Is this the cause of a flooded E34?

[Bimmer Nut Ed]

I found this information on the Internet somewhere and I want to know your opinion as to whether you believe it's true of our E34's. It would explain exactly what has happened a couple times to both my daughter and her e34, and her best friends e34 BMW.

"The last time you started the car before the problem, did you start it from cold and just move it a few yards the switch off, i.e. run it for less than a minute?

I'm told by my dealer that the E34 (I've the 525 1996) has a minimum run time on the fuel pump of 2 minutes. so if you just switch it around on your driveway then shut it off the pump will run on and the pressure in the fuel system will force fuel past the injectors and flood the engine.

The remedy is 1st never run the car for less than 2 minutes particularly from cold. If the engine is warm then it can evaporate the fuel from the cylinders."

[Ferret]

The M30 definitely didnt do this - we had a 535i that blew an injector seal - the fuel supply shut down the instant you took the key out.

I'm pretty sure the M50 wouldnt do it either - usually the pump shuts off immediately - I remember it didnt piddle fuel everywhere for 2 minutes the last time it blew a high pressure supply line and I kicked it over... if that makes sense.

The amount of fuel the rail kicks out during the first few seconds of running though is frightening - if you started it up and pretty much immediately shut it down again I wouldnt be surprised if it got flooded.

Try turning the injectors over out the car and kicking the engine over to see what I mean :)

[Ross]

Ed, What dealer are you talking about??
First, the pump doesn't run with the car off. The injectors ought to be able to hold correct fuel pressure even if it did.
Brief running of a cold engine over and over will load up the plugs and make it prone to flooding. So, yes it's a good idea to run it longer than a couple of minutes but the reasons given you are wrong.
I think I know where your info comes from and am astounded you were given this explanation, tell me it wasn't a mechanic who told you this but one of the service writers.

[Bimmer Nut Ed]

I found it posted on the Internet. I did not ask a tech personally. According to Ross and Ferret's reasoning "flooding" can happen under these circumstances. That's all I need to know. The exact cause, I agree, the system stays presurized anyway, so who cares if the pump is pumping.

Thanks guys. At least I can tell the girls to run the car a tad more to prevent this.


Ed, What dealer are you talking about??
First, the pump doesn't run with the car off. The injectors ought to be able to hold correct fuel pressure even if it did.
Brief running of a cold engine over and over will load up the plugs and make it prone to flooding. So, yes it's a good idea to run it longer than a couple of minutes but the reasons given you are wrong.
I think I know where your info comes from and am astounded you were given this explanation, tell me it wasn't a mechanic who told you this but one of the service writers.

[ahlem]

The s-14 motors definitely have this problem. You foul the plugs and have to replace them before it will start.

[rob101]

I found it posted on the Internet. I did not ask a tech personally. According to Ross and Ferret's reasoning "flooding" can happen under these circumstances. That's all I need to know. The exact cause, I agree, the system stays presurized anyway, so who cares if the pump is pumping.

Thanks guys. At least I can tell the girls to run the car a tad more to prevent this.
I read similar things written in the UK Magazine "total BMW" regarding e38s

[winfred]

the pump only runs when the computer gets a signal that the engine is turning over, and the second or so pulse when you turn the key on, someone fed you a load of crap with the minimum run time, as for flooding, i think it's a variety of things that can start it, old plugs, really old diluted oil combined with a bobbled starting attempt on a cold damp day seems to be the most common, a certain combination of things will cause a m50 to loose compression at which point it needs to dry out and a good hot battery to handle the very long crank it'll take to start, m42/44s are very bad about this

[Bellicose Right Winger]

My M50 has the same problem. If you run it briefly and let it sit overnight, on the next start the engine will run very rich and rough for a few minutes. I don't believe it has anything to do with fuel pressure since the fuel pressure is not controlled by the DME. I suspect its a quirk in the DME programming, related to cold start enrichment. The E34 M30 and the M50 are the first BMW engines to do away with the cold start valve. If you run it for 2 minutes or longer there is no problem. A SA at my dealer told me about the 2 minute "rule" when I asked during a visit to the parts counter. I've had no problems since following the 2 minute rule.

Paul



I found this information on the Internet somewhere and I want to know your opinion as to whether you believe it's true of our E34's. It would explain exactly what has happened a couple times to both my daughter and her e34, and her best friends e34 BMW.

"The last time you started the car before the problem, did you start it from cold and just move it a few yards the switch off, i.e. run it for less than a minute?

I'm told by my dealer that the E34 (I've the 525 1996) has a minimum run time on the fuel pump of 2 minutes. so if you just switch it around on your driveway then shut it off the pump will run on and the pressure in the fuel system will force fuel past the injectors and flood the engine.

The remedy is 1st never run the car for less than 2 minutes particularly from cold. If the engine is warm then it can evaporate the fuel from the cylinders."

[bubba966]

As has been mentioned this is a problem on M50's. Don't think it has anything to do with excess pressure as has been said the pump won't run when the ignition is off.

But on cold start up the M50 dumps a lot more fuel into the chambers since it doesn't have a cold start valve. If you don't run it long enough to burn all of that excess fuel (2 minutes or so) you will be left with unburnt fuel in the chambers. Cold start it again the next day and the unburned fuel from the previous day along with the very rich mixture the DME is using on cold start and you flood the engine.

I've really only heard of this problem with M50's. Not sure if other engines of that era are also effected.

[Litespeed]

I'm told by my dealer that the E34 (I've the 525 1996) has a minimum run time on the fuel pump of 2 minutes. so if you just switch it around on your driveway then shut it off the pump will run on and the pressure in the fuel system will force fuel past the injectors and flood the engine.

The remedy is 1st never run the car for less than 2 minutes particularly from cold. If the engine is warm then it can evaporate the fuel from the cylinders."

Exactly what happened to me with my '92 525iT. The evening before, I'd started it up to back it from the drive into the garage. It was very cold out and I ran the engine for < 30 seconds.

The symptoms next morning were identical to those of a failed fuel pump, which had just been replaced. I figured that the replacement pump must have failed prematurely, so I had the car towed to the shop. The manager asked what happened, smiled, rolled the car off the tow truck, got in, cranked it for ~30 seconds straight, and it started.

Grr. BTW, 30 seconds is a very long time to listen to your car cranking over.

Peter W.

(Back from a long time ago... hello to all you old-timers, I'm still alive. So far.)