Straaaaange starting issue

Hi all,

I've got a mk1 with R32 engine conversion, had it for a couple years now (thank you to CrazyQuiffs for the work!).

Got a weird starting issue at the moment, I'll describe it as best I can.

When the car is in regular use (previously it was used once a week for a couple hours) there were no issues. I would use the car, come back, park it up, remove the +ve battery lead and lock up. Then, next week, reconnect the +ve lead and away I go.

Through this last lockdown, the car hasn't seen the same use, and in fact it's been up on axle stands for a couple weeks while I replaced the rear brakes. Yesterday, back on the floor and wanted to take it fora  drive to bed in the new brakes. I reconnected the battery, turned the key over (I get the usual lights on the dashboard etc.) and I get a single "click" from the engine bay, but the engine doesn't even try to turn over. I figure the battery is low, so I charge it up overnight and try again today, same issue. Single "click" and nothing.

I clean the battery terminals and leads with a wire brush, same issue. I get a jump pack on the battery terminals, same issue. The only thing that works is I connect the jump pack from -ve terminal of the battery and directly to the +ve terminal on the starter motor. Once I do that, the car fires right up, remove the jump pack and it's happy to sit there idling.

Now I have had this issue before, and I replaced the entire starter motor and it didn't help the issue. The issue just seemed to "go away" after I returned to regular use of the car. So now it's been sat for a while again, it seems to have come back.

All the other electrics in the car are working when I key on, it's just I get the single "click" and the starter doesn't even try. Seems to me there's something going on with the battery cable itself between the battery +ve and starter motor +ve? (although a connection test with a multimeter doesn't show anything wrong) Or am I off base?

I'm confused why this would only come back after the car has been sat without the battery connected for a while.

Appreciate any thoughts you have!

Cheers

Corrosion on weak connections.
I would check your main battery cable from the battery to the big starter lug for voltage drop, that is the Battery + to ground voltage should be the same as Battery to the Big lead on the starter, if there is differences, then I would first clean the battery negative to frame, then from the frame horn to the engine/tranny.  

The single click would indicate to me that the Starter solenoid is engaging, but the contacts from the Solenoid to the engine Jumper are iffy or the starter solenoid is bad.  So you may want to remove your starter and have it tested as Starters do go bad.

But on these guys, it is usually a 2 prong issue that you have a flaky grounds or earths.  So I would do a voltage drop check, then have the starter tested.

Adding a heat soak relay fix to the starter solenoid is a good thing to do on Automatics as well as Manuals transmissions, it shortens the run of wires from the starter solenoid to the battery and allows massive current to tell the starter to engage.

www.cabby-info.com has a tutorial on that.  

As a Quick check.
Car in Neutral e-brake full on.

Take a good set of battery jumper or booster cables and attach them from the Negative side of the battery to the Frame a strut mount nut is a good quick place to get to, and then the other cable from the battery to the engine.

(you are by-passing the ground wires)

See if the car starts, if it does, then you have bad grounds.

If the car still doesn't start.  remove your temp grounds.

With a length of wire (good sized) Car still in N, and ebrake full on, turn the key to the run position.

Take the wire from the battery 12+ side straight to the starter solenoid (the little wire on the right side of the solenoid) does the starter click and spin the engine?

Yes/no.  
Yes, then clean your wiring up to the solenoid.
No.  Take the same lead from your Battery b+ 12v side straight to the big lead on the starter, does the starter spin and the engine start?  
Yes/no.
Yes, then you have a bad starter solenoid or corroded connection from the solenoid to the starter (big braided flat strap from the solenoid to the starte)r.  if that is clean then you have a bad solenoid.

No, the starter is bad. Remove it and have it tested.

This is an awesome response, thank you! Nice step by step process, I'll find some time and will get down there and check it all through!

Thanks a lot, really helpful!!!

I've had this before when the gear gets jammed on the shaft in the starter and just needed greasing. They are simple to strip down and clean out

Thanks trucker,

Yeah I thought it could be that too, but given jumping directly to the starter made it fire straight up, and then take the jump leads off it won't start next time, I figured it was electrical rather than mechanical.

When storing your car and unplugging the battery you should remove the negative lead, ve- not the positive, ve+ As stated in your first post. It saves the battery from "sparking" when you connect the leads.

mark1gls said

When storing your car and unplugging the battery you should remove the negative lead, ve- not the positive, ve+ As stated in your first post. It saves the battery from "sparking" when you connect the leads.

Will do from now on, cheers.

Hi all,

Went down and did some testing today.

Started on the earth side. Jumped the ground wires as suggested and no change in the car not starting, so didn't seem to be a ground issue.

Then, took the jump leads (they're not the best jump leads but they're all I had) and connected +ve battery straight to +ve big nut on starter. Turned the key to fire and the engine struggled and turned a couple times, just single turns, so I stopped and removed said wiring to clean it all up.

Cleaned up the wiring from +ve battery to starter big nut and tried again with the jump lead, this time a single click, and small struggle and then the car fired up.

Does this insinuate then that the solenoid is bad? (or the braided wire is corroded, though I couldn't get a good look).

I find it odd that this has happened twice now in only a few years of ownership. Any reason my car would be chewing through solenoids?

Cheers

Well, that or the ignition switch.  
A heat soak relay for the starter takes the high current off the ignition switch, good for Manual as well as necessary for Auto's.

New parts go bad.

I'll take a look at the heat sock option as a good practice thing to do. I've still got some work to do to track this down, I hate intermittent electrical faults!

Yesterday the car fired up fine in the morning, drove it 30 minutes and parked up for 30, then it needed a jump straight to the starter.

Drove it another hour, sat for 2 hours and then started by itself again (although it did struggle). And on the way home the fans now don't work and my heater temp gauge seems to have failed xD

I would say its the +ve wire from the battery to the starter motor. It sounds like it has an intermittent/poor connection, which might be heat-related.

Its also possible, that this is marginal anyway but when the engine is hot its more difficult to turn over on the starter - for example if the rings aren't gapped properly, or some other internal issue. So it shows up when warm/hot as a non-starting issue.

Obviously replacing a cable is easier than replacing piston rings!

The starter is wired as follows.

From the Battery +12V to the large lug on the Starter solenoid one side of the contacts.

The starter motor itself is connected by the large flat braided cable to the other Starter solenoid contact.

The Starter solenoid is connected to the Ignition switch via the little spad connector on the right side of the rear of the starter solenoid as you are looking at it.

Ground to Each is provided by the Starter to Tranny/block bolts and the Frame to engine ground.

When you turn the key to start:
You are providing ground, a path via the Starter Solenoid through the Pick side to Battery +12v side.

When the Solenoids pick sees voltage then current flows and the Solenoid Clicks, as that is the Click is the external indication that the contacts are mating.  When these contacts mate together, they allow Ground to flow back through the frame via the motor, then the BIG leads out of the motor to the motor contact on the starter solenoid, out the other contact to the BIG Honking Lead of the Starter to the Battery +12V causing the motor to SPIN this spin throws out the Bendix, to engage the starter ring on your flywheel, and or flex plate if an Automatic.

Not rocket science, but basic current flow.

Current in a electric circuit flows from the Negative Lead of the battery to the Positive side, and not how you would think.

In electrics, think of voltage and current as a River.

Voltage is felt in a Circuit at any point similar to you sticking your foot in the River to say it is wet/cold.

Current which is really the workhorse it the Rate that the water is flowing over your hand or down stream, it is the current that carries the load. Like sticking your arm out the boat or shore and you feel it flow against the your hand.

Hi all,

Went around this morning upgrading all the battery cables to much beefier ones and brand new. Cleaned up all the grounds etc. and the car fired up straight away. Starter motor sounded better than it has in years, honestly think it was spinning at twice the rpm haha. Will check again tomorrow to see if all is well.

However, I tried the heater fan again and once I switched it to "1" I heard it pulse for half a second and switch off immediately, same with "2" and "3" and then after just completely dead. Also definitely smelled a hot / burning electrical smell after that.

At the same time, my coolant temp sensor on my cluster doesn't read anything at all, so I changed the temp sensor today and still nothing.

Any possibility the wiring for the coolant temp sensor and heater are on the same circuit / fuses etc.?

Any electrical help / starting points to hunt down the issue much appreciated as always.

Thanks all!

no, the heater box and the cluster are two separate things, if the fuel gauge works, but the temp don't then you probably have cold solder joints or a broken wire from the sender to the unit.  I have how to's on that in the archive section under briano 1990 or click the link and sort through them as it is in sectional order.

Remove the cover for the blower in the scuttle area and check the fan can spin freely, you will also see the electrical connections, check everything is connected and in good condition.

mice love knawing wiring

Lol at the mice, no mice that I know of down there. I've had a look at the cabin heater connections and the fan itself, all are ok. I did re-crimp a dodgy wire off the fan speed selector knob behind the dash some months ago - possible that's come adrift again so I'll check it out.

But otherwise, all the heater fan connections / the fan itself were fine a few months ago. "shrug"

Thanks again Briano, will scour through those links.

Cheers all!