OT: Problem with fuel injection...

[breskit]

This is a little off topic from Cobras, but as you guys are hlaf-way competent mechanics, and this is holding me up with my Cobra, I thought I'd try my luck. Please shout if this is abuse!

I'm having trouble with my main family car (Vauxhall Carlton 2.0i) in that it refuses to start. I've replaced the HT completely (plugs, lead, cap, rotor arm) and fitted a new fuel filter yesterday. When I turn the ignition, the engine turns but will not fire.

Now here's the interesting bit. If I remove the main fuel supply (there is also a return) the engine will run for a little while and then stops when the fuel in the injectors is used up. Re-attach the fuel line and same story, will not start.

Does anyone have any ideas what is happening? There is a fuel pressure regulator but I'm told these rarely go wrong and before I splosh £60 +VAT on a new one, I want to (try to) make sure that I'm replacing the right part.

Help, please.

Tony B

http://homepage.ntlworld.com/tony.breski

[Kelvin]

Hi Tony ( 'Tony from the Web Page )

I only have experiance with my cavalier but if you put your hand on the electronic fuel pump does it vibrate when you are trying to start your car ?
also there is a relay passenger side back of the engine bay which does the power for the pump. Might be worth a try if the pump isnt working.

HTH

Kelvin

[kdavies3]

Tony, I suggest you rig up a fuel pressure gauge at some convenient connection at the fuel rail and check the delivery pressure, it sounds like you may be flooding the system. I don't know where the regulator is on Cavaliers but it may be near the fuel tank or on the fuel rail if it's a more modern model. Also if it's on the fuel rail check the Vac pipe that goes to it is ok.
Just a thought you could try restricting the fuel flow partially using a carefully set pair of mole grips (don't damage the hose though) to simulate the regulators function.
Next thought ( WOW! that's two today) check that the fuel return line is clear, blow down it with an air line you should have bubbling in the tank.

I hope one these gives you a clue.

Makes a change from Cobra chat great as it is!

Kev Davies:+

[kev]

when you switch on the ignition the fuel pump should run for a short while to pressurise the system. When you crank the engine this should restart the fuel pump to provide the constant pressure the injectors need. If you block off the supply pipe this will reduce the presure to the injectors until the pressure gets too low to be injected. The pump will still pump and could well generate up to about 90psi depending on th etype of pump and its rating, so be careful of blocking the pipe. if the engine runs with the pump not supplying fuel and won't fire when the pump is in circuit then this suggests that the system is overfuelling and when the injectors operate too much fuel is being injected and swamping the spark. This could be because the fuel pressure regulator has packed up and too much pressure is being generated in the fuel rail, or something has gone wrong with the injectors control and they are opening for too long again injecting too much fuel. Try to locate the fuel pressure regulator, and disconnect the return to the tank, switch on the ignition and see if there is a steady flow of fuel from the return pipe. (obviously take the necessary precautions !!!). The fuel flow should last several seconds before the pump is automatically switched off. Alternativley put a fual pressure gauge on the fuel rail and read the pressure, I don't kow Vauxhall pressures but I guess it should be around 30 to 40 PSI ish.

If the injector control has gone AWOL it is most likely a sensor gone faulty and providing the EMS with duff data, possible a temp sensor gone OC, or a throttle pot gone the same way, difficult to say.

Is there a strong smell of fuel when you try to start the engine?

Another possibility is that the shock switch that turns off the pump in the event of an accident, has tripped, but this usually means that the engine runs for a short while then stops.

hope this is of some help, good luck

regards
Kev

[mikey]

Have you checked if your fuel cut off switch has clicked off. Its there in case you have an accident and cuts out current to the pump. I had this happen once to me on my Rover. Its a bit like a contact breaker exept it cuts off when it gets a jolt. It may be worth a quick look in your manual to see where it is located and just check it has not activated.
Mike.

[gartrac]

Tony

Had a similar problem turned out to be a bad connection on one of the fuel injector wiring plugs

Make sure that all four injectors have a good connection with the wiring harness

The ECU needs the load of all four injectors across it to work out it's duty cycle if one injector is out of circuit the engine will overfuel

No guarentees but it might help

Pete