Fuel Injector Problems

[jdhughes17]

My 1981 Spider has been dead in the driveway for 2 and a half months now, and it still won't start. My dad and I found that the fuel injector, upon turning the ignition, is not receiving an electrical pulse to turn on. The car will chug for a few seconds, then stall. The fuel pump still works because we can hear it running when I turn the key half way. [EDIT: the fuel pump comes on when key is turned to start position. So that's fine.]

I have read other posts that mentioned the ECU being in control of the fuel injector. We originally though it was the fuel injector relay, which we replaced, but that still hasn't done anything. We also checked all the fuses, and they're fine. Last night we detached and cleaned the ECU ground on the bottom of the car, but it still won't start.

If you have had any similar problems, help would be appreciated. I need this car running asap, because it is my daily driver and I can't get to school or work very easily without it.

Thanks, Jared.

[76was124]

So when you say the fuel injector, do you mean fuel injectorS (all of the main ones)?

How did you test the electrical circuit to determine its not firing the injector(s)? Did you use a Noid light (recommended)? A digital volt meter won't work very well because they are too slow to see the on/off pulses. Some analog meters can work, but you'll only see a rhythmic flicker in the voltage reading, as the on/off is happening very fast and can't be fully represented by a meter.

The injectors should have 12 volts [edited note: fixed typo that said 24volts]on one pin constantly in the run mode, and the second wire on each injector is then pulled to ground to complete the circuit to energize the injector coil.

There should be two ground wires on ring terminals mounted to a bolt on the top of the intake manifold near the driver's side firewall. There Should also be a third ground wire on the passenger side firewall wall connected to the back of the exhaust cam box. Make sure these connections are there and clean.

Also, regarding the fuel pump running with the key turned part way. That is not per factory wiring, the fuel pump shouldn't run until the key is in the start mode. Once air flows through the AFM , there is a contact in the AFM that keeps the fuel pump running while the flap is at least partially open. The idea is that if you have an accident, you don't want the fuel pump running if the engine isn't. If your car was previously working, it's probably unrelated to your current problem, but something you may want to fIx.

[divace73]

The injectors should have 24 volts on one pin constantly in the run mode, and the second wire on each injector is then pulled to ground to complete the circuit to energize the injector coil..

Most probably a typo, it will be 12V not 24V

[ORFORD2004]

The injectors should have 24 volts on one pin constantly

12 Volts

[GeorgeT]

Check the Double Relay.

[joelittel]

http://www.hiperformancestore.com/ljetronic.htm

The above article was written for an Alfa but it discusses the Bosch L Jetronic system, which is what our FIATs have. I'm not sure if it covers your particular issue but it addresses just about every other known problem.

Since you're "already in there" I suggest running through the maintenance steps the article outlines.

Good luck

[azruss]

if the fuel pump runs with the key half way, good chance the dual relay has been bypassed.

[KevAndAndi]

JD, are you talking about the cold start injector?

if the fuel pump runs with the key half way, good chance the dual relay has been bypassed.

Yes, but there's perhaps a greater chance that the fuel pump contact arm in the air flow meter has been bent. I say that because it can occur through both spontaneous or intentional means. But again, that's a secondary issue to be corrected later.

[wizard124]

My 1981 Spider has been dead in the driveway for 2 and a half months now, and it still won't start. My dad and I found that the fuel injector, upon turning the ignition, is not receiving an electrical pulse to turn on. The car will chug for a few seconds, then stall. The fuel pump still works because we can hear it running when I turn the key half way.

If you are talking about the cold start injector, this is only energized when the key is in "start". Disconnect the electrical connector, touch the 2 prongs of a multi-meter (set to 12V scale) and watch for fluctuations as you crank the engine over. It is a grounding circuit with the NEG coming thru the thermo time switch to the CSI connector.

If you mean the fuel injectors, they are not triggered until the car is cranking. The ECU sends a NEG signal, but only when the coil sends an electrical signal which the ECU modifies into an injector pulse. Without the rotor spinning inside the cap causing a coil discharge, there is no FI pulse sent.

I would disconnect the fuel line at the CSI and make sure you are getting a strong flow of fuel when you crank it. Have a pint jar at the ready to catch the fuel. You may have a bad pump or clogged filter causing your problems.

Then test for spark and ignition problems. Rule out the simple before you dive into the FI system.

[KevAndAndi]

If you are talking about the cold start injector, this is only energized when the key is in "start". Disconnect the electrical connector, touch the 2 prongs of a multi-meter (set to 12V scale) and watch for fluctuations as you crank the engine over. It is a grounding circuit with the NEG coming thru the thermo time switch to the CSI connector.

You can also diagnose with a test light between the two contacts of the cold start injector electrical connector. The light should stay on for 1 to 8 seconds at normal temperatures when the engine is cranked. (Note: The cold start injector will not operate at very high ambient temperatures.)

How exactly did you determine there was an electrical failure at the injector?

[76was124]

The injectors should have 24 volts on one pin constantly in the run mode, and the second wire on each injector is then pulled to ground to complete the circuit to energize the injector coil..

Most probably a typo, it will be 12V not 24V

Typo...should have stated 12volts...thanks for correcting

[bradartigue]

A few things:

- they all fire at once - all four injectors
- the cold start injector, the one in the side of the plenum, only fires when the engine is cold

If you know you are getting gas and the injectors are not firing then run through a few tests (some noted above):

- if the fuel pump runs with the key on but the engine off then someone has bypassed the "dual relay" or modified the air flow meter by bending the fuel pump control rod. This situation should be corrected.

- if you have a large air leak then the engine will not "know" to fire the main injectors because the AFM door never opens. Make sure everything air related is solid, hoses, connections, etc.

[GeorgeT]

A few things:
if the fuel pump runs with the key on but the engine off then someone has bypassed the "dual relay" or modified the air flow meter by bending the fuel pump control rod. This situation should be corrected.

I had the injector side of the relay go bad but the fuel pump side was okay; just because the fuel pump is working doesn't necessarily mean the injector side is okay.

[jdhughes17]

To 76was124: None of the main injectors are working, nor the cold start injector. We checked the pulse using noid lights. We know that the fuel is getting TO the injectors, because we checked that, but it isn't making it PAST the injectors. If we continuously spray starter fluid into the intake manifold, the engine will keep running, so the problem is just fuel not getting to the engine, and nothing else.
- We checked and cleaned the two grounds on the intake manifold, near the driver's side firewall, but not the one on the passenger side on the exhaust cam box. We will check that tonight.
-- We just checked for the one on the passenger side, and the only ground goes from the housing of the coil box, to the exhaust cam shaft box, on the right fender. Is that the one you are talking about?
- We also cleaned the ground wire that is on the underside of the car. This ground went from the transmission to the frame.

To KevAndAndi: I am talking about all the injectors. The 4 main injectors AND the cold start injectors are all missing power.
- I found that there was an electrical problem at the injectors by using a noid light. There is no signal reaching the injectors.

To wizard124: I haven't looked at any of those things, but I will get on it asap, then get back to you with a response.

To bradartigue: The fuel pump runs when the key is in start, but before I turn it the last bit to ignition. I think that's normal though.
- I don't know anything about an air leak. We will go through all the other tests that people have mentioned first.

To GeorgeT: I replaced the fuel injector double relay, so that can't be the problem.



Edit to original post: The fuel pump comes on when the key is in the start position. By "half way" I was referring to the start position, before ignition.

[bradartigue]

Nope, your fuel pump should never run unless the engine is turning. The correct operation: air turns the flap in the AFM. The AFM has a tiny switch in it that is closed when the flap turns. This switch turns on the relay, which turns on the fuel pump. If yours is running under ANY other circumstance then your FI system has been modified. This isn't the end of the world; if the pump is running then you may want to diagnose the problem before trying to fix the pump configuration. At least you're getting fuel.