I ran the first test on voltage I was using a pretty crappy multimeter, I now have a digital one which arrived from Amazon this evening. I am going to run the Voltage tests again to see if it works as above mentioned. I check using continuity test to see if fuse 11 was blown and seems to be working fine. I also swapped fuse just incase. As for fuel pump, If I was able to connect the fuel pump directly to a power source and had it turn on and even pump some fuels for me to get several second start, doesn't that mean that pump "should" be in good condition??

So you were able to get the car to run while the pump was hardwired to a battery, or you got the pump to run while it was hardwired to a battery? Just because the fuel pump turns on, doesnt mean that it is capable of supplying the required flow of fuel at the required pressure for the engine to run. But you still don't know what's wrong, so there's no reason to buy stuff.

Start by following the flow of electricity to from the battery to the pump plug. Caperix makes a good point about the DME not grounding the fuel pump relay trigger unless it sees a crank signal. You can jumper the Fuel Pump relay pin 85 to ground to bypass the need for the DME to provide the ground. If you can't get power to the pump (even by jumping the relay), that's where you need to start.

If you need a new Fuel Pump, here's some info about converting the stock pump to a TRE Pump, which is cheaper and an easy replacement.

Caperix what do you mean by "tac"? Is this a poor man's test to see if the engine is turning or is it some way of telling if the crank position sensor is functioning? I am starting to think now that the crank position sensor might be at fault since everything else seems to be okay and from what I have read, as you mentioned the resistance test is not the most reliable to diagnose CPS problems. Unfortunately I don't have a scan tool, it would be very helpful right about now (seeing I have spent the better part of 2 days trouble shooting this).

Is there anything else that I should check before reaching to exchange the CPS. I am not looking forward to unbuttoning up front of Engine again, I just did timing belt change change just 2wks ago.

Also if I must change CPS is there an easy way of doing it w/o having to undo the radiator pipes? I just put brand new coolant.

Also I am still very puzzled by how the problem started in the first place. Removing fuse to fuel pump.

He meant, when you crank the engine, does the tachometer on the cluster move? If not, then your car doesn't see the engine spinning. If it does move, that's a good sign.

The CPS can be replaced without taking off coolant hoses and/or opening up the engine.

I would probably get an aftermarket CPS, but I'm also willing to do more work and replace it again in the future. The BMW sensor should just work for another 30 years.

[Gk-89E30]

I have some great news! I got her to run today. But don’t give me too much credit because I still don’t understand what was actually wrong.

I still had 2 more fuel hoses that needed swapping so I swapped them out. After I performed the voltage checks McGyver suggested and they all matched up. So I shorted pin 30 & 87 head the fuel pump come on and was able to run the car.

Took it for a drive around and had no issues with it.

I LITERALLY DON’T UNDERSTAND WHAT WAS HAPPENING.

Is it possible that having some sort of open system in the fuel system triggers a no start situation with the DME?

as for questions about what happened with the fuel pump when I plugged into directly, it turned on and then pump fuel into the engine.

THANK YOU ALL FOR HELP WITH THIS. I update you all if and when I ever figure out what when wrong.

[Caperix]

If you jumped the relay & the car ran your issue is either a bad relay or an issue with the control side of the relay. Check for power from the main relay & ground from the dme, it may just be a bad fuel pump relay. Does the relay click? Even if it does click the contacts can burn & cause issues. So best case you have a failed fuel pump relay, worse case the ground transistor in the dme has failed.

[Gk-89E30]

That problem that I had, that went away on it's own but never figured out ..... IT's BAAAACKKKKK 🤦♂️. The two times that I have had this problem I have been able to start the car by plugging fuel pump directly to the battery for a few seconds and voila the car starts. (of note I have changed the fuel pump in the mean time, thought the engine was running a little rich). Any thoughts?

Could this be a fuel injector issue?? Fuel pressure issue?? Also one other note is that when the car is in this state when I jump the terminal 30 and 87 on the fuel pump relay the pump DOESN'T turn on which tell me that the the fuel pump relay is fine. Could the ground transistor in the DME like Caperix mentioned be intermittently failing? but why when I jump the fuel pump with the battery can I suddenly over come the issue.

[Digitalwave]

You need to start doing more diagnostics. Guessing that the fuel was rich, and then replacing the fuel pump (how could the fuel pump make a car rich?), is just stabbing in the dark.

There's a lot of good questions that were already posed in this thread that weren't answered.

[Gk-89E30]

I think I may have described my reasoning for replacing the fuel pump incorrectly. I suspected the problem might be from fuel pump after it started making a very high pitched sound and from time to time at idol the car would sputter (slow revs, almost like grunts). Some of my research at the time pointed to a dying fuel pump. Thus the change.

As for diagnostics, I have done a lot of diagnostics, see above. The problem as I understand it doesn't seem to be with the DME or Pump relay. Feel free to correct any errors if I overlooked something. I think one thing that I have yet to do is to check the fuel pressure.

Digitalwave do you have suggestions or ideas, I would love some input to send me in the right direction. I don't know what it means that the one moment the car doesn't start but as soon as I plug in the fuel pump to a direct to battery it and then try to start the car it runs.

[jbontke]

I am going to assume that if you hard wire the fuel pump at the relay the car runs. While the relay is bypassed, the ECU should ground the fuel pump relay at "#85" BRW/GRN wire. Test that by connecting a voltmeter to #86(pos) and *85(neg). You should see 12v on the voltmeter. If not, then you should test "#86" for power (key in the run pos) and "#85" for ground (engine running).