5 replies to this topic

[babsbrown]

Good morning guys,


I'm attempting to bench test my newly rebuilt engine.

The problem is the wires are getting very hot to the touch, after about 10 seconds of cranking. Does anyone know the issue?

I have the following:

Battery + to coil (thin wire clamped on)
Negative coil to dizzy condenser
Battery jump cable from battery - to earth on engine
Battery jump cable from battery + to the starter terminals.
I'm then bridging the terminals with a screwdriver.

The coil also got very hot to the touch.
I'm now letting everything cool down.

I get 60Psi after about 10 seconds of cranking every time. I have a small leak (oilfilter housing gasket) but other than that the engine seems good for pressure.

I'm half tempted just to fit it and get it running in car as opposed to messing around with wires everywhere.


Thanks, Luke

[68+86auto]

Which lead is getting hot? If it's the jumper leads then that's to be expected. Most jumper leads are useless as they use thin wire with very thick insulation. I've seen regular jumper leads get hot trying to start a mower. They can't do much at all despite the crazy amp ratings the sellers claim. I use nice thick jumper leads made from proper wire or welding leads.

 

In regards to the coil getting hot, check that the points are actually opening and that the negative side isn't shorted to ground. One time I was trying to test an engine and didn't realise that the locking pliers holding the coil on had moved to contact the coil negative.

Edited by 68+86auto, Today, 11:52 AM.

[babsbrown]

Excellent thanks,

That's answered a lot of my questions. Yes the jump leads were getting really hot. I'll double check the dizzy mate sure the points are opening. Cheers

[viz139]

If your cranking for oil pressure disconnect coil and remove sparkplugs. With new bearings ,new cold oil I would expect a higher (75 psi) reading. 

Only connect the coil + when attempting to start the engine otherwise if the points are closed it can heat up quickly. 

This is why when radios started being fitted to cars they had to add an accessory position to the ignition, to stop people burning out coils when parked with the radio on. 

As above check that the points are opening and closing.

[babsbrown]

If your cranking for oil pressure disconnect coil and remove sparkplugs. With new bearings ,new cold oil I would expect a higher (75 psi) reading. 
Only connect the coil + when attempting to start the engine otherwise if the points are closed it can heat up quickly. 
This is why when radios started being fitted to cars they had to add an accessory position to the ignition, to stop people burning out coils when parked with the radio on. 
As above check that the points are opening and closing.

Thanks mate, I've tried that with the coil and it's much better. I do have a gasket leak on the oil filter housing that pours out when I crank it over. I'm sure once this is sorted I should see more than 60psi. Although I'm still happy with that.

Not getting fuel to the bores either, but dash pot is full, but I think a lot of that is because the battery is on half charge. A good power up should see it go I think.

[Steam]

Not only are jumper leads usually very thin wire with thick insulation but the connector clamps only touch on a small area compounding the issue.