I am working on this car for a buddy of mine and he said that one day he parked the car and the next day it wouldn't crank. It will turn over and will fire if you spray starting fluid. I have narrowed it down and found out the injectors are not getting power to them. I am just a backyard mechanic and don't work a whole lot with fuel injected vehicles. Any suggestions as to what might fix this issue would be much appreciated.

 

the 940's get their injector power from the 'radio interference surpression relay' under the hood. this relay should be switched on when you turn on the ignition.

 

Ok so I found the relay and it turns out good. It was actually not plugged in all the way. Now my injectors are getting constant power but don't seem to be pulsing. Does that same relay control the pulse or does that come from the ignition control module?

 

the ECU (fuel injection control unit) provides the signal to fire the injectors, all 4 injectors are tied together, and the ECU has a power transistor that grounds them to fire them. so if you probe an injector with a volt meter, one side should be always +V, while the other side should pulse high/low/high/low

a 1993 940 is LH 2.4, this uses a crank position sensor (CPS) to provide the timing signal on when to fire the injectors (also timing for the ICU to fire the ignition spark).

 

The cps has been changed as well

 

The cps has been replaced and still the same results

 

if you're getting spark, then the CPS is working. the CPS is actually wired to the ICU, which forwards a timing signal to the ECU.

with LH 2.4, when you turn on the ignition, both fuel pumps should run for about 1 second then switch off until you crank the engine over... when the engine is turning, the fuel pumps should start back up, then stop about 1-2 seconds after the engine stops moving. when the pumps are running, the fuel pressure at the injector fuel rail should be 42-44 PSI above manifold vacuum (0 if the engine isn't running, like if you're manually jumpering the fuel pumps). The fuel pumps are controlled by the ECU via a fuel pump relay. Note this relay has 2 sections, one section powers the ECU itself and most other injection stuff, it also turns on that radio supression relay, so we know thats working. the other section of this relay powers the fuel pumps themselves. the engine will run even if the pump in the tank is dead as long as there's a half tank or better of gas, but it won't run at all if the main pump under the back seat is bad..

does the diagnostic block show any errors on the ECU side (pin 2) ? if you don't even get the 1 blink, there's a possibility your ECU is totally fried (never seen it, but anything is possible).

here's a whole bunch of trouble shooting tips: https://www.volvoclub.org.uk/faq/Eng...eSymptoms.html that covers LH2.2 and 2.4 cars, you have 2.4.

 

Where would this diagnostic block be? I was not aware there was one.

 

its near the left side strut tower, its a little rectanguler plastic block with a cover that comes off... under the cover are like 8 holes numbered, and there's a little probe wire, plus a pushbutton and LED. you put the probe wire in position #2 for ECU codes, turn igniton on w/o starting, press the button for 2 seconds (not more than 3), release it, and count the blinks. 1 pause 1 pause 1 blink (1-1-1) means no errors logged. more important here, the fact that it even does 1-1-1 blink means the ECU processor is running...

full details on LH 2.4 OBD here, https://www.volvoclub.org.uk/faq/Eng...agnosticCodesi

do note, this is a fairly primitive system and if you do get error codes they are often side effects of a somewhat different problem than the actual code, so they are best treated as hints.