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Faulty Diesel Cutoff Solenoid?


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#1 AMacdonald

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Posted 05 January 2012 - 10:10 AM

My Alhambra died last night. There was a little hiccup from the engine and it cut out. Turns over fine but no firing.

After a little troubleshooting this morning I suspect the fuel cutoff solenoid has gone short circuit. Its' fuse has blown (if I've found the right one) and the resistance to earth is only a few ohms. If I connect a wire to it from the battery the wire gets warm and the place where it touches the solenoid glows red and smokes! Not good.

So, is it a big job to replace (the Haynes manual thinks not but I respect the views here more) and has anyone found a good supplier in the past?
Thanks
Angus

#2 zorgman

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Posted 06 January 2012 - 08:28 PM

doddle to change, as youve got a haynes ill leave it to them to explain
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#3 AMacdonald

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Posted 07 January 2012 - 02:46 PM

I'm looking at the Haynes now and they seem to gloss over a few of the details :lol: Instructions are to remove the electrical connection (done) and unscrew the solenoid. However, there's very little wriggle room for a spanner in there and it looks like I'll have to remove the top of the fuel pump to get a socket on. Is anything bad likely to result from taking the top of the pump off?

#4 daddyfixit

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Posted 07 January 2012 - 08:21 PM

I'm looking at the Haynes now and they seem to gloss over a few of the details :lol: Instructions are to remove the electrical connection (done) and unscrew the solenoid. However, there's very little wriggle room for a spanner in there and it looks like I'll have to remove the top of the fuel pump to get a socket on. Is anything bad likely to result from taking the top of the pump off?



can you get a socket in there? i am not familiar with were it is but i wouldnt go taking the pump to bits !!

#5 zorgman

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Posted 07 January 2012 - 08:23 PM

shouldnt have to take top off, and wouldnt advise it. use 2 spanners to make a T so ones on the valve and other for turning, il av a look at mine morro
sharan 1.9 tdii 110hp, 99 model
audi style daytime led lights,
235/45/17 alloys off a6 2.7t
blanked off egr.
.216 injectors,
ported heads and manifolds.
switchable evry mod home made
no cat or backbox twin out pipes thru bumper
full vagcom and handheld diagnostics for vw/ford/seat plus other brands
free diag for forum members if near sunderland
fit early mk1 dash for miles remaining (any one got one off a 95-97 tdi)anybody??
now making bio diesel for own use

#6 AMacdonald

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Posted 07 January 2012 - 11:15 PM

No space to get a socket on, unfortunately. The fuel return blocks it. I can get a 24mm open end spanner on but there's almost no space to get any movement started. I'll see if a ring will fit over, when I get one tomorrow. Very wary about messing the pump up.

#7 AMacdonald

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Posted 08 January 2012 - 03:23 PM

Well, I managed to get the old one out by grinding the edge of a 24mm ring spanner to virtually nothing. The new one is in but the car still doesn't start. Fuse 14 blows as soon as I turn the ignition on. On the plus side, I can now run a wire to the solenoid from the battery with no smoke or flames, so that's good. Doesn't help to get the car going though.

#8 chrispb123456

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Posted 08 January 2012 - 07:55 PM

Hi Angus

Thinking a few possibilities first of all Fuse 14 feeds your stop solenoid via the engine ECU which in turn is fed from relay 109 (second layer in fuse box), this is where I would look first as they are prone to bad solder joints, the second is the engine ECU which is behind the instrument cluster and have heard reports of chaffing on the loom caused by the cluster rubbing through the wiring.
Am surprised you found the stop solenoid shorted to ground but not the cause of your non starting.

2003 Mk2 52 reg TDI Auto Ghia AUY. Upgraded to 7 Day programmable Ebersp├Ącher Booster Heater
2012 Mk3 61 reg Titanium TDCI 163ps six speed manual
And now!! with working VAG-COM/VCDS Lite (full edition) what does it all mean!!
Need a code clearing in my area PM me. All done in the best possible taste! a pint of Magners please that will do nicely.


#9 AMacdonald

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Posted 10 January 2012 - 10:12 AM

Thanks Chris. I've just got to the bottom of it. For posterity and future searches, this is what I did.

I unplugged the 3-pin connector that feeds the solenoid and fuel pump and attached a multimeter to the black/yellow wire that comes off fuse 14, and ground, set to audible continuity. The annoying beep meant the short was audible. I then gently moved wiring looms around until the beep/short cleared, eventually narrowing it down to the MAF connector, which is also fed from fuse 14. The wires at the connector were chafed and perished where it turns round a sharp corner at the connector end and the black/yellow was shorting to the adjacent, also chafed wire. A good clean and application of hot glue to the area should fix it for as long as I still have the car.

I can't believe I forgot my own golden rule - "It's always the MAF"!

Relays would have been my next stop but I couldn't think of a good reason why one would short to ground and blow the fuse.

The solenoid wasn't exactly shorted and was still operating when I attached it directly to the battery but was definitely drawing a lot more current than it should have, hence the sparks/smoke/glowing wire/three wasted troubleshooting sessions. Perhaps the ECU limits the current the solenoid can draw and so the solenoid wasn't the cause of the failure but it was definitely a bit faulty, just not completely ;-)

#10 chrispb123456

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Posted 10 January 2012 - 01:36 PM

Hi Angus

Glad you found it M8, reasoning behind relay 109 was as they suffer from bad solder joints there is always a possibility of shorting inside the relay when this happens, and as said all pump controls N75, N18, MAF etc all run off engine ECU so any short on any of these will cause F 14 to blow.

The wiring and insulation is known to be of poor quality and causes no end of problems especially in door and tailgete wiring. :lol:

2003 Mk2 52 reg TDI Auto Ghia AUY. Upgraded to 7 Day programmable Ebersp├Ącher Booster Heater
2012 Mk3 61 reg Titanium TDCI 163ps six speed manual
And now!! with working VAG-COM/VCDS Lite (full edition) what does it all mean!!
Need a code clearing in my area PM me. All done in the best possible taste! a pint of Magners please that will do nicely.


#11 AMacdonald

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Posted 10 January 2012 - 04:49 PM

I know, I fixed the tailgate wiring (again) today as well ;-)