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Old 04-23-2018, 06:21 PM   #51
ZVOLV
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Pinch the relay shut on the other side, the LH side of the relay. Half powers the fuel pump, the other half of the relay powers the LH system.

Do this and do you have power to your injector relay yet?

If so do you have injector pulse? Sounds like your ECU is dead or not powered up.


Have you checked for power to the ECU?

Use a test light, not a meter, to check for power to a component. 12v can be seen on a meter, but there may not be enough current.
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Old 04-23-2018, 06:41 PM   #52
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The right side of the relay (looking at it from the passenger side) is engaging properly. I have to manually hold the left side.
I have power at the injector/radio suppression relay as well as at the injectors, however I do not have injector pulse. I will check once more for pulse while holding the relay, it's hard to do that without any help. I take it they weren't getting pulse since the car didn't start.

I will check again, but I am pretty sure I have power to the ECU.
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Old 04-23-2018, 08:50 PM   #53
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Another weak point on that car is the hall sensor wiring on the dist. I have seen cars run on brake cleaner with the ignition timing way off due to this. However, I don't see how you would have a spark, but no injector pulse if that were the case.

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Old 04-23-2018, 11:23 PM   #54
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Yeah, I would think that would cut spark.
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Old 04-24-2018, 02:52 PM   #55
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I am getting power to the ECU through pin 18 with the key on. This says it's the signal from the ignition switch.
The only thing I noticed while testing is that I don't have any power on pin 17. According to the pinout I posted I should be getting 11-14 volts on that pin.
Pin 17 is the connection to the fuel relay 86/2 and the boost over pressure sensor. I tried putting a jumper between the terminals of the boost over pressure sensor to bypass it and there was no change.
I thought maybe the 12v comes from the ECU to the relay, so I hooked the ECU back up and tested 86/2 for voltage with the key on. Nothing. Am I supposed to be seeing power here or does that part not apply to the 740?

I am really leaning towards the ECU being a problem at this point. I'm totally stumped.
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Old 04-24-2018, 03:07 PM   #56
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Let me look at a wiring diagram. You say you have now managed to get 12v to the injectors and the main pump, but why not now?

What are you doing to test injector pulse? I recommend a noid light.

A jumper wire can be used in place of any relay. If I had your car I could easily get power to the pumps and injectors, crank and look for injector pulse and spark.

You say it runs on ether. Does it actually stay running if you keep pulsing it into the intake?
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Old 04-24-2018, 03:42 PM   #57
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Okay... pardon my absolute stupidity. I was measuring the wrong terminals on the ECU connector. For some reason I keep mixing up the pinout diagrams.
Pin 17 shows 0.07V when I don't have the relay pinched. When I pinch the pump side I get 0.2V. When I pinch the injector side I get over 11V. That's fine now.
Pin 18 still gets 12V.

The two problems I'm noticing are that the fuel pump relay isn't engaging the pump when it should and the injectors are not getting pulse. I get voltage at the pump when I pinch that relay.
At one point the pump was running when it was supposed to (while cranking and for a moment after letting off), but for some reason it's not anymore. I don't know what changed before or after that. It was only for a few minutes while testing.
I was testing pulse by attaching a wire to the ground clip of my test light and probing the other side. I don't have a noid light set, so that is going to have to do.

I didn't have anyone to help me at the time, so I can't confirm if it would continue to run when continuously spraying ether. I only got it to run for a couple seconds after spraying a generous amount into the throttle before cranking it up.
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Old 04-24-2018, 10:36 PM   #58
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Isn't pin 17 grounded by the ecu?
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Old 04-24-2018, 11:09 PM   #59
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Quote:
Originally Posted by lummert View Post
Isn't pin 17 grounded by the ecu?
Yes actually, that’s what the Volvo diagram shows.
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