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Old 05-10-2017, 11:30 PM   #51
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on 84-87 760 this switch is on or near the EZK.
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Old 05-11-2017, 07:55 PM   #52
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I finally found where they're supposed to be. I have the LH pulled and ready to ship to Electronik Repair, in Mesa, AZ, along with two AMMs, for full testing and/or repair along with the EZK.

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Old 05-12-2017, 03:47 PM   #53
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Nicely buried above the pedals, aren't they. The pressure switch has no vacuum line attached. How to test it is my next search.

I found the trick to remove it in another thread: the one phillips screw right behind the steering column, then the whole metal mount slips out of other bracketry.

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Old 05-12-2017, 04:41 PM   #54
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Turbo with slushbox always feels really limp off the line to me, not having driven your car I can't really say if what you're describing is normal. The next thing I'd check is ignition timing and the timing belt. I got the belt off by one tooth on a car once and it had almost no power at low RPM, could barely even get the car moving but then it would take off like a rocket when the turbo finally spooled up.
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Old 05-12-2017, 07:09 PM   #55
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I am going to check belt timing soon; thought about that when advancing the distr. helped driveability.
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Old 05-12-2017, 07:49 PM   #56
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If it hasn't been mentioned already, closely inspect the harmonic balancer. When they fail, the outer portion which also has the timing marks tends to spin on the inner portion and the result is the timing is not where you think it is. Pull the #1 spark plug and verify the engine is at TDC, then check that the timing mark aligns precisely with 0 degrees.
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Old 05-13-2017, 05:39 PM   #57
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If it hasn't been mentioned already, closely inspect the harmonic balancer. When they fail, the outer portion which also has the timing marks tends to spin on the inner portion and the result is the timing is not where you think it is. Pull the #1 spark plug and verify the engine is at TDC, then check that the timing mark aligns precisely with 0 degrees.
Thanks. It was but I waited 'cause the engine is rather new, from Sweden. Now, that doesn't mean one heckuva lot, but..

With the brains enroute to AZ, I'll try to check this.

Some Saabs and some Porsche 928s used a very similar system, and the AZ shop primarily works on the latter. His reply to my query was friendly, which is a good start.
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Old 05-13-2017, 06:49 PM   #58
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Wow, you're still actively fighting this.... You need to go to a JY and pluck some stuff... For the amount of time and effort you've put in, a fairly easily found lh2.2 740 could have given you a coil, dist, some "free" sensors, etc.

And.... EZKs and ECU's don't often go bad with these models. Probably not fighting the overboost switch and hitting fuel cut.
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Old 05-27-2017, 01:10 PM   #59
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EZKs and ECU's don't often go bad with these models. Probably not fighting the overboost switch and hitting fuel cut.
Yeah, thanks. I should have the rebuilt parts back in a few days. Putting unknown, used parts complicates the troubleshooting, unless absolutely certain that they are good, which is why I made this move.

The intermittent, but seemingly heat-related problems are so hard to find.

Both AMMs are similar and off calibration about 20mv, but the tech says usually won't cause problems until >30mv.

He said:1) the fuel box was fine, but soldered every connection, to be sure, and 2) the ICU is rarely a problem, being well built. He did replace a few aging capacitors in it.

I'm going to check the Hall sensor wire, but the tach has always read properly.
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Old 05-27-2017, 02:05 PM   #60
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The no power and low boost problems sound like a clogged/restrictive exhaust to me. Try driving on an open downpipe.
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Old 05-27-2017, 06:17 PM   #61
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Add to that, the low vacuum, which is why I checked the cat. I cleaned out all its internals but won't install the new one util the car runs. Hopefully, none of the pieces moved back to the muffler.
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Old 05-29-2017, 05:46 PM   #62
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I have a non-turbo 740 which had similar problems. Turns out mine was all corrosion related - I started measuring block to battery resistance through ground, and had well into the 15 ohm areas. intake manifold to battery was closer to 400 ohms. I took a bit of 10 gauge wire, and just went and tied everything together, block, alternator, battery, frame, manifold, headlight grounds, etc.

Next start, I have GREAT lighting again, but the engine runs SUPER cruddy. So I disconnected the battery, and turn everything on that I could find - so as to discharge any remaining capacitance. Reconnect battery, fire her up, and it's running OK, but not great. Took it down the road, by the time 5 miles was past, the rig runs great again!

Read this thread, and while it looks like you've been dealing with corroded insulation, don't for get to take a look at the grounding straps and the reading from them to ground on bat.

Just a thought. works for me!
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Old 06-01-2017, 07:36 PM   #63
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Thanks for that. I'd checked grounds, having had plenty of ground loop problems in another car and knowing the sensitivity of all newish cars to proper signal paths, including grounds, which are oft overlooked. Such is frequently solves the noise issue in car audio systems.

Unlike many, we live in a warm dry climate and rarely see rust or corrosion of nay type. I could not recall the resistance readings I'd taken in this car trek, so I redid that and found a maximum of 1 ohm, which was at the metal panel that holds the ECU.

Having just gotten back the electronics from a shop, I started the engine after reinstalling them all. It ran for about 3 seconds. I tried again and saw there was no tach indication either, which I think points to the Hall sensor. Going to research that now.
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Old 06-01-2017, 07:42 PM   #64
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If the hall sensor is bad the engine won't start, was the engine running without the tach doing anything? That sounds like a wiring problem to me. The tach is driven directly off the ignition coil IIRC, if it's getting a spark then the tach should do something. I suppose a bad tach could cause lack of spark but I've never personally seen that.
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Old 06-01-2017, 07:50 PM   #65
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The engine is idling, to see if it will quit. I found 6.4 vdc at both coil primaries, so pulled the FI relay (looks new), then checked the noise relay in/out at 12vdc. Hmm. Decided to check the coil again and found proper (12v) at both primaries. When I pulled the FP relay after it idled for a few minutes, it felt warm, telling me something may have high resistance, so I contact cleaned the socket, then let it run for a stretch.

Boost below 1300 rpm is non-existent, still.

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If the hall sensor is bad the engine won't start, was the engine running without the tach doing anything? That sounds like a wiring problem to me. The tach is driven directly off the ignition coil IIRC, if it's getting a spark then the tach should do something. I suppose a bad tach could cause lack of spark but I've never personally seen that.
I was so surprised the engine started, I failed to see if there was a tach indication! It had been working just fine.

Prior, there was no spark and I'm about to check again. I smell fuel so am quite certain the pumps are working. There is no spark... again!!

Time to peruse the troubleshooting flowchart.. AGAIN.

Someone disconnected the vacuum line for the overboost switch, for whatever reason. I tested it okay and am reconnecting it via a T to the boost gauge and CC pedal switch. (The cruise wasn't working either).

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Old 06-01-2017, 10:48 PM   #66
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On my 88 765 Turbo the tach was erratic when the aftermarket powerstage was failing. Installed a good used Bosch powerstage and cured the issue.
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Old 12-10-2017, 10:53 PM   #67
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Yeah, old thread. Old guy, too with real old problem! I needed a long break from slow-Volvo-World. Car has a history of worsening boost levels.

Engine runs great, sort of; starts right up after sitting for months, then idles like a purr-fect engine. Tis a replacement Swedish red block of relatively new stature.

Today, I installed the brand new, CARB certifed cat (old was cheap aftermarket w/melted core). With no boost and vacuum gauge readings indicating 'maybe', I'd checked for exhaust blockage. A (easily missed) sticker on the box says to do a run-in procedure to set its guts properly: 5-10 minutes at idle, then 2 minutes at 2500 RPM, then drive the car.

So I did. The boost is non-existant, until 3rd gear, under hard acceleration, where it was maybe 2-4 pounds. Car is a real bow-wow from a stop. I'd checked the vacuum-actuated device (looks shiny and new) on front of the turbo and for leakage in its vac hose from the intake. Audible clicks heard when adding/stopping vacuum to the actuator and vacuum held solid at 22# when I connected the IM end to my hand pump instead of the intake.

I'd checked for end play and free spinning of the turbo 'back'when'. Both okay and no blue smoke from tailpipe.

I was surprised to see any boost indication, as w/o the cat the dash never indicated anything but vacuum. Previously, I'd adjusted the waste gate lever with no real improvement in this long-existing problem. Maybe it's time again, after the new cat?

Son's graduating and we want this car for him.

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Old 12-12-2017, 06:54 AM   #68
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i still think there is something fundamentally wrong in the wastegate + control setup: wastegate not properly closed when it is supposed to be = no or very late spool-up
Your story reads like there is no closed wastegate inside the turbinehousing...wastegate port open all the time...
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Old 12-12-2017, 03:11 PM   #69
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i still think there is something fundamentally wrong in the wastegate + control setup: wastegate not properly closed when it is supposed to be = no or very late spool-up
Your story reads like there is no closed wastegate inside the turbinehousing...wastegate port open all the time...
Thanks for that, truly!

I don't know how to check that, so will look for that procedure.

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Old 12-13-2017, 04:33 AM   #70
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you could investigate the wastegate by undoing the downpipe and use a small mirror and a torch to take a look inside the turbine housing. Look for a closed wastegate port.
manually open the wastegate by pulling on the actuator rod. and see if the gate opens up.
Also see if you can find evidence of cracks in the wastegate port and/or wastegate valve.
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Old 12-13-2017, 11:57 AM   #71
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I got in there today, fun as it is. Thanks so much. There is such a dearth of info on this car, even via AllData at my pal's shop.

I was unable to see much of anything with light and a mirror, but I have a (invaluable) Snap-On boroscope. Bending the lighted tip and moving it around, I was able to see the flap that closes off the exhausted gases, thereby using all that energy to spin the turbine; controlled by the shiny newish vacuum pot at turbo's front. There was no way the control rod length was allowing it to close and after detaching it, I found some binding in the flap's movement. Exercising it back and forth a few times seems to have freed it so it moves easily, full swing. that cpontrol rod is way off in adjustment, probably wrong since the vacuum pot was changed by a PO. Sadly, I did not see enough detail for cracking.

Tomorrow, with more light and energy, I'll address that rod length issue, then reassemble the down pipe and shroud. I expect and feel this old Swede brick may hop away from stops quite spritely. The minimalist Haynes manual at least has the adjustment procedure.

I'm still quite sure there is a incorrect vacuum hose setup, akin to what I found, done by a PO, with the wiring. I have a number of vacuum hose diagrams, for various cars, but this '87 turbo has no underhood sticker. At least at this point, that may just mean the CC won't work and the vacuum pump runs too often; neither a safety issue.

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Old 12-15-2017, 04:51 AM   #72
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progress! let us know how that correctly adjusted wastegate does.
I predict a nice improvement.
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Old 12-15-2017, 02:08 PM   #73
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True progress and thank you for your help. This 765 has near perfect leather and paint; shows very well. Despite the improvement, which I'll TAKE, I feel I'm back to the performance issue of months ago.

Haynes says proper wastegagte adjustment is accomplished with 7psi applied then adjusting the lever length. Compressed air does activate the mechanism, but I've no easy method to apply exactly 7psi. I readjusted it to be fully closed, with urtrher slight closing pressure at zero pressure. Perhaps it needs another turn?

Drive: The car is very slow from a stop, until around 2000 RPM. Unlike earlier, it shows some boost, then more as the car anemically accelerates. More boost is indicated at higher revs/velocity, but never more than 1/3 gauge deflection. There is some engine stumbling with added boost, accompanied by poor acceleration. At best it drives reasonably well as long as the revs stay above 2000 RPM, though I don't think it's truly up to par. I was also told that this aged engine control has no learn capability. True?

A professional mechanic (not a Volvo guy) mentioned that some cars employ a computer controlled solenoid to limit boost until the engine can handle it. I recall reading about them, but don't know if this car has one. I'll check the wiring diagram, assuming it's corrrect. I mentioned that the removed cat's internals had melted, probably from whatever condition existed, perhaps running too rich.

I've not made an apparatus to verify proper fuel pressure.

I did get some vacuum hose diagrams and am seeking where to post them for others' use.

I feel close to a solution; then again, Ive felt that before!

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Old 12-15-2017, 04:10 PM   #74
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Not much change in idle when pulling the vac hose from the newish FPR, but... one thing at a time!

Cranked 1 1/2 turns more pressure on the WG rod; still a dog from stop, but better elsewhere. I think the still-existing stumble may be erroneous A/F ratio, due to mismatch between boost and fuel injected, least for now.

I tried another 1/2 turn in the adjustment, but it worsened. I'll back off a notch, then try to find a way to check the fuel pressure, having a gauge but no port. I saw how to make a tool, but haven't yet.

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Old 12-17-2017, 08:54 PM   #75
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For things as they are, that 1/2 turn out is the sweet spot; still a bow-wow and when accelerating, i have to 'feather' the throttle to find where the car will accel best; not stumbling some, despite the boost seemingly normal. I hear a whistling (suppose it's dumping boost) at halfish boost needle, under load in say, 3rd gear with RPM 3k+/-.

With fresh gas, I rechecked idle vacuum and FPR. Still very little, if any change when pulling the vacuum from it. The MAC shows 15psi vacuum, rather low, and slow variance of about 1/2 psi. along with a slight variance in idle speed. Interestingly, I recall 22 psi earlier from a different port on the intake.

"Vacuum readings at idle much lower than normal can indicate leakage through intake manifold gaskets, manifold-to-carburetor gaskets, vacuum brakes or the vacuum modulator. Low readings could also be very late valve timing or worn piston rings.

James10952001 said maybe the cam belt is off a notch; I've still not checked, but with the vacuum diagram finally in hand and known leakage in parts (iwth frequent pump runs), that's where I am headed first.

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