No power to coil

An alchemy of sparks, copper wire and earth

Moderators: Moderators, User administrators

No power to coil

Postby skred » 06 Oct 2018, 20:08

UPDATE: if I give a direct power from the battery to the coil, the engine starts so it confirms my suspicions about a break in the power feed. However, I still have my original question about where the power to the coil for a CU engine comes from. Is it the same as the DG which was asked in a similar post?


Hi all, I have a problem of no spark with my 2.0 CU engine. The van did a 700 mile journey over a week and wouldn't start the day after I returned home.

I've done a number of checks but basically the coil king lead doesn't create a spark on cranking so I checked the coil over and I'm getting no reading on my hall sensor. My coil is an old green label bosch with a -ve (#1 terminal) connecting to the green wire and the +ve (#15 terminal) connected to three black wires. With the ignition turned in the on position, I would have expected one of these wires to be 12v?

The problem, I think, is that the coil is not receiving any power so it would follow that it can't create any. What I can't get to the bottom of is where the power for the coil actually comes from? The fusebox in the glove compartment doesn't suggest it comes from there but I am stumped. I heard the 12v may come from the electronic ignition module but I can't work that out. Does anyone know where the 12v supply for the coil comes from? I'm hoping if I rectify this it will start but it's not a quick fix like I hoped.
Thanks all
skred
 
Posts: 13
Joined: 21 Jan 2017, 23:33
Location: Highlands
80-90 Mem No: 0

Re: No power to coil

Postby 937carrera » 06 Oct 2018, 21:02

https://www.thesamba.com/vw/archives/info/wiringt2.php

US wiring diagrams, but should be of use for tracing, scroll down to 1980-81

Decent chance it's the ignition switch, but work your way through logically
1981 RHD 2.0 Aircooled Leisuredrive project, CU engine
1990 RHD 1.9 Auto Sleeper with DF/DG engine
User avatar
937carrera
 
Posts: 1941
Joined: 05 Apr 2015, 19:29
Location: N Yorks.
80-90 Mem No: 16333

Re: No power to coil

Postby bigherb » 07 Oct 2018, 05:53

If the indicators still work then unlikely to be the ignition switch. The coil (black cable) power comes from the input side of fuses 11 or 12 in the fuse box (but doesn't go through the fuse) to a multiplug in the connector box in the left of the engine bay check connections at the fuse box and in the connector box and look out for any added hidden immobiliser switches.
1982 Camper 1970 1500 Beetle Various Skoda's, Ariel Arrow
User avatar
bigherb
 
Posts: 2081
Joined: 27 Mar 2008, 13:50
Location: West Kent
80-90 Mem No: 5789

Re: No power to coil

Postby skred » 08 Oct 2018, 08:01

The ignition switch was replaced only 2 months ago so I hope it isn't duff again but I'll check it out. Thanks for the diagram and confirming the power does actually come from the fusebox. You say the power comes from the input side of the fuse box without going through a fuse? I don't quite grasp this but I'll get my head stuck in and hope it becomes clear. Thanks again for the help, I couldn't find the wiring diagram anywhere.
skred
 
Posts: 13
Joined: 21 Jan 2017, 23:33
Location: Highlands
80-90 Mem No: 0

Re: No power to coil

Postby 937carrera » 08 Oct 2018, 08:15

Spend a bit of time reading the wiring diags

Current track 7-9 is the feed
Follow through to track 57, see the connection to fuse 12 ?
Now follow back to the ignition switch

See why indicators working is a good diagnostic ?

Unfortunately the link from 57 to 7 doesn't give the detail of the connector in the junction box that Bigherb mentions

Arm yourself with a meter and then you can start checking the circuit :)
1981 RHD 2.0 Aircooled Leisuredrive project, CU engine
1990 RHD 1.9 Auto Sleeper with DF/DG engine
User avatar
937carrera
 
Posts: 1941
Joined: 05 Apr 2015, 19:29
Location: N Yorks.
80-90 Mem No: 16333

Re: No power to coil

Postby skred » 11 Oct 2018, 09:57

Just to give an update.

Long story short, I traced all the wires from the ignition at the front and from the coil at the back to the fuse box. The indicators worked fine and was getting 12v as I was expecting at fuse 12 thankfully but 0v at the coil. The wiring for the coil was one piece from front to back (it skipped the connector box entirely) and passed the front headlight behind the grill where I discovered an aftermarket immobiliser. Suspecting this, I removed the plug and shorted what I thought was once upon a time just one black cable and she started straight away. I reckon it was once a good piece of kit but totally pointless now so I removed it and out poured about half a glass of water from the casing - the last day I was on the road was that storm about 3 weeks ago where I did 150 miles in torrential rain. Don't know how it gathered where it did but sorted now.

Thanks herb and 937 for the pointers - great forum
skred
 
Posts: 13
Joined: 21 Jan 2017, 23:33
Location: Highlands
80-90 Mem No: 0

Re: No power to coil

Postby 937carrera » 11 Oct 2018, 10:50

Great, thanks for posting the solution, it's always good to hear the end of the story and stop us wondering if the problem got solved

:ok
1981 RHD 2.0 Aircooled Leisuredrive project, CU engine
1990 RHD 1.9 Auto Sleeper with DF/DG engine
User avatar
937carrera
 
Posts: 1941
Joined: 05 Apr 2015, 19:29
Location: N Yorks.
80-90 Mem No: 16333


Return to Electrical & Instrumentation

Who is online

Users browsing this forum: maxstu and 26 guests