Duff Battery or Something else?

[virden]

Trying to start X/F after 6 mths SORN, battery (a Yuasa) fluids OK and it had  been given a days charging every month during lay off. Shows 12.7V on starting, but only has energy for  2 starting attempts at normal turnover speed, then rapidly slows to stop after a further  5 goes.  Voltage at end 12.4v.   Even with aid of a Clarks Quick Starter there is insufficient power  for more than three normal speed start attempts.  Recharged  battery and then left lights on full beam  for five mins, voltage did not drop.   Is it a duff battery  or a short somewhere?

[Jonathan Kay]

Shows 12.7V on starting, but only has energy for  2 starting attempts at normal turnover speed, then rapidly slows to stop after a further  5 goes.  Voltage at end 12.4v.

I'm not sure what you mean by "on starting". What's the voltage at rest, and minimum seen during cranking?

Has it fired at all?

I'd check all the relevant wiring and connections, including the battery terminals and engine earths: inspect, wiggle, disconnect, clean and reconnect.

I'm not familiar with a Clarks Quick Starter: what is it? Do you have another battery or vehicle you can use to jump the 7?

Jonathan

 

[virden]

 Hi Jonathan,

By "starting" I meant cranking, voltage on initial cranking drops rapidly to 7.8v.  The plugs are sparking, the fuel is coming through, but she has not started.  All relevant connectors undone cleaned and re- tightened.    I am using a Clarkes Jump Start 900, which works on other cars.

[Jonathan Kay]

Sorry, I don't have a good explanation. A few thoughts...

7.8 V while cranking is far too low. As well as the starter not spinning fast enough electronic stuff might drop out.

You've got sparks and fuel... but has it ever fired?

The battery is probably duff, but we still need to see it starting reliably off another electrical source. That JumpStart device has a lot of nominal oomph, but is it fully charged and working properly? I'd try starting by jumping it with fat cables off another car with the engine at 3,000 rpm and again measuring the lowest voltage seen while cranking. 

Fuel is at least 6 months old... I'm not convinced that it gets tired but others are. Try a puff of ether in the air intake?

Jonathan

[AlexanderJ]

battery seems too low to me - surpirsed it doestn start on the jump pack

[colindavies56]

put a jump lead on battery +post,and the other end of that lead on the back of the starter motor so it has maximum volts up its bum,does the starter spin fast.put  ignition on 1st.

[revilla]

That sounds rather risky to me. The main supply terminal on the starter is only mm away from the block, one slip at that end and you'll have fireworks. There's already a substantial battery cable direct to the starter terminal anyway; if you suspect that is faulty then use a multimeter to measure the voltage between the starter terminal and battery positive when cranking; it should be close to zero. Even then, be very careful probing the starter terminal; I'd be tempted to make up a lead with a ring terminal on it and fit that to the starter, then measure at the other end of it, and disconnect the battery negative whist fitting and removing it. If you do have to remove the nut from the main starter terminal be very careful not overtighten it when refitting or you will crack the black plastic back of the solenoid.

[virden]

I put the battery on a long period of charge and observed the amount of bubbles rising to the surface of each cell, two barely gave off any gas, so have assumed the thing is duff and have ordered a Banner.