Faulty starting question

[pleasestartnow]

Hi there, I have my van in dry storage in a shed nearby and recently the shed owner had to move the van to get at something. Now he regularly does this, i.e .he starts it, drives it into the yard, gets what he needs and drives it back in without any issue. However, yesterday he said it wouldn't start and he eventually got it started by 'squeezing a wire'. Went down today to have a look and it wouldn't start for me, 12.85 across the battery terminals. However, as I was fiddling about the shed owner came down and pointed out the wire he squeezed, I did the squeeze and the van started up sluggishly after 2 or 3 more attempts.

Now I think the wire squeezing is a coincidence and I think the issue is either the age of the battery or dirty earth's, things I have repeatedly said to myself to sort, but the wire he squeezed has a 35A in line fuse. My question is, is this the line going to the zig unit and irrelevant to the starting process or is it something else that maybe would effect the van starting?

Any suggestions are appreciated.
1.9D 1990

[mioba]

You need to follow the wire.
Zig will (should) have a relay on it.

[pleasestartnow]

Ya thats what im afraid of 

[pleasestartnow]

So went up to the van earlier to have a nose around, that cable is definitely going into the zig. I have done nothing to the zig and last time it was used back in the summer. It is disconnected from the leisure battery . When i turned the ignition key i can hear the solenoid activating, i have 12.92v on the battery and no start. Gave a small squeeze to spade 2 on the zig unit cable and it started up no hassle then. Makes no sense to me really but the fact that its started the last 4 times after giving that cable a squeeze is making doubts start to creep in. 

I checked continuity along the cable to the zig unit and i have continuity from the battery to the other side of the to spade 2 and i can measure 12.92v between spade 2 and the earth on the chassis. 

Im just looking really for reassurance that this cable should have no influence on the van starting. Im still of the mind its either bad earths or battery is dying. 

[AngeloEvs]

Is the Leisure Battery completely isolated?   It sounds to me as if the Leisure Battery is helping the main battery during the start process  - disconnect the leisure battery completely and see if  it starts (including squeezing the wire) then report back.

[pleasestartnow]

Yup leisure battery is completely disconnected. It started away today without any squeezing on the second go. I was bringing it to a guy to sort out rust along a panel and he said he would have a look while he is doing that to see if anything stands out. When I get it back I will go over the earth points and get a new battery and replace some of the existing electrical cables and hopefully that will sort it then.