D-jetronic has no injector pulses while cranking.

[crustychief]

The car is a friends 69 squareback VW.
I can get the car to start and run by adding a little fuel to the intake manifold, it runs good, it just will not start without that assistance. The car has no cold start circuit.
Cranking voltage is 11.7 at pin 18. Fuel pressure is 29psi while the engine is running. I had a new CHT sensor so I put that in and the temp sensor beside the distributor had resistance that was within the specs provided by Bentley. There are no injector pulses while cranking. I started the car by putting some fuel into each cylinder while I had the injectors out. It does run good. The owner asked about adding a cold start circuit, I told him that its better to treat the cause rather than treat the symptom. He agreed. I will not be able to get out to the car for a couple of days, so if anyone has any ideas I am listening. What makes up the injector pulses when the engine is cranking? Is it a different circuit than the "run" circuit? Thank you in advance for your help / advice.

[Tobra]

are the trigger points good?

[crustychief]

I am pretty they are. The car runs great after I add fuel to get it started. They checked out as per the Bentley. I posted on theSamba and was a little underwhelmed by the responses. Any help is welcome though.

[Tobra]

try go here
914/4 Tech Notebook

[crustychief]

Thanks for the link! some pretty good stuff on there.

[Tobra]

I would read the Kjell one first

Yeah, it is a pretty groovy link

[Dave at Pelican Parts]

Sounds like the voltage is OK. Since the trigger points work when the engine is running, they should be OK. You have verified that there is no injector pulse when cranking, and that there is one when running? (I'm trying to make sure your setup can measure injector pulses accurately.)

You have fuel pressure when cranking--is the fuel pump running while you crank the starter? Do you know if the pump is controlled by the ECU in the same way that the 914's is?

Check the voltage to the ECU (one of the pins in the T-4 connector, I forget which) while cranking. Hopefully it's not dropping to nothing.

Could be a wonky ignition switch, but I hesitate to suggest that because they're not that cheap, and it sounds like the quality of the new ones isn't as good as it could be...

--DD

[crustychief]

Dave, thanks for the reply,
I checked for pulses with a noid light.
fuel pressure is 29 while cranking and while running.
I had 11.7 volts at the ECM on the wire that comes from terminal 50 on the starter.
I replaced the switch with a brand new one because the old one was not reliably cranking the car.
I am reading the material on the link Tobra posted.
I have also went through the harness and cleaned / tightened all the connectors. At this point I am at a total loss as to what is going on, I need to learn more about this system and enjoy a challenge.
What conditions have to be met to receive an injector pulse during cranking? I.E. AAR range, throttle switch, temp switch ranges ETC ?

[bowlsby]

FI harness Grounds?

[Dave at Pelican Parts]

Check for voltage on Pin I (left-front pin) of the four-pin connector. That should get +12V when the ignition is on, and also when the starter is cranking.

As Jeff said, check the FI grounds. They're at the rear of the crankcase seam, up near the flywheel end. There should be a ring terminal with three male lugs coming off it around one of the case through-bolts. It should have three spade lugs plugged into it, with two wires crimped into each lug. All connections should be clean and tight.

What else? I'm not sure... Look for a missing ground or missing power where there should be ground or power.

--DD