20 minutes driving then stalls

[Kombi]

Hi all I bought a 412 back in August. It's a 73 automatic with D-jet.
I had some earlier woes with this car but worked through them.
see this post http://www.shoptalkforums.com/viewtopic ... highlight=
BACKGROUND
To follow up with that post I drove the 300km (180 miles) home with no major problem other than smoke blowing up from the vents... so with weeks of frustration surrounding the 412 I chose not to drive it through the winter. Now that this season has begun I pulled it out to give it another chance. First thing this year I changed the pushrod seals, head gasket seals, and the oil. This eliminated the smoke blowing up through the vents and all was looking good.
A few short trips driving around revelaed no problems requiring imediate attention. So I was ready for the first important trip, our clubs Season opener.
PROBLEM
It was about 20 minutes drive from home and with an added detour I was driving for about 30 minutes. NO problems hesitation or any indication of a looming problem. But just around the corner from the show it stalled at a stoplight. I restarted and drove around the corner into the parking lot (location of the show) and it died... plenty of witnesses and cameras to capture my 'new' car for the season.
It would crank but would not fire.
It refused to restart untill later that day (2hrs later)
I drove it to the restaurant after the show then home without incident.
When I drove to work Tuesday (about 25 minutes) it did the same thing as I got to work, and again about a block from home on the return trip.
I won't have time to look at it until this weekend, so if anyone has a suggestion before then It would be great.
Thanks in advance!
Dave

[vwfye]

this is exactly what my 59 bug did for 500 miles on a move. since it was carbed i thought 'vapor lock' and if i did open the line at the fuel pump it would bubble and then start againl. so, i thought vapor lock.. upon getting to my new home i found that it was actually the sock/filter at the petcock of the tank and the hard line was fouled too. so i took out the sock and blew out the hard line with compressed air and never had a problem again. check the sock/filter in the tank!

[Kombi]

check the sock/filter in the tank!

Sounds good, I'll double check when the tank gets lower, but I think I removed the sock when I had problems last time. (last time the problem turned ot to be a cloged fuel return line)

[raygreenwood]

Ah....I was looking back at your original problems. Did you ever replace the CHT? The lower end reading of 150 ohms is not bad. When hot it may go all the way to 70 ohms or so. But when cold...it should be higher than what you read on it....like between 2300 and 2500 ohms. If its way off...it could be forcing the fuel ,ixture to be too lean...or simply breaking ground. Ray

[vwfye]

mild hijack here...

based on everybodies 'shut down' issues on this site (including mine on the car i haven't gone to get yet) i just ordered a replacement (or back up) CHT for my 412. it was 27.50 through a portland, or VWFLAPS.

we are going to do the full FI test of the system with the VW FI tester this saturday. then, check the sockfilter. if that isn't it, then, the CHT will be the 1st item to check for ohm issues. second with be the air flow sensor as this is an L-jet.

[Kombi]

Did you ever replace the CHT?

I was wondering the same thing... I called my brother to order in another CHT and he said he still had one for me... So I guess I didn't
It was also sugested that since I had the rockers off to remove the pushrods.. It could be as simple as adjusting my valves... loosing compression as it gets hot. I've got three hours before I leave for a few days so I'll adjust my valves then pick up the CHT.

[raygreenwood]

DO NOT...mess with the pushrods....but do check the valve adjustment. D-jet out of all the systems is very critical on proper valve adjustment.

If your valve adjustment were so tight that you are holding the valves open and losing compression....you would know it instantly...as you would have major explosions/backfiring in the intake manifold . It generally will waste the AFM on L-jet in a heartbeat.

If they are too loose...you get lousey timing, noisey valves, runbly idle, flat spots....but will not by any means prevent running.
You also mentioned in your old problems that you had a generic pump. It could very well be overheating...stopping fuel flow...and shutting down to cool off. Itsworth it to see your fuel pressure again at the stll point.
Also...remove the FI triggers from the dizzy. Check themagain for cleanliness. This should be done at each oil change. They collect oil from the distributor shaft. They also can get grease from the cam on them. It can start to melt and flow. Also...if the triggers are worn and out of spec....as they heat up they can distort just slightly causing the failure of one pair of contacts or another. If one pair fails...the car will notstart. Then when it cools off...the point frame contracts and the car runs again.

I know you filched the apir from the rebuilt dizzy...but I have not found one new set in a rebuilt dizzy that I did not literally throw in the trash.

The critical problesm with hem...is either high resistancee from poor soldering...or to wide of a gap between the rubbing blocks. The gap should be between .915" and .925". Ray

[vwaddict]

Always check the easy things first. I got a steal on a 74 412 because of the same thing. Their mechanic replaced 2 fuel pumps, air flow meter and intake boot, 2 injectors and the fuel pump relay. It would run for about 15 minutes and die; sit for a few minutes and do it all over again. Turns out, the fuel filter was on backwards starving the motor of fuel.

[Kombi]

Status update:
I didn't get time until today to adjust the valves,
#1 was very loose, #2 was very tight , #3 was ok, and #4 was extremely tight. So i'm surprised it was running as well as it did.
So with the valves adjusted I figured might as well change the Head tempertaure sensor.... well I should have left it alone. It broke off... ie I have the nut and wire, but the sensor part is still in the head Guess I'll have to wait on that road test. sadly next day off isn't until Tuesday. Maybe before end of summer i'll get this running right

[albert]

hallo, kombi , go to look your fule pump , wend your car stop , you year the noys from the pump , some time the pump come over-heat and stop afther 20-30 minutes , for long life for your pump put smal quantitys of motor oil in the gaz thank (exp. 1or2 table spoon of oil in the ful thank of gaz ) albert

[vwbill]

Hey Kombi, how did you check for TDC? Just seemed funny she was running so well, but you can never tell! Did you go through the firing order then recheck afterwards? Not to question how you did the job but that sounded kinda the same I had gotten once and when I rechecked it was off again so I thought I wasnt setting the order right like number one closed and two exhausting, I think. So did you say the CHT broke off at the threads or the top of the sensor came off? Did you have the intake runner off? Maybe some of the guys have a better idea about that stuff. bill

[wallacehartley]

A fine looking wagon there, sir..............

[albert]

allo, kombi , i have suggestion for you, take smal 12 volts lamp , and connect the lamp with long wire at the fuil pump under the car , you instal the lamp inside the car , and the wire direct on the plug-in for the pump , and wend you go for the smal ride you see wend your pump stop , ok the pressure sensor start and stop the pump ,but if the light is on and if the pump d,t run ,the problem is with the fuil pump , (over heathing and stop or different problem, inside ) ,,,albert

[Kombi]

hallo, kombi , go to look your fule pump , wend your car stop , you year the noys from the pump , some time the pump come over-heat and stop afther 20-30 minutes , for long life for your pump put smal quantitys of motor oil in the gaz thank (exp. 1or2 table spoon of oil in the ful thank of gaz ) albert

allo Albert, the fuel pump is still running it was another problem.

[Kombi]

Hey Kombi, how did you check for TDC? Just seemed funny she was running so well, but you can never tell! Did you go through the firing order then recheck afterwards? Not to question how you did the job but that sounded kinda the same I had gotten once and when I rechecked it was off again so I thought I wasnt setting the order right like number one closed and two exhausting, I think. So did you say the CHT broke off at the threads or the top of the sensor came off? Did you have the intake runner off? Maybe some of the guys have a better idea about that stuff. bill

Removed the inspection plug, turned the engine over by hand until the notch was aligned on the fan, and the distributor was aligned with it's notch.
adjusted #1 passenger front, then rotated counterclockwise 90 degrees on the distributor adjusted #2.. etc...

the CHT broke off at the threads... not just a broken wire, but a broken sensor...
ie I have to remove the rails, the tin and drill it out... or I might swap the head, not sure yet. Tomorrows project if it's not raining. Unfortunately I have to have the engine rebuilt for my wife's T3 before I get much time on the T4.
I'll keep you posted.
Cheers!