Defective fuel pump or something else?

1970 Views 76 Replies 14 Participants Last post by Psimitar, 2 d ago

mittortz

Discussion Starter · 1 mo ago (Edited)

Hi all - I replaced my fuel pump a week ago after my M3 died at a stoplight. It had a rough idle for a couple months and a couple random issues here and there before it fully went out. I bought a Hella branded pump off bimmerworld b/c it was $99 with a 2 year warranty, I figured they're an OEM so it should be legit. Worked perfectly for a week, no rough idle, pulled strong, no issues whatsoever... Until today. Every time I start the car and I get crazy rough idle, it repeatedly jumps between 500 and 1500 RPMs several times, gassing it doesn't change the situation, until it finally dips low enough that the engine dies. Have tried about 6 times now and get the same result each time.

I also have a new code that wasn't there before: D7 KOMBI tank lever-type sensor 2

Should I get my pump replaced under warranty or could it be something else? Thanks.

EDIT: just tried something else: started the engine and immediately drove off in 1st. Acceleration was inconsistent for the first minute or so, it felt like it was coming in that same jumpy rhythm that the idle was doing even though I had the pedal pressed normally. And then after the first minute it appeared to become normal, and when I came to a stop it idled normally. Turned off car, started again, idle was a tiny bit wobbly at first and then went to a solid 1k RPM and held normally. What the hell is going on?

Edit 2: drove it around, got it warmed up. seems engine cannot hold an idle. If I stop, engine dies half the time. If I start and don't immediately take off, engine just dies. Sometimes it can hold an idle but usually not. It seems to die the most often when coming down from a higher RPM, as if the momentum of the tach needle is too much for it to keep up (if that makes sense). Thanks again for any advice. I'm wondering if it's the ICV?

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All2kool

· #2 · 1 mo ago

You don't tell us what mileage is on the car.

And it's always a good idea to replace the Fuel Filter when you replace the Fuel Pump.

Reactions: 1

Psimitar

· #3 · 1 mo ago

Replace the filter as this contains the regulator too. It would also be a good idea to get a hold of a analogue pressure gauge to connect to the fuel rail so you can see what pressures you get with engine on and whilst off for set time periods as per the workshop manual.

mittortz

Discussion Starter · #4 · 1 mo ago

All2kool said:
You don't tell us what mileage is on the car.

And it's always a good idea to replace the Fuel Filter when you replace the Fuel Pump.

Good idea. I'm at 177k, fuel filter was last replaced at 135k

Toxic0n

· #5 · 1 mo ago

Your fuel level sensor code might be unrelated, there are two sensors in the fuel tank and the fuel gauge will work with just one of them working properly. Your symptoms could be the fuel pump again or something like an ignition coil or a camshaft position sensor.

No other codes?

mittortz

Discussion Starter · #6 · 1 mo ago

Toxic0n said:
Your fuel level sensor code might be unrelated, there are two sensors in the fuel tank and the fuel gauge will work with just one of them working properly. Your symptoms could be the fuel pump again or something like an ignition coil or a camshaft position sensor.

No other codes?

I have some other codes that have been sitting there for several months, but I have no SES light currently:
"A - Error line active seat left (no response from control unit) / Plate light right / Sunblind motor, open circuit"
"3D - GM: Boot-lid unlocking: mechanism"
"5E1A - DSC ECU: ECU internally: serial peripheral interface (SPI): translation error multi IC / CAN DME / DDE signal failure / CAN ENGINE 1 MOTBK speed signal invalid / Coil outlet valve (dump) shorted rear left"
"4F - Exhaust gas temperature sensor"
"F - Power-on reset"

Side note: I use carly and don't really like it. What's the best tool under $500 to read codes and understand what they mean? I hate being in the dark when diagnosing, and googling these cryptic codes to find basically nothing reliable online about them.

I just ordered a fuel filter and fuel pressure regulator from FCP. They should be replaced anyway. The debate right now is whether or not I need to try to RMA this $100 Hella fuel pump I bought and/or put up the $500 for a legit BMW pump instead. I'm relatively new to auto-mechanical work, so please excuse my noobish ignorance. I'll take any advice on how to proceed, I want to get better at this.

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RRRM8E

· #7 · 1 mo ago

Have you considered the possibility that it wasn't a bad fuel pump( or filter) in the first place?
Having said that, a 177k pump should be replaced anyway. Vdo is a better choice.
You could check fuel pressure for fun.
You can download software on here. See links at top of home page.

Reactions: 1

burntoutrubber

· #8 · 1 mo ago (Edited)

mittortz said:
Side note: I use carly and don't really like it. What's the best tool under $500 to read codes and understand what they mean? I hate being in the dark when diagnosing, and googling these cryptic codes to find basically nothing reliable online about them.

search for BMWTools on this site. Guide by @Bali

Psimitar said:
Replace the filter as this contains the regulator too. It would also be a good idea to get a hold of a analogue pressure gauge to connect to the fuel rail so you can see what pressures you get with engine on and whilst off for set time periods as per the workshop manual.

M3 filter and regulator are separate.

Reactions: 1

Alex323Ci

· #9 · 1 mo ago

well it does sound ignition/fuel related. lack of codes for: vanos, throttle position switches, pedal, and not going into full “limp mode” does lean more towards fuel. and although Hella was a reputable brand it now (in later year car parts)is mnftrd often in China. so that $99 pump could be the issue since it performed great at first. the rub here is that an ignition issue could also just hide during that time and get worse suddenly. like the eight prong FP relay going intermittent.
in your favor is that 177k on an M3 pump is over average so you didn’t waste parts buying it. but not buying top quality may be an issue.
at this point I’d be guessing, sorry that’s not helpful.

Sapote

· #10 · 1 mo ago

RRRM8E said:
You could check fuel pressure for fun.

It is a must in this case.

mittortz

Discussion Starter · #11 · 1 mo ago

RRRM8E said:
Have you considered the possibility that it wasn't a bad fuel pump( or filter) in the first place?
Having said that, a 177k pump should be replaced anyway. Vdo is a better choice.
You could check fuel pressure for fun.
You can download software on here. See links at top of home page.

Always open to all possibilities, I guess what makes things difficult for me intellectually is that I was having severe problems (unable to run the engine at all for more than half a second) which were totally fixed by the new fuel pump for exactly 1 week. I drove it every day that week, lots of miles and stops/starts/idles without issue. Suddenly, on day 8, I can get the car going, but it won't hold an idle. It's weird, and if I were swimming in cash right now, I'd have paid the extra $400 for the BMW/VDO pump so I wouldn't be wondering about it right now. But $400 is $400. I may end up paying it if a new fuel filter and pressure regulator don't make a difference.

Sapote said:
It is a must in this case.

I'll pick up a fuel pressure gauge at harbor freight tomorrow. Any advice on how to run these tests while the car is jacked up? Annoying that they put the valve on the bottom of the car for the M3.

glesly said:
Interesting I have the same problems.

Please let me know if you get anywhere!

Alex323Ci said:
...although Hella was a reputable brand it now (in later year car parts)is mnftrd often in China. so that $99 pump could be the issue since it performed great at first. the rub here is that an ignition issue could also just hide during that time and get worse suddenly. like the eight prong FP relay going intermittent.
in your favor is that 177k on an M3 pump is over average so you didn’t waste parts buying it. but not buying top quality may be an issue.
at this point I’d be guessing, sorry that’s not helpful.

1. Good to know about Hella - that's what's killing me.
2. Can you explain further what you mean about a hiding ignition issue and the "eight prong FB relay going intermittent"? I'll take your guesses. I've had a couple people point towards camshaft position sensors (of which there appears to be both an intake and exhaust one of these), and I spent the day getting the intake manifold out so if it's economical and makes sense, hell, I'll express ship those and throw them in too. But wouldn't I get codes for those?

Side note: not that anyone asked besides me, but it wasn't the ICV. I finally got it out and it flops around like a fish out of water. It's a good thing I'm not flush right now, b/c I'd be ordering a carbon airbox after that ordeal otherwise.

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RRRM8E

· #12 · 1 mo ago

So it runs fine except it won't idle?
Connect pressure gauge, un-jack car, turn on ignition.

Read codes.

Consider all the possibilities before buying parts

mittortz

Discussion Starter · #13 · 1 mo ago

RRRM8E said:
So it runs fine except it won't idle?
Connect pressure gauge, un-jack car, turn on ignition.

Read codes.

Consider all the possibilities before buying parts

The filter/regulator are worth replacing, but I'll stick with my Hella pump for the time being. Will report back with fuel pressure readings ASAP.

Toxic0n

· #14 · 1 mo ago (Edited)

For the scanner, either check out BMW Tools as suggested or PA Soft - it's even easier to use although less functional, but good enough to do a deep scan on all modules with proper codes. It costs $80 for the legit version it seems although I got one on Amazon for half price:

bmwpasoft.com

BMW PASOFT SCANNER

Comes included with the software and cable to connect from device to computer. No need to purchase the software as well. If your car has OBD1 under the hood you will need the 20 pin to 16 pin OBD1 Adapter. The best BMW Scanner v1.4.0 intended for diagnostics, expert analysis and modifications of...

bmwpasoft.com

For what it's worth, when I had an ignition coil go, I had similar symptoms - very rough idle, car strugglingly to stay on and basically no power. I had zero codes so it was tough to diagnose. I don't remember how I figured it out at the time, I did end up just replacing all the ignition coils on my M3

mittortz

Discussion Starter · #15 · 1 mo ago

Toxic0n said:
For the scanner, either check out BMW Tools as suggested or PA Soft - it's even easier to use although less functional, but good enough to do a deep scan on all modules with proper codes. It costs $80 for the legit version it seems although I got one on Amazon for half price:

BMW PASOFT SCANNER

Comes included with the software and cable to connect from device to computer. No need to purchase the software as well. If your car has OBD1 under the hood you will need the 20 pin to 16 pin OBD1 Adapter. The best BMW Scanner v1.4.0 intended for diagnostics, expert analysis and modifications of...

bmwpasoft.com

For what it's worth, when I had an ignition coil go, I had similar symptoms - very rough idle, car strugglingly to stay on and basically no power. I had zero codes so it was tough to diagnose. I don't remember how I figured it out at the time, I did end up just replacing all the ignition coils on my M3

Thanks for the recommendation and your experience. I'm working on setting up BMW Tools now but I'll probably pick up the PA Soft so I can keep something in the car that isn't Carly w/ its subscription fees.

As a general update, I cleaned my ITBs, ICV, and MAF today, for fun I guess, and put everything back together. Started the car and sure enough, same situation as before. I took a video to better document what exactly is happening. I also picked up a fuel pressure gauge at harbor freight, so tomorrow I'll jack up the car and replace fuel filter, regulator, and get those pressure readings after that's done. That should point me in one direction (fuel pump) or... many others, it seems, lol.

bmwm3sports

· #16 · 27 d ago

mittortz said:
Hi all - I replaced my fuel pump a week ago after my M3 died at a stoplight. It had a rough idle for a couple months and a couple random issues here and there before it fully went out. I bought a Hella branded pump off bimmerworld b/c it was $99 with a 2 year warranty, I figured they're an OEM so it should be legit. Worked perfectly for a week, no rough idle, pulled strong, no issues whatsoever... Until today. Every time I start the car and I get crazy rough idle, it repeatedly jumps between 500 and 1500 RPMs several times, gassing it doesn't change the situation, until it finally dips low enough that the engine dies. Have tried about 6 times now and get the same result each time. I also have a new code that wasn't there before: D7 KOMBI tank lever-type sensor 2 Should I get my pump replaced under warranty or could it be something else? Thanks. EDIT: just tried something else: started the engine and immediately drove off in 1st. Acceleration was inconsistent for the first minute or so, it felt like it was coming in that same jumpy rhythm that the idle was doing even though I had the pedal pressed normally. And then after the first minute it appeared to become normal, and when I came to a stop it idled normally. Turned off car, started again, idle was a tiny bit wobbly at first and then went to a solid 1k RPM and held normally. What the hell is going on? Edit 2: drove it around, got it warmed up. seems engine cannot hold an idle. If I stop, engine dies half the time. If I start and don't immediately take off, engine just dies. Sometimes it can hold an idle but usually not. It seems to die the most often when coming down from a higher RPM, as if the momentum of the tach needle is too much for it to keep up (if that makes sense). Thanks again for any advice. I'm wondering if it's the ICV?

Yeah it sounds like the pump is bad now did you change your fuel filter it's due every 60,000 miles and I wouldn't go but $30,000 also your fuel pressure need to check the bar minimum on that and your line pressure once you get that all sorted then you could easily determine it's the fuel pump

burntoutrubber

· #17 · 27 d ago

mittortz said:
Thanks for the recommendation and your experience. I'm working on setting up BMW Tools now but I'll probably pick up the PA Soft so I can keep something in the car that isn't Carly w/ its subscription fees.

As a general update, I cleaned my ITBs, ICV, and MAF today, for fun I guess, and put everything back together. Started the car and sure enough, same situation as before. I took a video to better document what exactly is happening. I also picked up a fuel pressure gauge at harbor freight, so tomorrow I'll jack up the car and replace fuel filter, regulator, and get those pressure readings after that's done. That should point me in one direction (fuel pump) or... many others, it seems, lol.

PASoft AKA BMW Scanner is part of the BMW standard tools install

LeverThis

· #18 · 27 d ago

burntoutrubber said:
PASoft AKA BMW Scanner is part of the BMW standard tools install

Nein (no) ... PASoft/BMW Scanner is a completely different & separate program than BMW Standard Tools (INPA, NCS Expert, etc). They also have different cables.

burntoutrubber

· #19 · 27 d ago

LeverThis said:
Nein (no) ... PASoft/BMW Scanner is a completely different & separate program than BMW Standard Tools (INPA, NCS Expert, etc). They also have different cables.

I know it has different cable, but I thought I had installed it in the same load. My bad

Reactions: 1

mittortz

Discussion Starter · #20 · 27 d ago

bmwm3sports said:
Yeah it sounds like the pump is bad now did you change your fuel filter it's due every 60,000 miles and I wouldn't go but $30,000 also your fuel pressure need to check the bar minimum on that and your line pressure once you get that all sorted then you could easily determine it's the fuel pump

Thanks - still working on those items, sadly. I finally got to change the fuel filter and regulator today, and broke the stupid plastic fuel line connector going to the filter. So I ordered the replacement fuel line and it's gonna take a week to come in... no other choice but to wait 😩

Reactions: 1

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