No voltage at fuel cut-off solenoid - wiring good to ecu

tongboy

Veteran Member
Joined
May 24, 2006
Location
Portland, OR
TDI
91 Jetta TDI Swap, 97 M3 LS1 Swap
This is the first time my tdi has actually left me somewhere :(

i've gone through all the standard electrical checks, I have a unique wiring job so I know it well and have checked all of my obvious points of concern.

I keep coming back to the fuel cut-off solenoid, I manually test it and get function, pull the ECU plug and test it from there all the way back through the engine and it functions without issue, I believe the ECU is not pushing power to the solenoid because something else isn't clearing before it enables the solenoid but I can't locate anything else, no related codes (glow plug indicator, n239, & CEL indicator are all the codes.) Engine speed sensor is still indicating on the cluster, mechanically everything is intact, etc.

99.5 alh

what else can cause the ECU to not enable the solenoid?
 
Last edited:

nighthawk62

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May 22, 2008
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BANNED
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I'm not an expert but if the cranking speed is too low the ECU will not call for fuel. Low cranking speed can be caused by a number of things; poor battery, poor wiring, poor conections/grounds, poor starter. I would check the wiring and grounds first and then move on to the battery.
 

rdkern

Top Post Dawg
Joined
May 21, 2004
Location
Humboldt Co CA
TDI
Passat 1997 silver (sold after 11 years), Jetta 2000 atlantic blue
you are getting the gp light when you turn the key to on?
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis, MO
TDI
There are just too many to list....
Check ALL the fuses. The ECU gets a seperate power feed for the stop solenoid from an independant fuse, in the interior fusebox.
 

bluejet99

Member
Joined
Nov 11, 2005
Location
Québec, Canada
TDI
1999 Jetta, blue
Hello
I had the same problem, coudn't find what was wrong, so i installed a swicht under the panel. One wire fron the + on the battery and the other on the selenoide. As for the cranking speed, i have welding size cable, new battery and starter, this trio make the engine spin fast.

Bluejet 99
 

tongboy

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May 24, 2006
Location
Portland, OR
TDI
91 Jetta TDI Swap, 97 M3 LS1 Swap
oilhammer said:
Check ALL the fuses. The ECU gets a seperate power feed for the stop solenoid from an independant fuse, in the interior fusebox.
all my fuses are good, first thing I checked, replaced relay 109 with another one as well.

I can log all of the cranking and everything else before and after with vag-com, leaving me to believe that the ECU has power throughout the entire event. I'm not seeing a log of more then ~250rpms cranking speed but according to the manual that's enough, it's also previously been enough as i've been driving it and it cranks the same speed as before.
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis, MO
TDI
There are just too many to list....
Sounds like you need another ECU then. I have replaced ONE of these that refused to power up the stop solenoid, so yours would not be the first one anyways. Just want to make sure you have covered all your bases first.
 

Drivbiwire

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Oct 13, 1998
Location
Boise, Idaho
TDI
2013 Passat TDI, Newmar Ventana 8.3L ISC 3945, 2016 E250 BT, 2000 Jetta TDI
Fuel selenoid shuts off after a period of time if no start is detected. Often this is mis-diagnosed as an issue with the selenoid circuit. This protects the engine from a hydro-lock.

I suspect you have another issue that is preventing the car from starting or delays the start to the point the ECU shuts the fuel off.

DB
 

tongboy

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Joined
May 24, 2006
Location
Portland, OR
TDI
91 Jetta TDI Swap, 97 M3 LS1 Swap
Drivbiwire said:
Fuel selenoid shuts off after a period of time if no start is detected. Often this is mis-diagnosed as an issue with the selenoid circuit. This protects the engine from a hydro-lock.

I suspect you have another issue that is preventing the car from starting or delays the start to the point the ECU shuts the fuel off.

DB
I'm also of the belief that there is something else going on that is preventing the ECU from turning the fuel solenoid on, I just don't know what else it could be. if I watch the fuel solenoid with a multi meter there is no point during immediately turning the key on to cranking for a number of seconds that there is voltage present at the solenoid. what are the other sensors that will keep the motor from firing? particularly ones that may not necessarily throw codes
 

steve17

New member
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Nov 18, 2013
Location
Midwest
TDI
1998 Jetta TDI Vegcar (RIP), 2014 Jetta TDI (RIP)
tongboy did you ever find out what was wrong? I am having this exact problem.
 

Whiskey_Mike

Member
Joined
Aug 2, 2018
Location
California
TDI
Suzuki Samurai AHU swap
Don't know if this helps, but I'm having the same problem. I had no power to the solenoid, did some digging and found out that it won't supply power to the solenoid if the ECU has no signal from the modulating piston displacement sensor on the injector pump. Check for power in at the #2 position on the connector. This comes from pin 7 on the ECU. If you have power there, check for continuity between wire #1 at the IP connector to pin 29 on the ECU, and then from wire 3 to pin 52. If all of that looks good, then something else might be the problem. Hope this helps anyone that stumbles on this thread with the same issue.
 

AndyBees

Top Post Dawg
Joined
May 27, 2003
Location
Southeast Kentucky
TDI
Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
Also, after the ignition is turned ON, the voltage to the Solenoid begins to drop off immediately if the engine is not started. I've never checked it during starting or after the engine is running.

Here are some pics of the voltage on the ALH in my Vanagon that I took several years ago on this topic. I did this check on my 2000 Jetta and got the same results.

These pics were taken about 4 or 5 seconds apart.







 

vincej

Veteran Member
Joined
Jun 26, 2015
Location
Calgary
TDI
2014 Golf Wagon
I don't know if this is related at all but here goes. My brother has an 06 that would not start and diagnosed as 1/2 of the computer was dead. I got a used one and relay 460 from the junkyard. Checked his relay was good. Changed the computer (ECU?) and car would start for about a second and shut off. He took it to someone who did something with the security code or something and the car now runs.
 

AndyBees

Top Post Dawg
Joined
May 27, 2003
Location
Southeast Kentucky
TDI
Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
The Computer you got from the Junk Yard isn't programmed for the Immoblizer in the Steering Wheel ... So, yes, the engine will start and run for a couple of seconds and then shut-down! The Immoblizer is what the "someone" eliminated to allow the engine to start!

Hope this helps!
 

vincej

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Jun 26, 2015
Location
Calgary
TDI
2014 Golf Wagon
I just thought I'd put it out there because in my brothers case it was also a case of not getting the fuel. He parked the car and after shopping it did not start. Maybe it is rare to have a dead computer but it does happen. He thought maybe he had contributed to the problem because his battery was not up to snuff and was occasionally starting it with a boost from a battery charger. I don't know how they had confirmed that 1/2 the computer was dead but it appears to have been a correct diagnosis.
 
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