the dreaded relapse

[Longbeach412]

Hmmmmm. I don't recall the conversation regarding having to modify the plug. It shouls have been a simple female connector , plugging straight into a T-1 male connector. It sounds like you had the wrong part.

Not the plug, the 13mm socket. We talked earlier about cutting a slit along the length of it to allow space for the sensor's wire. As to the difference in wire size, I did some tinkering with the old sensor,......turns out that the wire is encased in 2 insulating tubes, one black, and the outer semi clear. But the wire itself is the same gauge in both sensors, its just that the new sensor came without those 2 tubes. With those tubes in place, its impossible to bend the wire in any shapes, but without them I managed to form the wire into a compressed coil and fed it inside the 13mm socket and didn't have to cut a slit into the socket.

[raygreenwood]

Ah...i understand. That little plastic tube of semi-clear plastic is UHMW polyethylene...or polypropylene possibly. It is strain relief to keep teh wire from whipping in the wind inside of the sheetmetal and wearing out. It is worth it, if you have crimpers...to install the sensor, sans the strain relief and terminal...then slip teh terminal down and fasten in pace with a drop of JB weld...then crimp on the terminal. Ray

[Longbeach412]

I was actually thinking the same, I figured it must be there for a reason and the area down there is tight and dark and its easy while fummling around for the spark plug or fuel line to abuse that wire. The new one came without the clear tube, and I installed it already. So am gonna do a little retrofitting and slit the old tube and snap it onto the new wire, then seal it with epoxy or JB.

[Longbeach412]

well, thing seem to be going backwards, last night I went to work on it some more and now its back to phase 1, back to no starting!! ......it seems to be getting too much gas just from the smell of things. I am now reading thru the L Jet diagnistics looking for clues but I have some questions stemming from ignorance, can a battery be good enough to crank the motor robustly but not strong enough to power the logic system? and, will disconnecting the cold start valve interrupt the logic sequence?
Just to rub it in, my type 3 is running like a swiss clock lately, and..........I had a carb kit flash by in my dreams last night

[DeathBus]

Check all your fuel lines, and your injectors, if there are ANY leaks in your fuel system it will either run funny or not run at all.

[raygreenwood]

Lets think about this for a couple. What could give you too much gas on starting with L-jet? 1) If you have vacuum leaks that do not show up on a standard vacuum gauge once the dar is warmed up...IE...fissures in seals that close up under heat, you could be losing vacuum that keeps your fuel pressure in the correct range. In simpler terms, for whatever reason, you may have low vaccum. 2) This system, not unlike D-jet, runs mainly on variables in resistance. If you have any wires from ...say the CHT, or leading to the AFM that are exhibiting higher than normal resistance, then it can cause fuel mixtures to run high. 3) If the cold start injector is running...possibly from a thermotime switch that is defective....it could cause this. If the Thermotime switch thinks its colder than it really is...it could be a problem.

Actual poor fuel usage can cause this. If you have vey low compression, it may have a problem using the normal amount of fuel. Also, your valve clearances must be spot on. Lastly, the timing could be a problem. You should have about 10 BTDC at idle for most efficient running. If you idle at "0" advance, it will be rough because it cannot burn all of that fuel effectively. Also, if the advance is really sloppy...usually loose springs...it can cause this. Likewise, if the advance is stuck...same thing.
Also, check th movement of the flap in the AFM. Also...check to make sure the bypass screw on the AFM has at least 2.5-3.0 turns out from totally seated, or the flap will move too far and run you rich. Ray

[Longbeach412]

Well, here is another update while I read you analysis guys. This after noon its back to phase 1 again, it starts, rund beautifully strong and robust, 30-60 seconds later it dies. no stumbling no hesitation, just clear cut dies. Almost like someone turned off the ignition. This is repeated any time you start it.

[DeathBus]

Is there gas in the tank?

[Longbeach412]

Yes DB the tank is 1/2 full, I also replaced the fuel pump relay with a known good one, tested the pump by actuating the AFM flap with the cold start line disconnected. It sounds like "something" is telling the motor or the fuel pump to shut down.

[DeathBus]

Well sometimes its the easy things, just wanted to make sure.

[Longbeach412]

You aint kidden. Been there many times

[vwbill]

I had that problem with thinking the gauge was right but when I put a hose in the tank nada,lol! Hey does it sound like the cold start system is working ok? All the books seem to be saying its the air flow meter. They say to test between term. 36 and 39 of the air flow meter and if Infinite ohms with flap closed to zero ohms with the flap slightly open then its ok but if no change the air flow meter is bad? Are you using the tank as the fuel source or another tank? Maybe you have something being drawn to the tank pipe. How long does it take for the cold start system to be at temp? What about the aux air reg but you said you tested that? Can you bypass the air reg? Its weird she is running normal then fails... Could a coil do this if it had a bad wind and was heating up? I think you have to use another fuel source to make sure its not the tank. Can he pull the plug on the cold start valve to see if that is letting it start and running? Hey what if you take a spray bottle and when she is about to do the stall thing you spray fuel in her to see if its fuel? How could he tell if the coil was heating up a break inside? If you can get her to run with a spray bottle or some other way you can rule out a coil heating up? bill

[Guest]

Man, that's tough. Hey LB412, it might be good at this point for you to recap all the troubleshooting you've done, to see where to go from here.

I'm thinking all the things that can cause the "runs 30 seconds then dies completely" symptom from an inspection of the schematic diagram and the L-Jet system book are:

Fuel flow stops suddenly (pump problem, filter blockage, line blockage)
Injector drive signal goes away (ECU thermal intermittant, resistor pack thermal intermittant, injector supply wiring intermittant, or main relay issue)
Injector drive signal goes full-on (ECU thermal intermittant)
Mixture goes totally out of whack suddenly from other causes (ECU thermal intermittant, AFM flap variable resistor has a bad spot in the resistance track, temperature dependant vacuum leak downstream from the AFM)
Ignition stops (coil thermal intermittant, points weld closed, condenser intermittant short).

You've taken one possible cause off the list with the new CHT sensor.

From and inspection of the schematic diagrams, the cold start injector in both L-Jet and D-Jet is powered by +12 Volts from the starter, so once you release the key and the ignition switch returns to the "run" position, the cold start valve is unpowered, and thus closes. If the engine starts and then dies later, it can't be the cold start valve not opening, because the valve shouldn't be open when the engine's running anyway.

[MGVWfan]

That was me

[DeathBus]

Check for loose connection at distributer trigger points

Check the pressure sensor both electrically and for leaks.

Check for voltage drops across connections from battery cables to battery posts.

Check for broken, dirty or loose connections at starter terminal 50 (on the starter)

also check for dirty or loose connections at the temp sensor.

Check for correct fuel pressure.