N108 Valve-R&R Without Removing The Injection Pump?

[BluFalcon]

My 97 Passat that I just picked up has been throwing a CEL and going in and out of limp mode. Sometimes the car runs great, then at others it just falls flat on it's face. Hooked up my Rosstech cable and pulled the code :

01269 Commencement Of Injection Valve (N108) 31-10 OPEN OR SHORT TO GROUND INTERMITTENT

I located the N108 valve on the bottom of the injection pump and inspected the wiring for any frayed or broken wiring, and couldn't see anything physically wrong with the wiring. I haven't had time to check for continuity from the plug to wherever it pins out on the ECU harness, but that's probably my next step.

I have a spare injection pump with a N108 valve on it, but from looking at where it's at on the pump and in the car, it might be a bit of a hassle to change out in the car, if it turns out the wiring is indeed OK.

So, has anyone ever changed this out on the car or does the injection pump have to come off? Also if it can be changed in the car, will this require the fuel system to be purged since I'm guessing pulling the valve out will introduce air into the system.

 

[bblume]

Quickly check And Measure resistance between connector terminals 2 and 3.
Specification: 12 to 20 ohms ( )

And continuity betweenTerminal 2 and Pin 51 and Terminal 3 and Pin68

 

[BluFalcon]

Had a chance to grab my multimeter from the garage and measured resistance between pins 2 and 3 on the harness connector.

Which showed:
194 k ohms (I think)


My meter is autoranging and that's what it displayed. I did this in the dark after work, so I didn't spend too much time in my complex's parking lot at 1 AM. I'll try and get a better reading tomorrow. I got the same reading when I probed terminal 2 and 3, and 2 and to ground.

I also measured the resistance on the solenoid itself. The one on the car and the one on my spare injection pump read about 16 ohms and had continuity when I switched the sound on my meter. I'll try and pin out for continuity to pin 51 and 68 on the ECU plug in the morning if I have time.

Thanks for the suggestions and help bblume!


*update*
I measured resistance across terminal 2 and three on the harness side of the injection pump wiring on the 96 TDI I sold today and it showed:

4.6 ohms

The N108 Solenoid also showed about 16 ohms resistance. I'm going to check continuity and look for a short in the wiring....once I figure out how to get the ECU plug off the ECU.

 

[BluFalcon]

Tried tackling my N108 issue some more today.

First I did as Abacus suggested in the "What Did You Do Tour B4 Today?" thread and inspected the wiring from the N108 sensor to the ECU. I pulled the wire loom and electrical tape off the wiring to where it exits the battery tray and couldn't find anything physically wrong with the wiring. No chafing, no broken wiring...nothing. Actually it all looked rather good, considering how old the car is.

I went ahead and re taped everything back up and reinstalled the battery. I did have one single spade connector by the oil filter housing that was on the same wire bundle as the N108 wiring, that I couldn't figure out where it went to. Judging by how it looked, I don't think it was hooked up to anything. Anyone have any idea what it might go to?

I then decided to check the wiring from the plug back to the ECU and got continuity between Pin 2 on the N108 Plug and Pin 51 on the ECU harness. Resistance was .4 ohms. Pin 3 and Pin 68 showed continuity as well, with a resistance of .6 ohms. According to a diagnostic guide I got a from a link on the board, those two wires should show no more than 1.5 ohms Maximum.

While I was checking for continuity, I moved the wires back and forth to see if resistance readings changed or loss of continuity with no change.

The N108 Solenoid itself showed continuity and resistance as well with 16 ohms. The guide said that the solenoid should have 12-20 ohms, so that appears to be in working order unless the solenoid has an issue internally that only shows up when power is applied to it or while in operation.

At this point, I think the only option I have is to replace the solenoid with another part and see if the solenoid itself is at fault. I was told that N108 couldn't be changed unless the injection pump was removed, and the solenoid changed out on the bench.

Is it possible to remove the rear bracket on the injection pump and access the fasteners for the solenoid with the pump in place? I have no problem shelling out the money for a pump R&R, so long as the problem is guaranteed to be fixed. I have an appointment to have the car in the shop in a few weeks, and can still drive it, but I just don't trust it for long distances at this point.

Anyone have any thoughts or ideas?

 

[annieneff]

I don't know what the resistance between all those connections is supposed to be, but if they all check out there are a few more things to look at before replacing the n108. You're going to have a hard time locating a replacement n108 if you do indeed need one. I can't remember if it's only on the alh, but I think on the ahu, you can't get it out without removing the pump. The bolts that hold it in there are behind some bracket.

But... things to check first:
The two sided 10mm nut by the fuel intake for the pump. Sometimes the little piston and spring in it get loose or jammed and it'll throw this code. Take out that bolt, make sure the assembly inside is together and everything moves freely.
When I had this code and a similar problem, someone said that when their n108 went out the car sounded loud-- like a tractor loud. Besides the symptoms, how does it sound?
On the alh, there is a way to test the n108 on vcds. Something about removing a fuse and seeing if some numbers change. I'm writing this on my phone from memory right now or I'd look it up but a simple search should turn up whether you can do it on ahu as well or not.

When I get home in a bit ill look and see if I can find anything else to check but that should give you a good start for now.

Good luck!

Andrew

 

[BluFalcon]

Andrew,
Aside from the intermittent loss of power and the CEL, it seems to drive fine for the most part. Even when it's "limping" the engine sounds normal. Occasionally when it's doing this, if I let off of the throttle, take it out of gear and go back into gear and reapply throttle, it will sometimes "clear up" and resume operating normally. The CEL is off upon initial start, but soon comes back on and stays lit while driving. I've never seen it flash.

I'll take a look at the fitting you described tomorrow before work. Also, I'll take a look at the bracket and see if it can be removed with the pump in the car. If it can't be removed completely, maybe it can be moved just enough to access the bolts for the N108. I have a spare one on another injection pump, but I'm thinking if the pump is going to have to come off, I might be better off ordering a brand new solenoid. Thanks for tips.

 

[BluFalcon]

What's the difference between the various Part #'s for the N108 Valve?

PN:028906283G is $406 from ECS Tuning and PN:028906283M is only $258.25 from there as well.

According to some of the threads on here, the part number associated with the N108 Valve was superseded by Bosch PN:0281002136, but since I can't find a picture of it or anyone in the US who stocks it, I'm thinking about going with the "G", unless someone can tell me what the exact difference is between the "M" and whether or not it'll work on my 97.

 

[annieneff]

Ok. Looked back over what I remembered from having this code and mine was a little different, but still worth checking out my suggestions before spending that $$$!

First check the case relief valve. That's the 10mm 2 sided but I mentioned earlier.

Also, you said it falls flat on its face and goes into limp. Do you have to cycle the key to get it out of limp or are you just down on power for awhile?

When I was having similar problems Robby (runonbeer) said he had an n108 go bad and it sounded like a John Deer tractor. And he said they very rarely go bad. Unless your car is loud, it's probably not the n108.

The spade electrical connection you asked about earlier (in the first post?) is for the oil temperature sensor for the display that you don't have on the instrument cluster. You have to get a temp sensor to plug into the oil cooler housing there, and a different instrument cluster, and a different wiper stalk. Now you know.

Hope that helps!

Andrew

 

[BluFalcon]

Andrew,
Where you throwing a CEL when the relief valve was bad on your car? Not sure where on the pump it's located, but I'll try and get a closer look at it when i get a chance.

I managed to get the N108 valve off of the spare IP I have, and it was kind of a pain in that someone else already stripped one of the Torx bolts on the solenoid valve. I think I'll try swapping it with the one in the car tomorrow. It's a 0281002136 solenoid, which is supposed to be one of the newer ones. Hopefully I can swap it without pulling the pump off the car.

I never restarted the car when it lost power. I usually just drove it until it cleared up, or I popped it out of gear and gave it some throttle to try and clear it up. Frankly if a different solenoid valve doesn't fix this thing, I'm at a loss as what to do next.

 

[annieneff]

Andrew,
Where you throwing a CEL when the relief valve was bad on your car? Not sure where on the pump it's located, but I'll try and get a closer look at it when i get a chance.

I never restarted the car when it lost power. I usually just drove it until it cleared up, or I popped it out of gear and gave it some throttle to try and clear it up. Frankly if a different solenoid valve doesn't fix this thing, I'm at a loss as what to do next.

Mine did throw a cel when the case valve was stuck and dirty. From your description of when it happened there, it makes me think that it's the case valve even more. It doesn't sound like limp mode, more like you weren't getting enough fuel.

Here is a picture of the valve in question .

 

[BluFalcon]

Checked out the case relief valve and it moves freely in its housing. Restarted the car, no change.

Tried swapping the N108 Valve without pulling the pump, and couldn't do it. The boss on the engine block that the gold IP bracket bolts onto prevents you from getting a straight shot with any tools to remove the inboard solenoid bolt. Put everything back together and I'll just drive it till I can get it into the shop and let someone else tackle fixing it.

 

[boisebiker]

Can the case releif valve be removed and cleaned(by your average Joe)? Is there any risk to removing and cleaning it?

 

[RIP TDI]

Can the case releif valve be removed and cleaned(by your average Joe)? Is there any risk to removing and cleaning it?

Yes, but there can be a wrench clearance issue, depending on where the flats are oriented. If that's the case, a Gator Grip socket can be used. Also, the usual issue with the relief valve is that the end stop loosens and moves out of position or falls out completely, resulting in incorrect case pressure.

 

[boisebiker]

How does one go about testing the case pressure? Can it be seen by VCDS? I have an issue where I loose all power if I get on the throttle too hard within about 10 minutes of cold start, acts like it sucked an air bubble. After it warms up I don't have any trouble. The problem clears itself after 10-30sec of very rough idling.

 

[annieneff]

Sorry it wasn't that Blufalcon. Worth a try. Let us know how it turns out!

As Chris said, it's a pita to get out of there without the right wrench. There's no way to test for it on vcds. But it sounds like you have air getting in your lines there, Boisebiker. Check the thermo T, and around the injection pump and the fuel lines between the injectors, really close, for leaks.

 

[BluFalcon]

Went to the dealer today and talked to the parts guy and was told that PN: 028906283M was what they showed as the right part number for a N108 Solenoid on a 97 Passat TDI. I ordered the solenoid and the seals for the install.

I figure if the pump is coming out, I'm not gonna put a used solenoid in there that may or may not be good. Hopefully this fixes the problem, and I can go back to enjoying my car.

Thanks for the help, Andrew.

 

[BluFalcon]

I think I finally have this issue sorted out. Turns out it was a wiring issue, just not on the side of the wiring harness that I thought it was.

The wire leading from the N108 sensor, had chafed against the pump body and worn through the rubber coating and the brown wire underneath. I nver considered looking at the wire going to the solenoid, because "Hey, there's no way that the wire could be broken or worn, especially with a bonded rubber covering protecting it." Right?

I ended up ordering the PN: 028906283M solenoid for the ALH motor as it was quite a bit cheaper than the 028906283G for the 1Z/AHU motor. The solenoids look identical physically and just need to have the leads depinned from the 2 pin ALH connector, and installed in your 3 pin 1Z/AHU connector.

Car seems to drive a lot better, and hasn't thrown a CEL for the last 60 or so miles. I'll be keeping a close eye on it.

Big thanks to Brian @ DigiSport for getting me in on a Saturday, so I could get this taken care of.