Another non-starter

[nzflash]

Hi all,

Just a quick question about the fuel pump.

In trying to determine why my car won't start I disconnected the fuel rail inlet pipe and piped the petrol into a can. When I turned the ignition on the fuel pump primed for a few seconds and then stopped. Is this normal behaviour or would you expect it to continue to pump when there is no back pressure?

Thanks.

[Classic Chim]

nzflash said:

Hi all,

Just a quick question about the fuel pump.

In trying to determine why my car won't start I disconnected the fuel rail inlet pipe and piped the petrol into a can. When I turned the ignition on the fuel pump primed for a few seconds and then stopped. Is this normal behaviour or would you expect it to continue to pump when there is no back pressure?

Thanks.

The ecu gives it a signal to operate for a few seconds to pressurise the rail.
It only flows constantly when engine is running I think.
Others more savvy will confirm.
Pretty sure it’s Ecu controlled so no engine signal would mean it won’t pump.

[Steve_D]

Yes that is just a fuel pump prime. The pump will only come on again when the ECU sees signals from the coil that the engine is turning over.

Steve

[nzflash]

Thanks guys for the help.

Next step, check the ignition module and coil. It looks to be producing a good spark but looks can be deceiving.

Typical it happens 2 weeks before it goes for full chassis restoration at the other end of the country.....

[nzflash]

So I've had the coil and ignition module checked by an auto electrician and he said they looked fine.

Latest symptoms are:

Fuel pump primes
Car turns over strongly
Engine fires but won't start

When I stop trying to start the car I can hear the fuel pump running before it stops. The fuel pump was replaced a couple of months ago.

Even though there is a spark, I'm wondering if the coil may have degraded can't meet demand.

Any suggestions/ ideas gratefully received.

[Steve_D]

Check you have fuel pressure at the rail not just flow.

Steve

[gamefreaks]

nzflash said:

So I've had the coil and ignition module checked by an auto electrician and he said they looked fine.

Latest symptoms are:

Fuel pump primes
Car turns over strongly
Engine fires but won't start

When I stop trying to start the car I can hear the fuel pump running before it stops. The fuel pump was replaced a couple of months ago.

Even though there is a spark, I'm wondering if the coil may have degraded can't meet demand.

Any suggestions/ ideas gratefully received.

There are two relays in the footwell that run the fuel pump. One fires to prime the system and the other takes over when the car is running.

Try swapping/replacing these. If the car fires up and then dies straight away, its proably priming but the other relay is not working.

[nzflash]

Steve_D said:

Check you have fuel pressure at the rail not just flow.

Steve

Thanks Steve. I haven't measured pressure or flow but when I piped the fuel into a can I tried to stop the flow with my finger and there was no way I was going to stop the flow. So rudimentary I know but I'm confident fuelling is ok.

[nzflash]

gamefreaks said:

There are two relays in the footwell that run the fuel pump. One fires to prime the system and the other takes over when the car is running.

Try swapping/replacing these. If the car fires up and then dies straight away, its proably priming but the other relay is not working.

Thanks gamefreaks. I'll take at look as suggested.

[Steve_D]

gamefreaks said:

There are two relays in the footwell that run the fuel pump. One fires to prime the system and the other takes over when the car is running.

Try swapping/replacing these. If the car fires up and then dies straight away, its proably priming but the other relay is not working.

Sorry but that is not correct.
There are 2 relays but they perform different functions. The fuel pump relay does all aspects of fuelling, prime and running.

Steve

[gamefreaks]

Steve_D said:

Sorry but that is not correct.
There are 2 relays but they perform different functions. The fuel pump relay does all aspects of fuelling, prime and running.

Steve

What is the function of the relays? I was under the impression that one relay is used to prime the system (fuel pump runs for a few seconds when you turn the key) and then the other relay is activated to run the pump once the car has fired?

I had exactly the same symptoms as OP a few years ago and replacing the relays cured it.

[Paulprior]

Fully agree with SteveD, one relay for fuel pump, the other for ignition

[Steve_D]

Paulprior said:

Fully agree with SteveD, one relay for fuel pump, the other for ignition

Again sorry no these relays do not have any connection to the ignition system.

The first relay often referred to as the main or ECU relay is triggered by the ECU (Pin 12) when the ECU sees an ignition +12v supply at pin 15.
Input to pins 30 & 86 is permanent +12v from fuse 2.
Outputs are:-

• Supply into the ECU pin 2.
• Supply to injectors banks 1 & 2, MAF, Fault diag. connector (not the one used by RoverGauge).

Second relay is known as the Fuel Pump relay and is triggered by the ECU (Pin 16).
It gives a 2 second pump when it first sees the ignition then goes off. It turns the pump on again when the ECU sees a 'spark pulse' from the coil at ECU pin 39 indicating the engine is turning over.
Input to pin 30 is permanent +12v from fuse 13.
Input to pin 86 is ignition switched +12v from fuse 12 via the immobiliser.
Outputs are:-

• Left and right lambdas (if fitted)
• Purge control solenoid, fuel pump (via immobiliser and inertia switch.

Steve

[gamefreaks]

Every day is a school day. Thanks Steve_D

[nzflash]

Had a fellow chimaera owner come over today so we could swap the coil and ignition module over. The car started first time... happy days

[Classic Chim]

nzflash said:

Had a fellow chimaera owner come over today so we could swap the coil and ignition module over. The car started first time... happy days

Excellent but which one was at fault? Lol
With the way new parts are these days I’d be inclined to swap one thing out at a time ( pita) I know but at least you know which or both were playing up.
Coils and modules can be fine until they are heat up so that’s the acid test to me getting it hot.

[nzflash]

Since I'm in New Zealand I ordered a coil and ignition module. I'll determine which is at fault when they arrive. I suspect the coil.

I'm just happy I've tracked down the issue...

[Classic Chim]

nzflash said:

Since I'm in New Zealand I ordered a coil and ignition module. I'll determine which is at fault when they arrive. I suspect the coil.

I'm just happy I've tracked down the issue...

I got you.

[Zener]

My money is on the ign module place your bets

[Penelope Stopit]

Will place a bet if the OP live streams the changing and testing of the parts