Please help me get her running (74 1.8 stock) [Repost from Rennlist]

[BobbyQ]

U can add a inline check valve between the rails and the pump like I did for about $7. If it still doesn't hold pressure then it's the regulator.

[Dave at Pelican Parts]

Originally Posted by rgare

I haven’t checked for vacuum leaks because I don’t think this will keep the car from starting.

A bad enough leak will lean out the mixture to the point where it won't light off.

Just to be sure: Have you verified that you have spark, you have fuel, you have compression?

--DD

[Jared at Pelican Parts]

Originally Posted by rgare

I haven’t checked for vacuum leaks because I don’t think this will keep the car from starting. .

Yes, a vacuum leak CAN prevent a car from starting. L-Jetronic is pretty sensitive to vacuum leaks as well

Check/replace ALL hoses including the valve cover gaskets and also the oil filler cap.

[Tobra]

It is pretty rare for the ECU to be bad. If you read that link Jared posted, you will know more than most mechanics would know about it, seriously.

If you have air leaks in the intake, you get unmetered air and it will run lean.

You want to replace the O rings on the injectors, and all the rubber lines, and replace the nylon, or whatever that clear stuff is that goes through the body for fuel.

Had a bug with that FI system for many years. For my application, it had a rubber boot that connected the air filter to the intake manifold that developed leaks. I still have a spare one of those intake boots.

I never saw an L jet on a 914, but would bet a bet there are places where old parts would develop vacuum leaks as well as on the intake side of the motor.

Not a bad system, very simple, but if air is leaking anywhere, it will tend to not run worth a damn, generally lean and hot.

[rgare]

Originally Posted by Jared at Pelican Parts

Yes, a vacuum leak CAN prevent a car from starting. L-Jetronic is pretty sensitive to vacuum leaks as well

Check/replace ALL hoses including the valve cover gaskets and also the oil filler cap.

I've gone through the vacuum system and replaced the hoses, the oil filer cap, and the valve cover gaskets. I checked the throttle body boot, and it has no signs of cracks, it's relatively new. Still no joy.

[BobbyQ]

You said u had spark correct?
Do u have 30psi fuel pressure while cranking?
Have you done a flow test with injectors pulled?
Compression test?

[rgare]

Originally Posted by BobbyQ

You said u had spark correct?
Do u have 30psi fuel pressure while cranking?
Have you done a flow test with injectors pulled?
Compression test?

Yes I have a good spark
- I have 35psi while cranking, drops to 20 when the pump stops (New pressure regulator)
- I haven't pulled the injectors yet (I had them rebuilt and flow tested)
- I haven't tested the compression yet. Hopefully I can get time tonight to do that.
- New head temp sensor

Still not some much as a stutter, cranks quick

[roboat99]

Check the injector wires that are connected to the (ballast?) at the baterry box. Loose wires will prevent the injectors from working.

[BobbyQ]

hmm...
I'd do a compreesion test just to be sure.
Flow test:
pull the injectors, leave them hooked up, and place a cup under them and turn it over to double check they are spraying. I believe you need to hold the gas pedal to the floor while cranking, and be sure to unhook the coil so there is no sparks.

[rgare]

I asked this question, about this time last year and got a ton of great info (Thanks guys for all your help) and then got distracted with family and house projects. I’m back at it (must be something about spring). I read through all the previous posts and the car is in about the same condition.


Here’s the new part: I did an injector flow test and the injectors don’t spray at all, not even a wif. I had the injectors rebuilt, but they have of course been siting a while since then.

1. I confirmed I have good fuel pressure (I said 60psi before, that way off) it in the mid 30s (psi) while cranking and drops to about 10/psi
2. I checked the electrical plug both are hot one pulses while the engine is cranking. (I don’t recall which side). I had assumed that one should be hot and pulse and one should go to ground. Can someone confirm that? (Recall that this is a 1.8 L-Jettronic)
3. I tried to get the injectors to fire manually with test leads, one to ground one to battery, and nothing. I had expected them to “click”. Can any say whether or not I should hear and audible “click”?


Now my thoughts are:
1. I burned them up
2. I’ve got something connected wrong
3. My EFI Brain is bad


I checked the connection to the coil against the schematic in Haynes manual and I ‘m confidant that I’m good. I don’t know what else I could have gotten crossed, most of the electrical connections that I can think of are keyed and/or pretty obvious.
Seems unlikely that the brain would have died in such a way that it’s providing power to a pin that used to be ground, I took the Brian out of its box to check for corrosion, and there isn’t any, it’s super clean.
I’d appreciate some advice on next steps, tools/techniques I can use to rule out Brain, Injectors and other pertinent components. Other things that I’ve missed.

As always thanks for you-all’s help


RMG

[Dave at Pelican Parts]

What electrical plug were you checking?

The L-jet injectors work by getting voltage from the dual relay. It goes through the resistor pack (which also hangs off of the battery tray) and then to the injector. The ECU provides a ground when it is telling the injector to open, then disconnects it to close the injector.

The ECU gets its power from the same circuit as the injectors, from the one half of the dual relay.

The other half of the relay runs the fuel pump.

The ignition points tell the ECU when it wants to open the injectors. That's why there is a white FI wire plugged into the (-) terminal of the coil.

--DD

[rgare]

Originally Posted by Dave at Pelican Parts

What electrical plug were you checking?

The L-jet injectors work by getting voltage from the dual relay. It goes through the resistor pack (which also hangs off of the battery tray) and then to the injector. The ECU provides a ground when it is telling the injector to open, then disconnects it to close the injector.

The ECU gets its power from the same circuit as the injectors, from the one half of the dual relay.

The other half of the relay runs the fuel pump.

The ignition points tell the ECU when it wants to open the injectors. That's why there is a white FI wire plugged into the (-) terminal of the coil.

--DD

I was checking the two pin connector for the front drivers side injector. Both pins on the injector connector were hot (I was using a test lamp while my son cranked the car), one pin was always hot, the other one pulsed. I check continuity between the injector connector and the ECU connector and it matched what the Haynes manual showed.

Should I check the injector connectors to the resistor block?