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Matt, Engineer
Category: Subaru
Satisfied Customers: 20399
Experience:  Mechanical Engineer with 20 years experience in the auto industry, 8 yrs in formula 1 engine testing
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1993 Subaru Loyale Wagon (SPFI) with no spark condition.

Customer Question

1993 Subaru Loyale Wagon (SPFI) with no spark condition. Tried new distributor, coil/power transistor assembly and ECU(used). 12 volts at both positive and negative coil connections. I don't have an oscilloscope but when I tested continuity on the yellow wire to the power transistor from the ECU I measured 40 ohms. That's a small amount of resistance but the other wires to the crank angle sensor in the distributor all had zero ohms. Any suggestions. I don't think the voltages should be the same at each coil connection....
Submitted: 7 months ago.
Category: Subaru
Expert:  Matt replied 7 months ago.


I'd 1st check if the ECU opening the fuel injectors,as this will show if the ECU is trying to fire the engine

if the injectors are working you can hear them click - its difficult to hear them with background noise so use a long screwdriver like a stethoscope, placing the handle end in your ear and the metal tip against the body of the injector whilst your assistant turns the engine over.

If you can't hear anything check the ECU power is present by measuring voltage at the fusebox and on its relay socket if OK then check the connections to the crank speed sensor and consider replacing this sensor if the wiring / connections look OK

if the ECU is opening injectors then you can then move onto tracing the coil wiring back to the fusebox and also check that the engine earth connection is on tight and is uncorroded

Customer: replied 7 months ago.
The car has Single Point Fuel Injection (SPFI). There is a single fuel injector in the throttle body.
Expert:  Matt replied 7 months ago.


that simplifies things slightly, is that injector clicking as described?

Customer: replied 7 months ago.
Could not hear injector clicking. Verified ECU had power. Verified continuity on 4 crank sensor wires back to ECU and got 0 ohm resistance. Again, should wire from ECU to power transistor have 40 ohms resistance? Shouldn't it be zero ohms?
Expert:  Matt replied 7 months ago.


I'd agree that does sound very high so it might be worth just replacing that wire with a fresh 1 to see if this helps as trying to locate a corroded/ broken wire within the loom is usually very difficult

Customer: replied 7 months ago.
Sorry, I got the wires mixed up. When I tested the correct wire it had 0 ohms. This car was at the Subaru dealer for 6 monthes and they couldn't fix it because they could never find a wiring diagram where the wire colors match what's on the car. The FSM has a schematic that is functionally correct but the wire colors don't match what's in the car. Next I was going to check continuity of the interconnection with the fuel pump relay. Any other suggestions would be appreciated.
Expert:  Matt replied 7 months ago.


if the ECU was recieving a crank signal then the injector should click on and off during cranking?

So I'd consider replacing the crank sensor as the next step

Customer: replied 7 months ago.
Crank sensor is part of distributor and this was replaced by dealer but still no spark
Expert:  Matt replied 7 months ago.

Ok I'm going to opt out here and try and get another expert involved who hopefully has direct experience with this issue

good luck