No start

[CMG]

I've dealt with a no start issue on 745i so many times over the years but unfortunately i don't always remember all the little details. Latest no start has it turning over but not starting. Only work done recently was a refresh of throttle cable. Haven't had a chance to look into things but suspect no fuel. I don't hear the walbro turn on with key on. Not orange main relay, not a fuse. Could be the ignition switch. Was there a fuel pump relay i don't remember? Am i forgetting anything else?

[jimsperf]

try switching the crank and cam sensor wires if it starts and runs shity you got it the crank sensor went out

[Hit Man X]

Hell, I have been dealing with this on a guy's car for months now. What have you tested up to this point?




Do you have spark at least?

Power on positive side of coil? If not, check through the ignition switch and the OBC (if equipped since ECE car)

Remember, ECU grounds the fuel pump relay. Easily the ECU should have shit the bed. BTDT.

The crank sensors are for engine speed and TDC reference, not camshaft. When the reference marker on the flexplate is gone (or when the sensor dies), the car is a dead duck with no spark and no fuel.

[CMG]

I haven't tested anything yet been too busy. I have a hunch it's no fuel cuz you can hear when a walbro works so that's first and easiest to check. I know there's a million things that could cause a no start but i think it's gonna be one of the simple ones. This is like the 5th no start and in the past it's been stuff like relays, ignition switch, distributor cap, etc. I'll hopefully be able to dig into it Sunday so i'll let you know.

[jimsperf]

ya i forget bmw call the sensors different than any one else but if you switch them and it starts and runs crappy its the ref sensor been about 7 or 8 years since i messed with that look in a bentley book and check it out

[BoolJames]

ya i forget bmw call the sensors different than any one else but if you switch them and it starts and runs crappy its the ref sensor been about 7 or 8 years since i messed with that look in a bentley book and check it out

"Reference sensors"

i only know this because I jus realized that's why my 745 won't turn over. Pulled mine out put the tab on one of mine broke into the plug Also when i pulled it up on real OEM 2 slightly different part numbers popped up so idk which one to order..Hmm

[jimsperf]

bosch # 261210002 bmw # 12141708619 should do it

[BoolJames]

bosch # 261210002 bmw # 12141708619 should do it

For both of them right? Are they usually the same?

[CMG]

Reference sensor? Never heard of that one. Where is it?

[offroadkarter]

Reference sensor? Never heard of that one. Where is it?

He's talking about the sensors that sit in the transmission bellhousing.

[Hit Man X]

For both of them right? Are they usually the same?

Jim is right on the money for the part numbers.



Yes, they are the same. $61/ea currently at Autohausaz.com

Top (speed) goes to the black plug on the engine hareness, bottom (reference) goes to the grey plug. Mark them or memorize...or both.

[jimsperf]

you guys its diferent for me because i have a scope thats what i use to tell the signal of both but my memory tells me its the crank sensor ( it reads every tooth on the fly wheel )

[BoolJames]

Jim is right on the money for the part numbers.



Yes, they are the same. $61/ea currently at Autohausaz.com

Top (speed) goes to the black plug on the engine hareness, bottom (reference) goes to the grey plug. Mark them or memorize...or both.

Have you ever had trouble pulling one of the plugs out from the tranny? One is stuck half out. It spins jus kant pull it out...should I really really pull at it? Would I break anything u think? (Will post a pic soon)

[Hit Man X]

Have you ever had trouble pulling one of the plugs out from the tranny? One is stuck half out. It spins jus kant pull it out...should I really really pull at it? Would I break anything u think? (Will post a pic soon)

I have not had to deal with a stuck reference sensor, but stuck ABS sensors a few times. Best advice I can offer is spray some sort of lubricant and/or rust dissolving spray and keep spinning that bastard around or pushing it in and out to help it come out. If that does not work, I guess I would break the thing apart and pull it out with Visegrips. That would be final resort.

When it does finally come out, put a small cylindrical wire brush on a drill and squirt some lube in there to hone the hole out a bit. Oh and I guess some antiseize on the metal of it upon reinstall.

Maybe someone else has a better suggestion

[offroadkarter]

Have you ever had trouble pulling one of the plugs out from the tranny? One is stuck half out. It spins jus kant pull it out...should I really really pull at it? Would I break anything u think? (Will post a pic soon)

Are you trying to replace it, or are you reusing it?

They do get really stuck, sometimes I'll use a flat head screwdriver to gently nudge it out, but if yours is half way out just grip it and pull. They have O rings on them that make it a tight snug fit. Anti-seize would work also, you shouldn't need a ton of it.

[BoolJames]

I'm tryna replace them. The one closest to the firewall is stuck. I didn't get around back to it lastnight but ima tackle it again today. Ima ad a tiny lib and sop in it around. I jus wanna make sure before I go hulk and pull it out that I don't break anything. I got one sensor out already.

[CMG]

Just like i thought no fuel. I tried changing out main relay and fuse with no difference.

[Hit Man X]

Just like i thought no fuel. I tried changing out main relay and fuse with no difference.

Relay not closing? Motronic grounds the FP relay. Do you have spark? Try just jumping the FP relay and see if your car starts.

Bad CTS causes a no start also.

[CMG]

By cts u mean coolant temp sensor? That was previously replaced. The only work done recently was i replaced all the aftermarket fuses with oem ones and refreshed throttle cable. Nothing was disconnected. Do i gotta pull a plug to check spark or is there another way? I have tons of extra relays so i should have a spare fp relay. Guaranteed it's something simple, i just haven't had the time to check everything.

[Hit Man X]

You can just stick a spare spark plug in one of the wires and lay it on the valve cover. I guess you could also use a test light and see if it flashes off the negative side of the coil

[SicStang03]

You can jump the relay and see if it starts. The pump relay sits on the side of the fuse. If you pull the relay, jump the top pin to the right pin. 87 to 30 I think... There are 4 pins, easy peasy. Try and start it while it's jumped and see what happens. The reference sensors should read 1000ohms +/-50 when the key is in the on position.

Since you replaced all the fuses, have you pulled them to check if any are blown? If the fuse for the cts is blown (same fuse powers the windows), the car will not start. Same goes for the radio fuse since it powers the OBC.

[Hit Man X]

Correct on terminals 30 to 87.



Also could do the AC test on the crank sensors. Speed will read 2-4V cranking and the reference will usually do 1/10 of that in my observations so, 0.2-0.4.

[CMG]

Thanks for the suggestions guys. Hopefully i'll have time to check stuff this weekend. I already swapped fuses and double checked them. I know it's something simple just need the time to look into it.

[CMG]

FP turns on when 30 and 87 are jumped but still no start. I checked at the coil and no power to coil. I've had the same symptons when the back pops off the ignition cylinder. Just one of many things to check, i just wish i had the time to do it. Do i gotta get under the car to check those ref sensors?

[Hit Man X]

Power to hot side of coil comes from ignition switch through OBC (if equipped) to main relay to positive side of coil to magnetic valve. Both sides of coil have 12V, key on engine off

Jump main relay and see what happens. That will power up coil, ECU, and power to FP relay. If ECU has no power, the FP relay will not ground to kick on nor will ECU pulse negative side of coil