1980 242 GT. A reasonable project.

Homer said:

Just gotta correct you here, concentric twisting has nothing to do with shielding. Only harness flexibility. On harnesses that move A LOT. Reduces the strain on certain individual conductors depending on how the harness is flexing. Aka, it's mainly (whether harness builders will admit it or not) for style points.

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Interesting. A lot of reading I have done regarding that topic made claims that it helped a great deal with noise suppression. Guess I was convinced by misinformation. Glad to know though.

Homer said:

Just gotta correct you here, concentric twisting has nothing to do with shielding. Only harness flexibility. On harnesses that move A LOT. Reduces the strain on certain individual conductors depending on how the harness is flexing. Aka, it's mainly (whether harness builders will admit it or not) for style points.

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its mil spec, bro.

Homer said:

Just gotta correct you here, concentric twisting has nothing to do with shielding. Only harness flexibility. On harnesses that move A LOT. Reduces the strain on certain individual conductors depending on how the harness is flexing. Aka, it's mainly (whether harness builders will admit it or not) for style points.

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He probably meant twisted pair, which IS related to reducing EMI.
https://en.wikipedia.org/wiki/Twisted_pair
Volvo used twisted pair in their harnesses quite a bit in the 1980s, but later gradually began increasing the use of real shielding. Twisted pair is an effective technique, just less so that shielding.

According this this guy, there is SOME relation with concentric twisting and reducing EMI.
https://www.youtube.com/watch?v=dsgUhNH7F7k

Now now, let’s not get our pairs all twisted up over this.

What is the difference between a twisted pair and concentric twisting?

blkaplan said:

What is the difference between a twisted pair and concentric twisting?

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Concentric twisting is twisting many conductors around a central core. Twisted pair is often used on data wiring that?s a balanced pair to help reject EMI.

Concentric twist:


Twisted pair (more accurately this is two twisted pair in a common jacket):

ohhh, got it... yea the concentric twist is just for tidyness... the twisted pair will actually help from my knowledge.

Funny, I never thought he was talking about anything but a twisted pair... but I guess I shouldn't assume that.

RvolvoR said:

its mil spec, bro.

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duh

Well, there's a MaxxECU Race in the car. Did a barebones install yesterday after lots of testing just to see if the trigger filtering could handle the noise and allow the car to start. It cannot.

Given that there was another whiteblock swapped 242 parked nearby, we decided to compare ground noise during cranking on both cars and mine has far far more noise in the ground.

We confirmed yesterday that the noise is coming from the starter (which was already replaced once during this whole ordeal) and completely isolated it from everything else. Harness completely unplugged, ignition off, manually triggering the starter.

I'm admittedly in way over my head here, but from what I can tell based on all the testing we did, either the newly replaced Bosch reman starter (which is the second to have this exact behavior) is bad or there's some sort of grounding issue. I've read a mention or two about similar issues occurring when the surface between the block and bellhousing isn't clean... feels like a long shot.

Feeling pretty gutted right now.

What’s your ground setup for the battery, charging, starting?

Bummer!

Can you add some filtering caps to the starter? Or is this way too much current to suppress the noise with something simple as that. They are in parallel with the terminals, they do not pass the current.

"Motor Noise Suppression - 4QD - Electric Motor Control" https://www.4qd.co.uk/docs/motor-noise-suppression/

Any help from the maxxecu guys in Sweden?

Could check for any difference in potential between the starter and the block too? (I mean measuring during cranking, as disassembly is more work. Did you paint the block?)

Similar issues:
"Starter Motor Interfering With Engine Management - XU Engine & Gearbox Service and Maintenance - ARCHIVE - 205GTIDrivers.com" https://www.205gtidrivers.com/forums/topic/123111-starter-motor-interfering-with-engine-management/

doucheNozzle said:

What?s your ground setup for the battery, charging, starting?

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2 gauge ground wire from battery negative terminal to engine block near starter.
6 gauge ground wire from battery negative terminal to frame rail near battery.
Braided ground strap from head cam cover to firewall.
Both starter and alternator ground through direct connection to block.

JW240 said:

Bummer!

Can you add some filtering caps to the starter? Or is this way too much current to suppress the noise with something simple as that. They are in parallel with the terminals, they do not pass the current.

"Motor Noise Suppression - 4QD - Electric Motor Control" https://www.4qd.co.uk/docs/motor-noise-suppression/

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I'm totally unfamiliar with this, but I did find that MaxxECU sells this interference suppression capacitor: https://www.maxxecu.com/store/engine-control-or-electronics/maxxecu-accessories/disorder-filter

That said, comparing directly to scoping the ground on another T5 engine while cranking, mine has far more noise in the ground, so it seems like there's something more that needs to be done to reduce the noise from being generated in the first place. Who knows, maybe I got unlucky and the starter was replaced with another bad one?

JW240 said:

Any help from the maxxecu guys in Sweden?

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I haven't asked them, but this isn't a problem with the MaxxECU. With the wiring harness unplugged, ECU and all components isolated from the starter, this noise is still occurring.

JW240 said:

Could check for any difference in potential between the starter and the block too? (I mean measuring during cranking, as disassembly is more work. Did you paint the block?)

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We measured voltage drop on the ground (assuming this is what you mean? sorry, this stuff is a bit over my head) and all looked good.

JW240 said:

Similar issues:
"Starter Motor Interfering With Engine Management - XU Engine & Gearbox Service and Maintenance - ARCHIVE - 205GTIDrivers.com" https://www.205gtidrivers.com/forums/topic/123111-starter-motor-interfering-with-engine-management/

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Yeah, I've read this one a few times. One of the only threads I've found with similar issues.

Thanks for the ideas!

So I was going to mention earlier in the thread that when I see no/hard starts and I have faults with white blocks, it is almost always an issue with the starter. When they draw too much amperage, they create too much interference, you can actually see the tach jump around during cranking. But you had replaced the starter, so I didn't mention it.

Someone else above asked if you painted the block? So, this isn't a far fetched question. I've had a number of no start cars after transmission rebuilds in white blocks. Paint between the block/transmission and starter creates resistance, creating a bigger amperage draw on the starter creating a bigger interference. Note on a white block, the big chassis ground is transmission to chassis and the starter bolts to transmission. It does sound like you're pretty well grounded though. Maybe worth a cleaning of grounds, maybe voltage drop checks while cranking? Check for any resistance on the cranking circuit.

GTJordan said:

So I was going to mention earlier in the thread that when I see no/hard starts and I have faults with white blocks, it is almost always an issue with the starter. When they draw too much amperage, they create too much interference, you can actually see the tach jump around during cranking. But you had replaced the starter, so I didn't mention it.

Someone else above asked if you painted the block? So, this isn't a far fetched question. I've had a number of no start cars after transmission rebuilds in white blocks. Paint between the block/transmission and starter creates resistance, creating a bigger amperage draw on the starter creating a bigger interference. Note on a white block, the big chassis ground is transmission to chassis and the starter bolts to transmission. It does sound like you're pretty well grounded though. Maybe worth a cleaning of grounds, maybe voltage drop checks while cranking? Check for any resistance on the cranking circuit.

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I haven't seen the tach jumping around, but my issue does sound similar to the 'bad starter' whiteblock issues with VR interference, despite this being a replaced starter.

I honestly can't remember if I ended up spraying clear coat on this block or if it was the previous one, but that's definitely possible. While everything 'appeared' clean on the mating surface, I wasn't aware of the possible issues it could cause so I didn't look closely at it. Especially with it potentially having matte clear coat on it, that wouldn't have been obvious at a glance. Also, I've always used blue loctite on the bellhousing bolts which I'm reading is advised against for this reason.

At this point, I'm thinking my only real option left unexplored is to pull the transmission and make sure the block to bellhousing mating surface is clean and free of any clearcoat, then clean the bolts as well. The grounds on the block have been cleaned and scuffed already. We checked voltage drop on ground while cranking and there was no concerning drop (but I didn't write them down and was trusting a friend, so perhaps I'll go ahead and test again so I have real numbers recorded). The starter is pulling 105 amps during cranking, which is healthy from my understanding. It cranks faster than any Volvo engine I've experienced (all new everything in the starting circuit).

All this said, the thing that still confuses me is there was no issue initially, and it slowly became an issue over a couple weeks, a month after putting the car back together.

The Full Banana said:

At this point, I'm thinking my only real option left unexplored is to pull the transmission and make sure the block to bellhousing mating surface is clean and free of any clearcoat, then clean the bolts as well.

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Or attach some ground straps to link them together.

dbarton said:

Or attach some ground straps to link them together.

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yea that's what I was thinking too...try directly grounding the starter before pulling things apart.

I can’t remember how much it sucks to pull the starter. Swap it with the other T5 car you’ve used for testing?

Wrap it in foil! Anything at this point

Adding a ground strap, even temporarily, sounds like the best way to test the theory that the starter isn't properly grounding through the engine/trans. Mucho less effort than pulling the trans!