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1981 vw rabbit diesel manual----no cranking issue!!please help!

4547 Views 11 Replies 4 Participants Last post by  briano1234
hello guys i am new to this form and i am in need of some help. i have a 1981 vw rabbit diesel manual. heres the full story. everything was working great. then one morning my dome lights did not come on when i opened the door. so after a few days of driving (put on 70 miles a day) i had some spare time so i decided to check the fuse. the 15amp fuse for the dome lights was poped. so i said hmmm i wonder why that happened but o well i will replace it..... tried replacing the fuse and it kept sparking as i was trying to replace it. (i had the door open obviously) so i decided before i arced anything that i would unhook the battery. so i unhooked the positive terminal, replaced the fuse. re connected the battery and boom the dome lights started to work.. closed the hood. went to start the car. all indicator lights come on glow plug light times out and the car does not crank. further testing i found that the signal wire to the starter was not getting power to it when the key is in the cranking position. so just to verify everything i took a jumper wire from the battery to the signal terminal on the starter and the car cranked..... hmmm so i go to the fuse box. all of the fuses are good. i changed what i think is the starter relay with the horn relay.. still no start. turn the key to the on position and i hear the relay click. turn to the start position i again here it click but no power to the signal wire... my question is where does that black / red signal wire go to or get its power from? i traced it back to a bigger rectangle connector in the dash and if i apply 12v to that the car will again crank so i know my wiring to the starter is good... it appears that after the black rectangle connector the red/ black wire goes to the ignition switch... but i am not sure if it goes to other places or not. anyone have any ideas on what could be going on or how to test it?? any wiring diagrams that can be sent to me?.. i do not have a book on the car and i am having trouble finding the diagram online.

all grounds at the battery are good. connections are good. fuse box is in excellent shape with no corrosion or loose pins. everything looks great there...
one other note---i do not know if this is normal or not but i tried a few differnt things----i left the headlights on an then tried to crank the car. and the headlights completley go out when trying to crank.
battery tests good and i have great voltage!

thanks in advance guys!
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could be a bad ign switch at the key
Maybe your battery needs to be load tested at a parts store.

For a mk1 diesel, I wire around a lot of those problems. Pushbutton starter, pushbutton glow plugs from a ford starter relay, relayed headlights, manual overide switch for the radiator fan, electric fuel pump for priming the injection pump, extra driving lights, I need to do the wipers still, but for reliable running and driving this is basic.

Not many cars make it 30+ years. You have to renew or upgrade it for it to work reliably.
Those battery connections, etc. may not be as good as you think. Sometimes corrosion and breaks are hidden - get a good multimeter and test voltage and resistance.
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BTW, the headlights are supposed to go out when starting from the ign switch. That's the "X" relay that all the power goes through.
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I would be looking at the connection plug that goes into the ignition switch. That is where the juice to the starter should be coming from. If the plug, up under the steering wheel column is slightly off the mark the connection might just not get a feed. Could be that the ignition switch finally gave up as well. They are a plastic and copper connection device and they do a lot of service. And they break. I tried to replace one and found that the current ones you can buy online like at are not very well built. Hey they are like 5 bucks, I ended up using the ignition wire to a relay that would then engage the starter.

I am not a fan of having all my switches and knobs replaced but for the starter it was the best way to go.
Not a hard thing to do and a simple relay will do the job.
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DITTO to ORCoaster and relaying the starter......X 37.......

Actually relaying the Starter Solenoid wire to engage a "Ford" starter relay is a well known fix for Starter heat soak issues on the 010 Automatic trannys.
It actually isn't a bad idea for the Manuals as well as you are taking 20-30 amps off the ignition switch and letting the relay run a possible higher current, and a shorter run of wire from the battery to the starter. It provides higher and more of a direct route to the starter solenoid. Taking the high current load off the ignition switch is a GOOD thing.

It makes diagnosing a bad ignition switch or is it the starter more easy.

IT was one of the first two improvements I have done to most of my "auto Cabriolets". The other one was installing relays on the headlights as you take the high current off of the headlight switch which increases the lifespan for each, and in the case of the headlights you increase the current and voltage to the bulbs giving you brighter lights.
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Thanks guys for all of the help. i think i am just going to convert it to a push button start as that should take eliminate any further issues. What is the best way to wire in that push button with a relay in your guy's experience?
Im going to do some tinkering and report back with my conclusion.
What is the best way to wire in that push button with a relay in your guy's experience?
Hmm would it be the way I did it? Maybe, maybe not.

I took a lead off the Ignition side of fuse block. That would make it so I had to have the ignition on to get the starter to roll. That 12 vdc hot wire went to a fuse then to a single pole switch and from there to a momentary push button, from there to the simple relay I tucked up under the dash. I have one of those GTI consoles in the Pickup so I simply drilled that with a couple of proper sized drills to mount the two switches.

I can see you asking yourself, why two switches? Safety and security.

If the car is running and I had a simple push switch to activate the starter I could bump it while idling or driving and that would not be a good thing. And as a bonus anyone trying to steal the car, even with the key in it has to flip the small switch down to get the push button to work the starter. I make a habitat of flipping it up after the truck starts.

I ran another always hot wire from the fuse box to the relay as well. The relay sends that voltage to the starter when the push button is engaged. Then of course a ground wire to some place on the metal parts of the dash supports.

Clean of an install as I could get.
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Use the wire that runs the Starter Solenoid from the ignition switch cut it, runt the side that goes to the ignition switch to power the Starter relay.
From a big lug of the starter relay you runt it to the solenoid pick wire that you cut. From the other big lug you run that to the Battery.

Only the ignition switch is used.

Everything you wanted to know about installing a heat soak relay.
Thanks Guys for all of the help and all of the information! it was much appreciated!!
I always try to have a 2' piece of wire with a female spade connector crimped on one end, stashed somewhere handy in the car. Just clip it onto the starter solenoid and touch the other end to the battery (make sure trans is in neutral). Quick solution to any ignition key circuit doubts.
Great when priming the metal injector lines so you can see when the fuel starts spitting out, meaning the air is purged.
I always try to have a 2' piece of wire with a female spade connector crimped on one end, stashed somewhere handy in the car.

Great when priming the metal injector lines so you can see when the fuel starts spitting out, meaning the air is purged.
I use the jumper cables. A bit more length but safer than poking around with a spaded end of a heavy gauge wire. IMO
You disconnected the main power from the battery...(to replace the dome light fuse), then all this started to happen.

If you jumper the main solenoid pick wire you can engage the starter directly.

So going back, you never disconnect the power lead at the battery, you always disconnect the Ground First.
Then the power...

I would be thinking that it is time to start replacing the main cables on your car, and the ignition switch.

If your grounds are still original that is unshielded twisted, they are probably really full of dirt, and corrosion.
You can use two off the shelf cables from a parts store. On the battery end you can get one of the with extra power take offs pig tails wires and do away with those various ring connectors that are attached. Main from battery to frame and frame to engine/tranny.

Same for the main power cables, get the ones with the extra pig tails and splice in to your main cables going back to the fuse panel and the extra ring connectors so there is minimum ways to have things attached to the battery.

Using push buttons to get around things is ok, but later on adds another thing to worry about. Getting it back to the OEM, and such is the good way to go.
But re-reading your original post this all started when you were disconnecting the "Power side" of the battery, and I think you are missing this. There are about 2-4 wires branching off the main power lead, and a flakey connection there can cause a variety of issues with back feeding things through various circuits....Electrons are sneakier than you want to imagine....They use different things to get what they want...or need.

The starter switch is a funny thing... it has a key in detect, off position, a run position and a start position. The Start position backfeeds to the run, but doesn't power the Load reduction relay. This relay cuts power to the head lights a/c circuits, (heater blower...) and a few other things also called the "X" circuit as that is the name of the wiring trace.

Adding a heat soak relay is a must on Automatic Cars, I know as I have 2 of them..the starters being under the Exhaust manifold even with the heat shields in place can get heat bound, or old and not start after a 20-30 minute drive until they cool off. The heat soak relay shortens the run of wire from the battery through a relay to the starter solenoid pick wire... you use the oem pick solenoid pick wire from the ignition switch to power the relay when you turn it to start.

Not having a book is a no-no. The haynes is a good thing to have, it is all I used to keep my 81 running for over 20 years...
Another good place for you to go is Chris's electrical wiring pages, down load them and get to know them...

Sure your 81 isn't listed, but the only book I could find for my Rabbit was a 78-80 Haynes...but I know it is really really are Chris's pages.

The ignition switch takes a lot of abuse, and lets see if yours is still original that is 2019-1981= 38 years old... it too is probably tired...
On the early VW's it is easy to replace and takes about 20 minutes. Order 2...

mk1 is a good place to get parts from, I have been for about 20 years or so, and Moogie, (AKA BEN) is a good guy and he doesn't sell crap parts.
I think that if you get back to the basics, you will find that you will fix your issues....
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