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Fuel Injector Woes!!!

OK Here goes!!!! The wife and I decide to take a nice mountain drive Sunday after my mechanic (Porsche race car certified) gave me a clean bill of health for my '74 2.0 liter. Drove about forty miles through some of the most beautiful country (near ski slopes), and decided to stop for early dinner. Fabulous outdoor dining, temp about 76, several adult beverages, you know!!!! Got back iin the car to leave dead fuel pump

Left car at the only garage in town, daughter came and got us. Next morning, called Nate in Sacramento(THANKS, NATE!!) He overnighted a fuel pump directly to the garage, DUMBASS installed it, and called to tell me it was ready, but it didn't run just right

Long story short, had car towed to my guy (sixty miles), who discovered that DUMBASS had not only kinked the fuel line, but didn't reinstall the fuel filter!!!!!!Who knows what got into my injectors

Update soon!!!!!!!!!





NOW WHAT???

After three weeks in the shop, running down all the FI components electrically, I'm getting no pulse to the fuel injectors. We even tried replacing the computer with a known working one. HELP!!!!!!!!!
Old 10-15-2007, 08:47 AM
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Witchhunter Performance will clean/rebuild your injectors for $17 each. Quick, excellent customer service. Injectors come back with a before and after diagnostic sheet. They're on the web.

I was having some difficulties with my engine earlier this year. I don't know if you tested each injector but here's what I did: run two D-cell batteries in series (basically just taped end to end), attach wires on the positive and negative sides, and touch one to each connector on the injector. The 3v is enough to trigger the injector. If nothing happens, it's a bad injector. That's how I found a bad one and decided to send them all to Witchhunter. a thousand miles later - no problems.

If all your injectors check out, then they're, obviously, not getting the signal. That is a little beyond my scope of understanding sitting at work without my manuals.

Post again if your injectors test OK.
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Old 10-15-2007, 11:16 AM
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If your injectors were clogged, you should still get an electrical pulse, so that's probably not it.

I would check the center wire to the contract trigger points, make sure it is still working. It feeds both injection pulses, so it would explain why both go bad at the same time. (not likely the trigger points would both go bad at the same time.

It's also possible the cylinder head temp sensor is an open circuit, needs to ground thru resistance.
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Old 10-15-2007, 12:08 PM
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Quote:
Originally Posted by hardflex View Post
It's also possible the cylinder head temp sensor is an open circuit, needs to ground thru resistance.
That's right. The CHT sensor will send the whole works haywire. Difficult to change out, takes time. Only costs $18 for the new part. Our local mech's first component to troubleshoot is the CHT.

You can check resistance both cold and hot to determine if it's functioning.
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Old 10-15-2007, 06:13 PM
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But no injector activity at all? Unlikely to be the CHT. More likely the trigger points, or the wires to them, or the wires to the MPS. If the MPS is unplugged, you get no injector activity.

Also check the multiple ground point at the crankcase seam at the top rear of the motor. You'll either be looking underneath the intake snorkel on a 2.0, or removing the air cleaner housing to see the ground point.

--DD
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Old 10-15-2007, 06:59 PM
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OK, Here's where we are now.

Fuel pump is delivering good pressure
Engine starts from cold start valve, but dies when that little bit of fuel is used up
Very weak pulse to injectors
Trigger points and wiring are good
Swapped out ECU for a known working one
Wire to MPS is good
All grounds are solid
All relays are good
Multiple grounds at crankcase seam cleaned & replaced

ENGINE WON'T RUN!!!!!
Old 10-20-2007, 04:51 AM
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If you turn on the key and pump the gas pedal, you should hear the injectors firing, injecting gas as part of the acceleration circuit. This should give you gas to run on for a few seconds as well.

The cold start valve shouldn't even be opening unless it's near freezing, how do you mean the engine starts with cold start valve?

I would try to bypass the Cyl Head Temp sensor with a known resistor to see if that fixes it.
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Old 10-20-2007, 05:35 AM
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Engine starts, but won't run without constantly feathering the pedal. Just won't smooth out enough to run.
Old 10-20-2007, 05:53 AM
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Do you have an ohmmeter? measure the Cyl head temp resistance. then wobble the wire around some while measuring to see if it is constant.


go to radio shack and get a 200 ohm resistor, crimp on a female (i think) electrical connector. disconnect the Cyl head temp sender and connect the resistor to the harness instead. ground the resister to the engine somewhere. cost you maybe 4 bucks .See if that makes a difference.

Or just replace the CHT.



I had a 73 squareback (same Djet system) and that was a problem I had once.
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Old 10-20-2007, 06:42 AM
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Have you plugged a noid into each of the injector plugs to confirm pulses to the injectors? Have you run the old fuel pump and pressure tested it to determine whether or not you are fighting the same problem or a new one?

If noids light on all 4 injector plugs I would suspect that you have possibly all but one injector jammed with trash from the old pump that got past where the filter was supposed to be.

I once bought a car from a foreign car shop. They were selling it because they could not get it to run. I found 11 jammed injectors, replaced them all, and drove it 3500 miles home. They were also Bosch injectors.
Old 10-20-2007, 08:18 PM
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OK, new info!!!

Injectors are squirting, and when the fuel pump pressurizes, engine starts and runs very smooth for a couple of seconds. Any attempt to throttle, and it dies out!

NOW WHAT?
Old 10-30-2007, 09:46 AM
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start car, don't attempt to throttle, drive car normally except don't throttle. LOL Just kidding.

First I would check the Fuel pump fuse on the main relay board left side engine compartment.. It's a big 30 or 50amp fuse towards the driver. Clean the ends of corrosion to make sure it's a good contact. If that checks out, put a guage on the fuel lines to make sure the pressure stays up around 30psi.

Will it stay running if you don't attempt to throttle? Or does it die after a couple seconds regardless.
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Old 10-30-2007, 05:06 PM
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Fuses are good
Pressure stays good @ 30

Maybe bad fuel???
Old 10-31-2007, 05:03 AM
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does it only fire as long as the starter is engaged? Will it stay running if you don't throttle it?

Brain working here... When the Throttle is closed, the contacts in the TPS send the signal thru an idle circuit which is different from the main circuit, and is a "fixed" signal, mostly controlled by the adjustment screw on the ECU. Therefore, the engine could run only with the throttle closed. Come off those contacts, and the rest of the system, sensors, MPS, etc would come into play.

I'm still thinking it's the Cyl head temp sensor is not making the circuit. Have you checked that?
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Last edited by hardflex; 10-31-2007 at 05:21 AM..
Old 10-31-2007, 05:13 AM
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ok reread the entire thread, and I want to summarize for clarity.

Fuel pump pressure is up and stays up.

Injectors work properly when signaled.

Key on, pumping gas pedal make injectors click (enrichment circuit working) this will put fuel in intake which will make car run till fuel is gone. Should also keep engine running if gas pedal is pump as engine stumbles , yes or no ?

Engine runs on idle, will stay running at idle, yes or no?
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Old 10-31-2007, 05:40 AM
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Engine only runs a few seconds when started

Any attempt to pump gas pedal kills it

Will not sit and idle
Old 10-31-2007, 08:54 AM
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If you start it and engine dies, does it fire again for a few seconds immediately afterward, or do you have to give it some time between before it fires again?

sorry for all the questions, but I'm trying to come up with possibilities or rule out others.
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Old 11-01-2007, 12:57 PM
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I think, from what I'm reading, that your Cold start valve is leaking (it shouldn't even open unless it's freezing or below) and that leaked fuel is what's making it run for a few seconds. The FI is not working but you say it's squirting. that's not making much sense.

Next time unplug the MPS before you try to start it. This will disable the Fuel injection entirely. If it still starts and runs on all 4 the cold start valve is leaking and needs to be addressed.

If the TPS is not working, or not even plugged in car should still run.

If the MPS is not plugged in, car will not run. A broken MPS Diaphram will cause the ECU to send a very rich signal to the injectors.
.
If the CHT has a dead short, the ECU will see it as very hot and send a very lean fuel signal.
If the CHT has an open connection, the ECU will send a very rich signal, or maybe none at all, not completely sure how it would react there.

You've said you replaced the ECU so that's likely not it.

You said the Fuel pressure stays up. Did you leave the gauge on there to verify that?
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Old 11-02-2007, 06:41 AM
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A disconnected CHT plug will make the mixture very very rich.

You need three things for the engine to run: Fuel, Air, and Spark. Do you know you have fuel going into the engine? Pull the injectors out and put them in empty mayo jars. Have someone crank the starter; does fuel wind up in the jars? (Bonus: You can see the spray pattern if you can watch while it's cranking.)

Do you have spark? Grab an extra plug and hook it up to a plug wire. Tape it so the threaded part (or the outer electrode) is touching a ground, like the fan shroud. Do you see sparks when the starter is cranked?

Do you have air going in? Compression test will tell you this.

After you verify all three (fuel is the most likely suspect with these symptoms) all that's left is the amount of fuel going in (too much or too little), or when the spark is happening. How's the ignition timing? Should be right around TDC statically.

--DD
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Old 11-02-2007, 07:17 PM
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