No start AHU mystery after running great

ken.fresno-tdi

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Jan 3, 2006
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Fresno, CA
TDI
95 Eurovan EVC camper with 98 AHU engine (VeganVan02); 01 Jetta ALH engine and parts - waiting for transplant into 97 Eurovan (VeganVan03);05 BEW Beetle
back story: I did a AHU TDI transplant into Eurovan over a year ago. 150K on engine and professionally rebuilt 10mm injection pump. Great running; 4000 trip last summer and almost daily 150 mile r/t in past month to go from Fresno to Yosemite where I am helping build a cabin. Some problem with boost control (separate thread) but generally very nice running van. Three days ago started up fine but died after 5 or 6 seconds, still in driveway. No restart though seemed like it wanted to - engine would catch and stumble but not really go, and then just crank. First made sure 109 was good and that stop solenoid was clicking. Glow plug light works. I have a BEW in-tank fuel pump installed that pushes diesel through fuel filter but still bypassed any possible fuel filter clog or air leak by sticking both diesel lines into jar of diesel. Still no start- wants to and stumbles then dies. Looked for codes and found P1248 - timing issue? Checked to make sure timing was good - all checked out but IP was a bit off center so decided to retime the whole thing. Retimed using proper tools and made sure all was EXACTLY right - flywheel, camshaft, IP all on center and IP in middle of rotation. No sign of start at all after priming several times/cracking IP lines properly. Then I remembered when I first installed engine I had timing problem and had to advance IP sprocket one tooth to get engine running. Strange but apparently documented and true. Redid timing with IP sprocket advanced one tooth. Result is back to original condition - fires up for one or two seconds, stumbles, but not quite starting. Aaghh! Now thinking back to original issue three days ago where it started and then just stopped after running for a few seconds I wonder if some electrical issue in IP is the problem? fuel delivery seems fine. Air intake is fine. timing seems fine. N108 valve? never touched it before... Other things to check? I have VAGCOM and am not afraid to use it but without starting engine can't really check dynamic timing or other possible issues. Where do I go from here? Thanks for any thoughts!
 

Mozambiquer

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2004 VW Touareg V10 TDI, 2012 Audi Q7 V6 TDI, 1998 VW Jetta TDI. 1982 VW Rabbit pickup, 2001 VW Jetta TDI, 2005 VW Passat wagon TDI X3, 2001 VW golf TDI, 1980 VW rabbit pickup,
back story: I did a AHU TDI transplant into Eurovan over a year ago. 150K on engine and professionally rebuilt 10mm injection pump. Great running; 4000 trip last summer and almost daily 150 mile r/t in past month to go from Fresno to Yosemite where I am helping build a cabin. Some problem with boost control (separate thread) but generally very nice running van. Three days ago started up fine but died after 5 or 6 seconds, still in driveway. No restart though seemed like it wanted to - engine would catch and stumble but not really go, and then just crank. First made sure 109 was good and that stop solenoid was clicking. Glow plug light works. I have a BEW in-tank fuel pump installed that pushes diesel through fuel filter but still bypassed any possible fuel filter clog or air leak by sticking both diesel lines into jar of diesel. Still no start- wants to and stumbles then dies. Looked for codes and found P1248 - timing issue? Checked to make sure timing was good - all checked out but IP was a bit off center so decided to retime the whole thing. Retimed using proper tools and made sure all was EXACTLY right - flywheel, camshaft, IP all on center and IP in middle of rotation. No sign of start at all after priming several times/cracking IP lines properly. Then I remembered when I first installed engine I had timing problem and had to advance IP sprocket one tooth to get engine running. Strange but apparently documented and true. Redid timing with IP sprocket advanced one tooth. Result is back to original condition - fires up for one or two seconds, stumbles, but not quite starting. Aaghh! Now thinking back to original issue three days ago where it started and then just stopped after running for a few seconds I wonder if some electrical issue in IP is the problem? fuel delivery seems fine. Air intake is fine. timing seems fine. N108 valve? never touched it before... Other things to check? I have VAGCOM and am not afraid to use it but without starting engine can't really check dynamic timing or other possible issues. Where do I go from here? Thanks for any thoughts!
If you loosen the injector lines does it spray fuel out when you crank it?

Sent from my S60 using Tapatalk
 

ken.fresno-tdi

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95 Eurovan EVC camper with 98 AHU engine (VeganVan02); 01 Jetta ALH engine and parts - waiting for transplant into 97 Eurovan (VeganVan03);05 BEW Beetle
definitely. each one loosened plus return line loosened at end of IP during each attempt to bleed fuel lines. evidence of sprayed fuel throughout engine bay : <
 

ken.fresno-tdi

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95 Eurovan EVC camper with 98 AHU engine (VeganVan02); 01 Jetta ALH engine and parts - waiting for transplant into 97 Eurovan (VeganVan03);05 BEW Beetle
I should also add that during attempts at restarting I physically advanced IP to most advanced position (rotated toward engine) and most retarted (rotated toward radiator). When most advanced it definitely did not catch at all; when most retarted it comes closest to starting. This made sense to me since IP is advanced one tooth.... But when IP was on properly (not advanced one tooth) and physically rotated most advanced it still wouldn't start.... and battery and starter are almost new; good cranking speed with battery charger on overnight to ensure full amps.
 
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KLXD

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Lompoc, CA
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I wonder if the advance piston is stuck at full travel since it wants to start when you retard it. I didn't catch where you fully retarded it when you timed it straight up. Only when advanced a tooth.

I doubt it since rotation of the shaft would want to push it back to the normal retarded position. I think.

N108? Should be able to hear it clicking by applying 12V to it, not by turning on the key. Other clicks going on when you do that. Or remove the guts to be sure. Just a spring and plunger.

At this point I would try running it from a bottle to eliminate the possibility of a fuel line obstruction.

As far as timing it a tooth advanced is concerned, I've had to do it and not do it on the same engine. I think it has to do with how hard I want to try do get the slack out of the new stiff belt that has built in bends from shipping.
 
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ken.fresno-tdi

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95 Eurovan EVC camper with 98 AHU engine (VeganVan02); 01 Jetta ALH engine and parts - waiting for transplant into 97 Eurovan (VeganVan03);05 BEW Beetle
thanks for the ideas. I'll work on them tomorrow, especially related to fuel. I just read through the post you and Mozambiquer and others helped diagnosing kurtzl's no start issue (AHU - Air in fuel system) and gave me some more ideas too. Yes, I too am wondering if there is some kind of fuel starvation/blockage issue - there is fuel coming out of loosened injector lines but perhaps not enough. I've dealt with hard start/no starts over the years (owned about 5 AHU engines since 06) but I can't recall one where I hadn't altered something on the car to cause the problem. Also, in rechecking VAGCOM codes it did throw a 01237 Fuel Shut Off N109 open or short to ground at one point while trying to start it but I've jumped the N109 solonoid straight to the battery several times to make sure it wasn't the issue with no difference, and the code didn't return after clearing. The 109 relay otherwise seems fine (looking for my spare to make sure).
 
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ken.fresno-tdi

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95 Eurovan EVC camper with 98 AHU engine (VeganVan02); 01 Jetta ALH engine and parts - waiting for transplant into 97 Eurovan (VeganVan03);05 BEW Beetle
so I got a fuel container and hooked up a gravity flow fuel supply directly to the pump, with return line bypassing the fuel filter T. Tried starting and same issue - starts for a second or two and then dies, again and again... Decided to take out the N109 solenoid since I had the code and the clicking sound did not seem strong when hooked up directly to 12v. To do so I removed all the injector lines first to try to get access to the N109 without removing the top half of the IP. No luck - very tight and you can't get a 24mm socket or wrench on it. So I took off the top half of the IP, carefully making awl marks on top and bottom to match when I put it together again, and keeping everything very clean. I actually didn't have to take off the top half of the pump, just loosened all the bolts and pushed it as far to the left as possible to give access to a 24mm socket. Removed the N109 valve and tested it on the bench. I could not get any response from the solenoid with 12V on the wire end and a ground wrapped around the threads. Tried the same on two old spare solenoids I had laying around and same issue. I assume I should be able to get some kind of response from a working solenoid...?! Anyway, it kind of made me hopeful because if that is the problem I can temporarily make do by removing the spring and plunger and just kill the engine with 5th gear and clutch out. I removed spring and plunger and put N109 solenoid back, aligned and tightened all the IP bolts, and reinstalled the injector lines. Used a mityvac to fill the IP with fuel and pull fuel all the way through to the return line. Cracked the injector lines and cranked for a while to remove air and then tightened things up and cranked. Nothing. Not even a hint of wanting to start. checked codes in VAGCOM and got the following:

4 Faults Found:
00532 - Supply Voltage B+
27-00 - Implausible Signal
01237 - Fuel Shut-Off Valve (N109)
31-10 - Open or Short to Ground - Intermittent
00626 - Glow Plug Indicator Light (K29)
31-00 - Open or Short to Ground
00668 - Supply Voltage Terminal 30
27-00 - Implausible Signal

The N109 error makes sense since it wasn't even hooked up (since I took it off) but the others look like the 109 relay isn't working. But the glow plug light comes on for a second so I assumed it was. Or perhaps a bad ground? Now I'm thinking one of three things:
109 relay is bad and I'm being tricked into thinking it is good because it still mostly supplies power to glow plug light
or
I have a bad ground - since I put the whole engine together in the van I should remember where the grounds are, but I'm thinking the ones that come off the large circular connector are the ones I should be checking, since most all the engine wiring goes through there... correct??
or
when I carefully moved the top half of the IP over to the left to make way for the 24mm socket on the N109 I accidentally pulled it up to much and dislodged the IQ adjuster from the sliding mechanism below, or when I was realigning the top half of the pump I just lined up my scratch marks wrong (though they look exactly right). I've done the hammer mod several times and replaced seals on the top half of an IP so I know the basics of what to be careful for but I also know that is an extremely sensitive piece of machinery.

Thoughts? So frustrating!
 
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ken.fresno-tdi

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95 Eurovan EVC camper with 98 AHU engine (VeganVan02); 01 Jetta ALH engine and parts - waiting for transplant into 97 Eurovan (VeganVan03);05 BEW Beetle
I went ahead and bought an new N109 solenoid ($35 from vwpartsplace.com)and a 109 relay (need one anyway as a backup) and will look for bad grounds while waiting for those to come...
 

ToddA1

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NJ 08002
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'96 B4V, '97 B4 (sold), '97 Jetta (scrapped)
If the GP light works and you’re able to pull codes, I doubt it’s the 109. Jumping 12v to the stop solenoid should back feed the circuit, bypassing the 109.

-Todd
 

Jetta SS

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Oct 30, 2006
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Grand Bay, AL
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'98 Jetta
I seem to recognize some of those codes from a no start I had. I had forgot to reconnect the IP electrical plug after doing some work. Maybe take a close look at the ip plug/wiring.
 

ken.fresno-tdi

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95 Eurovan EVC camper with 98 AHU engine (VeganVan02); 01 Jetta ALH engine and parts - waiting for transplant into 97 Eurovan (VeganVan03);05 BEW Beetle
thanks. will do.
 

Mongler98

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COLORADO (SE of Denver)
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98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
Wireing harness. Sounds like something came unplugged or broken. Probably kn the ip harness. Mark6 has a similar issue. Turns out broken wire.
 

ToddA1

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'96 B4V, '97 B4 (sold), '97 Jetta (scrapped)
Abacus, always finds broken wires, inside the loom. It’s worth investigating.

-Todd
 

ken.fresno-tdi

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95 Eurovan EVC camper with 98 AHU engine (VeganVan02); 01 Jetta ALH engine and parts - waiting for transplant into 97 Eurovan (VeganVan03);05 BEW Beetle
Update on my no-starting issue on 98 AHU. Reminder that the engine had been running great and then suddenly no-start in driveway. Appreciated responses that related to the several fault codes (post #7) that seemed to indicate an electrical problem. I realized that those codes had only occurred one time so I made sure the two IP connectors were seated well and tried starting again. Checked fault codes on VAGCOM - none at all. Then I waited till I received a new 109 relay and new fuel shut off solenoid. Put those in place this morning and then:

- made sure that the IQ adjustment pin seated in correctly when putting the top half of the injection pump back on and tried to make sure the scrawl marks were lined up exactly right on the top and bottom half of the IP.
- removed the injection lines from the pump and put down paper towels to catch diesel as it squirted out of the pump.
- Set up 1 gallon container of diesel from above engine directly gravity flowing into IP.
- Trickle charged battery overnight to make sure it was strong.
-turned key to on position and then touched wire from starter solenoid to battery so I could watch what was happening to fuel coming out of IP.

Result of cranking: no fuel coming out of IP injector ports, or, to be more accurate, a dribble that continued after ending trying to start - from, I assume, gravity fed fuel lines.

- Checked VAGCOM codes. Nothing.
-glow plug light comes on for a second and goes off - normal.
- Directly hooked up 12V to 109 fuel shut off solenoid and tried starting.
- Still no fuel coming out of IP injector ports
- Still No codes at all

So now I am stuck again. N108 solenoid? I assume that the solenoid could be bad even if VAGCOM says that the electrical connection is o.k.? Something else blocking fuel inside IP? I've never gone further than changing seals on an IP and doing IQ adjustment but assume that IPs just suddenly go dead. What am I missing?
 

Mongler98

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Mar 23, 2011
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COLORADO (SE of Denver)
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98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
do as i asked
go through the wire loom from the IP. inspect ALL WIRES especially near the trans where it flexes the most.
chances are you have some broken wires.
stop buying parts and start testing and inspecting things.
you could have easily tested the 109 relay and the fuel shut off solenoid vs just tossing money at the issue.
Let's work the problem and not make things worse by guessing!
 

ken.fresno-tdi

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95 Eurovan EVC camper with 98 AHU engine (VeganVan02); 01 Jetta ALH engine and parts - waiting for transplant into 97 Eurovan (VeganVan03);05 BEW Beetle
I will do some more testing as you mentioned. Thanks. When I purposefully unplug the 3 wire plug Vagcom immediately recognizes it and gives me the 108 and 109 error. When I plug it back in and clear the codes they don't return. When I purposefully unplug the larger 8 pin (?) IP plug Vagcom immediately recognizes that and gives me the fault codes connected with that plug. When I plug it back in and clear the codes and again crank the starter the codes don't return. No codes at all. If it is an electrical issue wouldn't Vagcom give me some kind of indication by throwing a intermittent or fault to ground code of some kind?
 

CasaEd

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1st place to look for me is here:-


- made sure that the IQ adjustment pin seated in correctly when putting the top half of the injection pump back on and tried to make sure the scrawl marks were lined up exactly right on the top and bottom half of the IP.
 

Mongler98

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Mar 23, 2011
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COLORADO (SE of Denver)
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98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
Read this thread
http://forums.tdiclub.com/showthread.php?t=500368
Might not be 100% your issue but every time there is an issue like this. It usually revolves around the same issue, broken or shorted wires to the ECU or IP or something. Sometimes it was a corroded fuse relay block I for one have an issue with my 109 relay that due to a leaking heater core it corroded a lot of weak contacts that make it difficult to get the 109 to seat correctly and make contact.
Usually if you have issues nut no codes (reguardless or cel or not) it's a wiring issue or the like
 

ken.fresno-tdi

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95 Eurovan EVC camper with 98 AHU engine (VeganVan02); 01 Jetta ALH engine and parts - waiting for transplant into 97 Eurovan (VeganVan03);05 BEW Beetle
Thanks for the suggestions. I did continuity tests on the 8 pin and 3 pin IP plugs. All the following continuity checked out fine according to the AHU wiring diagram here: http://www.haywood-sullivan.com/vanagon/TDI/1996_Jetta_TDI_wiring_LONG4.pdf .

8 pin to ECM:
1 - 29
2 - 7
3 - 52
4 - 17, 33
5 - 45
6 - 49
7 - 63
8- blank

3 pin
1-53
2-51
3- 68, 45, 23


there may be a problem with current flowing to the IP, of course. I'll look up what the voltage to the various components should be...

IP was primed prior to cranking using mityvac on the return fuel line.

Now I'm wondering if the pin going into the QA was installed correctly. Is there a way to use VCDS to check if the QA pin is seated correctly without starting the engine? Visually it was all lined up until the last inch or so, until one is close to closing the top off over the bottom of the IP. But, of course, the QA pin was installed correctly prior to ever taking it apart so I'm confused why it seems I'm not getting fuel through to the injection lines.
 
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garciapiano

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Southern California
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1997 Jetta TDI (1Z)
It’s rather bizarre you are getting no codes despite this malfunction. Any ways to check readiness with the VCDS? Any communication with the pump-level code blocks?
 

ken.fresno-tdi

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95 Eurovan EVC camper with 98 AHU engine (VeganVan02); 01 Jetta ALH engine and parts - waiting for transplant into 97 Eurovan (VeganVan03);05 BEW Beetle
Just ended this saga. Since I had the injection lines off and had triple-checked the timing, and had re-checked all the electrical connections (still no codes from VCDS), and was ready to take the pump apart again to check the QA pin was in place correctly, I figured that swapping out the entire pump was not that much more work. I was also needing to get the van running for some planned camping trips. So I found a used IP on ebay that looked in good shape and swapped it in. I set the mechanical timing right in the middle of the IP's movement and hooked up the fuel line directly to a gravity fed gallon container, used a mity-vac to pull the fuel through the new-used pump, made sure the battery was charged, and cranked. No luck. I advanced the IP a little (toward the engine) and cranked again. Started right up. Quickly got VCDS running and checked timing - it was way advanced. Had to shut it down and go to work but the engine is running again. So I still don't know for certain what the problem was - I'm going to carefully take apart the original IP and see if the pin was dis-lodged, but that still doesn't account for why it just stopped in the first place. Frustrating but I had reached the point of needing to move on and get the engine running. I don't know the internals of the pumps well enough to know if something can suddenly mechanically go wrong but that seems to be what happened. Seems strange though.
 

garciapiano

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1997 Jetta TDI (1Z)
Just ended this saga. Since I had the injection lines off and had triple-checked the timing, and had re-checked all the electrical connections (still no codes from VCDS), and was ready to take the pump apart again to check the QA pin was in place correctly, I figured that swapping out the entire pump was not that much more work. I was also needing to get the van running for some planned camping trips. So I found a used IP on ebay that looked in good shape and swapped it in. I set the mechanical timing right in the middle of the IP's movement and hooked up the fuel line directly to a gravity fed gallon container, used a mity-vac to pull the fuel through the new-used pump, made sure the battery was charged, and cranked. No luck. I advanced the IP a little (toward the engine) and cranked again. Started right up. Quickly got VCDS running and checked timing - it was way advanced. Had to shut it down and go to work but the engine is running again. So I still don't know for certain what the problem was - I'm going to carefully take apart the original IP and see if the pin was dis-lodged, but that still doesn't account for why it just stopped in the first place. Frustrating but I had reached the point of needing to move on and get the engine running. I don't know the internals of the pumps well enough to know if something can suddenly mechanically go wrong but that seems to be what happened. Seems strange though.
Let us know what you find. Could be an edge case scenario where the cold advance solenoid just decided to give up the ghost. I think in that situation you'd still start, just maybe with an extended crank.
 
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