Car Won't Start - Fuel Supply Maybe??

[TheMonzta]

My wife told me her '88 318i two-door wouldn't start today. I've had a go myself and the engine's turning over but it's just not catching. At a guess I'd say fuel starvation was the problem.

One of my missus' more infuriating habits despite us living opposite a petrol garage is to let the tank run low. With that in mind I noticed she was again extremely low on fuel (well below the red mark ) so put two cans of finest BP in and gave it another go but still nothing doing.

One course of action is to replace the fuel filter in case she's sucked up some grot but I'm wondering whether the fuel pump is actually working at all. With the ignition on should I be able to hear it? On my old Opel I can hear it as plain as day buzzing away.

Also, where is the fuel filter and pump on an E30? Is a filter swap an easy job?

[JJ26]

The pump wont start spinning untill your engine is cranking. There will be 2 or 3 relays mounted under the bonnet on the bulkhead under the plastic clip on cover. One of those is the fuel pump relay. The Filter is usally mounted down by the passenger chassis leg under the bonnet. The pump is either the in tank type, accessed throught a plate on the drivers side under the rear bench or its the older type mounted on the passenger inner sill at the rear.

[TheMonzta]

That's great JJ26, very helpful indeed. I'll take a look for the filter tomorrow and order up a spare. Thanks.

If it doesn't solve the problem......I'll be back.

[mrLEE30]

if someone cranks the car you can hear the pump running (best way is to pull up the rear seat base or listen from underneath)

if not definitive then remove the fuel pump relay (normally orange) and jump pins 30 and 87 with a piece of wire. now with ignition back on the fuel pump should continuoisly run, if so does it start now?? yes? Change the relay>

if it does not run then check the fuses (11 i think but no reference book here with me now)

if the pump runs but engine does not start then its not the pump.

remove the wire jumper and dont replace the relay (so no fuel in engine), remove one spark plug and check for spark while ctanking.

If no spark then check for voltage at the coil, or look if there is an old immobiliser fitted somewhere

this should give you enough to get you started (or at least started on a diagnosis of the problem!!)

mrlee

[TheMonzta]

Thanks indeed for that excellent reply MrLee, that really does give me plenty to go on over the weekend. I shall report back with, I hope, good news.

[TheMonzta]

if someone cranks the car you can hear the pump running (best way is to pull up the rear seat base or listen from underneath)

if not definitive then remove the fuel pump relay (normally orange) and jump pins 30 and 87 with a piece of wire. now with ignition back on the fuel pump should continuoisly run, if so does it start now?? yes? Change the relay>

if it does not run then check the fuses (11 i think but no reference book here with me now)

if the pump runs but engine does not start then its not the pump.

remove the wire jumper and dont replace the relay (so no fuel in engine), remove one spark plug and check for spark while ctanking.

If no spark then check for voltage at the coil, or look if there is an old immobiliser fitted somewhere

this should give you enough to get you started (or at least started on a diagnosis of the problem!!)

mrlee

OK I finally got some time/weather to get out and do some diagnostics on the car.

I've fitted a nice, new fuel filter - still won't start!

Using your excellent advice I've ascertained that the fuel pump, fuel pump relay and fuse are all OK.

I popped out a spark plug (which was drenched in unburned fuel) and turned the engine over and got not so much of a hint of a spark.

There's no sign of any old alarm/immobiliser on the car.

I've checked the voltage at the coil and that seems healthy too.

Where do I go from here?

[JJ26]

Take the main HT lead that goes from the coil to the centre terminal of the dizzy cap and put that to your removed plug. See if you have a spark like that. If yes then you have a buggered dizzy cap, otherwise i think you might possibly have a failed coil or crank sensor problem.

[mrLEE30]

as above, but try a selection of spark plugs (it could be a duff plug!!)

then look to the crank postion sensor next, in particular the wiring from the sensor to the ECU..i think on the 318 the sensor is found on the front crank pully but not 100% on this!!

[JJ26]

If its a m40 then yeah the sensor wire passes very close the water pump pulley across the front face of the block. Should have a small plastic shroud clipped over it. If i remember right theres 2 wires crossing, the other is a position/cam senser which takes a signal from one of the HT leads. Dont think this is crucial for running.

[TheMonzta]

Thanks for all your great help and advice guys. I followed as many pointers as I could that you gave me until I ran out of talent. The car still wouldn't start so I had to call Britannia Rescue and use their Homestart service.

The chappy that arrived spent 90 mins on the car but did finally get her started but he was doing a lot of head scratching though, it certainly had him foxed for a while.

It was still running a little hesitantly so I took it to Dave at Eden BMW in Yeovil who resolved it in 30 seconds......it was a faulty Engine Management relay. £12 and a new relay later and she's running much happier. Thank you Dave!!!

Now I can get the car washed, polished and ready for sale.

Thanks again gents for all your great advice, I learned a lot.