Oil buzzer, no light, shaky tachometer, dies when hot - 1.9 TDI ALH

[gldgti]

I would seriously check your ignition switch! Sounds like you have a circuit that is flaky.

[$hitblast]

Ok. Will the steering wheel have to come off to do that? I took off the plastic covers, and wiggled the contacts, without making any difference.



I also steel-brushed all the contact points atop the battery, inside the terminal shoes, the first negative ground connection below the battery and the connection on the diesel solenoid. They all looked fine, with no rust or crud at all. That didn't make any difference. Edit: The portion of the main ground cable, under the battery, where the ground-connector bites into it, was visibly green from copper-corrosion. I wasn't sure if that mattered any, and guessed it would be cleaner under the biting clamp.

Then I checked the air-intake valve by the EGR-regulator, to see if it was open and could move freely. It moved freely and was in open position. Not much slag in there either.

Then I checked the 109-relay; which seemed to be working fine:


Edit: BTW, I read somewhere on TDI-club, that the ignition-switch must signal the ECU through fuse 29 (not 100% sure about the number), for the ECU to wake up and open ground to 85 on relay 109, so it can close and send more power to ECU. The relay is working, so is there anything else the ignition switch is supposed to do, but not doing already now?

[gldgti]

Just FYI on your fault code, this is copy/paste from ELSAWIN:

Output on the fault reader -V.A.G 1551- printer Possible fault cause Possible effects Fault elimination
17656 P1248
Injection commencement regulation
Control difference t Defective commencement of injection valve -N108-
t Needle lift sender -G80- defective
t Fuel tank empty
t Fuel supply not OK., lack of fuel
t Start of delivery not OK.
t Engine runs rough
t Reduced performance
t Increased exhaust emissions
t Poor cold starting
– Check commencement of injection valve -N108- → Chapter, Final control diagnosis
– Checking needle lift sender -G80- → Chapter
– Fuel filter or fuel line blocked
– Checking and adjusting

[gldgti]

How VW Ignition Switches Fail - YouTube

[gldgti]

in your video, I notice that you dont have any glow plug light on the dash when you switch to on.
(Sounds like you need a new throwout bearing on the starter motor too

[$hitblast]

Yes, I've been reading about the missing GP-light. The GP-light supposedly indicates that the ECU is fully on. A failure of GP-light is usually caused by faulty relay 109, according to the DIY on TDIclub. 109 gives main power to ECU. I pulled the 109 and bench-checked it. It was nice and clean inside, with no visible corruption, and clicked fine, both at room-temperature, and when heated with a dryer.

[gldgti]

must be something other than the relay then. All the symptoms you describe would seem to indicate an intermittent electrical fault... thats why I suggested ignition switch.

[$hitblast]

I see, but if the igntion switch is reliably closing relay 109, what else could it be failing to do? I don't know much about ALH ignition switches.

[$hitblast]

I replaced the 109-relay. That seems to have corrected the problem. There is no GP-light-delay when twisting the key any more, and it starts and drives nicely. Been driving it for somewhat more than two hours on steep inclines, with no incident thus far.