-
no voltage at fuel cutoff solenoid by Settings on 08 Dec, 2010 19:34
-
As I was getting on the highway this morning my '93 AAZ just died. It cranks strongly with no weird sounds or smoke.
Towed home where I find that there is no voltage at the fuel cutoff solenoid. If I jump it straight from the battery the solenoid clicks open and the car starts and runs fine.
Fuse 18 is good, so on to the relay (#104...also listed for glow plugs). To be honest, I'm not really comfortable with how relays work, or wiring diagrams.
Here's the relay.
30 receives 12V when ignition is on.
On the bench, there is resistance between 30 & 85. When I apply voltage to 30 & 85 it clicks...and 87 has 12V out. No other combination has any noticeable effect. As far as I can tell, it seems fine...but I don't really know what I'm talking about, and I still don't get any voltage at the fuel pump
My only conclusion is that it's between the relay and the pump...but it's a straight run from the relay panel to the cutoff solenoid.
Where should I start? I've just pulled the fuse panel down as far as I can and am attempting to figure out which connector I'm dealing with on the back (Bentley is flipped and reversed to my current perspective
)
It's my daily driver so I'd like to figure it out sooner rather than later.
Thanks for any insight.
Jer -
#1 by Vincent Waldon on 08 Dec, 2010 21:38
-
That's the glow plug relay, but on MK3s all it carries is the high current directly to the glowplugs themselves.
The ECM (Electronic Control Module) controls the glow plug relay and other thingies... including supplying power to the fuel shutoff solenoid:
-
#2 by Settings on 08 Dec, 2010 22:35
-
Thanks Vince.
I noticed the control module on the wiring diagrams but could make heads or tails of where it is. I checked the fuse that powers the ECM and it was blown! New 10 amp fuse and it started (all that over a fuse
). Hopefully whatever caused the fuse to blow while driving won't return. Any known causes for this fuse to blow?
On a related note...my relay panel looks a little different. I assume my ECM is the #120 on top
-
#3 by Vincent Waldon on 08 Dec, 2010 23:13
-
Ah... a happy ending... love it!!!
Yup, I'd say 120 is your ECM... my picture's from an MK3 Golf... betcha yours is a Jetta?
Because that module controls a bunch of things it's hard to say what would have blown the fuse... it might come back or you might never hear from it again.
It controls the EGR system and fast idle as well... are there any funky wiring under your hood around the injection pump, or near the solenoid valves bolted to the passenger-side shock tower?
My other thought on this is that 10A is a pretty wimpy fuse that probably represents a pretty good percentage of that particular system.... so could just be a nuisance pop. You could consider going to a 15A fuse if it goes for months and then randomly pops again. -
#4 by Settings on 09 Dec, 2010 06:50
-
Correct again...it is a Jetta (Do you know tonight's lottery numbers?)
Nothing funky that I know of. Electrically it's all OEM. Perhaps, that's probably part of the problem...18 year old wiring
I was also surprised that the fuse was only listed as 10A. Then again, you mentioned in an earlier post that the fuel cutoff solenoid only draws something like 400mA. At that rate it could control lots of stuff under 10A. I always have a few extra in the car, so if it goes again soon I'll try a 15A while I further diagnose the problem.
Next is to see if I make it to work today. I'll be particularly observant as I do that first hard acceleration up the on-ramp. -
#5 by Henchman on 09 Dec, 2010 07:43
-
Let me know which relays you want to try swapping and I'll send you some.
You should see the fuse panel on the 93 passat. The ecm is so far up the dash as you'd never know it was there.
Ian -
#6 by Settings on 10 Dec, 2010 06:16
-
Made it to work and back no problem yesterday. The real rest is that I have to drive about 500km this weekend (back and forth to Ottawa Saturday AND Sunday)
The only change seems to be that I'm idling a little higher. That being said, I had a LOT of stuff apart before I discovered the lack of voltage at the cutoff solenoid (think almost everything to do with air, timing, compression, then fuel...wait, that's everything!). Now I know to look for juice at the solenoid early on...a quick non-invasive test. The good news is that I'm much more comfortable adjusting idle speed