Fuel Injection fuel pump problem.

[Poohbear]

Help!!!! x( x(

I've got a very weird problem with my Fuel Injected Rover V8 (Pilgrim Sumo). Couldn't get it started, then today I needed to take the fuel tank out to fit seat belts and do some other bits. This meant disconnecting the fuel pump.

I forgot I had done this and tried to start the engine - fired up straight away, and ran wonderfully. I then remembered that the fuel pump was disconnected, so turned off and re-connected it - wouldn't start. Then re-wired the fuel pump directly into a supply through a switch so I could turn it on and off manually.

Fuel pump switched off, engine runs perfectly, but as soon as I turn the fuel pump on it dies.

WHAT IS GOING ON??????? ;(

Cheers,
Steve

"Oh bother!", said Pooh.

[kev]

No way on this planet can a EFI RV8 run without pressurised fuel in the fuel rail. The injectors need c.35psi of fuel when they open to get the spray pattern of fuel for the engine. Somehow something is pressurising the fuel rail when the fuel pump isn't wired in. Nothing in the injection system at the engine end can do this so double check the wiring at the pump; have you any other injection pump in the circuit? don't forget the fuel pump relay is on a timer if the engine doesn't start and from memory switches the earth side. Double check the wiring.

Kev

[Philip]

Totally agree with Kev, thats impossible, unless the fuel supply was still pressurized, but it would soon stop, maybe run for a few seconds. What system is it, flapper / hotwire? When you wired in the switch did you just piggy back the supply to the existing cable? The fuel pump should be fed via a relay that goes through an inertia switch to the pump.
Phil

[Philip]

Just another thought, If the fuel tank is from Pilgrim you will have trouble with it. The fuel feed comes out of the top, should come out of the bottom as the pumps cant prime themselves very well, they need a hea of pressure. Also pump needs to be low in comparison to the fuel. I guess your running low on petrol, when pump runs the returned fuel is bubbling and splashing into the tank causing the pump to pickup a lot of air, so it wont run well. Then when you turn the pump off the air settles and it will run on the pressurized fuel for a bit. Fill it up with petrol and try it, better still get another tank with a built in catcher and with fuel feed at the bottom of the tank,
Phil

[Poohbear]

That's exactly what I thought, but it must be running off the residual pressure. It will still run for a minute or so with absolutely no voltage supply to the fuel pump - and there is definitely no other fuel supply.
Not a problem with the Pilgrim tank, as I'm not running from that.
Checked the fuel pressure, and the regulater is fine, giving around 30psi - the RV8 manual says the UK spec one should be 26-36psi.
However, engine will only run when the fuel pressure drops - is this a possible indication that an injectore is stuck open, so once the pump runs there is too much fuel getting through? Perhaps one of the temperature sensors is bust, so forcing the codl start injector to stay open?
Any ideas how I can check these other than the resistance checks it says in teh manual, which all appear OK?
Any other broght ideas would be great as I am completely stumped on this one.

Cheers,
Steve

"Oh bother!", said Pooh.

[Philip]

Is it a flapper type? Fuel pressure should be 36psi with engine not running but pump running. If your injector had failed when open then you wouldnt be able to get it to run at all as pressure would drop immediatly and flood the cylinder that the injector was open on, anyhow, that would be a very rare fault. I doubt its the CSI, disconnect it if you want to, its only used for around 3secs when engine really really cold, fed from TimerTemp sensor. Throw the CSI away if you want, they can leak and that is a bit dangerous.
Phil

[Philip]

Has it ever ran? Is is it a flapper or hotwire? What exactly does it do when the pump is connected up?
Phil

[kev]

This is a strange one, first off where are you measuring the fuel pressure?, the flow should be from the pump then filter, then inlet to fuel rail, then pressure regulator then return to tank. The fuel pump will run for a few seconds until the engine starts then it runs continuously. Agree with Philip about the csi, I junked mine and it didn't make a difference to startup. What pressure is in the rail when the engine runs? What have you done to the engine? the flapper type system should compensate for changes to the engine as it works as an air mass meter so putting in a KN filter for example should still let the engine work ok, ditto a different cam, although you would need to play with it to get the best performance. If no joy try calibrating the throttle pot as this is a potential problem area, does the air flap move freely?

Kev

[Philip]

Could be that the coolant temp sensor has gone open circuit. It should be 2.4-2.6Kohms at 20C - 5.7-5.9Kohms at 0C 500-700Ohms at 60C This would make it run rich and add too much fuel. Really need to know what system it is and whether it has ever run. The throttle position pot should be 0.35V +-0.025Volts at throttle shut position on wires green and red,
Phil

[Poohbear]

Hi Philip,

This sounds promising. I'll check it out this morning.

The only things I've done to the engine are clean it, and replace the air filter, as the original wouldn't fit under the bonnet. It ran fine when I first fitted the fuel pump, although a bit rough with no exhausts. It was then left standing for about 6 months while I fitted the body etc. When I next tried to start the engine (a couple of months back) it wouldn't go at all, and it's only over the last few days whilst running without the fuel pump that its started.

The fuel route is exactly as stated - pump, filter, fuel rail, pressure regulater, return to tank. I measured the pressure by putting the gauge in place of the cold start injector.

I don't know what sort of system it is - how do I tell? It was straight out of a SD1 Vanden Plas, and it's got an air flow meter, to which I've added a K&N air filter.

Cheers,
Steve

"Oh bother!", said Pooh.