starting trouble

[tim96]

1990 320i auto. just started happening today.
car runs fine once it is started. If i am driving around and turn it off, leave it for 1 minute then come back and start it again it will start fine. But if i am driving around, turn it off and leave it for 5-10 minutes plus, when i try to start it the engine just turns over and doesnt fire even if you hold it down for like 5 seconds. after 3 or 4 attempts of this result it starts and then runs fine.
It doesnt make a difference if i try to start it in park or neutral. any ideas?

[marti5]

Hmmmm... sounds like fuel pressure as after say a 1min the pressure is still there but diminishes after being stood and you have to keep cranking it up until the pressure returns, could be your fuel pump..as there's a non- return valve and if this goes the fuel drains back to the tank.

[tim96]

i did a cold start after it had been sitting in the garage over night and it started fine i turned it off and tried a couple more times - no problems. Would this mean that it isnt loosing fuel pressure as it certainly would have lost it over night or would the different settings for "cold start mode" compensate the loss of fuel pressure

[marti5]

Not fuel pressure then....it may be coil breaking down when its hot...

[tim96]

Originally Posted by marti5

Not fuel pressure then....it may be coil breaking down when its hot...

is that possible even though it runs fine once started and starts fine if i only leave it for 1 minute?

[darkhorse737]

Originally Posted by tim96

is that possible even though it runs fine once started and starts fine if i only leave it for 1 minute?

it happens. it would be a short inside the ignition coil winding if that be the case.

If you can get you hands on a known good coil, it's an easy switch to test.

fuel pressure like marti sez, very possible too. either the lack of pressure at start-up... or too much of it like flooding; and good indication is if u smell gas fumes when the hard start episode displays.

OR, pull out your plugs when u have those hard start periods. plug condition will tell you a lot black & dry; black & wet, brown, grey, white...

TIP: maybe time for a tune-up? esp. if you hv been using platinum plugs. ur bimmer series does not like platinum, or the bosch +2 or +4 plugs. Stay with good ole' copper core.

[tim96]

Originally Posted by darkhorse737

it happens. it would be a short inside the ignition coil winding if that be the case.

If you can get you hands on a known good coil, it's an easy switch to test.

fuel pressure like marti sez, very possible too. either the lack of pressure at start-up... or too much of it like flooding; and good indication is if u smell gas fumes when the hard start episode displays.

OR, pull out your plugs when u have those hard start periods. plug condition will tell you a lot black & dry; black & wet, brown, grey, white...

TIP: maybe time for a tune-up? esp. if you hv been using platinum plugs. ur bimmer series does not like platinum, or the bosch +2 or +4 plugs. Stay with good ole' copper core.

i use ngk zgr5a's thanks for the heads up about coil and fuel pressure its given me some things to think about

[tim96]

i bench tested my ignition coil although i am a little confused. The haynes service and repair manual says their are two type the tci system and later motronic system. My car is a facelift and has the motronic system (as it says motronic on the ecu) but my ignition coil says "TCI - ignition coil" ?

The haynes manual has two sets of resistance figures for motronic and tci on page 111..
Ignition coil
Primary resistance
TCI system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.82 ohms
Motronic system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.50 ohms
Secondary resistance
TCI system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8250 ohms
Motronic system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5000 to 6000 ohms

I havnt tested resistance before so didnt really know what i was doing but..

Primary coil, i set the multimeter to "200" and got 01.1 (the leads touched together by themselves were 00.6) so the would mean 0.5 ohms ?

Secondary coil i set the multimeter to "20 k" and got 6.72 which would mean 6720 ohms ?

I will test it again after the car has been running as you said above it might have a short when it is hot.

[tim96]

update i tested the coil after it was warmed up, i used the same multmeter settings as before "200" for primary and "20 k" for secondary

After about a 10 minute drive..
Primary 0.5 / 0.6 (resistance of multimeter leads was 0.5 / 0.6 and reading was 1.1 for primary coil)
Secondary 6.99

After more driving..
Primary 0.5 / 0.6
Secondary 7.33

[tim96]

update i tried another ignition coil and it didnt make a difference so i doubt that is the problem..

[darkhorse737]

Originally Posted by tim96

update i tried another ignition coil and it didnt make a difference so i doubt that is the problem..

if you've ruled out coil:

*check fuel filter. make sure it is clean*

1) main relay;
2) crankshaft sensor.

these parts in e30's are prone to failure, and will cause the symptoms you are experiencing.

[tim96]

ok i am guessing..
left , the white relay is ?????????
middle, the blue relay is fuel pump?
right, orange is this the main relay?

[darkhorse737]

Originally Posted by tim96

ok i am guessing..
left , the white relay is ?????????
middle, the blue relay is fuel pump?
right, orange is this the main relay?

per illustration:

WHITE = Main Relay
BLUE = Fuel Pump Relay
ORANGE = Oxygen Sensor Heater Relay

[tim96]

hi, just to give you an update ..
I changed the main relay and it didnt make a difference. I am now halfway through replacing the crank shaft sensor, the allen bolt holding it in place was to tight for my 3 inch long allen key so i am letting it sit in crc over night, hopefully the bolt will have loosened up by morning.. i have to be somewhere at 10am

[tim96]

well this is starting to be a real pain in the ass. I changed the crank sensor went for a test drive of about 10 - 15 minutes. Came home, started it up about half an hour later andit cranked for about 7 seconds then fired and ran like crap at idle for a second or two and then died. Started it up again and then it was ok..
things i havnt checked

fuel pressure (remember the car cold starts fine)

Fuel filter, it looks old but this problem just started happening all of a sudden which makes me think it would be electrical and a dirty fuel filter would make it slowly harder to start over time wouldnt it.

Is it possible it could be the fuel pump relay?

anything else you can think of?