Help: Coil/Starter Wiring Issues 1978 320i

[alsimma95]

Hey guys, first time poster here. I've been trying to get a 1978 320i running in my free time and was hoping some of you guys could help me out.

Car will turn over but wont start, and after replacing the starter, fuel pump, and cleaning/rebuilding the carb attached, I finally found some corroded wiring hidden under electrical tape at the ignition coil plug after it started smoking when i replaced the coil . Unfortunately, I can't really tell what this wiring is as the only bit of tubing thats left does not match any of the diagrams I've looked at, and I'm not the best at reading these diagrams either. Is this the ballast/resistor wiring thats broken? And what's the best way to go about repairing this? Unfortunately I can't find any new aftermarket harnesses and I'd rather just repair this if possible. Relevant diagrams and pictures will be attached.

Also, I had originally thought there wasn't a ballast resistor before purchasing a 3 ohm Flamethrower ignition coil, because I was unaware there was a resistor wire. Would it be possible to leave the resistor wire broken and run a 3 ohm coil, or should I repair the wire and get a 1.5ohm coil. From what I've read there are setups with and without ballast resistors, and for ones without I should use the higher resistance 3 ohm, but ones with I use the lower 1.5. But I don't know what the implications of leaving that wire broken are, it probably cant be good right??

Finally, I'm going to attach a picture of the starter motor, could anyone confirm if everything is properly wired? I installed everything how it was before I took it off, but I'm worried it could've been wrong in the first place. The coil wiring smoking leads me to believe there could be an electrical issue somewhere besides the faulty wiring at the coil, and this car is making me a nervous wreck Was the higher resistance coil in addition to the resistor wire responsible for the 'electrical incident'? I'm extremely inexperienced when it comes to these older setups and their electrical problems...

I have a ton of other questions, but I'll keep it on the short side for now, appreciate the help.

https://gyazo.com/b8bbf16e681f3bdb1f698afd12149534
https://gyazo.com/6178efc3e33228a825b5be3c9766e5f8
https://gyazo.com/66ce52b6f45f3aa3ac32b37a44ecde21
https://gyazo.com/121da592287d728ab4965a08c735fb06

Since I can't post attachments I hope these gyazos work...

[GDAus]

Hi ...

First off here's a diagram of the connections on the starter solenoid.

Umm ... What colour are the wires you have connected to the second stud (the one on the left in your photo) on the solenoid?

If they're Brown .. then that is so wrong!

Brown wires are negative(-ve) and that stud is the other side of the switch in the solenoid that connects the starter motor to Battery positive(+ve).

Secondly .. The 3 ohm Flamethrower ignition coil will work fine without using a ballast resistor without the RED/Black wire from the starter solenoid which is the by-pass for the Ballast resistor normally fitted.

Cheers

[alsimma95]

Ok so I cleaned up the wires and what I thought were dirty red do appear more brownish in color, and im coincidentally missing 3 brown wires on the engine ground about an inch away..

I moved those wires, but now I don't have anything connected on that stud. The starter still cranked so I'm not sure if I'm missing something thats supposed to be there? I couldn't find another cable where the diagram you provided says there should be one 'to inside starter motor.' This car was messed around with a lot from previous owners but it still ran (albeit hardly) when I got it, so things cant be too far off..

Theres no ballast resistor, but I believe theres a resistance wire in the harness and I'm not sure where it is or if I can remove it. Following the directions that came with the coil to test for resistance, I attached a jumper cable from the negative end of coil to earth, i used a nut on the valve cover. Then attached the positive end of voltmeter to + side of coil, and negative line of voltmeter to valve cover, and was only getting ~7.6v. If there were no resistance wire this should be the full 12 right? This was with the broken wire wrapped around the spade terminal on the coil, leaving the red/black wire unplugged, the black wire on negative end of coil, and the key turned in the ignition. The broken wire has to be the green wire thats connected to the start-run bus? There's not much green left...When I got the car, that bare wire and the red/black one were both (spliced?) into a single terminal that connected to positive end of the coil.

Would it run in this set up? Popped the fuel pump fuse back in and gave it a go for a few seconds, had fuel pressure but still wouldnt start. Didnt want to keep trying and potentially damage anything further ... I think I need a 1.5ohm coil with the integrated resistance wire, although I didn't try starting it with the bypass wire connected as well.

[GDAus]

Okay a bit of science content to help explain things ..... This is part of one of my previous posts about ignition systems:

Pre '80 M10's have points type ignition and use a system to boost the coil's high voltage output during engine start. They use a coil rated at 8 volts and connect it through a "ballast resistor" which drops the voltage at the coil to around 8 volts. Most car makers who use this system use an obvious external resistor (usually a long, square, whitish ceramic one mounted on the coil bracket) but BMW on the e21 don't.

BMW use an "inline" resistor .. the connecting wire to the coil +ve is manufactured with a piece of special resistance wire in it, so it looks like an ordinary wire, but if you measure the resistance it should read about 0.9 ohms. (sometimes you can find a little lump in the insulation where the joints are at each end of the resistance wire section)

The way this system works ... on the starter solenoid the is a male spade terminal connected to the motor side of the switch in the solenoid. When the starter is energised, this terminal is at +ve battery voltage and there is a wire running from this terminal (on an electronic ign model there is nothing connected to this terminal!) direct to the +ve on the coil so it by-passes the ballast resistor .... so that when the engine is cranking over, and the battery voltage is being dragged down by the load of the starter, a higher than normal voltage is applied to the 8 volt coil .. boosting it's high voltage output and making starting easier. As soon as the starter is released, +ve supply to the coil is back through the ballast resistor.



Before this type of by-pass system was developed the ballast resistor was inside the coil and they worked off battery voltage.

Since you have all ready bought the flamethrower coil ..you might as well use it! It does have a higher output voltage than the standard coil ... (the 40,000 volt claim is under perfect conditions just to get the max voltage out of it so it looks good in the marketing.) But it will have I better output than a a standard 12 volt coil under start conditions.

I'll have to check the wiring diagram just to refresh my memory and I'll get back to you on what wiring is needed.

You will probably have to replace the green and the black wires from the rectangular plug on the side of the fuse box to the coil at least. There is a strong chance they have been cooked by the resistance wire that they share a loom with.

Cheers

[alsimma95]

Thanks for clarifying. I'm no electrician and lack any decent critical thinking or problem-solving abilities when it comes to these types of electrical issues... I'm not confident in saying I have a basic understanding of this stuff.

When you say I'd have to replace the black wire, I was under the assumption that wire ran from the coil to the condenser. Is that the black wire you're talking about? Or do you mean the red and black wire that goes to the starter? Is there some other black wire I'm unaware of?

And when I replace the green wire, should I just forgo the resistance part of the wire and wire the bus directly to the coil without any resistance, which would make the 3ohm coil viable?

Appreciate all the help, I'm not sure I'd be able to figure this out on my own in any reasonable amount of time.

[GDAus]

Thanks for clarifying. I'm no electrician and lack any decent critical thinking or problem-solving abilities when it comes to these types of electrical issues... I'm not confident in saying I have a basic understanding of this stuff.

When you say I'd have to replace the black wire, I was under the assumption that wire ran from the coil to the condenser. Is that the black wire you're talking about? Or do you mean the red and black wire that goes to the starter? Is there some other black wire I'm unaware of?

And when I replace the green wire, should I just forgo the resistance part of the wire and wire the bus directly to the coil without any resistance, which would make the 3ohm coil viable?

Appreciate all the help, I'm not sure I'd be able to figure this out on my own in any reasonable amount of time.

Okay .. I just added a few things to the wiring diagram to hope it makes more sense.

BMW have used black wires for different things around the engine and under the dash .... it is #@*^%$ annoying and confusing!
But I've shown on the diagram the way it connects. You can delete the green resistor wire and add a new wire from the fuse box end from pin 8 in the connector to the +ve terminal on the coil. If you trace the Green wire from the fuse box end you should be able find a small lump in the wire ... that's were the resistor wire has been connected to the normal wiring back to the plug. That's where you can splice in the new wire. Do the best job possible .. soldered joint with heat shrink tubing to seal the joint. Using crappy crimp connectors in the engine bay environment will cause problems in the future, they will eventually get oxidation in them and the joint will fail.

Disconnect the RED/Black wire from the coil +ve terminal and from the upper spade connector on the starter solenoid.

The Black wire from the coil -ve terminal may be damaged so you may have to add a new wire from the coil back to the fuse box connector ... BUT note that it connects to the fuel pump relay and the diagnostic connector and also the Tacho! With a multimeter you can do a continuity check to see if it is intact. If it is .. do a voltage check between the Black wire at the coil end and a ground with the ignition on. If you get a voltage reading, then it is shorted somewhere to the +ve side. Since you mentioned smoke ... then this is highly likely.

Since I don't own a pre '80 model, I don't know the exact way the wires have been routed through the various looms. The wiring diagram shows how the circuit connects not the physical paths the wiring takes in the car. So you will probably have to do a bit of digging to trace the right wires

And when I replace the green wire, should I just forgo the resistance part of the wire and wire the bus directly to the coil without any resistance, which would make the 3ohm coil viable?

Yes!

Annotated one of your photos to show how the solenoid connection match up to my drawing and answer one of your earlier questions.

Hopefully this make some sort of sense for you

[alsimma95]

Annoying and confusing seems to be the theme of this project ...

Pulled and stripped the harness, the hot wire to the coil was corroded from the coil all the way down to what im assuming is the resistance wire. Is the rectangular portion the only resistance part of the wire? I couldn't find any other distinguishable segments.

When I check for resistance from the c20h connector to right before the rectangular portion it reads .2 ohm, which is what my cheap multimeter reads testing against itself, so unless im doing something wrong or missing something I think trimming it there should be alright?

The black wire seemed alright, it has continuity from the connector to the coil plug. Forgot to do the voltage check before i ripped things apart... I'll check before i re-wrap the harness and button things up. That green wire was awfully corroded but I'm not convinced it's the only thing left to fix...

Couldn't find anything on the wire size, is 16 gauge alright?

IMG_0294.jpg

[GDAus]

You've done well, that's the splice from the normal wiring to the resistance wire (when the insulation sheath is intact, it's a lump).

The resistance wire is the wire that runs the rest of the way to the coil

Replace that bit and you should be back in business. Just remember you don't need the RED/Black wire anymore.

Wire size : For future reference

Bottom left hand side of the wiring diagram there is a note:

Wire size is .75 MM unless otherwise marked
Wire Insulation Colour is Brown Unless Otherwise Marked

This actually means MM² ie square mm so nearest AWG is 18

Cheer

[alsimma95]

Unfortunately, things are not looking too great over here.. So I did the wire repair, reinstalled the harness, got 2 gallons of fresh fuel and hooked up the battery to my running e46 just for good measure, the e21 would crank but still would not start...

I ended up pulling the plugs and manually checking for spark, and each plug had visible spark, although I'm not sure the strength of it to be fair.. The plugs were gapped to spec, new condenser and contact point, which was also gapped to spec with car at TDC.

Decided to invest in a compression test beforehand as well, and the numbers do not look so great. 1234 were 115, 105, 105, and 125 respectively. From what I've read, these numbers are fairly concerning.

However, I would still think the engine should have started? I had spark, and I tried both pulling the throttle cable with someone cranking it and running it on carb cleaner... The carburetor seemed to be functioning, although I recently rebuilt it so I may have made a mistake somewhere?...I think I may try just pulling the carburetor off completely and using carb cleaner alone, just to ensure there is both air and fuel.

I'm just not exactly sure what else I can do... I didn't see any obvious spots of vacuum leaks, but I didn't necessarily check every hose with a magnifying glass either...

I'm sure if I was a half decent mechanic I'd be able to get this car at least running, but alas I am not. I'm very quickly losing patience and energy for this project... Interested to hear your guys thoughts on the issue...

[DavidF]

Maybe put 12v directly to the ignition coil to help ensure a strong spark. You should be able to get some action even with the compression figures you listed.

[alsimma95]

Good news.

Cleaned some grounds and removed all the old varnished gas that was still in the carb and it fired right up! Got it to idle decently enough, I'm not great at tuning carbs but I'll get the hang of it eventually... Car is a work in progress but I'm just happy it's running

Thanks for all the help

[cgifool]

Not that you need it anymore, but my '78 has an external ballast resistor mounted on the drivers-side inner fender well, sort of below the fuse box (rather than a resistance wire).

And congrats on getting it running again!

Did you happen to have also cleaned out the tank really well and replaced the fuel filter?

[alsimma95]

The car came with an electronic ignition conversion kit, so I was planning on running that eventually which would require me deleting the resistor anyway.

I siphoned the old fuel out, from what I saw things looked well enough in the tank. I installed a clear fuel filter under the hood a while back, and there's some debris but not much, but I guess they're so cheap it wouldn't be a bad idea to swap it out anyway.

I've been trying to figure out what I want to do about the compression issue. Checked it again hot and it was ~110 across the board. I'm thinking its the rings, need to get a compressor and leakdown test kit to confirm.

It runs and drives but I'm not that happy with it, idle seems a bit shaky and I can't seem to fix it. Spent a decent amount of time tuning the carb and trying different plug gaps. Using NGK BPR5ES gapped to .026.

I'm assuming I'm going to have to pull the engine sooner rather than later..

[GDAus]

The car came with an electronic ignition conversion kit, so I was planning on running that eventually which would require me deleting the resistor anyway.

I siphoned the old fuel out, from what I saw things looked well enough in the tank. I installed a clear fuel filter under the hood a while back, and there's some debris but not much, but I guess they're so cheap it wouldn't be a bad idea to swap it out anyway.

I've been trying to figure out what I want to do about the compression issue. Checked it again hot and it was ~110 across the board. I'm thinking its the rings, need to get a compressor and leakdown test kit to confirm.

It runs and drives but I'm not that happy with it, idle seems a bit shaky and I can't seem to fix it. Spent a decent amount of time tuning the carb and trying different plug gaps. Using NGK BPR5ES gaped to .026.

I'm assuming I'm going to have to pull the engine sooner rather than later..

Hi again ...

You can do a "wet" compression test to get a better idea of what might be you problem.

This involves injecting a small amount of oil (about 5 ml or 1 teaspoon) into one cylinder at a time ... it forms a temporary seal around the piston rings.

If the pressure increases more than about 10 % then yeah it's likely to be worn rings.
If it doesn't increase much .... it would be more likely to be valves.
But it could also be a blown head gasket. In your first test you got identical readings from cylinder 2 & 3. That could indicate that there is a gasket leak between those two. Also, if you run the engine up to operating temperature with the radiator cap off and see if there are gas bubbles in the water.

Always wear eye protection when doing this !!!

When doing the compression test make sure the engine is at least warm and all the spark plugs are out and the throttle is wide open to let air flow freely into the cylinders.
Also make sure the battery is fully charged too. If not, then the cranking speed will be slower and can give inconsistent readings.

Glad you got it going.

Cheers

[DavidF]

Yeah, do a leak down test on all the cylinders as well to see how well they seal. If the engine has been sitting a long time, it may improve as you run as a stuck ring or two might free itself. Look for and fix vacuum leaks...especially breather/vapor lines back to the tank.

Before you blame the engine, get the ignition system 100%, set timing, and adjust valves. Then move onto the fuel delivery system. If you do all that and it still runs like crap, well.....

[alsimma95]

Well some more good-ish news.

Have been playing around with tuning and timing and I seem to have it running well enough. Did the whole ball visible at 2200 timing procedure, carb is running at just about factory specs, ~4 turns mixture screw ~3 turns idle. Plugs looked a bit fouled/rich when I pulled them, but I've really only idled it and have been messing with the mixture, so I'm not sure it's too great of an indicator of the AFR at the moment, I'll keep an eye on things down the road..

In regards to compression, my oil squirter can finally came in and I was about to perform the wet test, but I figured I'd test it dry again beforehand. Cylinders 1-4 came back 130, 137, 137, 135, which is a considerable increase to say the least. I guess just running it a bit over the course of the past couple days is breathing some life back into it after all. I did the wet test anyway, and it came back 155, 142, 145, 150. There seems to be some consistencies with the middle 2 cylinders again, and when I purchased it I noticed there was an oil leak coming from the head gasket area so I had assumed at the very least the top end needed to be resealed. I'm just glad I don't have to pull the bottom end out, even if the rings may be a bit worn

Next steps for the car are an alternator replacement and exhaust manifold/headers. I noticed when the battery is fully charged and the car is idling it only sits about 13.1-13.2, ~12.5 with ac/radio running. Replaced the voltage regulator with a Hella unit and that did not remedy the situation. Luckily I found a decently priced 65 amp bosch reman, so waiting on that to come in, and will inspect bushings when I get it.

The car was at one point in its life a California smog vehicle, but that had all been butchered out when I got it, and was not exactly sewed back up properly. There were a few flagrant exhaust leaks, and I had patched one of them with some quiksteel thermosteel epoxy, but there is still an extremely audible exhaust leak and I found another tube that had been cut but never welded shut. I've driven it around the block but it gets so violently loud and 'slappy' over 3000 I'm worried there might be some engine pinging that I can't hear, so that needs to be addressed before I do any real driving. Currently shopping around looking at a 2002 tii manifold or some used headers off ebay. The car isn't quite nice enough to deserve a new exhaust, so I'm trying to find something both cheap and bolt-on.

Oh yeah and I found out the throwout bearing is shot

[alsimma95]

Well today was an eventful day.

After struggling with the exhaust manifold last night, managed to pull the head off today in less time than the manifold took...and have been busy cleaning the head the rest of the day... man this thing was dirty.

Noticed two things and I'm curious if you guys have any opinions on it. It seemed as if the intake rocker shaft had started working itself out and was rubbing against the cam sprocket. I managed to push it back in but I'm not sure why it worked itself loose in the first place.. Is there something I should/could do? (shaft in center of pic at the bottom is the one im talking about)

Also I noticed some gasket like material in the timing chain area, and it doesnt seem to be doin so well... any idea what that is? (picture below, black wrinkled stuff)

Cleaned the head to the best of my ability, but couldnt get all the material off and I'm not too confident in myself to not damage it.. Just going to bring it to someone to get a better look at it and deck it if needed, I'd prefer to not have to do this job again anytime soon..

If anyone notices anything please let me know !! Thanks

ps. extra timing chain cover pic, the whole head was coated like this....gonna try to get the block looking decent enough...how does it even get this dirty ????