cutting out

[mhewitt]

g'day -
my first post... & it's bad news...

my mk3 gl has started cutting out intermittently

i searched this - & a couple of overseas fora - & have seen a few threads describing the same symptom, not no definite solution

perhaps someone who has been there could tell me how they fixed it?

here's the scenario:
- once up to temperature (but not overheating) the engine will cut out on overrun
- sharp cutout, like ignition failure
- all other electricals stay on
- engine will fire & run a few minutes later

i had this problem a few months ago; the auto sparky changed coil and crank angle sensor - which appeared to have fixed the problem until about a week ago, when it recurred

i have a wild theory:
- debris in fuel tank
- fast, consistent running sucks it into the fuel pump pick-up, dropping fuel pressure
- ecu has low fuel pressure ignition cut-out (here's where my theory could fall down...)
- once engine stopped, debris falls out of pick-up, allowing engine to run again

does anyone know if this theory stands up?

any ideas at all?

[h100vw]

Bad fuel pump relay or crappy VW fuses associated with it. In fact for a few bucks replace all the fuses with new ones. Then go from there.

Gavin

[Golf Houso]

Hall and crank angle sensors often go, and the car suffers like that as well, get the car put under VAG-com or another type if diagnostic tool.

[mhewitt]

Bad fuel pump relay or crappy VW fuses associated with it. In fact for a few bucks replace all the fuses with new ones. Then go from there.

Gavin

gavin -
thanks for the idea; it raises a question:

if the fuel pump cuts out - due to bad relay or fuse - wouldn't i get a slow engine cut-out, rather than an instant one?

(i have, however, checked the fuel pump relay & cleaned its pins & contacts - but i didn't think of fuses)

[h100vw]

gavin -
thanks for the idea; it raises a question:

if the fuel pump cuts out - due to bad relay or fuse - wouldn't i get a slow engine cut-out, rather than an instant one?

(i have, however, checked the fuel pump relay & cleaned its pins & contacts - but i didn't think of fuses)

It would take a moment for the fuel pressure to drop, yes. The fuel pump relays often end up with dry joints in them. You should pull the lid of it and touch up the soldered joints with a soldering iron and some fresh solder. The ECU relay is another that I have seen fail in a similar way. Same deal.

Gavin

[mhewitt]

Hall and crank angle sensors often go, and the car suffers like that as well, get the car put under VAG-com or another type if diagnostic tool.

golf houso -
it's recently had a crank angle sensor (although there's nothing to say it hasn't already failed again...)

the hall you speak of - is that a hall-effect sensor? used as ignition sender?

[mhewitt]

It would take a moment for the fuel pressure to drop, yes. The fuel pump relays often end up with dry joints in them. You should pull the lid of it and touch up the soldered joints with a soldering iron and some fresh solder. The ECU relay is another that I have seen fail in a similar way. Same deal.

Gavin

gavin -
ecu relay would make sense of the instant cut-out

as with the fuel pump relay, i have checked & cleaned - but i'll take your advice & run a soldering iron over the boards within them for dry joints

thanks for the advice

[h100vw]

Yeah, that would stop dead. No worries, seen snags like this before, no point in sitting on the info, or replacing expensive parts first!!

Gavin

[Bora Sport]

I reckon that it is the ECU relay. Part number 165 906 381, Black in colour, position 3 on the Fuse Box Relay Plate.

[Jmac]

Number 30 stamped on the relay mate, and if it is doing it when its warm i would jump on that. The crank sensor G28 generally cuts the engines throat. You can in fact watch the voltage that the ecu is getting via VAGCOM or anything really that gives you live data. WHen did you change your fuel filter last???? Dizzy caps are bad for carbon build up. GIve it a good clean too. HAve seen the fuel pump relay play up too , this is the relay on the bottom right of the relay plate, no harm also changing this one.
CHeers
JMac