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mechanicaltone, Mechanic
Category: Car
Satisfied Customers: 233
Experience:  Hi my name is Tony. I have been a qualified mechanic for over 12 years.
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Vauxhall Estate: Cold start problems Vauxhall Astra 1999 1.6

Resolved Question:

Cold start problems Vauxhall Astra 1999 1.6 8valve
Petrol pump relay not tripping in when ignition turmed on. Voltage on relay coil shows 12v both sides and 12volts to main input wire but relay switch not closing.
Petrol pump can be starte by jumper wire to both wires to petrol pump for a few seconds and relay switch connects then all ok.. Once engine has been running briefly car starts normally.
When car is starting normally the relay switch only trips in when ignition switch turned to start position i.e. actuate starter No problems starting when warm weather or engine warm and engine runs fine.
Relay has been changed for new and new engine temperature sensor on manifold has been renewed
I have not had car connected to diagnostics but I suspect possible ecu fault. ECU bulb blown so no ecu light showing
This car is getting on a bit but has only 80000 on the clock and apart from a suspected blown head gasket, I can fix this myself, is in very good condition and an excellent work horse. However if ecu faulty the cost of fixing both leaves me in a bit of a quandry
Submitted: 4 years ago.
Category: Car
Expert:  mechanicaltone replied 4 years ago.
Hi, the fuel pump relay is run off the ignition. Sound like you might have a fault in the ignition switch or a bad wire somewhere in the circuit. If there was a issue with the ECU, the car would not start in any position the ignition switch is in.
Expert:  mechanicaltone replied 4 years ago.
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Customer: replied 4 years ago.
A fault in the wiring was my first thought. How ever I am mystified as to why the relay coil wires show 12 volts both sides but the relay switch is not closing under cold conditions.when the ignition switch is turned on.
This problem has been ongoing throughout the cold weather and sticking a fan heater under the engine to lift the temperature under the bonnet on frosty mornings has always solved the problem. I note that one of the relay coil wires runs through the ecu hence my suspicions that there might have been a fault in the ecu
S a matter of interest I experienced a similiar problem, would start and then cut out as sson as switch turned back to run position, on a VW Golf years ago which turned out to be a burnt contact on the ignition switch. Problem only solved after contacting VW who informed me that this was a common proplem on that model
Any way its looks as if checking the wiring is the first option or a bit of jury wire rigging just to start the car on cold mornings, Button on the dash board wired direct to the petrol pump??? probably not reccomended??
Expert:  mechanicaltone replied 4 years ago.
Hi, on the relay you should have a trigger wire which receives power when you turn the key to start the car and should have a wire with permenent power. If you bypass the circuit you my have a quick fix but could be doing more damage in the long run. What ever the problem is its only going to eventually get worse and you might not be able to start the car cold or hot. It is highly recommended you don't run straight power to fuel pump for safety issues.

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Customer: replied 4 years ago.
The relay does show 12v on the the permanent side of the relay coil. The coil trigger wire runs into the ecu. I have not yet tested this to see if this is showing the correct voltage on start up as we have not had any cold mornings i.e. close to freezing and below. The mystery is to me that this fault only occurs on cold mornings and be cured simply by warming up air under bonnet, hence my suspicions of a fault in ecu. It would appear to me that I may have to bite the bullet and have the car tested on a diagnostics machine.
Expert:  mechanicaltone replied 4 years ago.
A diagnostic machine will only tell you if a fault has been logged what you need to do is to get the car tested when it's cold and all the wires traced and tested to find out where the short circuit is at the time. It's not a easy fault to find so you might need to get a professional to carry out diagnosis on the issue.

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