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

I own a stock (original fuel injection) 74 1.8 914, it was my first car and for many years my daily driver, but then one day it wouldn’t start. I had another car and a fiancé so I let it sit in the garage. My fiancé became my wife and four kids and tens later it’s still in the garage. So now I’m fixing it. But I’m stuck, and I could use some help. The car doesn’t start at all.

This is what I’ve done.

Fuel: I drained the gas (yes I let it sit in the tank for all those years) took the tank out and had it cleaned and coted. Sent the plugs out and had them cleaned, new seals, flow tested and repaired (one of them leaked down)

Fuel Injection: I have a pressure gauge inline, just before the driver’s side fuel rail (under the air box). When I crack the engine the gauge reads around 60 psi and then drops to around 10psi. I’ve check the injector’s connection with a circuit test light and the light pulses as the engine cranks. Pull the sparkplug and there is faint smell of fuel.

Based on this I think the fuel system is operational

Ignition

New: Sparkplugs, points, coil and condenser. When I turn over the engine I get a good spark jump from the plug wire to the case. Plug wires are old but show very little resistance. Plug wires are plugged in according to diagram from repair manual.

Based on the fat spark I think the ignition is operational.

Head temperature sensor: I removed this from the car and tested resistance. Measured 1.7K at 70F. Put the sensor in the freezer for around 10min. Measured 3K ohms and then rapidly decreased to around 1.7K. Manual says that sensor should read between 500-2500 ohms, and should be at 2500 ohms at 68F. Is the sensor bad?

I can’t really think of other things to test. Every so often I charge up the batter so the car cranks well, but not even a sputter of a start.

Please give me some ideas; I’d really love to get her started again.

Have you checked for vacuum leaks?

I assume its a D-jet?
If you have fuel and spark it should do something.
How long does the gauge stay at 60psi? It should be reading about 29 psi. That is what your regulator is suppost to be set to. Does it stay above 30psi while your turning it over?

Vacuum leaks are very important I agree. But it should still be trying to kick over some.

Stock FI for a 1.8L is L-jet. Mine is down too. I'll be watching this thread.

I thought fuel pressure should be something like 29psi?
I'm not familiar with L jet, so I could be wrong.

did you re-connect the wires on the coil correctly? fuel pump relay on l-jet is a common problem 10 psi seems low. did you try starting spray to verify she will fire up

ok, I didn't know. I have a '74 2.0 w/ d-jet.

spark, fire, compression= running

You have spark
Rent a compression tester from local parts store
Wire fuel pump direct and let it run full time and try that.

Have you replaced the fuel filter? It may be all gummed up from the old fuel. The L-jet has a cold start injector (at least the 912E has one). Is yours functional? Did you get it cleaned?

Fran

I agree + CHT, will not start without the CHT

"One day it wouldn't start." Have you considered this? Remove passenger seat. Locate box with thick yellow wires running into it. Disconnect battery. Then snip the two wires. Peel back the insulation wire nut them together. It is a Seat belt interlock. 1974 Cars won't start unless your seat belt is buckled. When the module fails, car won't start. You can replace it $, or bypass it. I would think the module would have failed years ago, but just in case...

I haven’t checked for vacuum leaks because I don’t think this will keep the car from starting. I think vacuum leaks would cause it to die, and idle/run poorly.

10 PSI is the residual after the pump stops, I'll go back and check it maybe 60 psi was wrong.

I did replace the fuel filter, and I made sure it's going the right way.

I ordered a new CHT, but it's not here yet, the temp sensor was in the car and connected while I was doing my trouble shooting.

Will the engine crank if this is the case? I thought it would just click, like the battery was dead. I'll check it.

Fuel pressure should be 35psi. How long after running the starter does it drop to 10psi? Pressure regulator may be shot.

http://www.bowlsby.net/914/Classic/zTN_Man08.pdf

Read..

Mine use to bleed down pretty quick after I shut it off.
As long as you have 20-30psi while cranking it should start.
U said u had spark.
The vac lines u can replace later. It should be tryin to start even with bad vac lines.

Fuel pressure drops off immediately, holds steady while pump is running, then drops off when pump stops, holds at 10psi till it slowly leaks down. I've never timed how long it takes but, it's long enough I don't stand there and watch it.

Talking this over with a guy at work he theorized that the connections to the ECU might need to be cleaned. Has anyone ever seen this to be an issue?

He thought something like this would be good.

Amazon.com: CAIG DeOxIT D100 Power Booster Metal Electric Connection Cleaner, Enhancer, and Lubricant: Musical Instruments

Thanks: I'll go through this, is the 914 L-Jet exactly the same as the 912s?

Similar enough for you to diagnose. The main difference is that the 912E motor is a 2.0 whereas you have a 1.8.

Fuel pressure should not drop off immediately. It should hold in the lines for a while. This could be a bad fuel pump check valve or the fuel pressure regulator.

Check to be sure you have the inlet fuel line connected in the proper routing. If you connect the inlet and outlet (return line) backwards the car will not run. Fuel line loop should run inlet, injector rails, regulator, return line. don't ask me how I know...

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.

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

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.

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.

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.

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 :confused:

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

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.

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

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?