M50TU dieing, causes?

[bubba966]

Working on a friends '95 525iT that's got about 173K on it.

It's currently stuttering and dieing. CEL flashes while it stutters, then it dies with most of the lights going on in the cluster as well as saying trans program and a few other things.

Volts at idle is 14.25, volts with engine off is 12.43. Battery is 4 years old (something from batteries plus that was installed by dealer they bought it from)

Haven't stomp tested it yet, will do it tomorrow.


This started yesterday after I spent all day replacing the crank sensor and swapping out the passengers side low beam. Crank sensor was a brand new BMW unit from Tischer, low beam used from Garret (though I don't see the low beam install contributing to this at all).

I'd put it all back together last night when it was dark out. As such I'd not noticed that one of the injectors wasn't fully seated and was spraying fuel all over the place on initial start up. Shut it off, reseated the injectors & fuel rail to fix the fuel leak. Then poured about 2 gallons of water over the intake manifold to rinse off the excess gas so it didn't catch fire and look like Brody's pics of his E34 BBQ.

Car ran beautifully after I reseated the fuel rail. Never ran so well that I recall.

But maybe 15 minutes after the CPS install it died. Let it sit for a few minutes while I had the DME disconnected then it started up again. Died another few minutes down the road. Once again unplugged the DME for a reset and waited a bit. Started again and ran for a few more minutes. Seems to run for a few minutes before it dies.

Am almost thinking that steam from the engine drying itself after the rinse has gotten into some connection in the engine bay and is causing it to die.

Tomorrow will take things apart and WD-40 the water out of things. Will also try putting the old CPS back in the car. Will have to measure the new and old CPS's while I'm at it.

Anyone have any other ideas? It's dieing like it's a battery issue, but voltage seems fine, and wasn't showing any signs of low voltage before the CPS install and was cranking over fine.
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[bubba966]

No one's got any guesses?

[BennyM]

I'd start with the stomp test to see what that CEL is trying to tell you. When it does run, what's the idle like? Does it stutter or fluctuate at all?
Also, check for vacuum leaks by pulling out the oil dipstick to see if idle gets rougher. Did you replace the o-rings on the injectors when you replaced the fuel rail?

This forum has seen a lot of cases where steam cleaning the engine bay caused a vast array of electrical issues until it all dried out. So, what you described sounds plausible.




Working on a friends '95 525iT that's got about 173K on it.

It's currently stuttering and dieing. CEL flashes while it stutters, then it dies with most of the lights going on in the cluster as well as saying trans program and a few other things.

Volts at idle is 14.25, volts with engine off is 12.43. Battery is 4 years old (something from batteries plus that was installed by dealer they bought it from)

Haven't stomp tested it yet, will do it tomorrow.


This started yesterday after I spent all day replacing the crank sensor and swapping out the passengers side low beam. Crank sensor was a brand new BMW unit from Tischer, low beam used from Garret (though I don't see the low beam install contributing to this at all).

I'd put it all back together last night when it was dark out. As such I'd not noticed that one of the injectors wasn't fully seated and was spraying fuel all over the place on initial start up. Shut it off, reseated the injectors & fuel rail to fix the fuel leak. Then poured about 2 gallons of water over the intake manifold to rinse off the excess gas so it didn't catch fire and look like Brody's pics of his E34 BBQ.

Car ran beautifully after I reseated the fuel rail. Never ran so well that I recall.

But maybe 15 minutes after the CPS install it died. Let it sit for a few minutes while I had the DME disconnected then it started up again. Died another few minutes down the road. Once again unplugged the DME for a reset and waited a bit. Started again and ran for a few more minutes. Seems to run for a few minutes before it dies.

Am almost thinking that steam from the engine drying itself after the rinse has gotten into some connection in the engine bay and is causing it to die.

Tomorrow will take things apart and WD-40 the water out of things. Will also try putting the old CPS back in the car. Will have to measure the new and old CPS's while I'm at it.

Anyone have any other ideas? It's dieing like it's a battery issue, but voltage seems fine, and wasn't showing any signs of low voltage before the CPS install and was cranking over fine.
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[ahlem]

How deep is the water around each spark plug? A friend of my son's pressure washed his motor and filled them up nicely. Same symptoms as you describe.
Compressed air dried them out and all was well.

[genphreak]

How deep is the water around each spark plug? A friend of my son's pressure washed his motor and filled them up nicely. Same symptoms as you describe.
Compressed air dried them out and all was well.

On the M50 they are all covered up. I'd suspect that you could have fueling problems. How did it run after the hose-down? Perhaps check the ECU is getting signal from the CPS when it cranks.

Did u drive it afterwards?

[ryan roopnarine]

On the M50 they are all covered up. I'd suspect that you could have fueling problems. How did it run after the hose-down? Perhaps check the ECU is getting signal from the CPS when it cranks.

Did u drive it afterwards?

Here in florida, i find that i have to drain my plug wells out with qtips once every 6 months or so, a function of the amount I drive, and the amount of rain here.

[ryan roopnarine]

You're gonna want to do that stomp test before you worry yourself anymore. IIRC, the o2 sensor connector, the CPS and CamPS, ICV, and oil pressure as well as both water temperature sensors hide under the manifold. Which injector was spraying? Might you have drenched the cps that was on there?


Working on a friends '95 525iT that's got about 173K on it.

It's currently stuttering and dieing. CEL flashes while it stutters, then it dies with most of the lights going on in the cluster as well as saying trans program and a few other things.

Volts at idle is 14.25, volts with engine off is 12.43. Battery is 4 years old (something from batteries plus that was installed by dealer they bought it from)

Haven't stomp tested it yet, will do it tomorrow.


This started yesterday after I spent all day replacing the crank sensor and swapping out the passengers side low beam. Crank sensor was a brand new BMW unit from Tischer, low beam used from Garret (though I don't see the low beam install contributing to this at all).

I'd put it all back together last night when it was dark out. As such I'd not noticed that one of the injectors wasn't fully seated and was spraying fuel all over the place on initial start up. Shut it off, reseated the injectors & fuel rail to fix the fuel leak. Then poured about 2 gallons of water over the intake manifold to rinse off the excess gas so it didn't catch fire and look like Brody's pics of his E34 BBQ.

Car ran beautifully after I reseated the fuel rail. Never ran so well that I recall.

But maybe 15 minutes after the CPS install it died. Let it sit for a few minutes while I had the DME disconnected then it started up again. Died another few minutes down the road. Once again unplugged the DME for a reset and waited a bit. Started again and ran for a few more minutes. Seems to run for a few minutes before it dies.

Am almost thinking that steam from the engine drying itself after the rinse has gotten into some connection in the engine bay and is causing it to die.

Tomorrow will take things apart and WD-40 the water out of things. Will also try putting the old CPS back in the car. Will have to measure the new and old CPS's while I'm at it.

Anyone have any other ideas? It's dieing like it's a battery issue, but voltage seems fine, and wasn't showing any signs of low voltage before the CPS install and was cranking over fine.
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[bubba966]

Took the coils out and two of them had damp boots. Blew them out with compressed air then took a hair drier to all of them to dry up any residual moisture. Didn't see any puddles in the plug wells, just the damp boots.

Started it up and it ran for about 18 minutes then died. Started it up again and it ran for 2-3 minutes then died. Wouldn't start up again after the second time it died. Didn't have time tonight to try a DME reset and restart.

But it's not much different than before. Last time it ran 15-18 minutes or so before it died the first time. Then it ran for 2 minutes or so before it died the second time.

It was the injector closest to the firewall that was spraying fuel all over the place. And I could've easily gotten the CPS connector and all of the other connectors in that area wet when I rinsed off the fuel with a 2 gallon pot of water.

Really weird that it starts up and runs fine for a bit then stutters and dies. Guess I'll have to pull the manifold off again and unplug everything and dry out the connectors. Not what I really want to do.

Currently my friend is driving my M-Sport until we get her touring running right again. She's kinda fond of my M-Sport and doesn't seem to mind having to drive it over her 525iT. Wonder why?... lol

[Grantus]

Those symptoms can mean that the fuel tank vent is blocked. I dont know what arrangement they have but it may be worth checking.

[bubba966]

Was thinking more about it on the way home from work just now.

What does anyone think about the possibility of the fuel pump is bad? Was thinking that it runs long enough to get something in the pump assembly warm enough to expand & bind causing the pump to either seize or seize enough that it stops supplying enough fuel and it stutters & dies.

That'd explain why it'll run for 15-18 minutes then die. Then will re-start immediately and run for a 2 or 3 minutes then die. Then it won't re-start after the second death. It'll crank and crank. And the more I think about it it's acting like it gets a tiny little bit of fuel (it's cranking like it's occasionally firing on a cylinder or two) but not enough to start.

I'm having a hard time figuring out any reason why it'd be a water in an electrical connection issue as when it starts up cold and runs great for the same 15-18 minutes or so, dies, runs fine for a few more minutes then dies, then won't start.

Or is this a possible thing that's fixed by that return line/check valve repair kit that's installed on top of the pump? It'd be awesome if that repair kit would fix this as I already got that kit and all associated gaskets to pull the pump & sender out.


Those symptoms can mean that the fuel tank vent is blocked. I dont know what arrangement they have but it may be worth checking.

Thanks, will have to look into that as well.

[Dave M]

Was thinking more about it on the way home from work just now.

What does anyone think about the possibility of the fuel pump is bad? Was thinking that it runs long enough to get something in the pump assembly warm enough to expand & bind causing the pump to either seize or seize enough that it stops supplying enough fuel and it stutters & dies.

That'd explain why it'll run for 15-18 minutes then die. Then will re-start immediately and run for a 2 or 3 minutes then die. Then it won't re-start after the second death. It'll crank and crank. And the more I think about it it's acting like it gets a tiny little bit of fuel (it's cranking like it's occasionally firing on a cylinder or two) but not enough to start.

I'm having a hard time figuring out any reason why it'd be a water in an electrical connection issue as when it starts up cold and runs great for the same 15-18 minutes or so, dies, runs fine for a few more minutes then dies, then won't start.

Or is this a possible thing that's fixed by that return line/check valve repair kit that's installed on top of the pump? It'd be awesome if that repair kit would fix this as I already got that kit and all associated gaskets to pull the pump & sender out.



Thanks, will have to look into that as well.

I've been watching this thread as it has similarities to my hesitation/no start episode a couple of years back (only occuring once car was warm). Eventually, after testing and or changing CPS, TPS, plugs, relays etc, I bought a used fuel pump from Jon K and swapped it out. At the same time, I changed a rotten coil (see pic below). In a sense, I wish I hadn't done both at once, so I could tell what fixed the issue. Anyhow, you might want to try a good used pump.

Dave

Rotten coil

http://img.photobucket.com/albums/v11/dave_macisaac/Bimmer/Engine/Vanos006.jpg

[Tiger]

Yep, I am thinking fuel pump also. Fix those leaky injectors.

[bubba966]

Yep, I am thinking fuel pump also. Fix those leaky injectors.

Injectors aren't leaking. They're new ones from fiveomotorsports about 2 years ago. Problem was that I'd reinstalled the fuel rail when it was dark out and hadn't noticed that the injector closest to the firewall wasn't fully seated. Found out real quick when I started it up and fuel was spraying all over the place.

Ended up replacing the o-ring on that injector the next day as the mis-seat of the fuel rail had deformed the o-ring and I felt it better to replace it rather than see if it'd bounce back to normal shape.

Oh, and the coils are new within the last 2 years or so as well. They're quite good.

[bubba966]

Tried a different fuel pump and it didn't fix the issue.

Here's a recap...

Changed out CPS for a new OE BMW CPS. Didn't have one of the injectors fully seated after CPS install and it sprayed fuel all over the engine on initial start up. Fixed mis-seated injector. Took a 2 gallon bucket of water and poured it over the intake manifold to no pressure rinse off the fuel that was sprayed all over the place by the injector leak.

After that it'd run fine for 15 minutes then stall. Would start back up and run for 2 or 3 minutes and stall. Then wouldn't start up again.

Swapped out the fuel pump assembly for one out of a '95 540 that was running fine before parting.

Then it'd run for 25 minutes then stall. Start back up and run for 4 or 5 minutes then stall. Start back up then run for a minute or so then stall. Start up and run for 20-30 seconds then stall. Then it wouldn't start back up again.

Added the check valve retrofit kit to the line out on the pump and changed the fuel filter. Didn't think the check valve kit was 100% needed, but it was under $7 and doesn't hurt. Old fuel filter was only about 2 years old. But draining the fuel out of the intake side of the filter showed the filter was full of crap as it came out cloudy and a bit brown. Tank had shown no sign of problems when I'd swapped pumps.

Then it'd run for 8 minutes then stall. Start it up again and it'd run a minute then stall. Start it up again and it'd run for 10 seconds then stall. Then it wouldn't start back up again.


So, a different pump lessened the problem but didn't solve it. Check valve & new filter made the problem much worse.

Anyone have any new ideas?

As it stands I can put the old CPS back in. And I can try throwing in the pump assembly from my M-Sport as I know that's fine.

[bsell]

To rule out lack of fuel you need to know the fuel pressure at the rail...

The pumps come with the pre-pump right? Or did you re-use the existing one in the car?

Could it be a bad fuel pump relay?

[bubba966]

Pre-pump?

And wouldn't a bad pump relay not allow the fuel pump to even operate? Could swap out the relay from my M-Sport to see if the one in the touring is bad. Where is it? Can give that a shot next time I'm messing with it.

This is making me wish that I had a pressure gauge...

[genphreak]

To rule out lack of fuel you need to know the fuel pressure at the rail...

The pumps come with the pre-pump right? Or did you re-use the existing one in the car?

Could it be a bad fuel pump relay? Check the hoses aren't deteriotated or loose. Also the connections under the manifold- both for pipes to manifold adn also the electrical connections that connect the cam and Crank sensors under the manifold. They may be corroded and the water and heat was enough to make them cause probs. Electrical contact repair kit would be very helpful if so. Also, not unusual to have bad Cranks sensors, which one did you get? I hear that cheapies have bad reps and are not worth using according to the gurus...

[bubba966]

I was a brand new BMW crank sensor that I put in. Hoses weren't deteriorated. Haven't popped it all out again yet to see if something didn't get put back right. Am trying to do the easy stuff first as I'm not really so fond of pulling out the intake assembly and CPS.

Yesterday I tried swapping out the fuel pump relay. No difference.

Think I'm going to have a look at the fusible link next to see if it's fractured and getting hot under use and opening up just enough to not supply proper power to the fuel pump causing it to stutter and die.

[Dave M]

This is a vanos M50 correct? Are these prone to o-ring/seal leakage and stalling like the M52s? The symptoms remind me a bit of my friend's M52 that we did the beisan system vanos fix on. As you've checked most other things, I thought I'd ask.

Dave

[bsell]

I was a brand new BMW crank sensor that I put in. Hoses weren't deteriorated. Haven't popped it all out again yet to see if something didn't get put back right. Am trying to do the easy stuff first as I'm not really so fond of pulling out the intake assembly and CPS.

Yesterday I tried swapping out the fuel pump relay. No difference.

Think I'm going to have a look at the fusible link next to see if it's fractured and getting hot under use and opening up just enough to not supply proper power to the fuel pump causing it to stutter and die.

Without a pressure guage, I guess the only other way to rule out the fuel pump dying is to tap into the electrical supply at the pump to see if the volts are dropping off. Knowing that the voltage supply to the pump is good does check off one of the to-do list items...wile you are there, you could hear the pump running or not.

[bubba966]

Yup, '95 M50 Vanos.

The vanos seals could use replacing. Which is why I've got the Beisan kit sitting by. But the problem isn't bad. And I've not heard of M50's stalling due to vanos seals. Not to mention this running perfectly fine (except the bit of vanos seal induced lag at 2,500-3,000 rpm) then stalling after X minutes business came on right after the CPS install. Would think that if it was a vanos induced problem it wouldn't have appeared so suddenly like that.

Not to mention that the period of time it runs for before stalling it fairly consistent. Initially it'd run about 18 minutes before it'd stall. After swapping fuel pumps it'd go 25 minutes. After adding the check valve retrofit kit it dropped to 8 minutes.

Am guessing that it's possible the check valve kit added enough resistance to the fuel flow that the pump has to work a little harder therefore drawing more current. More current means something is heating up quicker which is why it dies sooner now. And what beside the fusible link would account for such an issue?

[bubba966]

Without a pressure guage, I guess the only other way to rule out the fuel pump dying is to tap into the electrical supply at the pump to see if the volts are dropping off. Knowing that the voltage supply to the pump is good does check off one of the to-do list items...wile you are there, you could hear the pump running or not.

That's a thought. If I check the fusible link (links?) and see no issue there that's a good idea. Any idea which is +12 & ground in the plug?

[Dave M]

That's a thought. If I check the fusible link (links?) and see no issue there that's a good idea. Any idea which is +12 & ground in the plug?

I believe Bentley states which is power. Check page 160-4 for pin #s and 160-6 for which ones to test power. When I was trying to diagnose a similar issue, I had extended my multimeter wires to the cabin and watched the voltage while I drove.

Have you replaced a fuel filter recently?

[bubba966]

Thanks for bentley pages. Will look 'em up when I give it a go on Friday.

And yeah, did the fuel filter when I did the check valve kit. Filter wasn't too old as I'd done it a year or two prior (and this car doesn't even see 10k/year). But on pouring the fuel out of the filter I found it to be full of a fine brown silt even though the tank looked clean.

[Ferret]

Have you checked the temperature sensors that sit on the side of the head at the back of the engine? It could be they're reporting a stone cold engine constantly and as it's warming up over 20 minutes it's dying?

[bubba966]

No, haven't looked at the temp sensors. Not sure that they'd be doing what it's doing. When the problem first appeared it was about 18 minutes before it'd die. Change the fuel pump and nothing else and it was 25 minutes then. Added check valve kit & new fuel filter and it dropped to 8 minutes.

The more I think about it the more it seems like a fusible link problem as all I've done so far is possibly change the current draw with the new (used) pump and then again with the check valve install.

[genphreak]

Good move, sounds like it is ambient temp related since all you cnameasure is time during warmup. You could jumper the fuel pump so that it can't get shut off by the ECU/relay failure. It actually sounds to me mroe and more like a hairline crack in a relay track/joint.

[bubba966]

Good move, sounds like it is ambient temp related since all you cnameasure is time during warmup. You could jumper the fuel pump so that it can't get shut off by the ECU/relay failure. It actually sounds to me mroe and more like a hairline crack in a relay track/joint.

Did swap the fuel pump relay with one out of my M-Sport with no difference at all. Really, really hope it's just a hairline crack in the fusible link that's not passing enough current when it warms up. Need to get either this car or my car back on the road. And my car is much more FUBAR'd than the 525 is.:(

[bubba966]

Well, the 50A & 80A fusible links under the seat by the battery were fine. So that's not it.

Unless there's another one somewhere I'm not seeing it's not that.

Am starting to wonder if the coil pack that shorted out a year or so back actually damaged the DME and is finally starting to show. Looking for a cheap replacement to try swapping.

[genphreak]

Here in florida, i find that i have to drain my plug wells out with qtips once every 6 months or so, a function of the amount I drive, and the amount of rain here. Wow Ryan, that's a lot of water. BTW, have you got all the little seals in place around the plastic cover? It is spposed to seal the whole top end quite well.

[genphreak]

Well, the 50A & 80A fusible links under the seat by the battery were fine. So that's not it.

Unless there's another one somewhere I'm not seeing it's not that.

Am starting to wonder if the coil pack that shorted out a year or so back actually damaged the DME and is finally starting to show. Looking for a cheap replacement to try swapping.Defaintely jumper the FP at the relay plug with direct 12V for a few days, taking care to turn it off when you are not using the car. That way nothing can stop the FP and you can narrow it down to ECU or some input to it. If going to the effort to check the fusible links, change them, they don't get hairline fratures so much as invisible corroision form arcing inside the riveted joints. Touching them the right way tends to make them work, but the symptoms are very heat affected :)

Note: A lot more stops if the fusible link goes. If the 80A one, your cluster, lights, high speed wipers (as well as ECU and engine systems) stop working. If the 50A one is failing, expect low speed wipers, OBC and radio etc. It won't affect the engine's operation though, or lights.

[bubba966]

So, I've already pulled the FP relay and replaced it with a known good one and it made absolutely no difference.

Today I'll pull the intake manifold all apart and try it with the old CPS and see how that goes.

Next is trying a different DME if I can find one.

After that I'm out of ideas.

[genphreak]

The FP relay is not likely to be faulty. You want to work out if fuel pump is causing the FP loss, or if it is the FP regulator or return valve. Maybe its just a faulty wire/ground somewhere. If the cause for the Sudden Death Sydnrome doesn't happen when the Fuel is jumpered, it narrows the firled down. Swapping ECU is a good move, but it is unlikely to be root cause, just channeling the symptoms...