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I assumed it was fuel pump failure as well so just replaced the pump but it wasn't that and when tested the old pump seemed to work fine. The relay didn't seem to be getting any power as when I bypassed it the pump still didn't start but taking +12v from the battery to the gnd on the relay socket started the pump running. I then refitted the same relay and the car started first turn of the key and has run sweetly since. I just dont want it to happen again, being stuck on a very busy motorway flyover with no hard shoulder was not a nice place to be!
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Will definitely replace the relay and get some contact cleaner, good advice, thanks!
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My e46 was the same . A no start after a petrol fill up . Gave the tank a thump and it started working . Guess it had a dead spot on the armature. Changed it anyway. About £90 for a Bosch unit .
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Yes, I used to do that on my focus! It doesn't explain why the relay was getting no power to it but now it obviously is! Does the pump run constantly?
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Yes it does run constantly once the engine is turning / running. The relay has a negative signal from the engine ecu to operate.
Edited by elekie&a/c doctor on 13/12/2023 at 13:22
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So its feasible that the ecu, for whatever reason, wasn't telling the pump to run? That could explain why there appeared to be no power to the relay. Question is, if that was the case, why did it happen?! I have a guy plugging it in on Friday as I have had to order the adaptor cable for the diag machine as my car has the round plug. Someone suggested cam or crank sensor but I am not nearly qualified enough to know whether that is possible or not. Thanks again for the replies, really helpful, thank you.
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Faulty crank sensor would stop it starting and disable the fuel pump circuit. Cam sensor would not affect this circuit. Are you sure it hasn’t got an obd socket under the instrument cluster , to the right of the steering wheel? Some of these cars on the break point can have both the 16 pin obd and the round socket under the bonnet.
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Great info, thanks! We couldn't find a socket inside but got adaptor cable coming today anyway. Hopefully something will show up so I know what route to go down next! I'll post my findings once the diagnostic machine has been on it! Thanks again.
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The fuel pump relay serves two purposes. One is its normal purpose as a relay, to carry the current the pump requires across its contacts rather than several amps in the switching circuit. The other is to ensure the pump stops in the event of the car being involved in an accident. If it continued to run then fuel would be pumped everywhere if a fuel pipe was severed making the situation even more dangerous.
A fused 12v supply from the battery will go to Terminal 30 of the relay. That same supply via another fuse will go to Terminal 86. Terminal 85 will go to the ECM and Terminal 87 will go to the pump.
When the ignition is switched on the ECM will earth Terminal 85 for a second or two to run the pump and prime the fuel system. Then when the engine cranks and the engine speed signal is received the ECM earths Terminal 85 which stays earthed all the time the engine is running. The relay energising coil circuit is now complete so the relay contacts are closed. Current passes across the contacts between Terminals 30 and 87 and the fuel pump runs. When the engine is stopped the engine speed signal is lost. The ECM then drops the earth to Terminal 85. The circuit is therefore incomplete so the relay contacts open and the pump stops.
If the car is involved in a crash either the engine stops and so does the pump, or if a fuel pipe is broken it'll only run for a few seconds before fuel pressure is lost and the engine stops anyway. And when it does the fuel pump will also stop.
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Railroad, that's superb as is all the advice I've been given, thank you so much. I've had the car plugged in and it showed an issue with the fuel pump relay which has now been cleared. I've ordered a new relay direct from BMW and will spray some contact cleaner in the relay socket beforehand and put the old one in and out a few times then fit the new one. I will drive it this week and report back but thanks SO much for all the replies on here, have a great Christmas and New Year.
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Well, unfortunately the story didn't end there!
I drove the car all over Christmas and New Year on short and long (80 mile) trips without issue. Last week I took the car out, performed faultlessly but stalled as I pulled into my drive. It restarted immediately and started fine for the 6 - 8 times I tried it while parked. Today I took it out, was faultless then died at about 50mph. Pulled over, car restarted immediately. This happened another three times on a round trip of under 20 miles.
I'm thinking crank sensor is playing up? As always, you guys are far more qualified to answer than me so any suggestions welcome! Thanks in advance!
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Could be crank sensor , time to get your scanner out to see if any codes logged . Above idle speed , engine will run using the cam sensor for reference if the crank sensor fails .
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My mechanic pal plugged his proper diag tool in before and found a fuel pump relay code but that might have been because I bypassed it during my own schoolboy diagnostics?! I will await his findings and report back. Thanks, invaluable knowledge and advice elekie, you are a legend!
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Ok, so the car was scanned using a snap on diagnostic.
Code 209 EWS Electronic Immobiliser Manipulation is showing which wasn't there before.
I have read that something needs to be re-synced by BMW Dealer.
This is an intermittent fault - the worst kind of course, and the car is currently running but I can't trust it until the problem is resolved.
Any thoughts gents?!
Edited by stuartl on 15/01/2024 at 11:46
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The ews module is the immobiliser control . Really only needed to start the car . Not convinced this has anything to do with your issues. For peace of mind , you can check the connector to it . It’s easy access, just behind the panel to the right of the steering wheel , below dashboard. It only needs to be re- synced if the unit is replaced. Snap on scanner , along with many others, wont do it .
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The ews module is the immobiliser control . Really only needed to start the car . Not convinced this has anything to do with your issues. For peace of mind , you can check the connector to it . It’s easy access, just behind the panel to the right of the steering wheel , below dashboard. It only needs to be re- synced if the unit is replaced. Snap on scanner , along with many others, wont do it .
After I posted my last message I spoke to the chap who cut and programmed my new key and he said the same as you Elekie! I will check the connector as he did remove the module to program in my new key ?? Do you think its worth changing the crank sensor? For £50 plus fitting I think it's worth doing just to eliminate it if nothing else?!?
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Out of interest, why didn’t you buy a new key from Bmw? They come pre programmed and ready to go .
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They quoted me £280! Independent did it for £150
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I would think the immobiliser code is from when the ews was removed to get the key cut . I’m not convinced there’s a crank sensor fault. This would usually show up on the diagnostic system. It’s possible the fuel pump is intermittent. I would pull it out the tank and check the wires where they’re crimped onto the underside of the connector plate . They can fracture.
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Hi Elekie, thanks for your reply. The keys were cut and programmed in October. The car initially broke down in December. At this point, I replaced the fuel pump but the car still didn't start. I tested the old fuel pump and it ran and pumped fuel perfectly. The fuel pump didn't appear to be getting power so I bypassed the relay and got the car running. I then swapped the relay for an identical one next to it but still no joy. I then recharged the battery which had gone flat. The car then started immediately. The fuel pump is new and the wiring seems fine.
I now had a running car but with no explanation why it stopped or, indeed, why it was now running perfectly.
I had the car plugged in and it showed a fuel pump relay issue. This was the only code and it was cleared.
The 209 EWS code has only just shown itself, some 3 months after new key was programmed m
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Running out of ideas here . Usually the system on the E 39 is pretty reliable. Just wonder if it’s a power supply fault to the engine ecu . I’m sure there’s a power control relay in the electrical box under the bonnet, where the ecu is located . Usually purple or green colour relay .
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Elekie your advice on this issue and and many others before has been invaluable and I thank you so much for your time in replying and sharing your valuable expertise. My car is an oldie but goodie and unfortunately not old enough to be able to be repaired by spanners alone! I will investigate the power supply to the ecu and in the meantime thank you again for your help so far
Edited by stuartl on 15/01/2024 at 19:20
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Well, as promised, here's an update! I booked the car into a local BMW Independent Specialist. Luckily, the car broke down while they had it. They discovered that the fuse in the boot for the fuel pump was 5A when it should have been 25A. Apparently it was arcing and when the car stopped the replaced it with one of the correct rating and the car ran without issue. So fingers crossed its solved.Thanks so much again for all the help and input.
Edited by stuartl on 02/02/2024 at 21:59
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Good show . Wonder who’s been in there and put the wrong fuse in ? . I’m surprised a 5 amp didn’t blow . It’s just on the limit of fuel pump current.
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Well I only bought the car in September so I guess someone had been fiddling before then! The garage said that when they tested the fuel pump it was drawing 4.8A ! Thanks again, as always, for all of your invaluable advice. You're great on here!!!
Edited by stuartl on 03/02/2024 at 18:25
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What an interesting read.
There are some clever Guys on here!
Quite astonished that a main dealer was able to sort it, after all you read about them being hopeless.
Glad it's all sorted now!
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Can’t see any reference to the car going to a main bmw dealer ?
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Can’t see any reference to the car going to a main bmw dealer ?
Ah!
Your quite right, my mistake. An independent.
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