Anyone here know about fuel injection?

[mr henderson]

I'm currently working on a car that has been fitted with the DOHC engine from a Sierra, mostof the original loom and bits have been used. The FI is controlled by an ESCIV.

I can't get it to start. It did run for a few seconds when I first tried it, but since then, nothing. I've tried all the usual stuff. I'm getting a good spark at the coil to distributor lead.

When I disconnect the fuel feed to the fuel rail and direct the pipe into a jar,then operate the ignition, there's an initial spurt of fuel, which then slows right down. I think maybe this is the action of the fuel damper?

Anyway, anyone got any ideas?

[Bonzo]

Hi
Probably not best placed to give advice on the workings of the EFI system. Carb & dizzy with points dinosaur !!

But I would imagine if you disconnect the fuel rail feed pipe & turned the igniton on, you would get a powerfull constant flow of petrol. This has been the case when I have checked for fuel in the past on an electric pump system.

I may be wrong, but I think the fuel pessure regulator is connected to & part of the fuel rail.

Possible fuel pump fault ??

I have known this type of symptom to be caused by a poor earth connection at the fuel pump.

I hope you get it sorted. OK

[mr henderson]

Originally Posted by Bonzo

Hi


But I would imagine if you disconnect the fuel rail feed pipe & turned the igniton on, you would get a powerfull constant flow of petrol. This has been the case when I have checked for fuel in the past on an electric pump system.

This has been my experience too, but although the Sierra manual doesn't cover that particular engine, it does mention a fuel flow damper on the output of the fule pump, so I think maybe as there is an initial surge, maybe the damper comes into effect to slow it down?

[Simon_K]

I am no expert, but it sounds like the fuel pump is loosing a signal (voltage) after cranking has stopped? Where is the fule pump getting its supply?

Are you able to test this?

Another factor to look into is the crash fuel cut-off switch.

Is it still wired in? If not, how have you bi-passed it?

I hope this has been of help.

[AshG]

a fuel flow damper is used on a mechanical pump system as the pump speed changes with revs the damper restricts over fueling by returning extra fuel to the tank.

With efi there is a fuel pressure regulator on the fuel rail. The electric pump runs at a constant speed producing well over the required pressure. (usually about 2.5 to 3bar is all that is required ). What the fpr does is detect the over pressure in the rail and opens to varying degrees allowing the excess fuel/pressure back to the tank. Keeping the fuel pressure the same throughout the rev range no matter how much fuel is injected.

So in summary a high pressure fuel pump should allways pump at a constant flow with the excess returned to the tank by the fpr. Try another pump on it if you have one. Also check for current drop on the motor.

There are non return injection fuel systems out there with variable high pressure pumps but i dont believe the sierra lump to be one of them

[mr henderson]

I must apologise for not comng back to this thread with an update. Amongst the various things I tried was a new set of spark plugs. The situation before fitting them was that the starting was difficult or impossible, and after fitting them starting was prompt and reliable. I'm not saying it was the spark plugs all along, but......

[AshG]

as long as you found the problem thats all that matters. my knowledge of fuel injection systems is somewhat limited to fiat/alfa/lancia. when you have a problem like that any little string of info can be helpfull.

[alga]

Once I tried leeching some fuel off my Civic by disconnecting the fuel rail feed pipe, putting it in a jerrican, and turning the ignition on. However what happened was that I got about 1 second and 50 ml of fuel flow each time I turned on the ignition, then it would stop. Probably the ECU turns on the pump on start to pressurise the system, but later pumps fuel only when the engine is running.

[7ishNZ]

It's a safety thing... the pump runs to pressurize the system, then stops till the motor has fired. It prevents the pump from sending 45psi fuel into a fire in the case of an accident...

[flyerncle]

Used to be once upon a time cotrolled by the air flow sensor on Bosch system's but in the days of MAF this is out of the window and as stated now ECM controlled through a relay.