OK-

Background: 1.8 1975 LJet. Recently refreshed engine to address myriad of sins from previous owner. Trying to put the FI back to stock from a megasquirt install which seemed problematic.

I am trying to get the car started again. I sourced and replaced the 'hacked' megqsquirt FI harness with an original confirmed 1.8L harness.

I am having difficulty getting fuel to the injectors. The plugs are dry. I can feel fuel being pumped, but there is no fuel delivered when I pull the injectors and place in jars to see if fuel is being delivered.

Fuel Injectors were refreshed and tested by Mr. Injector.

So ... before I start addressing fuel, I wanted to confirm that there is not a 4PIN block on the regulator board that I'm missing.

I've poured through Jeff's site (what a service you provide!), and I think what I have is correct, but wanted to confirm. For my own sanity.

Notes in red and question in green.
Many thanks in advance.

See attached graphic
Click to view attachment

Yup just one goes to the relay board.

You're sure everything else is working? It sounds like the resistor pack may be having issues. It's a small, rectangular, aluminum covered set of resistors located (typically), under the battery tray, screwed to the battery tray support. The wires, over 40 years, have a tendency to break right at the resistor. You may not see it unless you pull the resistor pack. Four resistors in there, stepping down the voltage to the injectors. If any of the wires are broken, at minimum one bank of injectors won't fire.

Good tip. I'll test the resistor pack as I have a spare. It has to be something basic. I'm pretty certain I have supply and return lines correct, but will double check again.

Thanks for the confirmation. I wanted to verify/eliminate the harness connection question.

Thanks

Greg

Keep us posted!

Also, if you look at the schematic, I don't believe all four of those posts have 12v power. I believe it's only the two that are closest to the side wall of the engine bay. Check a schematic to be sure.

Thanks. Will do.

When I pulled the resistor pack connection, the poles where a bit oxidized on the harness side. I'm going to test the resistor pack and clean up all the poles and apply a bit of dielectric grease.

Next plan would be to pull the whole FI harness and verify continuity.
I do know that my grounds are good on the ganged 3-way prong on the engine block.

I did put the old butchered megasquirt harness and Megasquirt ECU back on (which worked before, but was problematic) and still was not getting the fuel injectors to pulse. That lead me to the original question as I was uncertain if I was missing a four-pin block harness wire on the relay board given the butchered harness that came with the car.

Also, have a new red top Optima battery on the car.

Appreciate the help!

I'll report back as soon as my real job quits getting in the way.

Check the injector trigger points in the distributor. If they stick the injectors wont fire!

Photos of Injector Trigger Points

L-Jet cars do not have trigger points, my friend.

Guess I missed that it was a 1.8L, reading to fast!!

Sorry never mind!

The L-jet only has the one connection to the four-pin plug where the "crank the starter" signal goes. That's how L-jet "knows" the starter is cranking. It uses that signal to power the fuel pump and the injectors and ECU.

L-jet uses the dual relay to send power to the resistor pack, which then sends the power to the injectors. The ECU provides the ground to the injectors, completing the circuit and making them open. Double-check that there is power to one side of an injector plug while cranking, then check for a ground/open/ground/open on the other pin in the injector plug.

How's the ground? I don't remember how the L-jet grounds, but it is definitely important that it does have a path to a good ground! (On D-jet, there's the multiple ground point on the crankcase seam; not sure if L-jet has the same or just uses a chassis ground.)

--DD

Just to confirm a few things. The injectors aren't pulsing? Or they may be pulsing but the car won't start because it's not getting fuel? Because those two issues have different routes to check.

If you have a chance, pull a fuel hose and turn it over (be safe around ignition sources!!!). I would choose the return line just before it leaves the engine bay. That way if you are getting fuel, you're safe in assuming that fuel is making it past all the injectors and the cold start valve and heading back to the gas tank.

If the fuel pump is working you should get a decent stream of fuel coming out of that hose when the ignition switch is turned on.

Next the dual relay comes into play. The fuel pump is controlled by the dual relay. You said you read up on L-Jet, so I'm sure you understand that the fuel pump turns on with the ignition switch 'start' key position on the dash, but then control and continued operation of the pump comes from the AFM. If the flap on the AFM has moved past it's resting position, the ECU and dual relay understand that to mean that the engine is getting air, and keeps the fuel pump running. If you have a helper you can check that too. You can manually move that flap and listen for the fuel pump running.

If the pump is pushing out fuel while the ignition is turned on AND the AFM has moved past it's resting position, then you've got fuel running through the fuel line loop, it just isn't coming out of the injectors. If that's the case, then the problem is most likely the resistor pack. You can use a stethoscope to listen to the injectors firing. Or if you don't have a stethoscope, put your ear on the plastic end of a long screwdriver and the other end on the metal body of the injector (Clay Perrine checked mine that way!).

If the resistor pack checks out we can move on to checking continuity, but between continuity and checking resistance values or components, I don't think you really need to pull the whole harness out. You should be able to check the continuity and resistance with the components in the car. But we'll get to that later.

All good advice.

Dave, L-Jet has a ganged ground on the seam of the case through bolt, identical (or almost) to the D-Jet ground.

Thanks for the help. I had a few minutes to test. This is where I'm at:

Fuel delivery confirmed at supply and at return. Confirmed delivery with yellow wire on Post II of regulator plate.


Swapped resistor pack. Tested. Same result. No fuel from injectors.

Swapped dual relay with a crusty one. Same result. No fuel from injectors.

Some additional info:
New 7MM fuel lines. As mentioned, recently serviced injectors' are: Bosch 022906031c

I have only been testing cylinder 3 and 4 injectors. I can test 1 and 2 injectors to see if it's a systemic problem.


I'll move on to the stethoscope test. And get a helper to test AFM. I also have another AFM I can try.


Appreciate all the help! Will keep you posted.

The 1.8's L-jet opens all four injectors at the same time. So it doesn't really matter which ones you test.

Do you have the white wire plugged into the coil (-) terminal? That's how the injection knows when to fire the injectors; this wire carries the points signal to the ECU.

--DD

Hi Dave, yes. Confirmed on Coil (-) terminal and thanks for info.

I think I may have a path to follow. But will post the following so the path doesn't turn into a rabbit hole!

I used the L-Jet trouble shooting guide found here
~~~
Test voltage supply to the ECU
Turn the ignition on.
Measure the voltage between terminal 10 and system ground at terminal 17 of ECU plug.
The reading should be 11-12.5 Volts.

No reading: Open circuit in cable from main relay to ECU, main relay does not energize, ignition switch defective (check for voltage at terminals 86c and 88y of relay against ground). Check cable 10 connecting main relay and ECU for continuity.
~~~

I tested Terminal 86c and 88y on double relay and they did not produce any volts when ignition on.


I need to pour through the wiring schematic a bit more, but could the root cause be a defective ignition switch?

Secondly, and this may be a dumb question, assuming the trouble-shooting guide means check voltage with ignition on and not check while engine is being cranked, correct?

Resolved!

Cylinder #4, FI connection #33 and Cylinder #1 FI Connection #14 BOTH had their respective female spade connections slip on the FI harness. Hardly noticeable at all.

There was also a modified AFM which I never noticed due to the housing (obviously from the old megasquirt connection). Fortunately I had another stock AFM and replaced.

I didn't notice until I started to go carefully through harness.

I will say the voltage supply test chart was invaluable. as I just kept working the steps.

Thanks for all who pitched in.

She's a squirting fuel! So now I just need to start working on timing. The stock distributor looks like it needs a good cleaning, so I think I'll have another fight as I dial in timing and dwell.

It will be so nice when this car is put back to stock as it's challenging to baseline work from the PO.

Cheers-
Greg