No Start Help Requested Please, 1975 1.8 L-Jet no start after 10 minute soak Options

[rbzymek]

So this is a conversion from a carb which was running great with the new FI. I had just installed an AFR meter and was adjusting the AFR to about 13:1 during a 30 minute run. Stopped at the grocery store and had a crank with no start after a 10 minute soak. The harness is newly fabricated, rebuilt AFM from AutoAtlanta, gas in the tank, I do have spark, fires with starting fluid, fuel pump runs when vane is moved, have power to the ECU, no difference with second ECU, voltage to the injectors with key on, new Pertronix III dizzy with Flamethrower III coil, have fuel pressure (40 psi), throttle switch doing what it is supposed to, AFM voltage output varies with movement, Air temp thermistor in AFM is in range, CHT reads 2.2 K ohms.

I'm kinda running out of ideas. Got any???? Thanks!
Ray

[JeffBowlsby]

40 psi fuel sounds high, did you verify that with factory specs?

[rbzymek]

40 psi fuel sounds high, did you verify that with factory specs?

Jeff,
Thanks for responding. The spec is 35.7 psi. I guess that extra 4 psi could keep the injectors from opening after a hot soak which would increase the resistance and lower the current. I do have an adjustable regulator I will try. It's just strange that I could go from a great running engine to a no start. Thanks for the suggestion.
Ray

[ndfrigi]

I believed 1.8 FI should only have between 28 and 31 psi on fuel pressure

[rbzymek]

40 psi fuel sounds high, did you verify that with factory specs?

Jeff,
Thanks for responding. The spec is 35.7 psi. I guess that extra 4 psi could keep the injectors from opening after a hot soak which would increase the resistance and lower the current. I do have an adjustable regulator I will try. It's just strange that I could go from a great running engine to a no start. Thanks for the suggestion.
Ray

Well I dropped the pressure down to 32 psi. still no start.
Ray

[ndfrigi]

maybe flooded with gas? did u try starting it while gas pedal all the way to the floor?

[timothy_nd28]

I had a similar condition on mine, hard start conditions when warmed up. I ended up retarding my dizzy a smidge

[ndfrigi]

finally Tim is here and he will definitely can help you Ray! His the best especially with ljet! Learned a lot from him on ljet system.

[rbzymek]

finally Tim is here and he will definitely can help you Ray! His the best especially with ljet! Learned a lot from him on ljet system.

ndfrigi,
Yes I did. I will take a closer look at the CHT sensor next.
Ray

[rbzymek]

finally Tim is here and he will definitely can help you Ray! His the best especially with ljet! Learned a lot from him on ljet system.

ndfrigi,
Yes I did. I will take a closer look at the CHT sensor next.
Ray

The CHT reads about 2200 ohms at room temp which is normal. I pulled two injectors and cranked the engine. There was no fuel spray. I pulled the connector and probed both wires with a LED tester and there was no activity. So the module is not firing the injectors. The coil wire has continuity to pin 1 so it is getting a firing signal.

What else besides the a CHT failure would cause the module not to fire the injectors?? I guess I will verify power and grounds to the module connector next.
Ray

[JeffBowlsby]

Ljet injectors ‘ground’ through the resistor pack. The wires on the resistor pack frequently break off at the resistors and this condition is easy to inspect.

[rbzymek]

Ljet injectors ‘ground’ through the resistor pack. The wires on the resistor pack frequently break off at the resistors and this condition is easy to inspect.

Jeff,
Yes, I understand that a broken wire at the pack can shut it down. I believe that the power is routed from the FI relay to the resistors then to the injectors. The other side of the injector goes to the module where a transistor grounds it to turn it on. Last night I put a scope on each side of one injector and found that I was intermittently losing power to the injector when cranking. When I placed a jumper from B+ to the main resistor pack feed the car fired up and ran. Woohoo! Later today I will place all four scope channels on the dual relay to determine the root cause. Thank you for your suggestions. I will let you know what I find.
Regards,
Ray

[Dave_Darling]

Power to the injectors comes from the dual relay, then goes through the resistor pack, then to the injectors, and the ECU either provides the ground (which opens the injectors) or no connection (which lets the injectors close).

Suspect the dual relay and the wires going to it, as well as the stuff in the path of the power and ground that the dual relay uses. (E.g., ignition switch, relay board, etc.)

--DD

[JeffBowlsby]

Our own Jim Hoyland documented the dual relay test protocol here

[rbzymek]

Our own Jim Hoyland documented the dual relay test protocol here

All,
Thanks for the tech support. I put the 4 channel scope on the dual relay and saw a lot of bad behavior. Then I popped the relay open and found the corroded mess below. I bought the relay from CIP1 in early May so it was damaged before I received it. They obviously have a quality process problem. My refund request is in and a new one is on order fro AutoAtlanta. It is surprising that it ran the car at all. (I also had to pay $90 to get it towed home.)