My inline fuse that leads from the coil to the reverse switch has (on the coil side of the fuse) 2 wires. One that goes to the coil and another black one that a PO left dangling. The fuse diagram shows only 1 wire but I've added the additional loose wire ..any ideas?
Ignition on live to feed something, maybe ran out of terminals on the coil or had no spade connectors to hand so that was an easy place to pick up the supply for whatever it was just using a screwdriver and no parts.
Cheers. The reason I ask is because I'm trying to track down a cold start issue I have. I've tried lots and it does seem to be an electrical issue. Yesterday, I pulled off the wire from my coil to the inline fuse to the reverse switch and the camper started immediately - it never does that in the cold. It repeated this again this morning and again all good without the reverse wire connected to the coil. So I'm trying to understand what part of that system could be pulling enough from the coil to cause a cold start issue. It might be a red herring and I'll try again tomorrow. Completely left of field thought.. the spare PO wire that was not connected to anything was coiled around the proper coil to fuse wire. I doubt it, but could this have been causing and electromagnetic field, even if it wasn't forming a circuit....?
No electromagnetic effect at below UHF frequency .. but you are describing something extremely similar to putting the reversing light wire onto the contact breaker side of the coil .. If you have an electronic ignition the thinner black wire is the contact breaker wire... with the electronic ignition red wire going to the terminal witha thicker black wire which is the 12 volt ignition feed.. Your reversing light wire should go to the ignition power feed. Then the loose black wire could have been a rev counter feed..
Thanks Mike. I didnt think the coiled wire was doing anything, but just following ideas. I'm not sure I understand what you are getting at with regards to the ignition. My electronic Petronix 1 black and red wires go to the appropriate coil tabs. The reverse switch wire I'm talking about goes from the positive of the coil via a inline fuse to the reverse switch on the gearbox. At the inline fuse as shown, there is an extra black wire. My experiment was without the reverse wire connected to the coil at all and the engine starts really well. As @Flakey said, it could be an old feed to a choke which I don't have on my Weber's bu might have been off use when the camper was FI...but let's not go there
Might have been a feed for a split charge relay as a lot of people do this when really you should feed it from the alternator warning light.
So, next experiment is read volts at the coil while starting with/without the reverse lights connected. Then you'd know something other than it seeming to start better with it removed.
You could try it without starting. Measure coil volts with and without the rev lights connected, see if anything's dragging the coil voltage down. Don't let your extra wire short out on the crankcase, btw.
No choke on my Weber 34 icts. The camper used to be FI so I haven't checked if this is a leftover from then, other FI wires have just be cut and left by PO
All that should be on the reversing light wire is the switch on the gearbox, until you engage reverse gear then its the 42 watts of reversing lights as well. As well as measuring voltages, check the DC resistance of the wire that you believe is the reversing light feed between the wire and earth. It should be very high, as its an open circuit switch until you engage reverse. Looking at a 1976 schematic on theSamba.com, I can see three black wires meet at the coil positive N, terminal 15. Feed from ignition switch : 1.5mm2 Feed to reversing light fuse (S21) : 1.5 mm2 Feed to double relay for fuel injection ECU : 0.5mm2 - this is probably the chopped off wire.
It's just as well it's an original wiring harness. Somebody at TE had a replacement and the builders of that harness had cheaped out and used two pieces of quite thin wire in parallel instead of one piece of 1.5mm2 for the ignition feed. Two things. 1. I hope they never short it out as it will smoke quicker ( thinner wires have less heat capacity) and more rapidly take out the loom from engine to ignition switch. 2. The voltage drop was twice what it should have been - with the contact breaker closed the 4 amps through the coil caused the positive terminal of the coil to drop 1 volt. On my T1 which uses the same wire, the voltage drop is more like 0.5 volts. This can cause Pertronix ignitors to play up. Maybe try points if you cant find anything else. One failure mode of that class of electronic points replacement is to become a bit slow at recognising the engine is cranking so it kills the spark until it feels like it. A bit like a dodgy condenser or badly adjusted or worn points.
Quick question. On testing the coil and connections, @mcswiggs and I noticed that the voltage on the positive coil terminal, with ignition on, went from 11.7 to 12.6 volts when the dissy positive wire was removed (Peteonix 1 ). None of the other feeds from the positive terminal made any difference to the voltage including the electric fuel pump and the reverse switch wire. I'm now confused and could do with some thoughts.
Thanks Zed. Reading up, it does say not to leave the ignition on for more than 30sec which would imply that they (Peteonix) do draw and maybe heat up when only the ignition is on. Hopefulky it will stop raining where you are, it's sunny in Surrey atm
In that case I'll stay in the dry and assume it's normal! Interesting though, I've left mine on for far more than 30 seconds many times. I'll disconnect the coil supply in the future. It always fires if there's petrol in the carbs, maybe... just maybe your cold start situation lies there.
