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Injectors Not Firing 87 924S

I have verified that the pump is running and I have flow across the fuel
rail. I cannot get the injectors to fire. I have spark and all
connections seem tight. It was just running fine I don't understand what
has happened.

Please advise as to where to look next.

Update:

I was replacing injectors since I had one leaking down overnight. I
replaced all the parts and started the car. I was getting a lumpy idle
and discovered that #3 was missing so I removed and replaced that 1
injector. (I have 6 used ones). I was turning over the car with the rail
out to verify operation. All looked ok but I could not see 1 fireing due
to my position. I re adjusted the rail to verify again and nothing...

I thought maybe I needed a ground on the rail so I re-installed and still
nothing...

Have spark, fuel pressure, no injectors. I unplugged one injector and
still no firing.

Hope this helps,

Aaron

Old 11-17-2003, 02:35 PM
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DME or break in the wires to the injectors.

Pull the plugs on the injectors and check that one pin on each has the same voltage as the battery with the key on. The other pin will read about 10 vdc. This comes from the DME.

If any pin is zero voltage then start checking the wires. If the wires are good then this could be a broken solder joint in the DME or a blown component.

The pins on the DME plug for the injectors are 14 and 15. These are taken to ground by the DME to fire the injectors.

The other wire to the injectors comes from the DME/fuel pump relay.
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Old 11-17-2003, 03:39 PM
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I will buy an injector tester tomorrow and test the output but I think I already knwo the answer... I don't think you should see 12V at the injectors at any time though, but I may be wrong.

Aaron
Old 11-17-2003, 07:52 PM
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if you're using the "used" injectors and they've been on the shelf for awhile it's possible they're frozen up. tap on the sides with a ratchet handle while someone is cranking it over. unbelievable but true, I had the same situation with a car that had been sitting for at least a year, I was stumped because all four of them wouldn't even work the slightest drip out.
Old 11-17-2003, 09:24 PM
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Ok, checked voltage at the connectors with the key on. All connectors
unplugged I get 10V on one pin and close to 0V on the other.


Plug one injector in, key on, I get 1.8-2.3V on both pins

Checked continuity to the pins and have no shorts between injector pins

Checked Injector and they show 2-3 ohms resistance in the coil.

Still no luck... any additional help??

Aaron
atsudds@cogeco.ca
Old 11-18-2003, 11:58 AM
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tired that first... still no luck
Old 11-18-2003, 12:50 PM
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the injectors are not active... that is the problem
Old 11-18-2003, 02:17 PM
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Quote:
Originally posted by asudds
I will buy an injector tester tomorrow and test the output but I think I already knwo the answer... I don't think you should see 12V at the injectors at any time though, but I may be wrong.

Aaron
I should have bet on this and given you the odds. I would have rent money for the next year.

You had better see battery voltage to one side of the injector connector with the key on. This comes directly off of the DME relay stage one contacts. This is the contact that closes when the key is turned on. It also supplies power to the DME. The 10 volts you are seeing could be because of a bad ground to the engine block or the DME side of the circuit.

If you have 10 volts on one side and zero on the other with the key on then I would first check the DME relay.

Note: The ignition switch sends 12 vdc directly to the coil. So if the coil has 12 vdc on the connector opposite the green wire the ignition switch is working.
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Old 11-18-2003, 06:43 PM
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Ok, just to clear it up for everyone... it is an injector problem... I am not getting fuel.
Old 11-18-2003, 07:32 PM
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Just to clear this up for you it's a DME problem as this what makes the injectors work.

Or it's a fuel distribution problem. Still related to the DME as it's the DME that turns the fuel pump on.

If one injector was not working then it would be an injector problem. When none of them "work" then it's not an injector problem.
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Old 11-18-2003, 09:21 PM
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I have a new DME relay to try tomorrow... from there I am getting a set of Noid Lights for the injectors... any other suggestions??

What DME is the same as the 924S??

Can I sub a 944S DME ???

Aaron
Old 11-19-2003, 08:40 PM
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try tapping the sides of the injectors?

Btw: '85.5-'87 944
Old 11-20-2003, 10:13 PM
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Quote:
Originally posted by asudds
... any other suggestions??
I've found burning incense and a bottle of wine helps. Now that I think about it forget the incense.

Quote:

What DME is the same as the 924S??
Can I sub a 944S DME ???
Aaron
The same year 944. The 'S' is a completely different animal.
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Hugh - So Cal 83 944 Driver Person
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Old 11-21-2003, 11:41 AM
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Update, still no luck, I borrowed a set of NOID lights and no injector pulse to be had... looks like I am looking at a DME or a new harness...

Does anyone know what to look for inside the DME?? Is there any replace-able parts that I can replace to make it work agian??

I know of Wilk's DME schematics... can you guide me o great one... I know I have the skills to replace parts, I just need to know what components I might require and if they are available... Where should I be looking, how did this happen and what can I do to keep it from happening again.

THanks everyone,

Aaron Sudds
Windsor, Ontario
atsudds@cogeco.ca
Old 11-23-2003, 07:07 PM
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How about the speed and reference sensors?

How do you know the fuel pump is running?
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Old 11-23-2003, 07:18 PM
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I hear the fuel pump, I also bypass the relay and make it run for sure... I feel flow through the rail and have also verified fuel volume and pressure while cranking... I have spark so the sensors are fine....

It is fuel injector pulse related.... lets all focus if we can...
Old 11-23-2003, 07:22 PM
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Focus here.

There are TWO sensors. One for the spark (reference) and one for the engine speed. The speed signal is used to determine how long the injectors are to stay open. It's also used in the logic to hold the fuel pump contacts closed in the DME relay.

The reference sensor will return a 2 volt pulse (or greater) and a continuous 2.5 volts (or greater) from the speed sensor. Best to use an oscilloscope.

Put a bifurcated jumper in place of the DME relay feeding both the DME power and the fuel pump and see if the car will start. From terminal 30 to 87b for the fuel pump and from 30 to 87 to power the DME and the injectors. The power for the coil comes directly from the ignition switch.

I would use terminal 86 in place of 30 as it is switched through the key while 30 is directly from the battery.

You should see 12 volts on one side of the injectors with the key on. If you don't then either the DME relay is bad or the harness to the injectors is bad. If you use the bifurcated jumper and there is no 12 VDC at one of the pins at the injector connector then the harness is bad.

In the factory DME Testing Procedure there are 15 test points. Twelve of these are for "Engine will not start".
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When was the last time you changed your timing and balance belts and/or cam chain and tensioner?
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Old 11-23-2003, 10:13 PM
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Thanks, that should get me going tonight... I'll have a look

Aaron
Old 11-24-2003, 05:57 AM
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bump
Old 11-27-2003, 09:10 PM
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I have no idea,but....did you checked if injectors fire when,with someone aid,you press down the gas pedal while you crank?Maybe the system logic thinks engine is turning enough fast-pedal at idle=no fuel...
No idea,tough,but id try it.

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Old 11-28-2003, 12:53 AM
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