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Urgent help needed!!! Voltage problem


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#1 Bigworm

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Posted 22 October 2010 - 06:23 PM

Hi guys just wondering if anybody knows where i have gone wrong with my 280zx?
I have just done an engine swap with another L28, but now i have got everything in and all hooked up it wont start.
It does kick over, seems like its getting fuel, but there must be a problem with the voltage in the car because the engine and body all the parts that are supposed to be earth give a positive charge instead of negative (with battery in the car and pos terminal on the battery, touching neg terminal on to the battery gives a big spark and putting the test light from the block to the neg battery terminal creates a circuit!?)
Does anybody know what could be happening???? Any help would be very appreciated!

Jesse 

#2 Zedman240®

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Posted 22 October 2010 - 06:42 PM

Have you mixed the main earth and +from battery cables to starter motor?  Main + from battery should go to the starter solenoid with the low profile nut and - goes to the gearbox/block bolt. I'm sure with the 280ZX's the wiring is similar under the bonnet.

#3 WA240Z

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Posted 22 October 2010 - 06:48 PM

Very interesting.

I would also check you have connected the main ve- to the chassis. If the main ground isn't connected the whole car becomes above ground. This will give the impression that the engine block and chassis is positive ve+.

Hope this helps.

#4 Bigworm

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Posted 22 October 2010 - 07:56 PM

hi guys
it looks like the starter is wired correctly but ill double check tomorrow to make sure, im thinking it has to be something simple but it is a strange thing as we didnt even take the starter out of the engine bay to do the engine swap we just moved it out of the way all still connected up! Im trying do find the problem myself as i dont have the money for an auto-electrician due to all the money i spent on the swap lol im now broke:(
thanks for the info

#5 MaygZ

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Posted 22 October 2010 - 10:57 PM

Something I would consider looking at is checking that you haven't pinched a wire while putting the engine in.  I would also double check that engine earth strap is secured, although if the engine weren't earthed, then it shouldn't crank!

What would be the chances of an error in wiring up the efi.  I would suspect that if the power for the injector pump were earthed, it would give the engine +ve power and also prevent the injector pump from running (no fuel).  jus a thought.

If this is rambling, please forgive me as it's late after a long day.

MaygZ

#6 Bigworm

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Posted 23 October 2010 - 03:26 PM

i have checked the wiring and it all seems ok to me its was completely out of the way when we put the engine in and then all reconnected to the new engine the same way it came off the old engine so i cant see why it is doing this, its cranks fine and you can hear the fuel pump going and feel fuel going through the line, it sounds like it wants to start and you can actually hear it start catching fuel and turning over but it seems like the electrics are fighting it somehow.
thanks guys

#7 KatoKid

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Posted 23 October 2010 - 03:47 PM

Nearly sounds like the ignition timing is too far advanced. Suggest you do a static timing test.

#8 MaygZ

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Posted 23 October 2010 - 04:45 PM

Nearly sounds like the ignition timing is too far advanced. Suggest you do a static timing test.


Yes it does.  Maybe the dizzy is 180 degrees out??

Doesn't really answer the block to -ve terminal making a circuit though??

#9 Bigworm

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Posted 23 October 2010 - 05:16 PM

Ok i have had a bit more of a poke around
Dizzy is on right because we have been adjusting the timing trying to get it to go, with no luck
from what i can tell there are 2 main issues
-if i put the pos battery terminal on the battery and then put a test light on the block and that pos terminal it doesnt create a circuit(when it should), but does create a circuit when put from the block to the neg battery terminal. Now when i put the neg terminal on the battery and put the test light on the block and the pos terminal it now creates a circuit and block to neg terminal doesnt create a circuit. for some reason it switches when i put the negative terminal on and off the battery????

-when both battery terminals are on the battery its is fine but when i try to crank it the negative terminal gets super hot almost instantly and it seems like its draining the spark away from the coil/dizzy/leads/plugs and heating up the terminal

has anybody heard of anything like this before??? or does anyone have any more ideas

thanks heaps
jesse

#10 Scoota G

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Posted 23 October 2010 - 05:47 PM

My 260Z had the same problem last week which was the starter was stuffed. It was taking most of the battery power to crank and was difficult to start.

#11 Bigworm

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Posted 23 October 2010 - 06:36 PM

the starter in my car seems good (i think i only replaced about 6 months ago) and it has been starting it fine but maybe with too much power is this what was happening with yours? how could u tell it was the starter??? i only ask as we actually got the engine to kick over and run for about 20 seconds the first or second time we cranked it after putting the new engine in but after it had started the terminal still got hotter to the point of it smoking, and that is why we turned it off and now we have this problem.
cheers ill look into it tomorrow.

#12 Scoota G

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Posted 23 October 2010 - 06:40 PM

I just swapped it out for a unit that i knew was okish. The starter was getting very hot. Try cleaning the negative lead where it joins to the body too.

#13 Zedman240®

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Posted 23 October 2010 - 06:47 PM

Hot wires means excessive current flowing > possible short. Remove the starter motor and check it with a set of jumper leads. Connect the negative jumper lead clamp to one of the mounting ears and the positive to the solenoid where that large braided wire goes into the motor itself. It should spin at about 2000ish RPM with a bit of a kick at the start. If you have access to a clamp meter, measure the current on the positive cable. It should be around 300 amps.

#14 Bigworm

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Posted 23 October 2010 - 08:36 PM

thanks guys ill pull out the starter and test it out tomorrow and ill let ya know.
By the way do you know if there is any difference between starter moters on l28's?? as the one i have on my car (79 model Series 1) looks different to the starter on my dads l28 (82 model Series 2) as i think the new engine i put in my car is a series 2 L28 (if there is such a thing???) maybe that could be part of the issue??
thanks again people ill keep ya posted :)


#15 MaygZ

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Posted 23 October 2010 - 09:16 PM

I completely melted the negative terminal off my battery while 4x4ing in my diesal Hilux.  That was a stuffed starter.  It still cranked the motor for a while, but eventually melted stuff inside it.

On the subject of starters, someone on this forum has said that the starter for an RB30 (VL or early skyline) fits the L28 and is about half the weight.  Something to consider if you need to replace yours.

MaygZ

#16 Bigworm

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Posted 23 October 2010 - 10:35 PM

well that may be an option as i have a few rb30 engines and parts laying around from my old skylines, ill see how it goes
cheers


#17 Six_Shooter

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Posted 24 October 2010 - 05:47 AM


-if i put the pos battery terminal on the battery and then put a test light on the block and that pos terminal it doesnt create a circuit(when it should), but does create a circuit when put from the block to the neg battery terminal. Now when i put the neg terminal on the battery and put the test light on the block and the pos terminal it now creates a circuit and block to neg terminal doesnt create a circuit. for some reason it switches when i put the negative terminal on and off the battery????

-when both battery terminals are on the battery its is fine but when i try to crank it the negative terminal gets super hot almost instantly and it seems like its draining the spark away from the coil/dizzy/leads/plugs and heating up the terminal

has anybody heard of anything like this before??? or does anyone have any more ideas


That is perfectly normal.

With no negative battery connection, the entire car will have a "positive charge". When you attach the test light, to the negative terminal of the battery, and then touch the block, or chassis in this case as well, the test light will light, since the test light is basically becoming that ground connection, conversely, when you attach the negative battery connection the "positive charge" of the chassis/engine block/etc will cease and become the ground plane.

#18 Bigworm

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Posted 24 October 2010 - 08:42 AM

hi there
I was just thinking that it was faulty due to the fact that i tested the same way on my dads 280zx and a stack of other cars and this is the first time i have come across something like this. When i test the other cars i can put the test light to the block and neg post on the battery and it doesnt create a circuit anytime(with neg terminal on or off) as the block is still earthed, but strangely not in my case.
the thing im most concerned with at the moment though is the terminal getting hot and not getting enough spark but ill play around with some different starters and see what i can come up with.

so much for me thinking i could just drop another engine in and have no dramas lol

thanks

#19 Bigworm

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Posted 24 October 2010 - 10:05 PM

Ok so i have had a play around with different starter moters and to no avail i have the same problem guess its time to bring in an auto elec to try and find the problem, thanks for all the ideas guys i will let ya know how it goes

jesse

#20 Six_Shooter

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Posted 25 October 2010 - 10:23 AM

All cars should act the same way in regards to the test light, in this use.

Placing the test light between the block and the negative terminal of the battery, with the negative battery connection removed would have the same result as placing the test light between the negative terminal of the battery and the negative battery connection. This completes the circuit, on ALL cars.




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