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As you know, I put the car on it's wheels at the weekend. The fuel lines are complete, and that leaves me with one more job before I can tell if my engine rebuild was successful - wiring her up.
I've not got the original Beemer loom, and neither have I bought the loom from Marlin. What I do have is this:
Broadly speaking, it should be easy with this - but I'm a little aprehensive about the whole process.
I'm a little unclear on somethings... Such as:
I have two fuel pumps - I assume that each will need it's own relay. There is a fuel relay on the engine harness, and one on the wiring module. Can I the engine one for the HP pump, and the module one for the LP pump?
Cable - I need to several different sizes to accomodate the current draw of different parts of the car, but how much do you think will be required? I don't want to buy 10's of meters of cable when 50cm will do.
I've also been thinking that I could do the whole car in a couple of colours of cable, therefore saving money as I can buy in bigger quantities of each size - but then identify each circuit with these:
I am a (lapsed) electrical engineer so I should be able to answer some of your questions.
1. I hope you have the loom that came with the engine and ECU. If not you will need to get one.
2. I think that I would run both pumps from the same relay - I did that and it seems fine. In theory you should start the low pressure pump first then the high pressure one a few seconds after. This allows the LP pump to fill the swirl pot before starting the HP pump. But I don't think its really necessary.
3. I would always use colour coded cable. I culled most of mine from the old BMW harness so that the colours AND SIZES match the original. It's easier than working out what sizes you need.
4. Pretty much impossible to guess how much you need cause it depends on the location of the various components. You need to measure I'm afraid and then probably add 25%.
5. Make sure everything is protected with the correct sized fuses! Electrical fires are pretty commom in Kit Cars!
6. Use relays for the large consumption items, headlights, horns etc.
7. Loom tape is OK - but heat shrink is easier!
8. Your list to start her looks about right. I also wired up the alternator as some of the wiring is incorporated in the engine loom.
A couple of other things.
I found the company - Vehicle Wiring Products - to be cheapest.
Get some good tools - cutters, strippers and a decent crimping tool. A soldering iron can also be usefull
Plan your wiring routes carefully!
Use multiway plug and sockets to seperate the loom into three or four chunks. A lot easier to make the loom and easier to fix those little mistakes... Front, Middle (all the stuff in the dash area including the fusebox) and Rear. I also added a sepperate connector for all the dash wiring so that I can unplug the dash and wire it on the bench. One of my next jobs....
1. I hope you have the loom that came with the engine and ECU. If not you will need to get one.
Yes, I still have that. It's on the engine and plugged into the ECU
MartinClan wrote:
2. I think that I would run both pumps from the same relay - I did that and it seems fine. In theory you should start the low pressure pump first then the high pressure one a few seconds after. This allows the LP pump to fill the swirl pot before starting the HP pump. But I don't think its really necessary.
Did you use a new relay or the one on the engine harness? AFAIK, there's the main and the BMW fuel relay on it.
MartinClan wrote:
3. I would always use colour coded cable. I culled most of mine from the old BMW harness so that the colours AND SIZES match the original. It's easier than working out what sizes you need.
As I don't have the original any more, I'll be buying a lot of cable...
MartinClan wrote:
5. Make sure everything is protected with the correct sized fuses! Electrical fires are pretty commom in Kit Cars!
6. Use relays for the large consumption items, headlights, horns etc.
The wiring modules have all of those, so I should be OK
Did you use a new relay or the one on the engine harness? AFAIK, there's the main and the BMW fuel relay on it.
I used the BMW one which is controlled by the ECU. I haven't added any relays as I also re-used the BMW power distribution box which has everything built in.
Mind you it upset the wife a bit unpicking the BMW loom on the kitchen floor so I couldn't recommend it LOL...
You've probably already considered this but another alternative is to buy a generic car loom from Premier wiring: http://www.premierwiring.co.uk/
I think this is what came with my Cabrio (ie could be the loom that Marlin supply) and it was reasonably straight forward to patch the BMW engine loom in to it (and you could still incorporate the CBS fuse/relay panel).
Good luck !
Simon
ps - I've still got parts of the loom from a 5 series if you want it. Its not complete but may be a useful (free) source of wire is you decide to go down that route.
Guys - I have a couple of leads coming from the loom that have lost the text on the identifiying tag I put on it when I took the loom out of the donor. Can anyone tell me where they need to go?
They're a thick and slightly thinner red cable (25amp and 17amp?), both terminating in a crimped on ring terminal:
I'm assuming that they need to go to the positive terminal on the battery, but as I can't remember where they went I thought I'd ask to save embarassment later.
Guys - I have a couple of leads coming from the loom that have lost the text on the identifiying tag I put on it when I took the loom out of the donor. Can anyone tell me where they need to go?
They're a thick and slightly thinner red cable (25amp and 17amp?), both terminating in a crimped on ring terminal:
I'm assuming that they need to go to the positive terminal on the battery, but as I can't remember where they went I thought I'd ask to save embarassment later.
I just had a quick look at my car. The larger one is definately the main positive battery feed to the engine loom goes to the positive terminal. I wired mine via a 60 amp fusable link. Not sure about the thinner cable as I cant see this cable on my loom (but mine be either under the dashboard or my loom might be different?).
i'll have a look through my pictures to see if I can see anything similar and dig out my wiring diagrams. Did your donor car have the battery in the boot?
Ah, so your loom might be different, as my battery was under the bonnet.
I found this photo in my archives......
There are the two cables screwed to the top of the battery positive terminal. The smaller one went to the fuse box; so this is the main feed to ignition, lights, pumps etc.
In my car this was a separate cable and not used as my new loom came with a brown feed cable that goes to the positive battery feed. Obviuosly, the big thick cable goes from the battery direct to the starter motor.
Guys - I have a couple of leads coming from the loom that have lost the text on the identifiying tag I put on it when I took the loom out of the donor. Can anyone tell me where they need to go?
They're a thick and slightly thinner red cable (25amp and 17amp?), both terminating in a crimped on ring terminal:
I'm assuming that they need to go to the positive terminal on the battery, but as I can't remember where they went I thought I'd ask to save embarassment later.
I'll take a look at mine. It's so long ago that I did the wiring I can't remember what it looks like now! My battery was in the boot so I guess it will be the same as yours.
I have three cables in all going to the +ve terminal
The huge one that goes to the starter motor via the engine loom. As I remember this also goes to the alternator.
A medium sized one (guessing about 6-8mm cross section) that goes directly to the BMW fusebox. This is the main feed for all the electrics except the engine management.
A smaller one, 4mm ish, that includes an inline fuse that goes to the engine loom that powers the engine management systems.
Thanks Robin - I guess I was correct in my assumption that they both need to go to the positive terminal then.
Although... I don't have an inline fuse on either of them. Well, not that I recall seeing one when I was re-wrapping the loom. And there's no huge cable going from the battery to the starter bundled in the loom - there is one that goes from the alternator to the starter. IIRC, the cable to the starter was separate on my donor car. That's how I've done it on the Sportster (via a battery isolator key)
I wonder if it's because mine is an older donor than yours? mine was an 85/86 model, and I know that differences crept into the design around then. I ran into that when I rebuilt the engine, as it has different bearings to later models. And I've noticed that my diagnostic connector is different to everyone else's, and if your remember the ECU connector on mine is the same shape as the ABS control unit connector - which caused much confusion at the time.
My donor is '89. It was also a left hand drive import from Switzerland! So I guess that is where the differences lie.
Personally - I would add an in-line fuse to the feed for the engine loom if you don't already have one. The one in mine (original BMW) is just a fusible link - I guess arround 40 amps.
Next question - fuse-able 'links' - I've googled it, and come up with nothing - I guess I'm not using the right terms. Where did you chaps get yours? Are they just inline 'mega' blade fuses? Where do you get holders for them if that's the case.
Next question - fuse-able 'links' - I've googled it, and come up with nothing - I guess I'm not using the right terms. Where did you chaps get yours? Are they just inline 'mega' blade fuses? Where do you get holders for them if that's the case.
Best place I found for wires and wiring stuff was Vehicle Wiring Products.
Next question - fuse-able 'links' - I've googled it, and come up with nothing - I guess I'm not using the right terms. Where did you chaps get yours? Are they just inline 'mega' blade fuses? Where do you get holders for them if that's the case.
My BMW loom had the fuseable link built in - so I didn't need to acquire one - but any large fuse and appropriate holder could be used.
I took a look at your wiring pictures. Are those self adhesive tie wrap bases you are using? If so I think you might find the SVA man doesn't like them (If he spots them of course...) I am sure I saw something in the manual that rules out adhesive type fixings...
I'm sure my loom had one at one point, but I've obviously ditched it some time ago - so I'll just have to get something to replace it.
As for the cable tie bases, they are self adhesive - but I put a rivet through the fixing hole just to be sure. The adhesive is just stopping it from spinning around the rivet.
Right - here's a question. If I fit a 60 amp fuse, as Peter has, its rated for 60 amps continuous draw, and will blow at 120 amps.
Does this mean that I would need to run 60 amp cable from the battery to the fuse? The highest rated cable I have is 39 amp (56/030)... and the cables the other side - well, you've seen them in the pic. I'm guessing they're not 60 amp cables.
Right - here's a question. If I fit a 60 amp fuse, as Peter has, its rated for 60 amps continuous draw, and will blow at 120 amps.
Does this mean that I would need to run 60 amp cable from the battery to the fuse? The highest rated cable I have is 39 amp (56/030)... and the cables the other side - well, you've seen them in the pic. I'm guessing they're not 60 amp cables.
How cables are rated is actually quite complex. For example a 39 amp cable will carry far in excess of 39 amps depending on the environment. It would probably take several hundred or even thousand amps to actually "blow it". The fuse is there essentially to protect the cable from overheating, melting the insulation and subsequently causing a fire.
For me I would probably have used a fuse with a lower rating - say 40. But there is a danger of using a fuse of too low a rating - it may be OK for a while but the heating effect caused by excessive current flowing through it will eventually cause it to fail. Is this fuse in the feed to the engine management system? Perhaps someone knows what it should actually be? Unfortunately the in-line fuse BMW fiited in my loom does not have any marking.
Sorry - I just realized that was a non-answer. :-(
Simple (engineers) solution. Fit a smaller fuse and carry a few spares in the car of a slightly higher rating just in case.
