North American Turbocoupe Organization



Issues after alternator swap
Not B Anymore Offline
Administrator
#1
Ever since I swapped in the 3G, I've had an issue with the rpm's dipping real low after I push in the clutch pedal while driving. When I'm slowing to stop at a light or something I'll push in the clutch, the rpm's will usually dip to around 500 and then they'll come back up to 1000 after a second usually and then it's fine until next time. A few times it has stalled because of it and occasionally it'll hang at 500rpm for 3-5 seconds before it recovers.

The thing is it never happens when there is no extra load on the electrical system. If the heater, radio, and lights are off this never happens. If one or all of them are on it always happens. And it only happens after the car has warmed up a bit. It doesn't matter at what rpm I push in the clutch. Whether it's at 1000 or 5000 makes no difference.

The other issue is the headlights kind of pulsate when they're on. It's hardly noticeable, but they always do it - at least at idle. They also dim when the music is turned up. My stereo system is not all that powerful and I feel like the 130amp alternator is more than enough to handle it. I honestly don't know if this has been happening since the swap, but it if has, I never noticed it until more recently.

Unfortunately I haven't had much time for troubleshooting yet. A couple months ago I upgraded my battery terminals and ground cables, added a ground from the battery to the body, and moved the charging wire from the starter solenoid to directly to the battery. I get 0 ohms resistance between the battery and the alternator on the positive and negative sides, between the engine and the body, and between the battery and the body.

Here are a few photos of the current setup:

This is just an overall view:
http://i798.photobucket.com/albums/yy270...G_2323.jpg

Rear view of the alt.:
http://i798.photobucket.com/albums/yy270...G_2320.jpg

Battery and terminals:
http://i798.photobucket.com/albums/yy270...G_2319.jpg

Body ground I added:
http://i798.photobucket.com/albums/yy270...2-edit.jpg

One thought I had was that the battery is pretty small and perhaps it can't handle the load? I am NOT an electrical wizard, though, so I don't know.

Sorry for the lengthy post and if anyone has any input I would be most appreciative.
Brian Leavitt
'86 TC 5-Speed -- MS2x w/COP | 83 lb. injectors | T3/T4 50 Trim Stage 3 .63AR | Full 3" Exhaust - No Cat | Motorsport FMIC | Ranger Roller | Ported E6 | Walbro 255HP | Kirban | 20psi | 120-amp 3G | 8.8" 3.55 rear | '03 Cobra Wheels
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RDOG Offline
Posting Freak
#2
I cant see from the pics where the power wire is going. Can you tell us the rout of the power wire?

It sounds like a ground issue,and I think knowing a little better how you routed the wiring from alt to solenoid to battery would be helpful.
1986 Turbo Coupe. Boport StageIII head, Boport 2.1, Performance Techniques 50 trim hybird, StageII.63, stinger 3" exhaust, Phenolic spacer, Boglog header,NPR FMIC intercooler setup, kirban fpr, bigrmotorsports fuel rail, diablo water meth kit, CAI, remote mount TFI, CHE rear adj control arms, MAC girdle, 8.8 rear disc, aluminum drive shaft, H&R lowerings springs Tbird Turbo Specific, y MAS!!
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Not B Anymore Offline
Administrator
#3
I thought the grounds may have had something to do with it which is why I added and upgraded all of them.

The original power wire from the alt to the solenoid is still in place. I added a 4-gauge with fuse from the alternator directly to the battery terminal. I was going to get rid of the original wire altogether, but was unsure if it was only needed for the amp gauge or if it is used for something else as well. It never gets hot, though, so I've just left it alone.
Brian Leavitt
'86 TC 5-Speed -- MS2x w/COP | 83 lb. injectors | T3/T4 50 Trim Stage 3 .63AR | Full 3" Exhaust - No Cat | Motorsport FMIC | Ranger Roller | Ported E6 | Walbro 255HP | Kirban | 20psi | 120-amp 3G | 8.8" 3.55 rear | '03 Cobra Wheels
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Not B Anymore Offline
Administrator
#4
I haven't had much time to look at anything yet, but I did do a couple things. On a break at work today hooked a DMM up between the battery + and chassis ground. Before starting the car I got a voltage reading of 12.45v. When I started the car up (cold) with the heater and lights off, the voltage read 14.62 and slowly, but steadily climbed to 14.68. Voltage read the same when I revved the engine and at idle.

After the car warmed up a bit the voltage dropped back down to and was jumping around between 14.46v and 14.59v on the dmm. I think with an analog meter it would be jumping around even more as the refresh rate on the dmm is pretty slow.

I also performed a voltage drop test between the output stud on the alternator and the battery + post and I got .126v. So I guess that's kind of high? This wire came pre-assembled from PA Performance. 4-ga. wire with inline mega fuse. I also measured between the battery - post and the chassis ground and got .021v.

Unfortunately that's all I've had time for so far.
Brian Leavitt
'86 TC 5-Speed -- MS2x w/COP | 83 lb. injectors | T3/T4 50 Trim Stage 3 .63AR | Full 3" Exhaust - No Cat | Motorsport FMIC | Ranger Roller | Ported E6 | Walbro 255HP | Kirban | 20psi | 120-amp 3G | 8.8" 3.55 rear | '03 Cobra Wheels
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Joe F Offline
Posting Freak
#5
JR had a similar problem. The rpm would occasionally drop, kind of like a hiccup. When I replaced my battery with an Optima, I went through the grounds around that area and found a plug-in sub harness that connected to the main engine battery ground and was then connected to a couple of other points to ground them well.

The connector was all green and corroded, so I ripped the whole mess out, got rid of the connector by soldering an entire new and improved wire assembly together, and very carefully reinstalled it, along with a new main engine ground cable as well.

The results were amazing; the engine ran smoother than ever before, all the lamps in the dash, as well as the running lights and headlamps were brighter than when new, *and* the "hiccup", which had always been around, completely dissapeared!!!

Moral? Grounds, my friends, grounds. An afternoon's work improved the electrical system immensely.

Just my experience, yours may vary, but I'd do it all again in a heartbeat, and that's all I know!
JR's Place - My '87 Turbocoupe
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frank-id Offline
Junior Member
#6
To solve any grounding issues, add several more ground conductors. Usually the most effective ground is a connection on the engine, or at altenator. Mininum size conductor should be at least AWG 10. good fully charged lead acid battery will indicate 12.6 volts as each cell will produce 2.1 volts X 6. Old mechanic. Frank
frank
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Joe F Offline
Posting Freak
#7
The only problem with blindly adding more grounds is that you can create what is called a "ground loop". With all the electronics in our birds, that can be a problem for the EEC.

35+ years EE. 25 years with TC. Generally though, grounds *are* good.
JR's Place - My '87 Turbocoupe
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Not B Anymore Offline
Administrator
#8
OK... here goes nothing...

Quote:Originally posted by Joe_F:
I went through the grounds around that area and found a plug-in sub harness that connected to the main engine battery ground and was then connected to a couple of other points to ground them well
My negative battery cable goes nowhere but to the engine block. There is nothing else connected to it either. BUT... there is some kind of ground with a plug that's screwed to the chassis near the one I added. You can see the ground location in the photo of the chassis ground I added in the shaded area near the top of the photo. I'll have a look at that and see where it goes and see if I can replace it. It is kind of crusty.


Quote:Originally posted by frank-id:
To solve any grounding issues, add several more ground conductors.
Where do I add them? I'm getting a reading of 0 ohms between the alternator case and the battery, the battery and chassis, and the engine and chassis. I added the ground from the battery to the chassis with 4-ga. Replaced the positive and negative battery cables with new 4-ga. wire, and replaced the ground strap from the engine to the chassis with 4-ga. as well. I also stripped all of the grounding points down to shiney bare metal before reattaching anything.

Quote:Originally posted by frank-id:
...you can create what is called a "ground loop".
I am aware of the term, "ground loop", but am unsure of what exactly it means. All I know is it will introduce noise into the electrical system if I remember correctly... which I may not. How do you avoid creating a ground loop, Joe?

Is the voltage drop test better for seeing how well something is grounded than simply taking an ohms reading? This whole voltage drop thing is new to me.
Brian Leavitt
'86 TC 5-Speed -- MS2x w/COP | 83 lb. injectors | T3/T4 50 Trim Stage 3 .63AR | Full 3" Exhaust - No Cat | Motorsport FMIC | Ranger Roller | Ported E6 | Walbro 255HP | Kirban | 20psi | 120-amp 3G | 8.8" 3.55 rear | '03 Cobra Wheels
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Joe F Offline
Posting Freak
#9
Quote:Originally posted by B:
OK... here goes nothing...

My negative battery cable goes nowhere but to the engine block.
OK, I'm doing this by memory as it was several years ago that these events transpired, so be gentle.

As I recall, the main big battery ground went down and connected to the engine block. However, there was also a secondary, smaller ground cable that also exited from the negative battery clamp and then was routed down underneath the battery tray, where it terminated at a two pronged plug.

The other side of that plug had two wires coming out, one which connected to the chassis/wheel well just behind the battery box, and another, larger one that snaked back towards the firewall somewhere. Sorry but I really don't remember where it wound up terminating.

The plug assembly was slimy with corrosion green and the wires, along with the main ground and the battery connector itself.

As a fix, I had a new ground cable made, and fabricated the secondary ground using some 8 gauge wire I had left over from an amp install. I used a ring connector at the battery post end, and eliminated the lossy plug. For the ground needed at that point I stripped the insulation off the wire and wrapped another (modified) connection ring around the wire and then soldered it, then carefully insulated around the connection using heat shrink tubing and silicon rubber to try to minimise the possibility of wire corrosion there. The sheet metal was cleaned, the ground made with a self tapping screw, and then coated with spray paint to eliminate corrosion.

The far end of the secondary ground was handled in a similar fashion at it's termination.

Quote:Originally posted by frank-id:
To solve any grounding issues, add several more ground conductors.
Where do I add them?

In my opinion it doesn't sound like you need any more grounds; you cleaned up and fixed the ones that were there, and did a bang-up job of it too.

Of course opinions vary, all I can say is that mine is all mine!

Quote:Originally posted by frank-id:
...you can create what is called a "ground loop".
I am aware of the term, "ground loop", but am unsure of what exactly it means.

Ground loops are caused by multiple paths for current to flow in. I.E. when there's a ground path through the sheet metal of the chassis, and a parallel running wire, too.

Current flows in each path, and because the resistance of the two is not identical, a different voltage drop exists across each path from start to finish, causing a secondary current to flow between the grounds/connections.

It's that secondary current that causes the problems. Mostly only with low level inputs, like in audio circuitry, or in circuits with relatively large currents flowing.

The main thing we need to look out for is that extra grounding does not create loops that affect the engine sensors to the EEC.

Is the voltage drop test better for seeing how well something is grounded than simply taking an ohms reading?

Not necessarily better, but it's easier to see the small voltages developed across two points with a DMM than it is to measure the very low resistance that exists from one to the other with the same instrument.

HTH, Cheers!
JR's Place - My '87 Turbocoupe
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Not B Anymore Offline
Administrator
#10
Quote:Originally posted by Joe_F:
However, there was also a secondary, smaller ground cable that also exited from the negative battery clamp and then was routed down underneath the battery tray, where it terminated at a two pronged plug.

The other side of that plug had two wires coming out, one which connected to the chassis/wheel well just behind the battery box, and another, larger one that snaked back towards the firewall somewhere. Sorry but I really don't remember where it wound up terminating.
I have something kind of similar to this. behind and above the battery there is a ring terminal grounded to the body. There were once two wires coming out of it, but one has been cut off at the terminal so no portion of it is sticking out. Perhaps this wire originally led to the negative battery terminal? I don't know, but I was not the one who removed it.

The second wire coming out of the ring terminal almost immediately enters a single-wire plug. On the other side of the plug, the wire goes into the big bundle of wires and I have no idea where it goes from there. I may have to break that split-loom open to check it out.

I just hooked the DMM back up and tested with the car running a little bit more and came across something I found to be odd. Output voltage from the alternator as measured directly at the output stud read ~14.83 volts at idle and DECREASED to ~14.7 volts when I revved the engine. Am I crazy or is that bass ackwards?

I also checked ripple voltage and measured .18 volts AC which as far as I know is well within spec (spec being less than .5 vac). So I suppose I can lean away from a diode problem within the alternator. I can't check for diode leakage right now since I'm at work. Well that and I'm not 100% sure of the proper way to do it.

EDIT: I think I forgot to mention previously that I ohm'd between the trunk ground for the amps and the negative battery terminal. Came in at 11 ohms if I remember correctly as this was a couple of months ago. I checked several different places in the trunk and came up with the same resistance everywhere I checked. I thought this was high, but is it bad enough to cause lights dimming when I turn it up?
Brian Leavitt
'86 TC 5-Speed -- MS2x w/COP | 83 lb. injectors | T3/T4 50 Trim Stage 3 .63AR | Full 3" Exhaust - No Cat | Motorsport FMIC | Ranger Roller | Ported E6 | Walbro 255HP | Kirban | 20psi | 120-amp 3G | 8.8" 3.55 rear | '03 Cobra Wheels
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