Author Topic: Disconnected the blue temp sender, revs dropped - not good?  (Read 3170 times)

Offline AdzCM

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Just finished my rebuild, an it still misfires on cold start-up :(

I'm thinking its either the blue temp sender or the hall sender.....going to check them now...

Anyway, when I disconnect my blue temperature sender, the revs drop. Looking at Pauls diagnostic guide, they're meant to rise or stay the same. Because my revs drop, is this an indication of a faulty sensor?
« Last Edit: July 03, 2014, 04:46:05 pm by AdzCM »

Offline cheys03

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Re: Disconnected the blue temp sender, revs dropped - not good?
« Reply #1 on: July 03, 2014, 05:05:27 pm »
Quick and easy to find out - measure it's resistance at around 20*C. From memory, both our cars are about 3K at this temp.
« Last Edit: July 03, 2014, 05:07:26 pm by cheys03 »

Offline hayesey

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Re: Disconnected the blue temp sender, revs dropped - not good?
« Reply #2 on: July 04, 2014, 09:18:06 am »
staying the same is bad.  Ideally it should rise, if it drops it suggests the ignition timing isn't set right. 

Offline AdzCM

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Re: Disconnected the blue temp sender, revs dropped - not good?
« Reply #3 on: July 04, 2014, 12:52:23 pm »
staying the same is bad.  Ideally it should rise, if it drops it suggests the ignition timing isn't set right. 

Ah right, thanks Paul. I tested the hall sender and blue temp sender, and they're fine.

How do you set the ignition timing when you have a non-g40 auxiliary pulley fitted with no 'z' ignition timing mark on it? The only way I could do it is by refering to marks scored into the distributor and cam cap. There are a few so I'm not sure which is correct. I didn't make these marks. They were there when i bought it.
Also, does the g40 ecu actually store faults and need wiped before the ignition timing/idle speed can be set?

Thanks

Adrian

Offline randombadger69

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Re: Disconnected the blue temp sender, revs dropped - not good?
« Reply #4 on: July 04, 2014, 01:29:33 pm »
Ecu doesn't store faults from what I can gather.

Might be worth buying or trying to borrow a strobe light with advance/retard. Easy to set 5 degrees btdc then.

I bought one, was about £50. Expensive but quick and easy to use.

Offline Andy

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Re: Disconnected the blue temp sender, revs dropped - not good?
« Reply #5 on: July 04, 2014, 02:19:02 pm »
How do you set the ignition timing when you have a non-g40 auxiliary pulley fitted with no 'z' ignition timing mark on it?
Spark plug out on cylinder #1, TDC feeler/pointer (or pikey alternative of screwdriver or 3/8" extension bar etc.) down the plug hole, rotate engine with ratchet on the crank bolt, and rock back and forth 'til you feel that the piston is right at the top of the bore.

Now you know the engine is at TDC, so you can make corresponding marks on the crank pulley and block/cambelt cover. You then use these as your TDC reference, and use a timing light with dial-in advance to set the ignition timing to 5° (+/-1°).

Whilst you're at it, set the idle speed with the blue temp sender unplugged too. Engine needs to be up to temp.

Offline AdzCM

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Re: Disconnected the blue temp sender, revs dropped - not good?
« Reply #6 on: July 04, 2014, 04:15:51 pm »
Pity they're so expensive. Ill see if I can borrow one. Thanks man.

That's brilliant Andy, thanks mate. Will do that as soon as I get a timing light :)

I take it the idle speed will need to be set by someone with a gas analyser? Or is there any way I can do it myself well enough?

Offline C0UP3

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Re: Disconnected the blue temp sender, revs dropped - not good?
« Reply #7 on: July 04, 2014, 04:39:50 pm »
Idle speed is just adjusted on the side of the throttle body. It's the co pot which controls idle fueling that is best set up with a gas analyser but doesn't need to be can just set resistance (can't remember figure somebody will know) and go by that. Not perfect but good enough

Offline Etches

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Re: Disconnected the blue temp sender, revs dropped - not good?
« Reply #8 on: July 04, 2014, 05:34:21 pm »
Tbf mate you'd be best off using a mate at a garage's gas analyser. Cant tell you how much of a difference it made when it was set up correctly.


Offline AdzCM

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Re: Disconnected the blue temp sender, revs dropped - not good?
« Reply #9 on: July 04, 2014, 06:10:58 pm »
Idle speed is just adjusted on the side of the throttle body. It's the co pot which controls idle fueling that is best set up with a gas analyser but doesn't need to be can just set resistance (can't remember figure somebody will know) and go by that. Not perfect but good enough

I know you adjust the screw on the back of the throttlebody, but to get it to the exact idle speed would be quite difficult when the rev counter in rather large increments?

Etches, I know of a guy nearby who has a gas analyser so I think I'll get it set properly.

Out of curiosity though, I've read that people measure the resistance across pins 1 and 3 on the co pot - but where on the co pot do you adjust? I've never checked this or have really had the need to do so until now, and cannot find anything on here that explains how to do it lol [haynes manual included].

Thanks for the help/advice guys!

Offline Etches

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Re: Disconnected the blue temp sender, revs dropped - not good?
« Reply #10 on: July 04, 2014, 09:16:57 pm »
There is a little cap which is blue from the factory, shows a flat screw which you turn to increase or decrease the resistance. Have you measured the resistance on it now?

Offline AdzCM

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Re: Disconnected the blue temp sender, revs dropped - not good?
« Reply #11 on: July 05, 2014, 01:17:09 pm »
There is a little cap which is blue from the factory, shows a flat screw which you turn to increase or decrease the resistance. Have you measured the resistance on it now?

Does that little blue cap come off to show the screw beneath it? Because the little blue cap on mine does not want to come off and I'm unsure if its meant to until you say otherwise haha. Last thing I want to do is break it.

I measured the resistance and got 1114ohms which is a little bit more than 550-650 lol..... why would it be this high? Am I doing it right? If it had been set at 650 before, then why would it ever change? Especially to a resistance nearly twice of what its meant to be...

Adrian


Offline Etches

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Re: Disconnected the blue temp sender, revs dropped - not good?
« Reply #12 on: July 05, 2014, 01:21:57 pm »
Well mine snapped off , its only a cover anyway

Offline AdzCM

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Re: Disconnected the blue temp sender, revs dropped - not good?
« Reply #13 on: July 05, 2014, 01:33:27 pm »
Well mine snapped off , its only a cover anyway

Got it off - I've adjusted the screw clockwise 270degrees and the resistance has only gone down to 1020ohms - is this normal and will I keep on turning it until 650? Just don't want to break it ;)

Thanks man

Offline Etches

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Re: Disconnected the blue temp sender, revs dropped - not good?
« Reply #14 on: July 05, 2014, 01:35:28 pm »
Keep going mate, I think mines on around 800  . 550-650 is normal. Mine was just to keep it cooler whilst idling plus my emmissions pass the Cat Test even without one