Efi Help

[Guest Flea]

Quick question about the fuel pump!

 

I have gone for the intank pump from the dohc sierra (not that this matters for the problem i have).

 

My understanding of the pump is that when ever the ignition is turned on the pump should come on for about 4 seconds, I believe it is supposed to push through 400ml of fuel.

 

My problem is that the pump doesn’t always come on, is this correct?

I know the pump works fine. I checked to see if there is any power where the pump connects and again this is intermittent.

 

Is this normal?

If not has it happened to anyone else?

Can any one help PLEASE!!!!!!!

 

Thanks

 

From a depressed RH builder

[Les Welsher]

Flea,

I just checked mine out.

If I switch on the ignition the pump runs for just over 1 second then stops.

If I turn the ignition off then straight back on, nothing happens.

After several attempts I found I had to leave the ignition off for 5 seconds before switching it back on again, then the pump runs for 1 second again then stops.

Obviously there is something in the pump wiring giving this time delay, most probably a fuel priming feature.

This must be what is giving you the intermittent power supply at the pump.

 

The pump must work ok when the engine is running otherwise my car would have cut out many miles ago.

 

Les

[Guest Flea]

Now thats the kinda answer i wanted to hear!

that it happens to other people and it is supposed to

 

cheers

[Guest Flea]

Well it turns out i had a problem after all with my wiring. After spending 3 days making it look nice and tidy for Mr SVA i only went and forgot a bloody earth. (how stupid did i feel)

 

well all is good now and fuel pump works fine (this was the intank option)

 

Got up this morning (feeling very brave) and set out to make her BRUMMMMMM. just needed a few things alternator bracket, fan belt, radiator, newcoil lead and some fuel (kindly taken from wifes car).

 

triple checked the oil/water/fuel, yes i was looking for excuses not to turn the key but eventually ran out so closed my eyes, turned key to number one position, then to number two (the fuel pump springs into life) turned it to number three!!!!!!!!!!

 

 

 

OH MY GOD

 

 

WHAT A NOISE

 

 

IT WORKS

 

 

YEAH BABY!!!!!!!!!!!!!!!!!!!!!!!!!

[Guest Guy]

Good on you Flea,

 

I've got a question,

 

I too have an EFI but with external pump mounted just below the Sierra tank,

 

When I go to start it for the first time, how long does it take to get the first drips of fuel to the engine? it's a long way from the pump, do I have to bleed it or anything?

[Guest SteveL]

Hi Guy

 

It won't take that long at all to get the pipework full. I did some experiments with the pump when I thought it might not be working, and it nearly emptied my tank before I realised! No need to bleed anything.

 

Steve

[Guest Mr Pid]

Yeh you will have to make sure the pump has pumped the fuel right up to the injection rail.

 

Where the inlet fuel line reaches the rail i think it is bolted on using a banjo bolt onto a nut (about 19mm i think) if you loosen this a bit, fuel should leak out if it is all present and correct.

 

Careful of too much fuel leakage though.

 

Stu

 

[Guest Ant]

If there's fuel in your return line then the fuel rail must be full. That's how I checked it. So long as the pipes are connected the right way around there's no need to test it really unless you suspect a fault.

 

Ant

[Guest Flea]

You are all correct with regards to fuel.

As I never asked the question I took the fuel line from the outlet of the fuel filter (this is fastened under the plenum chamber) and in no time at all I had fuel everywhere (good job I don’t smoke but at least I new the pump worked).

 

Fastened it back on and away it went. I think there was some air trapped in because for the first minuet or two if you looked at were the return comes out instead of being a nice steady flow it was a little erratic but soon settled down.

 

Well as I have your undivided attention can anyone give me any advice on why at low revs she idles a little rough?

If I let it idle at anything below 2000 rpm then it seems to drop between 850 and 1500 rpm, not erratic but more like a pulse up then down, up the down, up then down, you get the picture.

 

So it’s over to the floor for suggestions look forward to your replies

[Guest Ant]

Possibly a dodgy potentiometer in the throttle sensor. Take the 3 wires off it and measure the resistances across any two as you open and close the throttle. Call them 1, 2 and 3. If the resistance between 1 and 2 is unaffected by opening the throttle then 3 is the ground pin. Then look at the resistance between 1 and 3, and then between 2 and 3. As you open the throttle one resistance should go up, and the other should come down. If you want some reference numbers I can do the test on mine if you like. However, a dodgy pot' usually means that the resistance will spike as you turn it - either to infinite (no circuit), or to zero (straight connection). If you've got one of these spikes then that will almost definitely be the problem.

 

BTW - digital voltmeters are useless for this test because they don't update fast enough. You need an analogue one. If the needle flickers as you open the throttle then that's your spike! If it's smooth then your pot sensor is fine.

 

Worth a try.

 

Ant

 

PS - Trouble at idle is usually the idle by-pass valve. I'm assuming you're trying to hold steady revs away from idle here.

[Guest Flea]

Sorry if didn’t explain myself properly but the problem is when it is at idle, not when I try to hold the revs away from this (although its still only smooth when at 2000 or more).

 

will perhaps have a look at idle bypass valve first especially as I don’t really no what the potent thingy sensor is/does or even were it is but sounds like you no what your talking about.

 

Will have to get my bible out (Haynes manual for sierra) and have a butchers.

 

Thanks for help and will let you no.

 

Flea

[Guest Mr Pid]

When i worked at a dealership the most common cause for running problems at idle was the potentiometer. Although doesnt necessarily mean that it is the only cause.

 

Im sure its fitted next to the inlet of the plenum chamber, cylidrical looking thing lying horizontal with a three pin plug at the other end, only two bolts holding it on easy to change. If you do change good idea to spray loads of carb/brake cleaner inside to clean it up a bit. Dont forget to re-seal it, i think there may be a gasket.

 

One other thought is that as you have been having grief with fuel, are you sure you have a steady supply of clean fuel being pumped into the engine- If the fuel is old - dirty - mixture level to rich/poor - clogged fuel filter- or it still fluctuates through the lines this may cause running problems.

 

Hope this helps a little

 

Stu

[Guest Flea]

Potentiometer, so that’s what that thing is, that’s in the way when you need to remove one of the rocker cover bolts.

 

I have taken this of several times but never replaced the gasket (have ordered on though)

 

More than likely this will be the problem.

 

Fantastic

 

Thanks very much

 

Not sure that the wife would say the same as it now means that I will be of to the garage again this evening.

[Guest Ant]

The idle by-pass is the cylinderical thing above the rocker cover attached to the side of the inlet manifold. You should give it a new gasket because air leaks here will cause idling problems too.

 

The pot which I was on about is smaller, a little lower down, on the shaft which goes through the throttle. The shaft at the other end has the lobe on it where the accelerator cable attaches to.

 

Ant

[Guest Flea]

Well thanks for help with this stuff.

 

I am a little baffled (not like my RH stainless tank) as to which part is which but I am sure all will become clear when i have a look.

 

Cheers