The STRANGEST Ignition System IN THE WORLD BMW V12 M70

[@markhoult599]

You Sir are a lifesaver .11 years owning a E31 850 and the reason i have kept it running is down to your forums. Cannot thank you enough !!

[@TimmsBMWRepairsandInformation]

Thanks Mark!

[@Tango_Alpha_Charlie]

My tech and I are trying to get an M70 to behave on both banks, not just one .... this was very informative. Thank you !

[@TimmsBMWRepairsandInformation]

Glad it was helpful!

[@kevinconstantine5244]

Everydays a school day learnt something new today.

[@TimmsBMWRepairsandInformation]

Thanks Kevin!

[@oldgtstrokers]

Highly interesting, very pleasantly presented! Looking forward to new topics!

[@TimmsBMWRepairsandInformation]

Glad you enjoyed it!

[@marioduran7913]

Tim, thank you so much, I got the job done, I couldn't do it without your response. Best Mario from Raleigh nc

[@TimmsBMWRepairsandInformation]

Well done Mario!

[@synthwavegarage]

Thanks for all the useful information. I have been following your channel for years. I saw all the videos.

[@TimmsBMWRepairsandInformation]

So nice of you!

[@ianmcwilliam1753]

Recently acquired a 91 850i 6speed LHD and I’ve been watching your e31 vids to get familiar with the oddities of this magnificent vehicle. Many of your videos contain exactly what is needed for this 850. The first and perhaps most important piece of advice was DO NOT JUMPSTART so I purchased new battery and went with the single battery setup… car maintenance and small repairs can wait until my 2000 m5 is back on road (rod bearings, T.chains&guides , clutch/flywheel are installed) But i didn’t want to damage the windows when opening doors with old drained batteries. Looking forward to seeing all the other videos you’ve made over the years. I also have the m62b44 in my 97 540i/6 daily driver and your inpa diagnostic overview has been eye opening. My 540 has a rough cold start , idles smoothly , tons of power but has some vibrations when revving up 900-1600 rpm’s. No doubt You’re m62 advice will also prove helpful. You deserve to be one the top KZbinrs in your area of expertise.

[@TimmsBMWRepairsandInformation]

Very kind of you!

[@alioral1358]

Never heard about it before Timm. Thanks.

[@TimmsBMWRepairsandInformation]

My pleasure Ali!

[@woocash2139]

Small correction, the ht leads are copper in the m70, the resistance is in the end connectors which is how they all have the same resistance but different lengths

[@TimmsBMWRepairsandInformation]

Thanks, I am always happy to be corrected!

[@bargla]

What I absolutely love about Bmw and what really bought me into these cars was fact that you can have a certain type, symbol and part number of a spark plug throughout a huge variety of bmw engine models, and it will be the correct one. For example M40 4-cylinder and M62 V8! Isn’t it just genius? Wow.

[@TimmsBMWRepairsandInformation]

It is!

[@drewmurray2583]

They should have had cam sensors, not a hard thing to design into the front timing cover. Nothing wrong with batch firing the injectors either, carburetors do the same thing with pooling fuel on the closed intake valves and I have never had idle or running issues from setting up EFI that way.

[@TimmsBMWRepairsandInformation]

Thanks Drew, the late 80's was all about economy and BMW were trying to make economic cars against a backdrop of fuel shortages - that's why they were going for sequential (or semi-sequential) injection. A cam sensor would have been a lot better though!

[@BMWRestored]

Fantastic content as always Tim. As always very informative videos, absolutely enjoy watching your videos. 👏👏 Channel should be called Tim's BMW e31/e63/e64 school 😁

[@TimmsBMWRepairsandInformation]

Thanks! I do Mini's and 1-Series as well some times, so the moniker might be a little long!

[@midik123]

Learned something again. Thanks!

[@TimmsBMWRepairsandInformation]

My pleasure!

[@thew3t_dude616]

Well my 1990 750il break lights are staying on i changed the break switch but they stay on any help with that one?

[@TimmsBMWRepairsandInformation]

Unfortunately that's your LKM - there's a small chance there's a wiring problem around the ABS/DSC unit, but much more likely to be the LKM

[@johan7507]

Love the video's Timm! Are you absolutely sure the injection is disabled fully when the signal is missing? I remember when the DME was missing the signal from the doughnut it would fire all 6 injectors of one bank at the same time instead of in groups of 3. Of course diagnosing this it is a pain in backside as the M1.2 Motronic doesn't spit out a code which the later M1.7 does do. Same setup is also in the late M30s with Motronic M1.1/M1.3 as used in the e34/e34.

[@TimmsBMWRepairsandInformation]

Yes, injectors off on the M70, M30 not sure.....

[@funfun5656]

Exotic ignition setups like this is actually quite common with V12s (or at least as "common" as any component can be in a V12 considering how uncommon it is to have 12 cyls) Check out the DB11S with the AE31. It reminds me of the same way an M70 is just a pair of siamese M20s as it were.

[@khrhee5]

Hello Timm, really enjoy your videos. Does m70 engine use ignition-cut type traction control?

[@TimmsBMWRepairsandInformation]

Thanks! It uses a combination of intervention, starting with closing the throttle (which it can do very quickly with the electronic throttle bodies), it can retard the timing and in the worst case remove engine power entirely, but this is quite unusual

[@antontaskinen1532]

Hi Tim! Very uselfull video. It has helped me a lot. But I have problem my m70 engine is burning fuel in right exhaust pipe. And then it is changing which bank of engine is not running properly. I checked sparkplug wires with tester pen. Now my guestion is should the lamp illuminate in its one when 2cm away from spark plug wires. I was thinking is my problem old wires that are leaking elctricity?

[@TimmsBMWRepairsandInformation]

The HT leads are really expensive to replace - but if they have been around a while then yes, replace them, it will always give better performance

[@kevinabalo]

I put a set of Magnecor 8mm on mine with copper plugs quite some years ago. Never bothered testing the resistance, and ... . she gets up and goes, coin on the cover etc. Never a problem. I guess I've been lucky, but I will satisfy my curiosity when I get her out of hibernation. Thanks for your vid tho, Tim, as always.

[@TimmsBMWRepairsandInformation]

Thanks Kevin, I should have made clearer that the resistances are in the elbow-joints rather than the leads themselves. I always think of it too late after the video is published!

[@philliproberts2737]

I came here for help because I'm out of mind already frustrated with this issue. The gremlin I seem to have on the 850 M70 is that Bank 2 doesn't work. But when testing the plug for the donut sensor coming from the DME, it doesn't have current. So voltage wise it's dead. At the DME it also doesn't have the 4.5-5V. In the hope that the DME is faulty I swapped the known working one from Bank1 and it does exactly the same thing. Does anyone have any idea why the DME would not send 5V current to the sensor? Crank sensor has power, it's just the donut sensor doesn't. Help please...

[@TimmsBMWRepairsandInformation]

Try swapping the DME relays in the E-Box: www.meeknet.co.uk/e31/Timms_BMW_E31_Relay_Finder.htm#google_vignette

[@azm850]

Tank's you. Great explication.

[@TimmsBMWRepairsandInformation]

Glad it was helpful Altor!

[@gewortsjitian1566]

What's the right sparks plug For the M70?

[@TimmsBMWRepairsandInformation]

Have a look at the video or description

[@gewortsjitian1566]

@@TimmsBMWRepairsandInformation thanks, you're the best 👌👍

[@WalterThorne-h5k]

You good man…thank you

[@TimmsBMWRepairsandInformation]

Thanks!

[@1magnit]

You drew the iron V8 ignition system wrong, The coil only has 3 terminals and the spark completes the circuit via the battery.

[@TimmsBMWRepairsandInformation]

Thanks, you are correct!

[@johnpatterson2157]

Good evening, I am experiementing with my 850i M70, lol, running NGK platinum plugs, ZFR6FGP, 5K resistance, with MSD blaster coils that are 40K volts if I am not mistaken. I just changed valve stem seals and started driving the car this week. So far it runs great! Seems to run smoother than before but the old plugs were fouled from bad stem seals. I am curious why it seems to run fine with this combination of coils and plugs? Do the DMEs have a CIS signal range where the MSD coils and platinum plugs are within that range? Thanks,

[@TimmsBMWRepairsandInformation]

With the MSD you get a good signal for the CIS's, so don't worry!

[@johnpatterson2157]

Thanks, Tim!

[@Crazzyboy14]

Hello Tim! Been watching your videos for a while now. Trying to get my E31 running on all 12 cylinders. You said to make sure the spark plug wires are 1k resistors vs 5k. How can i check?

[@TimmsBMWRepairsandInformation]

Remove an HT lead from the distributor and from the sparkplug. Use a cheap multimeter and measure from end to end - it should be 6000 Ohms

[@jrobpat0154]

In order for the HT leads to be 6000 ohms each wouldn't they all have to be the same length, seems unlikely

[@jrobpat0154]

My guess is that 6000 ohms is the maximum resistance and it reduces as the leads get shorter. The longest leads, and the slightly weaker spark, go to cylinders 12 and 6 which has the sensors so if these 2 plugs are firing OK it probably means that the other 10 are as well

[@TimmsBMWRepairsandInformation]

The resistors are in the connectors rather than the HT leads themselves - hence why the differing lengths make no difference - I should have made that clearer in the video!

[@kmlumd44]

Timm I have the 04 e63/64 w n62 and SMG transmission. The transmission is leaving me stranded every time I drive the vehicle for over an hour in 90+ degree weather. Do you have a reference for me to get information on the hydraulic pump that controls the clutch, and information on how to diagnose or repair the transmission using the INPA computer software. I want to figure out how to overhaul the transmission so that the vehicle is reliable again, but I want to do the work myself without rebuilding the transmission. I have seen someone say that sometimes the transmission shifting needs to be 'retrained' after the vehicle is hot or warmed up completely but I have no idea how to do that. Can you please help? Also, I had to reseal my headlights because moisture was getting in and it corroded the electronic components that power the adaptive headlights so I had to replace those components as well. I completed the rebuild for the drivers side light successfully, but when I disassembled the passenger side light the halo glass was so rotted from moisture that the halos crumbled on contact. Do you know anyone with a cheap 645 headlight? Online they're quite expensive. Also, I used your video in the past to clear the front drains for my 645. Water was flooding the carpet, but after using your video I successfully cleared the drains and had no more water drainage issues, so thank you.

[@TimmsBMWRepairsandInformation]

Hello Scotty, sorry I know nothing about the SMG system, I only learn about systems in my own cars. But, your first port of call should be the 6-Series Forums on Bimmerforums.co.uk (not .com - that's dead), there are many helpful, knowledgeable people on there. Good luck!

[@kmlumd44]

@@TimmsBMWRepairsandInformation okay thanks. I will. Keep doing e63/4 updates. I really appreciate them and find them useful. Im doing the valve seals tomorrow and utilizing your video. You're a bigger help than you realize. Thanks again!

[@andrewthompsonuk1]

My m30 e23 does not have that system, it just fires all the injectors at once.

[@TimmsBMWRepairsandInformation]

Does it still have a doughnut?

[@andrewthompsonuk1]

@@TimmsBMWRepairsandInformation It does not have a donut. Most early 80s cars did not have sequential injection.

[@sebastianjoh5320]

Is the M73 a lot different?

[@TimmsBMWRepairsandInformation]

It is a lot different Sebastian, with proper camshaft sensors!

[@nurburgrinding]

Magnificent, unless it goes terribly wrong i guess

[@TimmsBMWRepairsandInformation]

Thanks!

[@repairitdontreplaceit]

m70 for sure is a strange one . those cps sensors are eom only . i tried 4 different brands and none worked properly , ended up with good used eom ones

[@TimmsBMWRepairsandInformation]

Thanks! That's a strange one, the CIS are only a couple of windings on a bobbin - possibly wired in reverse or something!

[@repairitdontreplaceit]

@@TimmsBMWRepairsandInformation all made in china or france , i measured the impedance and none where the same as oem

[@jasoneyes01]

OMG this sounds like something Jaguar would do back in the day.

[@TimmsBMWRepairsandInformation]

They used the same processors, so you never know Jason!

[@robertbowe2672]

I wonder if this is broadly the same for the S70B56 engine in my 1996 CSi? This engine is in the same general BMW engine family as the M70. But I believe that its 2 x DME M1.7 systems are somewhat different from what the M70 has. Also, I have Bosch F8 LCR 2 spark plugs in my engine, I guess this could also just be another difference from the M70?

[@TimmsBMWRepairsandInformation]

Hello Robert, S70B56 has proper camshaft sensors - at least the Performance division knew what they were doing!

[@robertbowe2672]

@@TimmsBMWRepairsandInformation Thank you Tim, I have found your E31 insights invaluable. BTW do you have a view regarding the Bosch F8 LCR 2 spark plugs? Or are they just another difference between the M70 and the S70 engines?

[@TimmsBMWRepairsandInformation]

@@robertbowe2672 I would stick with BOSCH FR8LC, they were the original specification Robert

[@mechtechmechanical1571]

good info there

[@TimmsBMWRepairsandInformation]

Thanks!

[@wernerdanler2742]

I can't believe I even followed that. I'm terrible with electronic/electrical stuff. Lol Would a cam position sensor make all your problems go away? I think I'll just stay away from BMW 12 pots though.

[@TimmsBMWRepairsandInformation]

The 850CSI got camshaft sensors Werner, at least they got the hang of it!

[@kevinmotorgasm6090]

i intentionally changed my M70 spark plug with Bosch FR7DP because i love the design of the insulation of that particular plug models that wrap around the electrode tip so well , preventing short circuit in wet combustion chamber commonly happens in old cars . But after that plug change , my car do start and die after 2 seconds ....... Then i search for help online and found your video , and you save my life !!!!! though i still wonder and hope that Bosch FR7DP has also 1000 ohm resistance, but i can't find any info on it online , any suggestions where to look as i don't have digital multimeter myself guessed i just have to clean and use back the old NGK plugs (I still keep them) or buy new NGK BKR6EK or Bosch FR8LC Another thing is before i changed the plugs my car always cold starts very easily, but sometimes don't have enough power , will not revv up , must wait untill it would revv up , sometimes must wait for so long , sometimes just wait a short while , BUT some other times it just cold starts and immediately have power and can be revved up immediately after cold start , now after watching your video i suspect that it may be caused by the old plugs resistance are not 1k ohm , or the doughnuts are also weak/unstable , so the engine is thrown into limp mode , what do you think ? Sorry my English is so fakin confusing THANKS Timm

[@TimmsBMWRepairsandInformation]

Hello Kevin, get yourself a cheap ($20) meter and check everything such as plugs and HT leads

[@andrewthompsonuk1]

So that's why those cars can be a nightmare to start if flodded?

[@marktolner2922]

Great Video Timm. Thanks. Would you happen to know if the early M73 V12 as fitted to my April 1996 E38 750iL has a similar system? There seems to be a donut around one spark plug lead on each bank that seem to be connected to the engine wiring harness. There are no coil packs for the spark plugs, there is simply a single coil pack for each bank of cylinders which have their sparks passed through the two distributor caps. Do you also happen to know if the following spark plugs are 1k resistance - BOSCH F 9 LCR2? I could not find information on their resistance on line. Thanks - Mark (from Kyiv, now in UK with my 760Li E66 and family, waiting to return ...). My E38 is waiting for me back home in Kyiv.

[@TimmsBMWRepairsandInformation]

The M73 has proper camshaft sensors Mark, so you are OK with most plugs!

[@311superfly]

Mine is waiting for electron excitement after 20 years of sitting silent.

[@TimmsBMWRepairsandInformation]

That's not going to help it!

[@killer1963daddy]

Only square heads can take something so simple and make it complicated.

[@TimmsBMWRepairsandInformation]

Good point well made!

[@jay_claricoat]

Hi Timm, sorry for this comment being irrelavent to this video but I'm graping at straws. Recently driving my E38 tones of smoke started pouring through the vents, ABS and Traction control lights came on and brake lights got stuck on. Soon enough I discovered the brake light switch has physically melted (bit strange). Have tried a new switch and the brake lights are still on, scanned the car for any codes using a launch scan tool, just to find an error related to the thermostat "DME : Activation, Map cooling P1622" Not even sure if that's relevant. If you've seen anything like this before or could point me in the right direction would be much appriciated. Regards, Jay

[@TimmsBMWRepairsandInformation]

Hello Jay, replace F44 in the front power distribution box and you should be up and running again

[@jay_claricoat]

@@TimmsBMWRepairsandInformation Thank you very much, this is going to sound super dumb but where abouts is that located. Thanks alot Timm

[@jay_claricoat]

@@TimmsBMWRepairsandInformation I have just actually done it so ignore the last comment. May I say you are a genuis, there was me thinking it was some horrid wiring issue and looking into it too deelpy, asking loads of people and no one knew. Thank you so much for sharing this knowledge, I owe you big time!!!!!!!

[@TimmsBMWRepairsandInformation]

@@jay_claricoat E-Box (four large screws) and the fuses closest are 33 (right) to 48 (left) - they will be marked in the lid

[@jay_claricoat]

@@TimmsBMWRepairsandInformation As above have managed to find it Timm. I owe you big time as it appears to have done the trick, you are a genius!! Just curious if you would know the reason for the brake light switch to burn out, quite scary and don't really want it to happen again. Thanks

[@311superfly]

Ohm don't mess around with the ,m70.

[@brucebratschi4300]

Interesting but puzzling. Why build it like that.

[@TimmsBMWRepairsandInformation]

It was a long time ago Bruce, they were really at the cutting edge, it was just that their pencils were blunt!