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Old 06-05-2018, 04:51 PM   #151
PromiseRing
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I guess at this point swapping injectors is easy enough. Takes no time. Got an extra set laying around?
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Old 06-05-2018, 05:50 PM   #152
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I guess at this point swapping injectors is easy enough. Takes no time. Got an extra set laying around?
Unfortunately not. I'm probably going to have to bite the bullet and buy a set.
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Old 06-05-2018, 06:05 PM   #153
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Unfortunately not. I'm probably going to have to bite the bullet and buy a set.
I have a set of high impedance injectors but I think they’re NA injectors which might throw lh2.2 off due to being the wrong size (you’d have to temporarily bypass the resistor pack anyway). Something like 850t injectors and a bypassed resistor pack would probably work perfect.

I’m willing to bet you could get a set of those or factory turbo injectors for next to nothing. If I had the correct set laying around still you could have them for the cost of shipping. Under $5.
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Old 06-05-2018, 07:01 PM   #154
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I have a set of high impedance injectors but I think they’re NA injectors which might throw lh2.2 off due to being the wrong size (you’d have to temporarily bypass the resistor pack anyway). Something like 850t injectors and a bypassed resistor pack would probably work perfect.

I’m willing to bet you could get a set of those or factory turbo injectors for next to nothing. If I had the correct set laying around still you could have them for the cost of shipping. Under $5.
I'll have to check the junkyard to see if they have any P80 turbos over there. I know my cousin has 2 or 3 S70 T5 blue injectors somewhere, but I'd have to find 1 or 2 more.
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Old 06-05-2018, 08:31 PM   #155
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$20 says injectors won't get it started. If you have a noid light that won't blink, what will swapping injectors do for you?
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Old 06-05-2018, 08:45 PM   #156
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$20 says injectors won't get it started.
I'm not the most confident either, but what IS the problem? Honestly I couldn't see it being anything else. Injectors are getting voltage, ECU is getting good ground. Everything else in between has been tested to be good.

Some ECU testing notes with questions...

Pins 5, 11, and 25 are grounds on LH2.2. They show 0 ohms to ground with the key off, and 18 ohms on 5 and 11 and 13 ohms on 25 with the key in position 2. What's that about? Is that normal or am I looking too far into things as usual?
Voltage shows trace amounts... only 0.01-0.02V.
Pin 19 (referred to as "code" on the document) shows 0.5V in KP2. Apparently that's also a ground, actually connected with a factory jumper to pin 11. That could have been a lapse in my testing or just me once again trying to find a problem.
Crazy enough, my old ECU shows 12V here. No idea why.

Then there's the issue of LH pin 21 only showing 1.72V in KP2, but showing a full 12 volts with the key off. Nobody has clarified that... should I have 12 volts in KP2?
It does show above the suggested 0-1V while cranking (1.6V).
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Old 06-05-2018, 09:07 PM   #157
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After a little reading, it's not unusual for the noid light to blink dimly, especially with low impendence injectors like the 740T.
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Old 06-05-2018, 10:50 PM   #158
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Labscope.
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Old 06-06-2018, 09:09 AM   #159
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$80 Hantek PC based scope is a step above blinking lights. Yellow is an fuel injector waveform. Blue is a crank sensor waveform. The flat section in the fuel injector waveform is the injector on-time.
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Old 06-06-2018, 09:37 AM   #160
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It would be great to have one of those, but what would that tell me? It really comes down to the ECU or the injectors.
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Old 06-06-2018, 09:46 AM   #161
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Well you could directly test the ECU itself with a scope. Or like I told you, with a test light.

One could connect one end of a test light to a positive source and then the other end of the test light to the injector control terminal, backprobed, at the ecu. Crank. Blink? =ECU inkector control circuit IS functioning.
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Old 06-06-2018, 10:13 AM   #162
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^ so what do you think his problem is?
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Old 06-06-2018, 10:27 AM   #163
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^ so what do you think his problem is?


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Old 06-06-2018, 10:42 AM   #164
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So no one knows. 740s are all cursed and an abomination to the Volvo name.
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Old 06-06-2018, 11:12 AM   #165
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I think the problem is aft of the wheel.
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Old 06-06-2018, 12:20 PM   #166
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I think we need a 740 magic 8 ball! I should have one made and attach it to my proverbial parts cannon.
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Old 06-06-2018, 12:29 PM   #167
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Rather than doing your fancy electric test on the resistor pack, can just take it off and clean the spade connectors? Or have you already done this. Volvos are so picky sometimes. It doesn’t hurt to try.

After 5-10 seconds of cranking, are the plugs dry completely?

Sometimes it’s those rudimentary tests that give the most conclusive results the fastest.
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Old 06-06-2018, 03:35 PM   #168
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The terminals on the resistor pack are clean. I'm afraid to take the terminals off the resistor pack itself in case it would break like my old one.

Last I checked the plugs, they were totally dry.

I'm really leaning towards the injectors.
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Old 06-06-2018, 04:02 PM   #169
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Repeat: Test light to a positive source, then other end to your injector control wire. Crank. Blink?

Or....... "Ho! Man ye rusty parts cannon!"
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Old 06-06-2018, 09:01 PM   #170
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Repeat: Test light to a positive source, then other end to your injector control wire. Crank. Blink?

Or....... "Ho! Man ye rusty parts cannon!"
I'll give it a try tomorrow just to check. Hopefully I can just get some new injectors and call it a day... and get this thing running once and for all.
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Old 06-07-2018, 11:01 AM   #171
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Just tested it, it blinks. It’s not a REALLY bright light, but it’s bright enough to know for sure that it’s blinking. With the key off, it’s bright and solid, once the key is on it turns off, then blinks while cranking.
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Old 06-07-2018, 11:34 AM   #172
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Is it supposed to light up with key off? They’re switched ground, so applying a constant 12v to one side of the noid light and then the injector harness to the other, shouldn’t it stay off?
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Old 06-07-2018, 11:48 AM   #173
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That was tested at LH pin 13 with a test light with the clamp on the battery positive, not a noid light. The injectors won’t have power unless the key is on.
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Old 06-07-2018, 11:58 AM   #174
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That was tested at LH pin 13 with a test light with the clamp on the battery positive, not a noid light. The injectors won’t have power unless the key is on.
Okay makes more sense. So you’re getting a pulse, but no fuel is coming from the injectors? My guess is either insufficient fuel pressure or dead injectors
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Old 06-07-2018, 01:32 PM   #175
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Mmmmm.....light shouldn't illuminate key off. Just blink while cranking. That sounds like your wiring is shorted to ground on that injector ground circuit. Remember that converstion???? I recall you saying you found bare wiring. Whatever happened with that!?

Replacing components when the circuit is no good is a bad move.

Current takes the path of least resistance. If you have a short to ground before the computer, most of the current will go thru the short instead of the ecu.
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