Fuel Pump power

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Donovan
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Fuel Pump power

Post by Donovan » Mon Feb 17, 2014 9:19 pm

Have had this problem raise it's head a couple of times in the past few weeks and not sure of two things that might be possibly causing it.

What happens is I go to drive the car, disarm the alarm turn the ignition on and crank the motor over and all it does is turn over. Usually when you turn the key on you hear the pump in the tank prime the system, but you don't get that in this case. Have pulled out the wiring to the pump when this is happening, and it is simply not getting any power rather than a fault of the pump.

I am suspicious of the alarm system and pretty sure it is that, but thought I would ask the question before ripping it all out, and replacing it with something else. The other thought was maybe the ECU was supposed to be sending some signal somewhere to prime the pump, but my money is on the alarm at the moment.

WideOpenThrottle
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Post by WideOpenThrottle » Mon Feb 17, 2014 9:27 pm

Recently pulled out a pump that burned out and had brown ooze over it..definitely shat itself..so don't discount the pump!

in order of possibility...alarm-pump-relay-connection.
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Donovan
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Post by Donovan » Mon Feb 17, 2014 9:30 pm

One of the times that it crapped out on me, was at Rod Millen's hill climb, and one of the guys there was an auto electrician, so he was checking the power to the pump, and the relay's, so the relay's are ok.

WideOpenThrottle
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Post by WideOpenThrottle » Mon Feb 17, 2014 9:31 pm

Might be ECU too!?
1989 NA 1650
1998 NB 1800
2005 NC 2000
1990 Landcruiser
Surfboard
Push-bike
Hiking shoes

WideOpenThrottle
I have stars, you haven't. Deal with it
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Post by WideOpenThrottle » Mon Feb 17, 2014 9:33 pm

Donovan wrote:One of the times that it crapped out on me, was at Rod Millen's hill climb, and one of the guys there was an auto electrician, so he was checking the power to the pump, and the relay's, so the relay's are ok.
Wouldn't the pump be going then if there was power to it?

You can have power to the pump but if the pumps knackered...no fuel
1989 NA 1650
1998 NB 1800
2005 NC 2000
1990 Landcruiser
Surfboard
Push-bike
Hiking shoes

Donovan
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I only think 5.
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Post by Donovan » Mon Feb 17, 2014 9:42 pm

The relay was ok, but there was no power to the pump, so the pump isn't going to go if there ain't power, so pretty sure it isn't the pump, plus the pump is only a year old.

Snapfrozen
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Post by Snapfrozen » Tue Feb 18, 2014 8:25 am

Does the relay have any dry solder joints? Can be a large problem in late 80's, early 90's Jappas as they used "Environmentally friendly" solder that cracks and goes brittle

Donovan
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Post by Donovan » Tue Feb 18, 2014 12:48 pm

Can't see any, the relay's tested out ok when the auto sparky had a quick look.

GRUVBB
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Post by GRUVBB » Tue Feb 18, 2014 2:37 pm

The electrical diagnosis is rather vague..... You say that the relay is ok.
There are two sections that need testing. The first is the coil. When this is powered it forces the contacts to change state.
The relay can be healthy but does not mean that it is working..... Is there power on the coil? Are the contacts changing state?
Is there power available at the common terminal of the relay contacts? Is the power coming through the contacts and then out the switched side of relay?
Is this power then reaching the fuel pump?
You can check the pump by placing a direct fused feed onto it. You will then know if the pump is faulty. Use a fused supply so that if there is an issue it does not sustain any wiring damage. The fuse is there to protect your wiring. If there is a short then a large amount of amps can flow which will be over the capacity of the conductors which will overheat and fry the insulation off.
You can check the coil of the relay with a multimeter. Not sure what relay you are using but would probably expect a reading of about 10 kilohms over the coil when connected to the meter. ( a trainspotter will correct me on this value)
The switched contacts should be 0.0 ohms over the normally closed contacts and open circuit over the normally open. When the coil is powered and the contacts change state the values will be the other way around as the normally open should now be closed and the normally closed should open. This can be tested on a workbench or in situ. Just disconnect your circuits from it while testing so as not to be reading other impedances.
Before you test resistance values you should test resistance between the two leads of the meter. This should be 0.0 ohms if leads and meter are healthy. A dodgy lead can have broken conductors which creates more resistance and a higher reading. The lead resistance is subtracted from the test resistance to give you the actual resistance reading.
Sometimes a little knowledge is worse than no knowledge.... Someone with no knowledge will seek expert advice whereas some who think they know can do something and not really understand what they are reading or doing... A mechanic mate of mine told me that once and k have always taken it on board. I am not criticising anyones efforts at diagnosis. I want yeou to get your issue sorted. If you need a hand or a quality meter i am available to assist if needed. Im off work due to a hernia op last week so sitting at home reading forums. Hence the time to spiel on..... Im in Te Atatu if you want to PM me for a phone number or advice. :idea:

Donovan
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Post by Donovan » Tue Feb 18, 2014 10:26 pm

Thanks for the offer and the reply GRUVBB, unfortunately can't take you up on your kind offer, as the car is still not starting up.

Have decided to throw it on my transport trailer (when the last bugger that borrowed it returns it) and going to take it to an auto sparky as there is a couple of other things I should get sorted out as I am sure those plonkers in Hamilton shorted out a bit of gear at their ham fisted attempts to do the wiring themselves.

Will get the alarm pulled out, as it is driving me up the wall, so just going to see if I can get the central locking/boot release setup with a remote, and just get a GPS tracking unit in the car

Donovan
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Post by Donovan » Wed Feb 26, 2014 10:54 am

Turned out to be a relay under the dash that I missed, that was dying off and on, all replaced and up and running.

GRUVBB
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Post by GRUVBB » Wed Feb 26, 2014 11:59 am

Donovan wrote:Turned out to be a relay under the dash that I missed, that was dying off and on, all replaced and up and running.
Good news that it was only a cheap component...... Thanks for keeping us all updated..... I have a feeling that there are many people with an interest in your car. I am one of them and looking forward to seeing it up close some day. :D

Donovan
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Location: Auckland

Post by Donovan » Wed Feb 26, 2014 12:09 pm

GRUVBB wrote:
Donovan wrote:Turned out to be a relay under the dash that I missed, that was dying off and on, all replaced and up and running.
Good news that it was only a cheap component...... Thanks for keeping us all updated..... I have a feeling that there are many people with an interest in your car. I am one of them and looking forward to seeing it up close some day. :D
Happy to go for a drive around AKL anytime that I have free if someone wants to take a gander at the car, it's always an excuse to take her for a drive.

KSCRIM
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Post by KSCRIM » Fri Apr 11, 2014 11:02 pm

I had an intermittent pump, let me down twice this year. Eventually found the problem, a faulty wire connector inside the fuel tank !.
Story here http://forum.miata.net/vb/showthread.php?t=535776
Kevin 2010 NC PRHT. (98 NB6C sold)

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