Ideas diagnosing 850i that starts, idles for 1 second, then dies?

[DanB]

I am going to be helping Braveheart61 diagnose one of his 850i's over the weekend (1991). As it says in the title it starts, idles for a second, then dies. The plan is to go through it as follows:

- Stomp test
- Visual inspection of intake / vacuum system for leaks
- Fuses
- Unplug MAFs and see if it goes into limp home mode (though now that I think about it, those don't usually go out at the same time do they?)
- Camshaft position sensors

Does anything else immediately come to mind for you V12 guys? I drive a lowly V8, so I'm probably 4-short on ideas.

[Timm]

The usual cause of running for a few seconds and then stopping is the lack of cylinder identification signals. These are provided by the inductive sensors on HT leads 6 and 12.

[legoman67]

fuel pump

[bruinbro]

I am going to be helping Braveheart61 diagnose one of his 850i's over the weekend (1991).

You're going back to 1991 to diagnose his car? Are you going to the factory? If so, would you please kick the C-pillar cover design engineer in the balls for me?

Thanks,
Steve

[m6bigdog]

Fuel Pressure Regulator!!

[DanB]

The usual cause of running for a few seconds and then stopping is the lack of cylinder identification signals. These are provided by the inductive sensors on HT leads 6 and 12.

I will swap the leads off his parts car and see if it makes a difference, thanks for the info.

fuel pump

Need to know which relay to bridge for this and where it's located.

Fuel Pressure Regulator!!

Will check.

You're going back to 1991 to diagnose his car? Are you going to the factory? If so, would you please kick the C-pillar cover design engineer in the balls for me?

Thanks,
Steve

Sure, I'll run the red exhaust tip idea up the flagpole while I'm there.

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Update; INPA stored errors:

Ti-signal 7-12th cyl

Throttle valve servo motor 1-6th cyl

Any ideas what the ti signal is? I assume throttle servo is idle control.

[Timm]

ti-signal is the injection time signal, the base timing is derived from the cylinder identification signal.

[DanB]

Roger that, thanks Timm

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Replaced throttle body on bank 1-6 with known good one, replaced cyl 12 wire with known good one, no dice.

[Timm]

Is it still running for a second or so and then fizzling out?

[shogun]

We had the same problem this weekend on an 850. Exactly as Timm said: lack of cylinder identification signals. In our case the ignition wire boot of cylinder 12 was lose/not connected to the spark plug.
Before we checked the usually subjects like fuel pumps, fuel pressure, ignition = distributors+rotors, crankshaft position sensors.

[DanB]

Problem solved - bad fuel pump. And the tank was full... Thanks for the help guys!

[Timm]

That's good news!

[DanB]

No tea around here, so time for a cup of beer.

[Timm]

Don't you V12 boys have a fuel pump per-cylinder-bank as the 750 boys do?

[DanB]

Don't you V12 boys have a fuel pump per-cylinder-bank as the 750 boys do?

I dunno, this is my first time working on a V12. I just went for the one under the right side rear seat.

[chinito03]

same symptoms I experienced on my 93 850ci. my car went nto lhm then died... car would start then die.. changed my fuel pump assy (passenger side $400+) . car started but still on LHM. stomp test gave me 2247. was thinking it was sensor but trned out to be a bad plug wires (#7 and #9)

daryl

[Braveheart61]

you're going back to 1991 to diagnose his car? Are you going to the factory? If so, would you please kick the c-pillar cover design engineer in the balls for me?

Thanks,
steve

rofl

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WOW

Big Thank You Dan!!!!!!!!!!!!!

Hell with the Tea, Ill bring the Tequila

[DanB]

rofl

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WOW

Big Thank You Dan!!!!!!!!!!!!!

Hell with the Tea, Ill bring the Tequila

LOL! It was a group effort. Hopefully there's a LOT to celebrate today.

Gary C is swinging down again, should be fun!

[TTTXGreg]

Don't you V12 boys have a fuel pump per-cylinder-bank as the 750 boys do?

yes

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rofl

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WOW

Big Thank You Dan!!!!!!!!!!!!!

Hell with the Tea, Ill bring the Tequila

Now we're talkin'

[shogun]

Don't you V12 boys have a fuel pump per-cylinder-bank as the 750 boys do?

Not all, the E38 750 V12 with the M73 only has one fuel pump, the E32 750 with the M70 V12 has 2 fuel pumps.

[toomanyparts]

You're going back to 1991 to diagnose his car? Are you going to the factory? If so, would you please kick the C-pillar cover design engineer in the balls for me?

Thanks,
Steve

This. Brand new pillar and no way to install. I think they put them in before the glass. I've decided.

[DanB]

This. Brand new pillar and no way to install. I think they put them in before the glass. I've decided.

Jackasses!

[sickle44]

Damned car has been giving me the kinds of ulcers that only 8 owners can really understand; doing the exact same thing as initial subject, fires, runs for a couple seconds if that then dies.

Thanks to this forum and all of it's threads, I was able to summize that it is quite likely the fuel pumps. Wasn't really looking there as it smells horribly of fuel and I had already replaced them just a couple years ago, good friggen reliability there for sure, NOT,

A special thank you to the forum member who suggested jumping a wire (with car off) from fuse 23 to 30amp fuse 25, then 24 to fuse 25 to see what's what with factory fuel pump wiring and what not. Very helpful diagnosis tool, very helpful indeed, makes perfect sense and a guy's thinking, shit why didn't I think of that; alas, one cannot think when all they want to do is put a stick of dynamite underneath a car and a piece of crap Peake Tool that's........ well,... that's another rant.

Thanks Gents

[alqatou]

hi
i need help please
my car 850i manual 1991 run really rough and it die checked the fuel pumps and both working replaced 2 cid sensors 2 crank sensors cap , rotors and spark plugs and i still have the same issue ?
my codes are 16 CAMSHAFT POTION SENSOR for both sides and when ever i clear the codes and start the car the codes come back at ones ?? and the car die ?
sometimes the car start normal like V12 but it start to stall then die and some time passenger side work and drive side shut off and when i turn it off and start it again the problem go to passenger side ?

please i need help
what i am missing here
i order 2 coils still waiting
do i have to order new spark plug wires ?? ecu , dme , wire harness ????
i love the car and i want it back to be normal
please any advice

thanks
ryan

[cartoonz]

the car is telling you what's wrong, the CID sensors...
You sure you have them plugged into the right plugs?
You sure they are actually any good? Bad "donuts" have been a common problem with some replacements...