starting my 1970 MGB Roadster

[CHG]

Hi I'm having trouble starting my 1970 MGB Roadster, I have a new battery but when you turn the key it seems like theirs not enough power coming through to start it over, I have tried starting it by taking the brown and white wire off the solenoid and attaching it to the right-hand side of the fuse box and connecting the bottom 2 fuses and it tries to turn over but with little power, I am getting 12 volts to the fusebox, any suggestions

[Equus]

First thing I'd try is cleaning up the connections on the main battery cables (battery-solenoid and solenoid-starter motor) and earth connections (battery-chassis and engine-chassis.

[Xcore]

Check the earth strap on the right hand side of engine

[classicaholic]

I have had the same problem most years, its usually the earth strap from the battery to body. Clean it all up and thats sorted. Then its the fuel pump so give that a nudge with a broom handle - the joys of British cars!

[paintman]

Connect a decent jump lead from a good clean metal point on the engine direct to the battery earth terminal.
See what happens.

[littleredrooster]

New batteries are often not fully charged, especially if they've been in a warehouse for many weeks. Try charging the battery before doing anything else.

[kambites]

Since you say "battery" single I assume it's been converted to a single 12 volt setup?

The earth straps are is the most likely culprit, check where the battery is earthed to the chassis and where the engine is earthed to the chassis for corrosion. Or alternatively try running a jump lead from the negative terminal of the battery to the engine block ( make sure you get the right terminal though!).

[s m]

littleredrooster said:

New batteries are often not fully charged, especially if they've been in a warehouse for many weeks. Try charging the battery before doing anything else.

How many volts is the battery showing exactly?

[CHG]

ok a ran a negative jump lead from a new 12 volt battery which is reading 12.6 v straight to the engine block, and the live to the live battery connector, I bypassed the ignition and tried to start it straight from the fuse box, it turns over very slow and just won't start

[Dogwatch]

s m said:

How many volts is the battery showing exactly?

OP says he is getting 12v, but the problem for the starter motor is not just the voltage - a batch of AA cells will deliver 12v - but the "grunt" i.e cold cranking amps. Certainly the oft-neglected earth return path should be viewed with as much suspicion as the battery to starter leads.

[Gary C]

Contacts inside the solenoid itself sound like they are failing.

Take it to bits and clean them

[CHG]

I have 2 spare 12 volt batteries and they are showing 12.3volts

[Gary C]

I take it, the cranking is very slow, do the lights dim greatly ?

What is the voltage at the solenoid main power connection when cranking ?

If all earths and supply are fine then its either the motor itself or the solenoid main contacts (ie the ones that actually turn on the starter motor).

Strip it down.

[CHG]

im bypassing the solenoid, taking the brown and white wire off the solenoid and touching the bottom of the lefthand side of the fusebox then joining the bottom 2 sides of the righthand side of the fuse box

[Gary C]

CHG said:

im bypassing the solenoid, taking the brown and white wire off the solenoid and touching the bottom of the lefthand side of the fusebox then joining the bottom 2 sides of the righthand side of the fuse box

Your bypassing the main high current supply and putting it direct to the motor terminal ?

[Gary C]

Gary C said:

CHG said:

im bypassing the solenoid, taking the brown and white wire off the solenoid and touching the bottom of the lefthand side of the fusebox then joining the bottom 2 sides of the righthand side of the fuse box

Your bypassing the main high current supply and putting it direct to the motor terminal ?

Ah, not a pre-engaged unit ?

[CHG]

yes its cranking is very slow, and the lights dim greatly, I will strip the solenoid and try again

[Matt_E_Mulsion]

12.3 volts is not that great. A decent battery full of charge should show 12.6v/12.7v.

[Gary C]

CHG said:

yes its cranking is very slow, and the lights dim greatly, I will strip the solenoid and try again

Sorry, might be giving you wrong pointers

So

Is it a pre-engaged starter with the solenoid mounted on the motor ?

If the lights are dimming a lot, that suggests either a higher than normal current draw dropping the voltage, or the battery cant cope dropping the voltage.
If the lights weren't dimming much, that would have suggested a lower than normal current suggesting high resistance, earth strap, solenoid main contacts or supply cable.

[julian64]

You need to jump the car from another car with the engine running.


You current problem is not to do with solenoids otherwise the engine wouldn't be turning over. Its to do with the 12.6 volt battery I think. A normal battery would have 13+volts on it. But that doesn't tell you much about the capacity of the battery to start a car.

You can rule this problem out but jumping you car from another car battery preferably with a working alternator running. Alternatively a good car charger with a 200 boost of the sort that clarkes do.

If the car turns over slowly while connected to this setup then you need to look at earths and connectors. Not before