Is there any way to tell if my L-jet brain is dead without swapping it Options

[jd74914]

Hi guys, heres the problem.

A few months ago my car was running great. I had just rebuilt the engine and put everything back on. After fixing some grounding problems it ran perfectly.

Then, I went on vacation, came back and did some welding and forgot to unhook the brain when I unhooked the battery. After this the car wouldn't start. It wasn't getting any fuel. The coil also got really warm at one point, so I replaced it with another known good, new one I had. Now with the new coil, and a new fuel pump (I also had a known good pump) put in, the car still won't start.

It turns over fine, but it won't even run for a second on the cold start valve (IMG:style_emoticons/default/sad.gif)

Is there a problem with the brain or is there something else I should look for? I can't think of any other things to go bad. (IMG:style_emoticons/default/idea.gif) I'm pretty sure the points are good.

Its a 74 L-Jet BTW

[jimkelly]

guess you gotta check for spark, is fuel pump coming on?, and check for power at the fuel injectors?

[jd74914]

The pump isn't coming on at all. Thats what has me confused. If I jumper is, and have it running no gas is still getting into the engine which means the injectors aren't working.

Can anything else but a bad brain cause the pump not to run and the injectors not to fire?

I made a mistake . . . there is spark so the points are definitely good.

[r_towle]

remove the big ass Air flow meter valve from the large intake rubber hose.

turn the key to the run postion, no jumpers on the fuel pump, just have it wired correctly.

gently slide your finger in the Air flow meter and move the plastic flapper door with your finger...
When you move the door just a bit open, the fuel pump will turn on.
These cars are kinda wierd to start with no fuel in the lines.
This is how I had to "prime" the system.
The fuel pump will not come on under normal conditions until the motor is running and sucking enough air to move that door open...
So, you replaced the fuel pump, yet there is not enough fuel pressure in the lines to get the car started to open the door to get the fuel pump running...its a catch 22.

When you run the pump, listen and you will hear the tone of the pump change and lower down because its under load. When it does that, the fuel system is now pressurized, and the car should start.

If your stuck, I have two unknown Ljet brains you can borrow to test..

Rich

[jd74914]

Ok, Thanks for that thought Rich.

I'll try priming the system when I head home on Saturday, hopefully that does the trick.

[Dave_Darling]

The pump should also run when the starter is cranking; that's what the wire hooked onto the four-pin connector on the relay board does.

--DD

[jd74914]

The pump should also run when the starter is cranking; that's what the wire hooked onto the four-pin connector on the relay board does.

--DD

Is that a single yellow wire? If so I unplugged it because it caused the starter to not stop cranking over (IMG:style_emoticons/default/screwy.gif)

[SLITS]

The single yellow wire to your starter is from your key switch which delivers the 12VDC to the solenoid in the "start" position.

If the starter continues to run, you've got problems elsewhere (Ignition switch, relay board connections, starter solenoid or incorrect wiring.

[Chris Pincetich]

I just went through this with D-jet and the solution was that my brain was loose. I pulled off the brain connector cover to expose the wires for testing, and the entire plug had wiggled to the point it LOOKED good but was not apparent until I PUSHED it in more. After that, fired right up and kept going! You can take off the air cleaner, pull on throttle, and spray Starter Fluid down in there and if it starts and runs for 5-10 seconds, you can rev it too, then you know you have good spark and stuff. Good luck! (IMG:style_emoticons/default/beerchug.gif)

[bd1308]

that yellow wire goes to the bottom RIGHT pin on that 4 pin connector.

any of the others get either ground all the time or get 12V all the time, neither of which is what you want.

I had an issue with the starter not quitting starting from that yellow wire being plugged in, but I eventually figured it out.

[jd74914]

Bottom right is i'm looking from the battery tray? or from the trunk?

[bd1308]

trunk

[jd74914]

mine was always plugged into the left thanks

[computers4kids]

mine was always plugged into the left thanks

Mine was always plugged into the top right and all worked great for two years.

[bd1308]

if you stood behind the trunk and was looking at that pin, is it not the bottom right?


thanks

[computers4kids]

if you stood behind the trunk and was looking at that pin, is it not the bottom right?


thanks

Tow/motto.....Toe/matow....tomatoe (IMG:style_emoticons/default/happy11.gif)

[bd1308]

alright here's what you need to do:

After the system was installed in my car, nothing worked.

The Ignition turns the IGN relay on the relay board, which feed power to the dual relay.

with the car off, you should be able to open the dual relay and press down either relay--one should turn the fuel pump on, and the other should turn the FI computer on (click! goes all injectors once)

when you turn the key, you should hear two relays ( or more I forgot)

one should turn on on the relay board, and one you should hear from the dual relay--if your dual relay doesnt click, its either bad or you need to check the relay board (on the 914).

i have a dual relay i can send you for testing--its in not prefect shape, but it'll do for testing and you wont have to open yours.

[jd74914]

I think I have heard the clicks . . . I'll check again this weekend. If not, then I'll probably send you a note Brit, thanks.

[ClayPerrine]

The Ignition turns the IGN relay on the relay board, which feed power to the dual relay.

Britt.. I hate to do this but the above statement is WRONG!


You can pull every relay out of the relay board on an L-Jet car and it will still run. NONE of them have anything to do with the injection.

The double relay is powered off the heavy red wire that comes from it and attaches directly to the battery positive lead.

The fuel pump is powered 2 ways, one by the starter circuit when the engine is cranking. That signal is obtained by connecting the yellow wire on the engine harness to one of the 2 rearmost spade connectors on the 4 pin relay board connector. Both of the rear pins are connected together. (And a trivia item, you can connect a remote starter button to those connectors and feed battery voltage to them to get the engine to crank).

The second way is when enough air is moving through the air flow meter, it closes a contact that turns on the fuel pump via the double relay.