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bigkiltedwarrior

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Reply with quote  #1 
Hi,

After a few months of trying to ascertain if my 2.0l big valve pinto twin 45s was overheating or not, I believe my higher than expected temperature gauge readings may be electrical rather than the actual temperature.  The coolant has never boiled over even with readings of 120.

I have had an erratic reading tachometer for some time, which randomly fluctuates and especially when the radiator fan kicks in or I turn the headlights on.  On this same basis, I noticed yesterday that my temperature gauge was reading about 115 but went to 120 when I turned the headlights on.  It went back to 115 when I turned them off.

This is leading me to believe that there is possibly a bad earth somewhere in the system?

Before I start stripping everything apart, has anyone else experience this or have any tips on how to go about isolating the problem?  I built the car myself so am familiar with the wiring and loom.

Any thoughts greatly appreciated as always.

Stewart

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overdriver

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Reply with quote  #2 
Hi Stewart,

Sounds familiar - see my post of 22nd March. My symptoms extended to seriously low oil pressure readings! Only after rebuilding the engine (without improvement) did I notice that on tick-over the headlights were 'pulsing' - so I started looking for an earth problem.

Eventually I traced it to the (disconnected) earth strap which goes from the bell housing/block bolt (conjoined with the battery earth lead - see pic) to (in my case) the bolt securing the battery clamp/header tank bracket to the frame supporting the battery tray. Essentially, the battery earth was going to the engine block but not finding an easy route to the chassis.

Hope this helps.

Michael.

Earth strap.jpg 


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Supercat, 2.0 Pinto, twin 45 DCOE Webers, Piper Ultimate Road cam.

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Spent it on fast women and loose cars.
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pauld

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Reply with quote  #3 
The tiger loom should have 2 separate. Earth leads which are part of the
Loom front and rear about 5 small black wires they all go into a 6 mm eyelet. Check for good contact. There regards Paul
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bigkiltedwarrior

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Reply with quote  #4 
Totally at my wits end with this. All earths appear to be fine, secured tightly and nothing loose.

What I have noticed is that when the headlight switch is flicked on the taco fluctuates and the ten gauge goes up. The temp gauge also goes up when I brake, which is noticeable whilst moving slowly and braking, or sitting with foot on the brake. This makes me think there is a short with the lighting circuit possibly.

I've also noticed the oil pressure light flickering periodically.

The car is running fine but obviously very annoying not being able to trace the source of the problems.

S
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TOC_Admin

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Reply with quote  #5 
This may sound like an obvious question, but you have run an earth strap from the chassis to the engine block haven't you? Is that connection okay?

Beyond that, I would start by checking the wiring from the gauges with a multimeter on the resistance testing mode - a connected wire will show zero ohms resistance, a disconnected wire will show nothing, anything else is a potential problem area - you will need to disconnect everything and trace connections using the wiring diagrams to help you.
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bigkiltedwarrior

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Reply with quote  #6 
Thanks, yes, the negative from the battery runs to the block at the bell housing and the live from the battery goes to the starter motor.  This is a recent issue which has appeared subsequent to me putting a new head on my Pinto.

This is also a possibility that my alternator is playing up a bit as the battery light does periodically glow but quite dull.  Would a knackered alternator cause this kind of issue?  I normally keep the battery on a smart trickle charger.

Sounds like I will have to get the multi-meter out and try and figure things out.

Cheers
S
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TOC_Admin

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Reply with quote  #7 
The alternator should be fairly easy to test and could cause strange meter readings if the voltage is not being regulated correctly.

Use the multi meter in voltage mode and check the voltage of the battery with the engine turned off using the meter in both battery posts, it should be somewhere around 12-13 volts.

Start the engine and blip the throttle to make sure the exciter in the alternator is 'energised', then check the voltage across the battery, it should be showing 13.5-14 volts. If it's lower, move the throttle to get around 1250-1500 rpm whilst doing the test.

Anything outside these running values may indicate a faulty regulator which can be picked up for a few pounds from eBay.
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rickwatton

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Reply with quote  #8 
When you did the head work did you repaint the block as paint between the earth terminal and block could cause a bad earth even if it is tight
Rick
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Paul_Turner

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Reply with quote  #9 
Quote:
Originally Posted by TOC_Admin
Use the multi meter in voltage mode and check the voltage of the battery with the engine turned off using the meter in both battery posts, it should be somewhere around 12-13 volts.


A healthy battery should show 12.6 or 12.7 volts after its been stood overnight, any less and the battery is knackered or you have something using power when the car is off.

Quote:
Originally Posted by TOC_Admin
Start the engine and blip the throttle to make sure the exciter in the alternator is 'energised', then check the voltage across the battery, it should be showing 13.5-14 volts.


Old Lucas alternators used to produce about 13.7 volts after starting a cold engine but Denso and other newer types (Bosch and Valeo for example) produce about 14.3 volts after starting a cold engine. Once the battery is fully charged and the alternator heated up this drops to about 14.1 to 14.2 volts, a Lucas can drop as low as 13.5 volts.

Genuine Denso alternators off an old Daihatsu are the best to use. The one on my car dates back to a 1989 Charade. Don't buy Denso alternators off E-Bay or from other well known suppliers. They are made of cheese and are not genuine. Bought one before fitting the old Daihatsu one, looked the part but did not produce the correct voltage and rattled. Checked with Denso and they confirmed from photo's of the label it was fake. Got a refund after some lively discussion.
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overdriver

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Reply with quote  #10 
Quote:
Originally Posted by bigkiltedwarrior
Thanks, yes, the negative from the battery runs to the block at the bell housing and the live from the battery goes to the starter motor.  This is a recent issue which has appeared subsequent to me putting a new head on my Pinto.

This is also a possibility that my alternator is playing up a bit as the battery light does periodically glow but quite dull.  Would a knackered alternator cause this kind of issue?  I normally keep the battery on a smart trickle charger.

Sounds like I will have to get the multi-meter out and try and figure things out.

Cheers
S


I would suggest that, if you haven't already done so, connect an additional earth strap from the block to the chassiss. As I said in my previous post, my almost identical problems were cured when I discovered this strap wasn't connected.

Michael.

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Supercat, 2.0 Pinto, twin 45 DCOE Webers, Piper Ultimate Road cam.

_______________________________________

Spent it on fast women and loose cars.
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bigkiltedwarrior

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Reply with quote  #11 
Well that was a lot easier than it could have been! Added an earth strap from the bellhousing to the chassis and erratic tach problem solved along with high temp reading. I wish everything was so easy.
S
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