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240 Electrical Black Magic ****ery

Fjergus

New member
Joined
Dec 5, 2014
Location
Seattle-ish
Car deets:
1985 240DL wagon with a freshly rebuilt B230F and LH2.2 w/ Chrysler ignition (no EZK yet)

Things I've tried/checked:
The ignition timing is set to roughly 15?, the valve timing is correct, and I've been searching for vacuum leaks for days without finding any. The idle air control valve and throttle position sensor are plugged in to the correct plugs (they are easy to mix up), and the TPS is adjusted correctly. Unplugging the IAC valve causes the idle RPM to drop, so I know it's working properly. Turning the air conditioner knob also raises the idle like it should. The idle speed is roughly correct, too. It starts just fine, and the electrical system works fine whether the car is on or not. The voltage gauge reads a solid 14ish volts with the engine on, the battery appears to be charging, and I am getting no alternator warning lights.

The problem:
The engine is newly rebuilt (a late model B230 from an early-90's car). It runs great at higher RPM's, but it idles like absolute dog****. Rough, wandering idle, the AFR wanders between 13.0 and 16.0 or so (I have an air/fuel ratio gauge), the works. All of the LH2.2 sensors and whatnot were swapped from my old engine, so that's not the issue. It's pretty obvious that I have something hooked up incorrectly, but until yesterday I couldn't figure out what the hell it was.

Yesterday, I think I got a lead. My battery cables are really janky, so I was fiddling with them with the engine running. I accidentally pulled the negative cable off of the battery and... nothing happened. The engine just kept right on running without so much as a hiccup. I played around with it for a bit, but it made no difference whether the battery was plugged in or not. The voltage gauge on the dash doesn't even twitch (it stays at an even 14ish volts).

It appears that the ignition and fuel systems are running directly off of the alternator, and the battery isn't in the loop at all. That would explain why it runs fine at high RPM, but won't idle for ****: the alternator isn't putting out enough juice at idle to run everything correctly when it isn't turning very fast. I'm pretty sure I have a ground in the wrong place somewhere, but I haven't been able to find it yet.

Here are the major engine grounds:
-Alternator ground post to the block through a bolt on the passenger side engine mount bracket.
-Battery ground to the fender through a screw in the ignition coil bracket.
-Battery to the block through a bolt in the driver side engine mount bracket.

...and here are the positive connections:
-Alternator positive to the starter positive terminal.
-Battery positive to the starter positive terminal.
-Battery positive to that goofy terminal block for the fuel injection and whatnot.

Soooo... what the hell am I doing wrong here? Did the wiring loom spontaneously grow another battery somewhere? Do Volvos normally run just fine with the battery disconnected? I don't think I've ever tried it before, honestly. Are there any connections I missed? I'm kind of at a loss here.

TLDR: 240 with LH2.2 and a freshly rebuilt/installed B230F. Very rough idle, and runs whether the battery is plugged in or not. The problem seems to be an incorrectly connected wire and/or incompetence on the part of the installer (namely myself).
 
...Do Volvos normally run just fine with the battery disconnected?...

Yes. As a matter of fact, on older cars this is perfectly safe and is the easiest way to determine if the alternator is good.

So, that's all you've really done there. You now have a known good alternator :-P
 
Might not be th best for the alt but a quick unplug of the batt and the car not dying usually indicates that the alt is charging to some degree if all you have handy are maybe 2 wrenches in the Volvo tool kit and nothing else...

Does the thing have any vac leaks?
Even compression?
Valve adjustment correct?
Crummy injector or not spraying properly?
 
Might not be th best for the alt but a quick unplug of the batt and the car not dying usually indicates that the alt is charging to some degree...

Have you ever watched with an oscilloscope?

I have and I was like... meh. I used to worry about doing this until a friend of mine and I had this same discussion. He convinced me beyond a reasonable doubt that there is negligible harm.

Also, this test will let you know if your battery is bad.

- Start car
- Test with a voltmeter at battery (for the sake of argument, get 12.3V)
- Test at alternator, get 12.8 (kinda suspicious, yes?)
- Disconnect ground wire from battery, retest with meter, get 14.4 at battery clamps and at alternator...
- Problem solved (bad battery).
 
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Yes. As a matter of fact, on older cars this is perfectly safe and is the easiest way to determine if the alternator is good.

So, that's all you've really done there. You now have a known good alternator :-P

Ah. Well... balls. On the one hand, it's nice to know I didn't do anything irredeemably stupid with the wiring. On the other hand, that leaves me back at square zero.

Does the thing have any vac leaks?

I haven't been able to find any, no.

Even compression?

I haven't checked that yet.

Valve adjustment correct?

I would certainly hope so, since these valves have a grand total of about 200 miles on them. I suppose it's possible the machine shop installed them incorrectly, but I really doubt it.

Crummy injector or not spraying properly?

That's a possibility, I suppose. It would be a little surprising, since all I did was pull the entire intake assembly off of my old engine and plop it onto this one. The old engine ran fine, despite having 290k miles and some really slap-happy pistons.
 

Hmm, possibly. Sounds like it was a combo of a borked Chrysler box and a gummy IAC? I doubt it's either of those in this case, because the car ran fine before I swapped the engine, and all of those components were swapped over. I might start looking there if I can't get it figured out though.

Did you verify that the correct engine temp sensor is installed?

Ooooh, you know what? I don't remember which one I put in there. The replacement motor was off of an LH2.4 car, so it's possible the 2.4 sensor is still in it. I'll have to check that when I get a sec...

Is there a visual difference between the two? I'm assuming they don't use the same sensor.

Edit: Ah, looks like the 2.4 version has a black bit on top, whereas the 2.2 version is blue.
 
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Well, I got curious and checked it out in the parking lot. Unfortunately, the sensor in my car is blue. Balls. That was a pretty good suggestion.
 
Hmm. I haven't had a ton of time to mess with it (I've been moving this past week, and work has been mad hectic), but I did pop a vacuum gauge on the intake, just out of curiosity. It's pulling almost exactly 15 in-Hg at idle, but it rhythmically pulses up and down between 14 and 16. If I goose it and let off the throttle, it pulls about 20-25. That sounds fairly typical to me, which makes me think there isn't a gigantic vacuum leak hiding somewhere. The pulsing thing is slightly odd though.

I also replaced the plug wires, since I had a set laying around. No change.

I still need to check compression, but it should be fine (remember, this engine rebuild has about 500 miles on it). Any other suggestions?
 
Chrysler Box oh all mighty show me the lovin, gummy IAC, split hose at IAC-Intake.. Mm lovin lovin
 
How's the engine wiring harness? Since it's an '85 model there might be some crumbly insulation somewhere that got knocked loose during the swap if the harness is OE.
 
Chrysler Box oh all mighty show me the lovin, gummy IAC, split hose at IAC-Intake.. Mm lovin lovin

I cleaned the IAC out not too long ago, and the intake hoses are all new. I've been spraying starting fluid all around in there, and I haven't found a vacuum leak, so I doubt that's it.


How's the engine wiring harness? Since it's an '85 model there might be some crumbly insulation somewhere that got knocked loose during the swap if the harness is OE.

The harness was actually swapped out a few years back, and it's in decent shape. I've been looking for crusty or broken wires, but so far I haven't found any.
 
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