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Old 06-18-2020, 11:46 AM   #26
mschultz373
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so I cleaned up all the washers, terminals and screws and areas for alternator ground and B+. I also put dielectric grease on all the metal parts. here's my measurements after:

battery @ idle nothing on = 13.85V
battery @ idle fans/AC/radio/lights ON = 13.48V
battery + to Alt B+ volt drop = 161mV
alt case to engine block = 174mV

so my cleaning up clearly helped the grounding, but I am still not happy with the battery charge being <14V.

but it looks to me that fundamentally, the alt is basically working, though not as well as it should. could the voltage regulator need replaced? that's the only thing I can think of since the brushes and the wiring appears to check out.
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Old 06-18-2020, 12:49 PM   #27
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Just so you know, silicone dielectric grease is an insulator. It works well as an external coating to stop oxidation of electrical connections - just like any other grease. If you want to improve the electrical conductivity in a bolted electrical connection you need to use something like Ox Guard which is a grease with fine metal particles embedded in the grease (available at Lowe's Home Depot, lots of places).

Check the service manual for the car. 13.8 volts may be within spec for a non adjustable regulator at idle. If your .161 v and .174 v drops were measured under load that totals .335v which is close to your load vs no load voltage difference. You did not do the battery negative to chassis ground voltage measurement. If you have some drop there that could explain the difference.

With a heavy electrical load on the alternator, measure from the B+ stud to the frame of the alternator (or its ground connection). If you have a higher voltage there then the voltage drop is somewhere in your external wiring. If the B+ to frame voltage is down around 13.8 volts, then it may be a regulator that is at the lower end of its spec range or it could be some kind of regulator problem.

Edit:
As an additional observation, a voltage above 12.4 indicates that the alternator is probably supplying the electrical load of the car. However, to restore charge in a battery within a reasonable period of time the voltage applied to the battery really needs to be a minimum of 13.8 volts. Also, what is happening to your voltage when the engine is spinning faster than idle. If the voltage climbs to 14.4 volts at 2500 RPM then you should recharge the battery quickly.

Last edited by 142 guy; 06-18-2020 at 12:58 PM..
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Old 06-18-2020, 01:42 PM   #28
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thanks for the info.

all my previous measurements were under load - lights, AC and fan full, radio.

this is what I am getting now:
battery @ idle w/ load = 13.25V
battery @ idle w/ load @ 2000rpm = 13.35V

B+ alt stud to alt frame= 13.55V

engine block to battery - = 18.4mV
battery - to chassis ground = 18.3mV

bentley manual says battery should be at least 12.6V with key off and at least 14V with engine running; but the troubleshooting principle is that, if the voltage does not increase from rest to running, then there is a fault with the charging system. so I am not in precise spec, but i am in accordance with the principle.

bentley also says that, in lieu of a load tester, run the engine @2000rpms with electric load and battery should not fall below 12V. so I am in spec here.
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Old 06-18-2020, 01:57 PM   #29
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You do NOT need to be above 14V.
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Old 06-18-2020, 02:00 PM   #30
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in which case, does it simply appear that I need to keep my eye on the alternator ground wire? currently it checks out in volt drop but it was the only stand-out problem.

thanks for your time and help everyone.
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Old 06-20-2020, 01:15 AM   #31
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my car made the 11hr trip. battery @ idle when getting gas was 13.68V during day, 13.48V at night with lights on.

i did have one blip. about 3hrs in, I hit a patch of very slow stop-and-go traffic on the interstate. i was stopped, waiting, for about 5min when suddenly my car died. I tried to start it and it would crank and, if it did turn over, then immediately die. I wrestled with this for about 10-15min - no blown fuses, no obvious wiring issue. I rapped on the fuel pump and top of the in-tank unit a few times, thinking that may jump-start either if one had stalled. i don't know if that helped, but after 15min or so, the car started and i was able to drive to the exit.

i was not able to replicate the condition. so i drove on.

the car did totally fine the rest of the 8hr trip. averaged 70-80mph, didn't dip much below 70 on hills even. when i stopped for gas a few times, i turned the car off and she would start up and drive fine.

after thinking of it more, i really doubt it's either fuel pump, since a fuel pump fault would presumably not allow a car to operate normally for 8+hrs. additionally, in april, i replaced the hall effect sensor and had troubleshooted the entire ignition system then, making me doubt if it's an ignition issue. finally, i put a fresh lh2.2 MAf in the car just a few weeks back - so again, i doubt it is the MAF.

my hunch is the IAC. mine has been finicky since I took it apart (stupidly), and I've intended to replace it with a known good unit. my manual lists faulty IAC as a possible cause of engine starting then dying.

i'll look into more tomorrow and write back. thanks again everyone.

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Old 06-20-2020, 01:36 PM   #32
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Good that you were able to make the trip mostly successfully.

Be aware that the motors on electric fuel pumps usually fail during a restart. They will run, you will shut the car off and they will not restart. Repeated attempts to start may get the pump running and rapping the high pressure pump may sometimes jog the pump rotor a bit to allow a restart. If you get the pump to run it will usually continue to run until you shut it off. Depending on the commutator segment that the pump brushes land on when it shuts off the pump may restart or may not (literally a roulette table). When these conditions occur my past experience has been that complete failure is 1 day to 1 week away.

You should be able to tell if the pump is the problem. When you switch the ignition key to the run position (but, do not engage the starter) you should be able to hear the fuel pump run for 2 seconds as it goes through its prime cycle. If you don't hear that prime cycle that is normally an indication that the pump is dead. However, given your other wiring issues I would also check the wiring and pump relay. My recollection is that the engine will run if the pre pump is dead; but, will not run if the main pump is dead. I do also seem to recall that a failed pre pump can lead to an early grave for the main pump.
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Old 06-20-2020, 06:38 PM   #33
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more diag today seems to confirm both pumps are operational.

voltage @ fuse for main pump = 13.84V (car on), volt drop of <30Mv
voltage @ fuse for in-tank unit = 13V, volt drop <30mV

in-tank unit is getting battery voltage and is drawing 3.21A. good.

jumpering from fuse 6 to fuse 4 to power main pump confirms that main pump is working also. it turns on. however, it does sound more like how cleanflametrap puts it on his site: "A hint is sometimes given by the noise the main pump makes when it is either starved for fuel input or electrical input. Instead of the smooth low pitch hum this positive displacement Bosch pump emits when all is well, a raucous buzzing noise warns it is trying to pump vapor along with the fuel." I will check the electrical wiring to the main pump tomorrow.

regarding fuel pump relay, i put a new unit in in late March. did not check but presume it is still good.

IAC appears fine. outer terminals yield 43 ohms resistance, inner terminals yield 22.5 and 20.6 ohms. not far from the 40/20 spec.

I was unable to check the continuity at the TPS. I cut off the TPS connector off my old harness, but still i couldn't measure anything. i am chalking this up to operator error and will need to check my meter's manual on how to test continuity (i know....), and re-test.

i checked my MAF too. resistance for the idle pot check (terminals 2-6) is 20.66 ohms, which is in range of accepted 0-1000ohms. However, my heated wire reading is 36.31 ohms on my meter? my meter was indicating it was 'k [ohms]' so I am unsure if that means the reading is actually 3.631 ohms or the 36.31 ohms. I know, i am still getting my meter chops together. but i may need to run the heated wire test again.

car will start normally, and I drove it to grocery and back today with no issues. it does seem like I have less acceleration than before my trip, though. and the idle in park is surging and low. the idle has a rhythmic ramping-up surge to it, cycling every 2secs or so. i have been pulling my hear trying to get that idle to settle and be normal for the past month....it seems that the idle screw is NOT doing anything, even with the IAC terminal grounded out. again, this makes me suspect, despite the test, a faulty IAC.

my general thinking is: confirm main pump is getting adequate power and wiring is good. then look at TPS and IAC again.

EDIT; while I am here, can I ask, honestly, am I deluded in thinking an 85 240 could be a 100% reliable car for 10hr+ trips? on one hand, old volvos are synonyms with reliability. on other hand, everyone says old cars are inherently less reliable. i love this car and will keep it regardless, but should i get a camry/civic for road trips and use the 240 as a local car only?

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Old 06-21-2020, 12:42 PM   #34
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Old 06-21-2020, 01:15 PM   #35
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A fuel pressure test would be a good step to confirm that both pumps are operating correctly.
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Old 06-21-2020, 04:04 PM   #36
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Old 06-29-2020, 12:49 PM   #37
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a week later and my car is still driving normally. i haven't had any break downs or strange fuel issues - the only persistence is an intermittent surging idle at start in P that disappears when I give the car throttle.
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Old 06-29-2020, 01:38 PM   #38
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if you have the car sorted out. it is reliable for trips. carry spares though and have AAA.
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Old 07-02-2020, 12:21 PM   #39
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thanks for the replies and inspiring confidence in the car.

i still wonder if I am chasing a gremlin here, given the 'car died on highway for 15min then started and ran for 9hrs' incident described herein earlier; and yesterday, my car started then died twice coming out of a parking spot. I had the AC on slightly and the stereo; turning off the AC allowed the car to start and drive normally without dying. If it's relevant, the heat index was 100F+. I seem to be able to run the AC after starting while driving without any faults (well, except that the AC doesn't blow very cold)

anyway, not sure if these could all be connected or if I am just worrying.
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Old 07-02-2020, 01:34 PM   #40
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There is a delay relay for the a/c. It prevents the a/c from running during starting if you leave the a/c on. Makes the a/c wait till about 20 seconds after starting before it runs. If that relay fails to give you the delay. Then it can be hard to start your car with the compressor engaged.
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Old 07-11-2020, 01:39 PM   #41
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thanks for that info. i didn't know that! that's likely the cause then.

the car is running fine mostly but I suspect there is an electrical gremlin. my battery is 12.7V static, idling unloaded at ~13.8V, but drops to ~13V under load - radio, blower, lights. my battery volt tach in the dash will even dip into the low orange at night with radio, blower, lights and turn signal on. additionally, I've had a couple instances, right after starting, where the car, under accelerations out of the hole, 'bucks' as though it lost power and then suddenly regained it. other times, at start, the idle will still have that rhythmic surge to it, like the power is cycling up and down.

I'm not too concerned, as I've only observed the 'bucking' twice in the past weeks - and I've done 3hr round-trips on highway without any issues. i can't find any loose ground or obvious wiring fault in the engine bay as of yet.

maybe i just let sleeping dogs lie.
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Old 07-11-2020, 09:42 PM   #42
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Bosch alternators. When the voltage regulator was failing or if the brushes are wearing out. You can get flickering in the lights and odd driving surging and such. If you pull up the parking brake you'll see the dash light flicker if it has that charging issue.
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Old 07-11-2020, 10:25 PM   #43
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thanks for all this good info 242. dash light is NOT flickering when parking brake is engaged and my brushes are in spec - i checked about a month ago. i'll keep my eye on the situation and check the wiring tomorrow, see if anything makes itself known.... thanks again
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Old 07-31-2020, 08:22 PM   #44
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wait, checking back in.... is the dash light flicker with car OFF/ignition ON or with car ON and lights on? (instrument cluster light thus on) I get a flicker ignition ON pulling up parking brake.
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Old 08-01-2020, 12:08 PM   #45
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Dash light - I assume you mean the charge indicator light on the dash? With the ignition switch in the run position; but, the engine not running the charge indicator light should be solidly on at max illumination. No flickering. When you start the engine the light should dim rapidly - so rapid that the go dim part may be un perceptible. With the engine running, the charge light will only flicker if the alternator output is failing or you have a sneak ground / short circuit somewhere in the charge wire circuit. Applying the parking brake should not cause the charge light to flicker. You may have a wiring issue; but, I would also be inclined to check the instrument cluster to see if there is any physical bridging on the circuit board traces that would cause a connection between the charge circuit and anything else.

Time to haul out the wiring diagram and do a little testing.
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Old 08-02-2020, 04:36 PM   #46
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Just to clarify what I wrote about the dash light. Car is fully warmed up, idling. If you pull up the ebrake and observe the dash light for it. If the light is steady and solid you are fine. If you see slight flickering of the bulb. Then that means there is probably some service required somewhere. Worn brushes or a bad voltage regulator can cause the flickering I was referring to. The ebrake light is just a good way to observe it. The flickering can get bad enough that you will even see it in the headlights.
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