Hard Starting

[heung]

1 owned as 1991 850i, which is running well (if I can get it running). My problem is once the batteries are disconnected and reconnect or car not use for more than 2-3 days. It's a donkey to start. Engine will crank over and immediately start but only runs for 2-3 seconds and die. Found out it's only the left bank that runs for this few seconds. Right bank I believed no ignition. ( I pulled the wire to the coil to test which bank was running). This starting can goes on for 2 days. Try not to start too many time too often or it will flood the plugs. every hour crank 3-4 time. same thing, start immediately but only for 2-3 seconds. Eventually when lucky, the left bank will stay alive(bearly) and engine will run to operating temp. Starting more frequently now will keep the left bank alive till operating temp. With luck a few time the right bank decided to join in. This is when I can go for a drive but that not the end, 10-20kms down the road., engine will suddenly loose power and bearly stay alive. continue to drive and a few mins later all will be normal. From then onwards if I use the car everyday, it will run well with no more incident, until if I leave it for more than 3 days. I have change Batteries, Temp sensors and the problem is still there. Please help..

[Omega man 1969]

Check the distributor caps and rotors are good. You also may have a problem with the pulse senders on the ignition wires. If you have spark on that side and dry plugs then check the fuel pump is running.

[heung]

There is fuel as I can smell fuel after a few attemp to run. THe cut off I believed is more on spark. There was no sparks on the right bank. Try to start again today and getting better life on one attemp. Runs about over 10 seconds but struggling. Could it be the Main Fuel injection Relay? Fuel Pump Relay? Where can I find the Pulse Sendor? What is the part number so I can try to order one. Thanks

[TxGR8White]

Pulse Sensor is the black "donut" that is surrounding the #6 and #12 sparkplug wires. They plug into the connector directly below the oil filler neck. Has this car been sitting for a longer period of time? What condition is the gasoline in? Is it fresh?

[heung]

Hi I found the Donut at #6 and #12. I have more starting attemped and this has help me finalised the conclusion. Check at night with extra spark plug on lead #3 and #9. Concluded both bank Spark is good. Many attemped to start only with the 2-3 seconds running. Finally dismental all 12 plugs to check. Right bank all 6 plugs are wet with fuel. Left Bank no fuel but sooth black. Wire brush all 12 plugs and reinstalled. (Took only 2 hours to do all 12 plugs) the last time I did that to my V-12 Jaguar took the whole day) Car starts with first turn key but not smooth, however it's running. Again check both bank for spark and they are positive. Check exhaust manifold with Temp gun and left bank is not running. With scope listen to injectors and conclude all 6 ingectors on left bank is silence. With temp in operating level engine is smooth but conclude only running on Right bank. Turn off engine. Start again, still left bank is not running. Finally I can conclude what happen.. At the first, when the car is started, there is a short bust of fuel to the left bank but no continue fuel delivery as the injectors will not open. THat is why the short life of 2-3 seconds. (Don't know why Right bank do not start) Continue starting become worst Right bank become flooded with fuel. Questions now is why does left bank continue to shut the injectors movements. What sensors actuvate and controls the left bank injectors??

- - - Updated - - -

After I have posted the thread earlier today. I went to start the car again. Whaa la. Both bank comes alive. Runs good for about 1/2 hour. Took it out for a drive this evening and again runs well when both banks are running. Left bank continue to shuts it's injectors on and off. Every min or two. ( I brought the scope with me, stop the car to listen to the injectors when power is down) My Questions is what causes the intermitten shut down of the left bank injectors. Where are the sensors related to this? What controls the left bank's injectors??

[cartoonz]

I think you're still not understanding why everyone has been directing you towards the pulse sensors

[Omega man 1969]

Swap spark plug wire #6 with wire #12...then see if the other bank runs. Even if you have spark, If the sensor is bad then the DME will assume there is no spark and shut the injectors down to protect the cats. swapping them over will prove this.

[heung]

For preventive maintainance I might as well change out both the pulse Sensors. I don't know when it was last replaced. Does the suppliers sell only both the sensors or I have to purchase all the complete set of 12 plugs wires? Any idea what it cost?

[Omega man 1969]

It's not necessarily the sensor, it could also be a bad coil, bad distributor cap and rotor. It's best to fit new caps and rotors before buying expensive parts .

[heung]

Where do you folks in UK (london) buy your 850 parts. I have somebody going to London soon and hope to pick up the parts I need.

[heung]

Hi, Gurus, Did the swaps today on the Plug wire 6 and 12 together with the pulse Sensors. The problem if intermitten injectors closing has now been transfered to the right bank. Looks like one of the sensor is getting bad. Which one? Will have to have somebody hand carried it from London. Anybody know where I can buy these Sensors? Cheers