Battery advice please

[StewRat]

Hi all

I've been wrestling for some time now with (hopefully) the final steps of getting the StewRat started.

It has run very briefly in the past (last year) but I had to make some wiring changes while addressing my pushrod problem and it's never started again.

There's a long thread about my testing and progress on Volkszone http://www.volkszone.com/VZi/showthread.php?t=1500481 but summary of where I am now is:

Master switch energises a master relay that powers fuse box and therefore coil and MSD.

When I start to crank the engine on the starter button, that master relay gets quickly de-energised and power to fuse box is gone. Starter motor continues to spin engine happily.
The voltage across the battery drops to about 9V during cranking. It may be dipping momentarily below that.

If I bypass the master relay, thereby maintaining power to coil and MSD, the starter turns the engine very slowly.

It seems the battery can spin the engine if it doesn't have to power ignition, but if forced to do both, it doesn't do wither well.

So is this battery simply not up to the job? 2276cc, about 10:1, MSD 6AL, Flamethrower coil and distributor with built in Pertronix II.
(Only a few months old, bought it for this)

Suggestions for what I should be using?

Is there any precedent for separate cranking and ignition batteries?

Thanks

[modnrod]

A common get-around/bypass fix for similar problems with high-comp motors with a heap of initial advance (or locked-in advance, no curve at all) is either a 10-degree start-retard function for the ignition curve, or an even simpler solution that's been around even longer is to crank the motor with no ignition power, then while it is cranking turn on the ignition separately.

A big high-current-draw battery (at least 600CCA) and/or a reduction starter fixes most of these issues normally though.

[richie]

I am not sure why you wired it like that, seems overly complicated and doesn't make sense to me but I am no electrician Mine typically have power to kill switch, there directly to main feed on starter, and another to ignition switch/starter button, then one wire off switch to fuse box and other to starter motor switched terminal

But couple things stand out, if timing is to advanced it will turn over really slowly[when it is sparking] and that battery probably isn't man enough on a fresh engine, as it loosens up it will turn/start easier but right now it will struggle, I typically use a battery in 700cranking amps range

cheers Richie

[StewRat]

Thanks guys

I'm no electrician either but as I understand it, using the relay like that avoids having all the power go up to the front of the car and all the way back.
I do actually have a kill switch that was in the car when I got it but I never got to the bottom of how it should be wired up - so all this may change again when I work that out.

For now, the good news is that the battery does indeed seem to be wimpy, and may be the main source of my problems, so that is fairly easily solved. Seems I can easily get a battery with 800,900,1000 CCA and 80-100 Ah. Apart from extra weight, is there any reason not to just go for the biggest?

Thanks again.

Stewart

[richie]

. Apart from extra weight, is there any reason not to just go for the biggest?

Thanks again.

Stewart

Cost?

[StewRat]

Haha. Funnily enough the hope that this will get me up and running meant I hadn't actually considered cost. What has happened to me


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[richie]

Haha. Funnily enough the hope that this will get me up and running meant I hadn't actually considered cost. What has happened to me


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Your not Scottish then? 

Also some of the better ones require a different/better charger

[paul_f]

Are you sure the timing is correct?  I have seen this when the timing was too far advanced

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[StewRat]

I *thought* the timing was correct because it *did* run a few months ago and I didn't think I had changed anything that affected timing.

However in the very little time I had today I traded in that battery for a 700 CCA one and that, combined with some crude timing adjustment (test lamp died) has made a vast improvement. Ran out of time before I got it running, but it was trying to, so nearly there ...

Thanks everyone for the input.

Stewart

[StewRat]

Your not Scottish then? 

I am, and while I think I have been very frugal in putting this car together, I suspect my wife thinks otherwise.

[Neil Davies]

There is a quote in someone else's sig on another forum that goes something like: "My biggest fear about dying is that my wife sells my stuff for what I told her it cost..."

I'm rubbish with electrics Stewart, so no use at all with this! All I can offer is that I ran a taxi battery in my old car - plenty of cranking power and enough juice in it to keep the MSD working with no charging system. The previous battery was changed out after I'd had a mysterious top end misfire when the battery wasn't 100%.

[StewRat]

Love that quote Neil

I've learned a lot about auto electrics on this journey - and indeed about building an engine etc - that's kinda why I jumped in at this level. I've been on various wild goose chases trying to fix various problems and while they have been massively frustrating at the time, when I take a step back I appreciate that I have learned so much more in finding the solution.

But I really, really want to get this car down the strip now

Actually, so does my wife, if only because I bought a zipped hoodie at Santa Pod during VW Action last year, I wear it all the time, and am refusing to have it washed until my car does a pass.

[pupjoint]

Optima Redtop 34/78 800 CCA

[StewRat]

Closing the loop on this chapter ...

The StewRat is now running!

In the end I think there were 3 different things in play that were conspiring against me:

1. Battery wasn't up to the job. 700CCA version is much better, though I need a bigger battery box now.
2. Timing was a bit out. Not sure how that happened but it's role was disguised a bit by the spark related problems from items 1 & 3.
3. Using the relay to switch on the master power. Having got it started without the relay, but proper timing and bigger battery, I put the relay back in the circuit and it did same as before - de-energised shortly after cranking started.

So far so good. However ...

Fired up for second time today to check dynamic timing and adjust mixture etc - and discovered the oil leaks!
There seems to be some oil coming from the base of cylinder 4 and maybe* from a push rod tube - I'm hoping re-torquing the heads may deal with hose. But there's a bigger leak between engine and gearbox which I guess may be the crankshaft oil seal. I only got as far as engine and clutch out today so I don't know for sure. The friction plates don't seem contaminated so it may be something else. Hope fully get time to investigate tomorrow.

I know people remove these engines in minutes but I was pretty happy with 2 hours for first time, single handed removal with a trolley jack and 4 axle stands!

*the maybe is because I very cleverly took some video on my phone while the engine was running to help identify the leaks later - but managed to repeat a favourite trick of mine, and pressed start when I meant stop and vice versa, so I in fact have no video of the leaks, and 20 minutes of the ceiling from the workbench.