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Old 06-23-2019, 08:20 PM   #1
cabinover
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Default '86 B230FT no injector pulse

Hi all,
Posted this on VolvoForums but from the looks there is more action over here for these antiques

1986 760 that sat for years due to bad harness. Gas turned to brown gunk of course so after replacing the harness I did get it running but not well. Time goes by and I have some time to play with it again. Pulled and replaced both fuel pumps and filter, cleaned to injectors, and got injectors to flow fuel with a battery and brakecleen. Put everything together and no start. Have fuel, don't have a ground for injectors to fire. Have 12VDC on green wires. If I manually ground out injectors all flow some fuel.

Where do all of the grey ground wires get their signal? ECU? I'm guessing I have a bad wire somewhere but wanted to ask you guys before cutting into the harness.

Also, one of the green plastic caps on #1 injector went into the intake and head. I cannot see it after pulling the intake so it's either already in the cylinder or hiding out of sight on the valve. I'll bring an inspection mirror home tomorrow and see. If it's in the cylinder I really don't see a problem with it getting crushed and spit out. What do you think?

Thanks ahead of time for your help.
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Old 06-23-2019, 09:02 PM   #2
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The hall effect sensor wiring is a common point of failure on these. It's in the distributor.

Do you have sprak?
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Old 06-24-2019, 05:56 AM   #3
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I do have spark, and fuel relay/pump action. Just no ground pulse to trigger injectors.
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Old 06-24-2019, 11:09 AM   #4
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Have you tried these for a reference? I'm not an expert in much, but these might help:
http://www.volvotips.com/index.php/7...repair-manual/

As far as the injector cap goes, have you tried placing the nozzle of a shop vac over the intake on the head?

Good luck, and I hope that you can find the fault!
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Old 06-24-2019, 11:42 AM   #5
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Do you have power to the injectors?

What are your test methods/tools?
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Old 06-24-2019, 12:02 PM   #6
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I have power to injectors verified through a test light. I can put a multimeter on them but I have battery voltage, no ground.
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Old 06-24-2019, 12:04 PM   #7
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Quote:
Originally Posted by durk80 View Post
Have you tried these for a reference? I'm not an expert in much, but these might help:
http://www.volvotips.com/index.php/7...repair-manual/

As far as the injector cap goes, have you tried placing the nozzle of a shop vac over the intake on the head?

Good luck, and I hope that you can find the fault!
Hadn't thought about a vacuum, good idea. Will look over the link at home, hard on cell phone.
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Old 06-24-2019, 01:15 PM   #8
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Have you tried cranking with the test lamp connected between positive and negative? Or were you saying no "pulse" due to a meter test you did?

A noid light works great here.

These cars are notorious for rotten wiring that year. Until 87/88 the wiring goes bad. I would inspect for rotten wiring under the intake. I would resistance test between the ECU and the injectors and wiggle the wiring and see if the circuit is open, goes open, or high resistance. There is a crimp down in there that goes bad.

A voltage drop test is your friend too--Google.

Or, you could check for pulse at the ECU. If there's no pulse there, you gotta make sure the ECU has good power, ground, andRPM signal in. It gets RPM signal from EZK. Im not sure what kinda signal it is.
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Old 06-25-2019, 05:55 AM   #9
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Originally tried a 194 bulb and got no light. Bought a noid light set last night. No light when cranking however if I ground out a different injector plug I get light so at least all injector grounds are still tied together. At least that's a plus.

Looks like I have to chase wires back to the ECU and find the correct pin to check on it.

Thanks for the help. This is a new wiring harness, replaced about 4-5 years ago and never subjected to heat. The car has run less than 5 miles in that time. I am leaning more towards an ECU problem.
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Old 06-25-2019, 09:40 AM   #10
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-Clean grounds on manifold (likely not your issue)
-Bypass radio suppression relay temporarily (this will probably fix your problem)
-Lastly, clean the resistor pack spade connectors.

Last 2 suggestions there will take the cake I bet.
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Old 06-25-2019, 11:55 AM   #11
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Quote:
Originally Posted by cabinover View Post
Originally tried a 194 bulb and got no light. Bought a noid light set last night. No light when cranking however if I ground out a different injector plug I get light...
I read this three times and it still doesn't make sense.
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Old 06-25-2019, 12:09 PM   #12
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Quote:
Originally Posted by ZVOLV View Post
I read this three times and it still doesn't make sense.
The grounds are all tied together at the ECU, he's bypassing the ECU ground by doing this. OP probably has Hall effect sensor issues either with the sensor itself out the wiring going to it, I'd bet on the latter.
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Old 06-25-2019, 12:12 PM   #13
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I originally had only a 194 bulb to test with. After plugging a noid light I still had nothing. The only way I could make either light up (or injector open) is to ground out the grey wire going to the injector.
All injectors have a common ground from what I can figure.
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Old 06-25-2019, 12:14 PM   #14
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Can the hall effect sensor trigger a spark while at the same time not send a signal to the ECU to fire injectors?
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Old 06-25-2019, 12:17 PM   #15
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Quote:
Originally Posted by cabinover View Post
Can the hall effect sensor trigger a spark while at the same time not send a signal to the ECU to fire injectors.
No, I must have missed the part where you have spark, sorry, you should have injector pulse if you have spark.
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Old 06-25-2019, 12:26 PM   #16
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So either I have a bad wire between ECU and injectors or my ECU has seen better days is what I'm thinking. Sound about right? No idea why the font size just changed, unless it's just in my phone.
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Old 06-25-2019, 12:32 PM   #17
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Quote:
Originally Posted by cabinover View Post
Can the hall effect sensor trigger a spark while at the same time not send a signal to the ECU to fire injectors?
Yes.

Quote:
Originally Posted by cabinover View Post
So either I have a bad wire between ECU and injectors or my ECU has seen better days is what I'm thinking. Sound about right? No idea why the font size just changed, unless it's just in my phone.

See post 8



I could figure this one out in probably 15 minutes with a $10 test lamp. Does it run on ether? Click my sig. I gotta get back to wrenching

Last edited by ZVOLV; 06-25-2019 at 12:55 PM.. Reason: Back from wrenchin'
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Old 06-25-2019, 12:41 PM   #18
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Quote:
Originally Posted by cabinover View Post
So either I have a bad wire between ECU and injectors or my ECU has seen better days is what I'm thinking. Sound about right? No idea why the font size just changed, unless it's just in my phone.
Did you check your resistor pack spade connectors? How about the the radio suppression relay wiring? I have fixed 3 7/9 turbo cars this year alone by tending to those 2 things.

It is very very easy to bypass the RSR temporarily for testing purposes. And I ditched the junk relay/wiring setup that Volvo uses, and installed my own Bosch style relays.

See if it runs on starting fluid first, that’s a simple test to narrow your issue down to being a fueling problem (which it most likely is).
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Old 06-25-2019, 01:04 PM   #19
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Get an oscilloscope.






Edit: Nah, get a test lamp for now.
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Old 06-25-2019, 03:16 PM   #20
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Have checked the RSR and bypassed it when fooling around with the fuel pumps to be sure they worked. As for the resistors I have cleaned all connections there also. To repeat, I have 12V at the injectors.

I have had all three lights in the injector plugs from positive to negative, a test light, a 194 bulb, and a noid light. No flashing going on. Will chase back to ECU tonight when I get home.

So even though I have signal to turn on FP relay I could still not have a signal to ECU from Hall Effect sensor to trigger injectors? Didn't think they'd make it that complicated but it is a vehicle.
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Old 06-25-2019, 03:48 PM   #21
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If your fuel pumps are powered up while cranking that means EZK box IS sending the RPM signal to the LH box. That also means the LH box IS powered and grounded.

That leaves the injector control circuit or the LH box as the point of failure.

Again, resistance check the injector control wire from end to end. I wouldn't wanna see more than 2 ohms. It should be close to zero.
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Old 06-25-2019, 03:55 PM   #22
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Quote:
Originally Posted by ZVOLV View Post
If your fuel pumps are powered up while cranking that means EZK box IS sending the RPM signal to the LH box. That also means the LH box IS powered and grounded.

That leaves the injector control circuit or the LH box as the point of failure.

Again, resistance check the injector control wire from end to end. I wouldn't wanna see more than 2 ohms. It should be close to zero.
Right, because isnít it possible to have 12v at injectors, but a weak 12v? Thought Iíve seen that before.
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Old 06-25-2019, 04:19 PM   #23
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That's why you use a test lamp and not a meter. A test lamp with a "weak" 12v will be dim or may not light up at all.

OP claims his lamps are illuminating at the injector positive wire to a good ground= RSR relay/wiring and the resistor pack/wiring are good.

Now it's down to the control side of the circuit....
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Old 06-25-2019, 05:34 PM   #24
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Is there a pinout for the LH box? I checked from injector plug to 3 wire plug by coil, .1 ohms, from other side of that plug to bottom left pin on LH, .1ohms, total circuit .2 ohms. Back to the wiring diagram to find 12v for LH.
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Old 06-25-2019, 05:50 PM   #25
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Hold up, things have changed. Now I have no fuel pump relay signal. Let me see what the Hall sensor is doing today.
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