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[05omegav6]

Pump operates at a fixed pressure.So running it for x amount of time will force y amount of fuel into the pressure regulated fuel rail...

As soon as the crank/cam sensors tell the ecu that both ends of the engine are moving at the same speed, it fires up the fuel pump permanently

[sjc]

I must be misunderstanding this... Surely if both ends of the engine are NOT moving at the same speed then you have far more serious issues than the fuel pump? 

[terry paget]

Begging your pardon, Al, I have just done a quick test. I removed the fuel hose from the manifold and had a friend turn on the ignition; no fuel emerged.  He then cranked the starter and fuel gushed out.

[zirk]

Begging your pardon, Al, I have just done a quick test. I removed the fuel hose from the manifold and had a friend turn on the ignition; no fuel emerged.  He then cranked the starter and fuel gushed out.

Now try doing the same thing with a faulty Crank Sensor. 

[terry paget]

Begging your pardon, Al, I have just done a quick test. I removed the fuel hose from the manifold and had a friend turn on the ignition; no fuel emerged.  He then cranked the starter and fuel gushed out.

Now try doing the same thing with a faulty Crank Sensor. 

I don't have a faulty crank sensor to hand, though reading reply 7 I would expect the same result.

[Kevin Wood]

I don't have a faulty crank sensor to hand, though reading reply 7 I would expect the same result.

It does depend on the engine, though. Some Omegas prime the fuel pump for a few seconds when the ignition is turned on, whereas others won't activate it until the crank sensor indicates the crank is rotating.

[zirk]

Begging your pardon, Al, I have just done a quick test. I removed the fuel hose from the manifold and had a friend turn on the ignition; no fuel emerged.  He then cranked the starter and fuel gushed out.

Now try doing the same thing with a faulty Crank Sensor. 

I don't have a faulty crank sensor to hand, though reading reply 7 I would expect the same result.

2.6 and 3.2 probably wont spark or pump fuel when being cranked with a faulty Crank Sensor, which is what the OP has, if that was the question.

On the earlier 3.0 Ive had some that do and some that don't with a faulty CS.

A faulty CS can throw some funnies, and don't allows through a Code, I've replaced CS before and they can fire up straight away, then Ive had others that will need the CS Code clearing before wanting to fire up.

[terry paget]

I assumed that the fuel pump not running unless the engine was turning at 400rpm was a safety measure. However, I have bump started a 2.0, it fired easily after a very brief tow. Maybe a much lower rpm is required.

[Kevin Wood]

The usual sequence when firing up a fuel injected engine is that the fuel pump runs for a couple of seconds to "prime" the fuel system when the ignition is turned on, then it switches off until crank rotation is detected. Once running, it will switch off again if the crank stops rotating for any reason.

Once the engine has stopped, it will retain fuel pressure for a long period if not indefinitely, since the only way the fuel pressure can escape is via the now closed injectors or FPR (which closes once flow from the pump stops) and return path back to the tank.

So, bump starting a dead car is possible either because there is likely to be enough energy in even a discharged battery to kick the fuel pump over for a couple of seconds or, failing that, because the fuel rail remains pressurised anyway.

Some Omegas (non-dbw V6s and some of the 4 pots, IIRC) don't use a priming procedure, so the fuel pump doesn't run until cranking is detected. I know for a fact that a 3.2 runs the fuel pump for a few seconds when the ignition is switched on.

[terry paget]

The usual sequence when firing up a fuel injected engine is that the fuel pump runs for a couple of seconds to "prime" the fuel system when the ignition is turned on, then it switches off until crank rotation is detected. Once running, it will switch off again if the crank stops rotating for any reason.

Once the engine has stopped, it will retain fuel pressure for a long period if not indefinitely, since the only way the fuel pressure can escape is via the now closed injectors or FPR (which closes once flow from the pump stops) and return path back to the tank.

So, bump starting a dead car is possible either because there is likely to be enough energy in even a discharged battery to kick the fuel pump over for a couple of seconds or, failing that, because the fuel rail remains pressurised anyway.

Some Omegas (non-dbw V6s and some of the 4 pots, IIRC) don't use a priming procedure, so the fuel pump doesn't run until cranking is detected. I know for a fact that a 3.2 runs the fuel pump for a few seconds when the ignition is switched on.

Thank you. Now all is clear. I did my test on a 2.5, non-dbw. I suspect I got my belief from the Senator Haynes manual. The dead 2.0 I bump started had a failed starter, it would not jump start. I suppose OP filled his garage with petrol
from the priming dose.