Ok ladies and gents. I just purchased my first volvo. It is a 1990 740 gl. I paid 400 cash delivered to my house for it. It is a clean car 247k miles on the clock but everything is clean and intact. Here is my situation.

I can crank the car but it will not start. It has a brand new fuel pump and in tank fuel filter, new fuel filter, new plugs, cap, wires, rotor, crank sensor, radio suppression relay, fuel pump relay. I am getting spark from the coil and from the wires. I am getting fuel to the rail but only when I have the relay removed and the two contacts jumpered. I can hear the relay prime when I turn the key to run and when I jumper it I hear it run constantly. I have also tried jumpering the leads on the radio suppression relay to no avail.

Now what i find weird is when I have everything jumpered out and everything should work all I get is the engine spinning it doesn't even try to start however after I return the system to normal with the relays installed it sputters to life but will only sputter for about 15 seconds or so before it dies. If I touch the throttle at all it dies immediately. I go check for fuel and again i have none but it is trying to run? Another thing that perplexed me is after we towed it home I joked with my wife about how it will probably crank right up. Well I get in it and sure enough it fires right up and runs great for about 30 seconds until it returns to the above issue. I have inspected all under hood wiring and grounds and have no corrosion or broken wires. I have only had the car about 20 hours and 8 of those I was sleeping. I am leaning towards a bad ecu or ICU or both. I will get the multimeter out this weekend and see if I can't find something with it. Anybody have any suggestions?

 

First, is it Regina or Bosch ignition? Regular type coil is Bosch, big finned box on the driver's side with a long coil wire is Regina. The symptoms of starting and dying, I'd look at the MAFS (Mass Air Flow Sensor), providing it's a Bosch... Go from there, don't do too much jumpering, bypassing etc, all that makes it harder to diagnose.

 

I had all that detail and meant to put in there that it is the Regina system with Bendix ecu. Sorry about that.

 

Ok little more work done today not much. Made sure fuel lines at the pump were not swapped they were not. How long should the system maintain fuel pressure? I bad the jumper installed on the pump relay and had awesome pressure. Pulled the jumper immediately went to the Schrader valve I installed and have no pressure at all. I also verified the fuel pump installed is not the low pressure pump found on the dual fuel pump cars. Once the smell of fuel cooks off I'll go out and troubleshoot the ignition system more and verify my injectors are pulsing.

 

So you have a car that starts but stumbles and stalls after a few seconds and also stalls at application of throttle? You have fuel pressure at start which then goes down to nothing? Your fuel system has been replaced already, unless some part is defective or installed incorrectly... The fuel pump is really the main suspect or the ECU which could be acting up.

 

Ok new discoveries. I am not getting my grounds on my injectors and from what I can tell those come off the ecu. The wire has good continuity from the ecu to the injectors so I guess its safe to say I have a dead ecu??? Or is there something that tells the ecu to pulse the injectors? Also I am not getting any voltage sent out to the crank sensor, o2 sensor or knocks sensor is this another indicator of a dead ecu?

 

the ECU pulses the injectors to ground when it gets timing pulses from the crank positions sensor by way of the ICU... the width of the injector pulses controls how much fuel to squirt on that cycle.

the O2 sensor gets its heater power from the fuel pump relay, I believe (if its not the fuel pump relay, then its the main fuel injection relay).

the crank position sensor is a magnetic coil pickup, it produces a small pulse for each notch on the flywheel. this pulse is probably too small to measure unless you have an oscilloscope or something and crank the gain up (and its a differential signal).

 

Does the Regina system have a radio suppression relay? If so, that may be the culprit. I'm not sure it's location (I only have 240s) but I think its near the windshield washer container. There are two identical relays there. Try swapping them and see if that helps.

 

if the 'radio' relay was out, there would be no power at the injectors. I'm kinda assuming when you said the injectors had no grounds that they DID have power?

 

The injectors ha e solid 12 volts just no ground. I ordered a crank sensor and both ecus. The ecus were one of those things of hey they are on eBay and cheap so might as well. Really hoping this crank sensor gets me going.

 

fyi, there's only one ECU, the other one is a ICU (Ignition Control Unit).

the test to do here is to put a test-light across the pins of one of the injector plugs, this is sometimes called a 'noid-light'. you crank the car, and if the injector is firing the light blinks. if its blinking, then the ECU and crank sensor are all likely working, and your problem is elsewhere.

 

Its alive... I put in the new crank sensor and got nothing. Put in the ICU and ecu and she fired right up. Drove it to work and have had no issues at all. Thank you for the help guys.