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Old 10-21-2020, 01:30 PM   #1
940wagon
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Default 1990 NA 740 regina, no spark/fuel

I replaced a heater hose that connects to the heater control valve, filled up coolant, drove it around the block and ran fine.

Parked it, replaced blower motor, now car wont start. Thinking I messed up the ECU or something down in the passenger footwell, but i never unplugged ECU and all connections appear to be tight.

Fuel pump doesnt prime when you turn the key, tried several different fuel relays with no success. Jumpered the pins, and fuel pump will run non stop without issue. Cranks fine, but still no start.

Pulled a plug to test spark, and no spark. Plug wasnt wet with gas at all, so injectors must not firing either? Replaced crank sensor with no change.

So I'm thinking it must be something down by ECU?

Could anyone point me in the right direction with what to start testing with the multimeter? I am garbage at electronics. Desperate to get this car running, any help would be amazing.

Thanks in advance.
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Old 10-21-2020, 02:26 PM   #2
dl242gt
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You can check for codes with the Rex/Regina setup. But my initial guess at the issue would be your engine speed sensor. You mentioned you were working in that area doing the heater hoses. It's easy to bump the wiring and affect a sensor that is on it's way out.

The way the system works is that it must think it has spark before it will flow fuel. So no spark = no fuel
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Old 10-21-2020, 03:17 PM   #3
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I see you did the crank sensor.

Inspect the female terminals for the sensor connector and make sure they are not bent, pushed back, corroded, spread.

Check for injector pulse. Unplug the injector and BACKPROBE a test lamp in there. Blink?

Check for codes.

Check for power and ground at the ignition module, and EZK unit.

Are the fuel injector rail grounds tight and clean?
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Last edited by ZVOLV; 10-21-2020 at 03:30 PM..
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Old 10-21-2020, 07:06 PM   #4
dl242gt
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I've had brand new cranks sensors bad out of the box.
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Old 10-22-2020, 11:03 PM   #5
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Quote:
Originally Posted by dl242gt View Post
The way the system works is that it must think it has spark before it will flow fuel. So no spark = no fuel
I didnt know that, thank you that is helpful.
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Old 10-22-2020, 11:07 PM   #6
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Quote:
Originally Posted by ZVOLV View Post
I see you did the crank sensor.

Inspect the female terminals for the sensor connector and make sure they are not bent, pushed back, corroded, spread.

Check for injector pulse. Unplug the injector and BACKPROBE a test lamp in there. Blink?

Check for codes.

Check for power and ground at the ignition module, and EZK unit.

Are the fuel injector rail grounds tight and clean?
Female terminals look in good shape. Connects tight together.

If the pump isnt priming, is it worth looking at the injectors at this point?

I will check codes and double check clean grounds from injectors, its pretty oily up in there,

Could you tell me how to check for power and ground at the ignition unit? Sorry for the basic question, electrical is black magic to me.


I remember pinching the ignition box in the door the other day when doing the blower motor... seems unlikely that broke it but im gunna see what a spare one would cost me.

Thank you all for the tips so far, ill have all day to look at it again tomorrow since the weather will clear a bit. 35F and sleeting today with several inches of snow on the ground...

Last edited by 940wagon; 10-22-2020 at 11:14 PM..
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Old 10-22-2020, 11:08 PM   #7
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Quote:
Originally Posted by dl242gt View Post
I've had brand new cranks sensors bad out of the box.
I swapped a known working one from a parts car.
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Old 10-23-2020, 12:13 PM   #8
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Do you have a test lamp?

You could unplug an injector, backprobed between the terminals, crank, blink?
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Old 10-23-2020, 02:52 PM   #9
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Should be able to use a low power test light and test for the trigger signal on the integrated amp coil driver unit on the left inner fender. The rpm sensor triggers the control unit in the car. The control unit sends a trigger signal to the coil unit on the inner fender. If you don't see a trigger signal going to the coil unit and you know the wiring is ok. Then it's usually either the engine speed sensor or the ignition computer.

The grounds are the one on the intake manifold that are attached to the bolts for the fuel rail. Have you checked the radio suppression relay?
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