1.6 Turning Over But Won't Start

[Cameron 16]

I'm having starting issues!

 

It's had an intermittent starting fault since I bought it, but now it's turned into a permanent starting fault. It will turn over happily for hours and hours but nothing will happen. I've just been out with my multimeter trying to check some things out and sussed out the following:

 

1 - No voltage at the fuel pump under any conditions

2 - Fuel pump has continuity across the supply - i.e. across the +ve and -ve wires from the car loom - when the pump is disconnected

3 - Fuel pump occasionally starts running on key-off

 

2 and 3 in particular have me completely stumped! I would have thought that there should be no continuity across the +ve and -ve supply wires otherwise it would indicate a short somewhere.. this disappears when the tachy relay is unplugged so I'm not sure if it's normal. 3 is a massive WTF!? Why would the fuel pump run when I've turned the ignition off and removed the key!?

 

Hope someone can help shed some light.. is this a common symptom of a buggered tachymetric relay? The wiring on this car is a complete nightmare so I wouldn't be surprised if the fuel pump took it's live off an indicator due to epic bodging..

 

(Ps I know there's several tachymetric relay threads, but none of them seem to have the key-off issue!)

Edited November 21, 2011 by Cameron

[Anthony 1,000]

First things first, I'd just bypass the tachymetric relay and see if the pump then works and the car starts - just link the three thick wires on the relay plug together (brown is the feed, one white is the fuel pump, and one is the injectors)

 

If it does, then replace the relay and see if that then addresses the randomly powering up the pump issue as well.

 

If it doesn't, then check the wiring and that any alarm/immobiliser is working properly.

[Cameron 16]

No joy.. the pump does run when I bypass the relay but it won't start.

 

There isn't an immobiliser fitted either, I removed that over the summer.

Edited November 21, 2011 by Cameron

[Anthony 1,000]

Do you have a spark? The relay is triggered the same way as the rev counter by the negative pulse from the coil, which is also what gives the ECU it's timing signal - thus no spark means no fuel injection, no relay energising and no start.

 

It's the only obvious link I can see between a non-start and a non-activation of the relay - although even then, the relay should also activate when there's power on the starter solenoid wire assuming that the wiring hasn't been chopped/bypassed to "fix" a starting issue.

[Cameron 16]

I can feel the relay click in my hand when it turns over, the last time I checked it (a few months ago) it had a spark but it won't hurt me to check again.

[Cameron 16]

So after 4 hours of checking EVERYTHING, it randomly coughed when I was checking that I still had spark after reconnecting all the ignition components again. I popped the spark plug back in and it ran perfectly.. for all of about 30 seconds. After that it wouldn't run again, so I whipped the plug back out and checked for fuel and spark, plenty of spark but no fuel. While I put the plug back in the fuel rail started fizzing, indicating the fuel pump was running, sure enough when I popped my head in it was - with the ignition off!

 

The next time I turned it over it coughed, presumably because there was still fuel pressure, but the pump had stopped. I hot-wired the tachometric relay and the fuel pump whirred, turned it over and it started straight away! As soon as I removed the hot-wire the fuel pump wouldn't run and it wouldn't start, so I'm about 95% sure it's the relay that's at fault.

 

I have a feeling that last night it would have run when I was hot-wiring the relay had I turned it over for longer, so I'll leave it for an hour or so then try it again.

[Cameron 16]

Hotwiring seems to have done the trick so a new relay is on order.

[Cameron 16]

Found a link for new relays in another thread (can't remember which one!), ordered one on Tuedsay afternoon and it got here last night! It now starts every time, fingers crossed it stays that way!

Edited November 24, 2011 by Cameron

[welshpug 1,627]

from Polevolt IIRC