no spark still, please help

[Astro14]

ECU are expensive...don’t fire up the parts cannon just yet (shoot parts at problem, hope to hit target).

Are you certain that the injector for no.2 is firing properly?

Since that was disturbed during your work, I would be certain that the connection and injector for no. 2 work. I’m not certain if the ME7 needs to see a signal to the injector to send a signal to spark, but I know that the reverse is true: without spark, the injector signal is not sent by the ECU.

You’re missing the spark firing signal, I reckon.

Either the wire between the ECU and coil is broken, or the ECU isn’t sending the signal.

If the ECU isn’t sending it, either the ECU is defective, or, perhaps, it’s missing an input for that cylinder.

Check the injector.

Check that wire.

[hoonk]

This is a repost of an issue I was having last week, but I've been testing everything and I really need some expertise here.

put her back together. She ran like a rock star for the first day

That issue is resolved but now my #2 cylinder won't fire.

Am I chasing a red herring?

In fact, the car runs remarkably well on just the 4 cylinders. But I've got to get to the bottom of this.

Any suggestions, tips, debugging ideas, anything?

when she was running, she ran like a champ with acceleration and power

she runs pretty much fine on 4 cylinders, just low power and not a smooth ride.

Please please help, any suggestions at all, will be appreciated,

OK - an engine running on 4 out of 5 will not run "pretty much fine". So, when you start grasping at straws (let's replace the ecu!) back up and take a new look. Review history and what's been touched.

In an earlier post you said you removed the intake manifold (not sure why?) to get to the alternator. Was that after "she ran like a champ with acceleration and power"?

If so - is it possible that you have a large air leak at the #2 intake manifold gasket? (maybe you missed removal of part of the gasket, easy to do)

If so- the car won't idle on #2 (too lean with the air leak) but may fire and run at higher rpm's.

[drgian]

this history is that I got this car with a broken valve and tore her down and rebuilt her to fix that. Once that was the fixed the bad alternator presented itself.

Removing the intake manifold seems to me the easiest way to get the alternator out, If you've worked on this particular car you'll know there isn't a lot of room to maneuver in there and I'm not sure how else I'd get the alternator out of the car. I read on set of instructions that suggested removing the radiator, but on this car the intake manifold comes off and on pretty easy. I had just replaced the gasket when I did the rebuild and when I pulled it and replaced for the alternator job I saw no issues with the gasket.

But the argument I'd make here is if there was some issue with air flow, the plug would still spark (as all the others do) when I pull it out and hold it up against the block. To wit: I have pulled out number 1 plug and coil back and number 2 plug and coil pack. had wife start the car running now on three cylinders. #1 spark, #2 no spark. I switched connectors, now #1 no spark and #2 spark. I think this rules out anything with the coil pack, plug and since both plugs were at this point out of the cylinders, also rules out any issues with air flow. This lead me to investigate the connector. the connector has 3 leads, a ground a + 14V and a feed to the ECU. Ground is good, +14V is good, so that leaves the feed to computer. I traced that wire back to the ECU and cut it at both ends and ran a fresh wire from the ECU (as close as I could get) to the connector hoping I had a discontinuity in the ECU feed wire. No difference there.

I believe I have ruled out everything else, I would not describe my looking into the ECU as grasping at straws by any means. I have rebuilt 4 of these engines successfully btw.

Does that ameliorate your concerns about a leaky gasket or an air flow issue? Also, I should mention that this issue persists at all RPM's and is not intermittent. And finally, I'm not getting any CEL, which may or may no be consistent with a bad channel in the ECU, but I think you could argue it would be consistent.

Finally, I'd just want to point out that I come to this forum for help and suggestions (which I genuinely appreciate) without condescension ('not sure why', 'grasping at straws').

[drgian]

that's a good idea. the wire is good, I replaced it from the ECU all the way to the connector. But the injector could be at fault and in fact, I replaced the injector with one from my wreck which is a 2002. That could easily be it and that's easy to check. I'm going out to do that right now.

BTW, ECU's seem to run for $100 on ebay so I'm not worried about the cost, but I'd hate to get it in the mail put it in and still see no spark.

I'm going out right now to put the original injector back in. I'll post back.

How do you check the injector? Have someone start the car and have fuel shooting everywhere seems like a bad idea, is there a standard procedure?

[pbierre]

The evidence is strong for the discontinuity or weak current in the coil-pack harness feeding #2. In suggesting to replace the harness -- it's not clear who supplies these.
You might need to hit the junkyard or place an online salvage part request - get the part number off the current harness. I know, it's a very complex harness with many branches
not related to the coil-packs.

Drilling down to a root cause within the harness: You've replaced #2 coil signal wire, but to no avail, right? The problem could be in the plug where the harness connects to the ECU.
Or, the 12V and Ground could be seriously corroded but still dangling by a thread. Did you use the ohmmeter to check plug-to-plug resistance through all three #2 wires? It should be < 1 ohm (measure with the engine off, connector unplugged at ECU). Not knowing any better, I'd disconnect the battery while the ECU is unplugged for testing.

Can you get a graphing voltmeter? You'd start by studying the coil trigger pulse on one of the good cylinders. Then, work your way backwards on the #2 coil trigger wire, all the way back to the ECU plug. I'd try to get definitive proof that the ECU is bad before replacing it.

You raise a good question about why the ECU is not reporting a #2 misfire - sorry, I don't know enough about the diagnostics internals.

[Astro14]

When I’ve had a coil pack fail, the engine runs like a paint shaker. More throttle=more vibration.

Sure wouldn’t call it “smooth” or “powerful”.

So, your problem is intermittent and I think Hoonk may be onto something.

I’m not sure you’ve got a misfire that is continuous or even the result of a bad spark.

[drgian]

I just got in from the garage. I swapped the injector with the original that came with the car and made sure the connectors look good. They do.

I haven't disconnected the coil pack connector and ran it at speed and so I'm inclined to believe you when you say that if that spark was truly not firing at all she would shake like hell. What I can say is that if disconnect any of the connectors at idle, there is noticeable drop in RPM, which is then compensated by the computer. If I disconnect #2, nothing changes and there is never a spark at idle. When running she shakes a little, it's consistent though, not intermittent. But she'll do 80 MPH and accelerate like the ford focus I rented last week while out of town.

So I'm looking for an air leak around the #2 intake port then? I can do that. The intake manifold comes off pretty easy and this issue started with the removal of it last time; in order for me to get the alternator out.

I'll pull it and check it out, I'll order a new gasket beforehand just in case.

I'll admit, she doesn't run like a car with a totally dead cylinder. When I bought her she had a tooth sized hole in on of the intake valves, that was a 2 hour ride I wouldn't want to do again. I was like urban cowboy. I assumed this was because even though the was no ignition, the compressed gas and air was pushing down on the #2 piston like a spring being released, rather than having no downward force when I had that hole in the valve. But this is a wild guess at best.

So you all have convinced me, I'll pull the intake mani and look for anything amiss. I'll report back. Thanks for the help.

[drgian]

Thanks for the link. I'll check it out, however, I have been able to trace the input signal wire to my #2 coil pack all the way to the computer, at least under the female connector jack and it just goes up into there, I can really shove it up in any further to make sure it's making contact and I can say that all the pins are clean on the computer and all the male jack ports looks fine. I did clean them with brakekleen and compressed air but I'm not sure what else I can do to rule out a contact issue.

What I'm chasing now is two things, the ECU or some sort of intake leak that would cause the computer not to send a fire signal to my #2. At some point, I was getting CEL codes 'misfire #2, but I'm not getting them anymore. I think this could support my bad channel on the ECU theory. But I didn't want to blow off the suggestions that it was an issue with a lean somewhere on the intake side. There are 6 bolts that hold up the intake mani. After the last post I got from Astro 14 I went back just to quickly check for any leaks, next time I have a few hour to spend on it, I'll remove the intake mani and replace the gasket and make sure nothing else is amiss down there.

But I'm still hung up on this no spark issue, the claims are that if I was indeed getting no spark at speed she'd buck and I'd know it. She's got no spark at idle, that's easy to test if you read the thread you'll see I've ruled out the plug, the coil pack the wiring and the connector. I got a wrench on 5 of the 6 bolts, the bottom left (as you face the car) on this car won't come out without removing the thermostat housing which in turn (unless you have better tools that I) involves removing the power steering pump. None of this is hard but I didn't want to get into at 7 on Sunday night. I was SHOCKED to find that while the top three bolts were snug the two I could get my wrench on were comically loose, like not even finger tight. I can't see how I just forgot to tighten these, but I have been known to make dumb mistakes like this in the past (in fact this entire rebuild is a 2nd try, after the first successful rebuild, I didn't tighten the timing belt tensioner and it fell off, timing belt fell off and to do the job all over again, this time paying to replace 20 valves and 20 valve seals.

I could hears what sounded like air leaking there as well. So I snugged down those bolts, not crazy tight, but I'd about 20-30 N-m, not sure the spec, but I don't want to strip them. I also put lithium on just in case that helps them stay and protects against stripping. The result? She runs a little smoother, but still no spark on #2 at idle and still sluggish performance.

You guys said that if #2 was really not firing at all, I'd know for sure. So to test this, I disconnected the #2 coil back and took her for a test drive. There was no difference. She ran OK, she shudders a little with the cruise set at 60 as we hit a small incline. If I put the pedal to the metal, she'll take off and not shake at all. The overall performance again, is like a for focus with a 2.0 and no turbo, and was all with the #2 coil back disconnected. So my issue is no spark, I'm certain of that, I just don't know why. All I can think of is the ECU, but I'm certainly willing to accept that it's not the ECU, but that the ECU is getting some signal that indicates it should not fire #2, but I don't know what that could be.

I will remove the intake mani as planned, check all electrical connections, hoses and replace that gasket. As a side note, although I doubt it's relevant, the thermostat housing is leaking, the thermostat itself has a rubber gasket built into it and it's hard and I'm sure that's the source of that issue. But I don't see how that could be related, but who know.

I have a code reader that reads the standard codes, but also has a volvo specific menu that reads volvo codes, she's throwing about a dozen of those. I have a screen shot I will post shortly of those errors.

Thanks again for all the help, please give me any ideas you have,

drGian

[drgian]

I’d love to get an oscilloscope just to study the signal from that signal wire, I haven’t used one of this since grad school. I could measure the pattern on a good cylinder and compare to the bad one. As for the ground, the wire doesn’t look that great but since I’m out there alone I just listened for the ‘Beep’ it makes when it’s got continuity. But replacing that wire and its closed circle terminator just to rule out a weak group would be easy enough, just to rule that and save myself or my kid the hassle when it finally just breaks. I didn’t consider that a weak ground could do it. I’ll try this th aka for the tip.

As for the connectors. I have a scrap 2001 xc70 and the connectors aren’t exactly the same but I had one of those on before the alternator was replaced when she was running smooth and with plenty of acceleration. Nevertheless, I did buy on that in the end seemed generic (it had 4 leads) but continuity tests indicate it’s doing its job.

I know there are lots of other theories (including mine) but none can explain why no spark at idle. All other 4 spark fine at idle and I can’t see any air leak or other issue that would cause just that one to flake out. That’s why I’m so hung up on this connector and it’s wires.

I’ll replace the ground wire in it and solder on a round terminator like the other 4 have and hang that off the bolt that holds the coil pack down and report back.

Thanks.

drGian

[hoonk]

without condescension ('not sure why', 'grasping at straws').

I apologize, I did not mean to write something that would upset you.

" not sure why" - As a shop I was constrained by how many hours I could charge for each job. Volvo suggests 1.7 hours as a replacement time for that alternator. Intake manifold is 2.3 hours.
Volvo suggests (in ViDA) removing the fan shroud, but not the intake manifold. - I remember taking the PS pump off and getting the alternator in and out from that tight space. Removing the manifold you risk damaging the pcv pipe that attaches to the bottom of the manifold at a weird angle.

A used Ebay ECU WILL NOT WORK IN YOUR CAR until it is programmed to talk to your CEM. Perhaps someone like Xemodex can do that, but before them that was not possible. Perhaps the same year and prayer it might - but I never had luck using used control modules.

As someone who has worked on cars since the early 70's and managed techs for 40 of those years - there have been many times, myself included, when trying to figure out what's wrong, they talk themselves into the wrong diagnosis. Unfortunately sometimes the wrong diagnosis is very expensive. One of my jobs was to try to catch those bad diagnosis before the part that wouldn't fix it was ordered and installed. Of course the techs hated being 2nd guessed -

I still remember the CEM I had to eat - LR turn signal would not work, tech says needs new CEM, replace and program CEM (before Xemodex rebuilt them) -still not fixed - turns out someone had rigged trailer hitch wiring on and draped a wire over the tailpipe, insulation melted and would ground out sometimes. Zip tying the rigged wire out of the way fixed it. I couldn't charge much for that fix!

So - since I have never seen a bad ECU on a 99+ car, I would be very reluctant to replace one. Possibly someone like Xemodex could test your control unit to verify your diagnosis (I have shipped them control units for testing many times when trying to solve problems)