Fuel flooding problem...

When turning on the ignition the fuel pump comes on as normal.
There is a squealing noise from somewhere and the engine floods with petrol, take a spark plug out and its soaked, and petrol is pumped out the cyclinder when turned over.
anyone give us an idea where to start looking for the problem? :dontknow:

EDIT: Engine is a 1.8 8v GTi (CIS injection)
Thanks.

This pressure is determined by the primary pressure regulator, situated within the metering head, [the bit above the air filter with the injector hoses on it ].


So thats where you have to look …………Has it been to bits ?

Quite a rare problem as usually all excess fuel would be sent straight back to the tank via the return pipe [also on the metering head] .

Good read here ………..

Domain parking page

It could be a faulty thermo time switch, or leaky 5th injector. Not too difficult to test. Another thing it could be is leaky injectors. Does the car start fine, if its left for a long time (many hours) but not start if left for, say, 10 mins-1 hour?

We thought it might be the metering head (could still be the problem  :dontknow: ) as the control plunger was stuck in. we free'd the control plunger so it moves in and out smoothly.
But still have the problem?

the car aws stood for 10 years, but weve had it running recently, but not correctly. Now the car wont start at all because it keeps flooding.

might a blocked return pipe cause the same problem?

paul_c said

It could be a faulty thermo time switch, or leaky 5th injector. Not too difficult to test. Another thing it could be is leaky injectors. Does the car start fine, if its left for a long time (many hours) but not start if left for, say, 10 mins-1 hour?

No the car wont start at all, cylinders just fill with petrol.  :dontknow:

wats8vgticab said

paul_c said

It could be a faulty thermo time switch, or leaky 5th injector. Not too difficult to test. Another thing it could be is leaky injectors. Does the car start fine, if its left for a long time (many hours) but not start if left for, say, 10 mins-1 hour?

No the car wont start at all, cylinders just fill with petrol.  :dontknow:

I'd unbolt the 5th injector and visibly check to see it operates properly - fires for 4-10 secs while the starter turns, but not once started (if started). It might be jammed on. If it is, then pull the plug and see if its still jammed on.

If the 5th injector checks out okay, then it could be the air flap not aligned with the centre of the cone, making it stick in an 'up' position. Another thing could be a stiff air flap lever, also making it stick.

wats8vgticab said

might a blocked return pipe cause the same problem?

Good idea to check that ……….if the fuel constanly being pumped has no where to go     :dontknow:

…the squealing could be injector pintle 'chatter' - they make that sort of noise - check out
Injector test pdf

…as above, sounds like a blocked return, or metering head - if you had probs with the control plunger….

Could also be an electrical problem believe it or not, i had this with my cabby.

Some bright spark who owned the car before me couldn't be bothered to replace the fusebox when it rotted, so instead wired the rotted part of the fusebox into another side (non rotted obviously) the rotted part of the fusebox happened to be the fuel pump.

But where he re-wired it (or bodged it) it wasn't intermittantly fueling like it should when the engine was engaged, it started fueling as soon as you turned to ignition key to part 1.

So basically, i'd have about half a second to turn the car over and if it didnt catch first time within that half a sec, it would flood.

Strange but true!

checked the return fuel line and it seems to be clear.
The squealing sounds like it is coming from the injectors when the ignition is turned on, so looks like it could be the metering head valve.

il have to look for another metering head i think.

thanks for the help

wats8vgticab said

When turning on the ignition the fuel pump comes on as normal.

Yeah but does it? It shouldn't come on when the ignition comes on, it should only come on for a couple of seconds (if that), then only run when the engine runs, then if the engine stops it runs for 3-4 seconds then stops again.

Even if the pump was continuously on, it should simply recirculate fuel around the feed and return line, since the air flap is resting at the bottom and there's not enough pressure in the injection feed side to open the injectors.

I'd be tempted to get a meter on the terminals of the fuel pump (or listen carefully to it) to check when it pumps or not. And also pull one of the injectors, place it into a jam jar  and observe how the spray quantity changes, including shutting off if the flap is fully down.

paul_c said

wats8vgticab said

When turning on the ignition the fuel pump comes on as normal.

Yeah but does it? It shouldn't come on when the ignition comes on, it should only come on for a couple of seconds (if that), then only run when the engine runs, then if the engine stops it runs for 3-4 seconds then stops again.

yeah, thats what its doing, so sounds like its working fine,

Today we changed the metering head, and checked the return lines to the tank (These are all clear and working), but the injectors still inject when the ignition comes on.

We can get the car running if we take the return pipe off the metering head and put a pipe from there into a jar. (im guessing this is because there is less pressure, the fuel isnt going to the injectors)

the 5th injector (cold start) squirts petrol when the key is turned for cranking engine.

could it be the pressure regulator causing this?  

Did you fit a new or secondhand metering head; and did you set it up properly? Also, have you done a fuel pressure test? If the air flap in the metering head is down, no fuel should come out of the injectors. I'd say the air flap isn't properly set up. Its also possible that the metering head is overpressuring (you can lower it by removing shims), or that the injectors are opening at below the specification 'opening' pressure.

It could also be the pressure regulator (warm up regulator) but only a fuel pressure test would really give you the definite info on this.

The metering head is second hand, but taken from a running car,

Havent done a fuel pressure test, but the injectors squel, just after the fuel pump comes on, then stop when the fuel pump cuts out (key turned to ignition) so fuel is getting to them when the air flap is down.

how would we go about removing the shims?

could it be the injectors that are knackered then, and cant withstand the fuel pressure (bearing in mind we just cleaned out the fuel filter so theres probably more fuel getting through now.)

wats8vgticab said

The metering head is second hand, but taken from a running car,

Havent done a fuel pressure test, but the injectors squel, just after the fuel pump comes on, then stop when the fuel pump cuts out (key turned to ignition) so fuel is getting to them when the air flap is down.

how would we go about removing the shims?

could it be the injectors that are knackered then, and cant withstand the fuel pressure (bearing in mind we just cleaned out the fuel filter so theres probably more fuel getting through now.)

It could be the injectors but it would be unusual for all 4 to fail in the same way. I think it would be possible to adjust the metering head so that they don't open unless the air flap is moved up (ie engine running and drawing in air).

Changing the fuel pressure in the metering head isn't too complicated. There's a 16mm nut at the rear left of the head, just to the right of the fuel filter. You can take this out and remove shims to lower the pressure (2mm shims removes around 10psi/0.7 bar). But, you'd need to be able to measure the fuel pressure to make sense of it. And also measure the control pressure provided by the warm up regulator, to eliminate this as the faulty part.