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1980 242 GT. A reasonable project.

The Full Banana said:
I have a couple local friends with maxxecu running their 5cyl 242s? There?s been a bit of pressure to jump on that bandwagon. I forgot about that harness, that could seal the deal. The price of maxxecu race is pretty attractive compared to some others.
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Do it.

I've been playing with the software the last few months. I like it. The fact you can buy a harness is nice. I've also been looking at a race for my car. It has so many of the options I want all in one. The price (I think) is pretty favorable also.
 
I've had a noisy VR signal during cranking on my T6 242 since I did the swap years ago. Megasquirt was very intolerant to it and made starting the car quite difficult. I eventually switched to a Link G4+ that has better input filtering and it has made the problem a bit less noticeable. I still get hacks and coughs occasionally during cranking but the car usually fires pretty quickly.

I haven't done a ton of troubleshooting on this since the car works ok as-is. I did try replacing the starter brushes and brush springs, this made only a minor improvement to the noise in the signal.
 
The Full Banana said:
I've tried disconnecting just about every component (coils, alternator, flex fuel sensor, fuel pressure sender, IAT, knock sensors, IAC, boost solenoid) in the engine bay trying to eliminate the interference and haven't had any luck. No voltage drop issue at ECU during cranking. No voltage drop issue on grounds during cranking. Sensor ground is isolated from other grounds. Rewired the crank sensor in a shielded twisted pair separate from the rest of the harness to physically distance it.

I figure I have about one more day's worth of patience for diagnosing this. Interested if anyone has ideas. Keep in mind this isn't a new setup that didn't work... this ecu and harness has been together for 5 years without any issue starting until this summer.
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I certainly can appreciate the pain & suffering with Megasquirt. I have a "fuel only" system running on my 70 Chevelle Malibu and SBC. It was a fascinating learning experience.... I loved Tuner Studio and plan to add spark in the future (when I'm retired).

One valuable thing I learned building that system was to properly shield your grounds. I've seen folks make the mistake of grounding both ends of the shield..... and others not even grounding one end. The electron wizards tell me that unless you "drain the shield" at one end only, you have created an antennae for noise.

We also just sold one home..... a fabulous time for that, but not so much for buying/building! Wood is heading back downward, so perhaps it will return to tolerable levels.

Good luck with your noisy wiring issue.
 
cosbySweater said:
Do you have a tach adapter or anything driving the tach?
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The tach is being driven directly by Megasquirt

Alex Buchka said:
I've had a noisy VR signal during cranking on my T6 242 since I did the swap years ago. Megasquirt was very intolerant to it and made starting the car quite difficult. I eventually switched to a Link G4+ that has better input filtering and it has made the problem a bit less noticeable. I still get hacks and coughs occasionally during cranking but the car usually fires pretty quickly.

I haven't done a ton of troubleshooting on this since the car works ok as-is. I did try replacing the starter brushes and brush springs, this made only a minor improvement to the noise in the signal.
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Yeah, I'm thinking a new, better ecu is going to be happening. New starter, have isolated just about every component and no change. I've been wanting to ditch Megasquirt for a little while, so this is probably a good time.
 
Have you tried using a hall effect sensor on it?

I only ask about the tach drive because I just had a car that I installed the ms3 box in have a no start issue and it was a tach adapter that caused it.

Tbh I've never had good luck using vr sensors with mega squirt, I've had 0 issues with hall effect sensors. Ms seems to like them better
 
cosbySweater said:
Have you tried using a hall effect sensor on it?

I only ask about the tach drive because I just had a car that I installed the ms3 box in have a no start issue and it was a tach adapter that caused it.

Tbh I've never had good luck using vr sensors with mega squirt, I've had 0 issues with hall effect sensors. Ms seems to like them better
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That’s interesting about the tach adapter. I have not tried a Hall effect sensor. What’s odd is that the VR sensor worked perfectly for years and then this year it slowly saw more and more noise during cranking after it came back from the dyno. I’m not opposed to a hall sensor, but there’s some other issue at play here. By process of elimination, it looks like it’s something in the ecu.


Homer said:
Tom, you're so close I can taste it. Ditch the MS.
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It’s happening.
 
If your ecu has the trim pots maybe try backing those out. But I 100% don't blame you for wanting to change the ecu. Mega squirt is a good system and all but it's not nearly as user friendly as alot of the newer options.
 
The Full Banana said:
That?s interesting about the tach adapter. I have not tried a Hall effect sensor. What?s odd is that the VR sensor worked perfectly for years and then this year it slowly saw more and more noise during cranking after it came back from the dyno. I?m not opposed to a hall sensor, but there?s some other issue at play here. By process of elimination, it looks like it?s something in the ecu.
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So...VR sensors can degrade significantly if oil gets into the tip. I don't know where the sensor is located on a whiteblock - if it's external then I'm sure that's not it. But if it does protrude into an oil cavity and there's a way for oil to get into the sensor, that can render it flaky and then useless after some amount of time. I have experience in this area ;-)

Even if the sensor is totally away from oil I suppose there could be a gradual failure mode of the sensor itself caused by vibration, heat cycling, environmental factors, or some combination of those.

Do you have access to an oscilloscope, and if yes have you tried scoping the VR sensor by itself while cranking?
 
Duder said:
So...VR sensors can degrade significantly if oil gets into the tip. I don't know where the sensor is located on a whiteblock - if it's external then I'm sure that's not it. But if it does protrude into an oil cavity and there's a way for oil to get into the sensor, that can render it flaky and then useless after some amount of time. I have experience in this area ;-)

Even if the sensor is totally away from oil I suppose there could be a gradual failure mode of the sensor itself caused by vibration, heat cycling, environmental factors, or some combination of those.

Do you have access to an oscilloscope, and if yes have you tried scoping the VR sensor by itself while cranking?
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The VR sensor is located in the same place as on a b230. The crank sensor has been swapped out for a new Bosch unit (twice actually) since these issues began. The shop scoped the VR sensor and found AC waveform interference only during cranking. Interestingly enough, I noticed while running the tooth logger in Megasquirt that you can actually see that the signal is very erratic while cranking the starter, but as soon as you let off you can see a clean signal for half of a second while the engine slows to a halt.

IF12FFVl.jpg
 
Sounds like adjusting the trim pot in the MS3X card would help you there. Concentric twisting and shielding the crank sensor harness could also be beneficial if you haven't done so already.

I'm pretty sure you knew this already, but it can't hurt to bring it up.
 
Harlard said:
Sounds like adjusting the trim pot in the MS3X card would help you there. Concentric twisting and shielding the crank sensor harness could also be beneficial if you haven't done so already.

I'm pretty sure you knew this already, but it can't hurt to bring it up.
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Crank sensor wiring is fully shielded with the drain connected only at the ecu. Ended up rewiring it separately from the rest of the harness as a test to make sure that physical proximity wasn?t the issue.

Adjusted the trim pots and it seems to have no discernible effect on the tooth logger. Also replaced the vr conditioner board to no effect.

Yep, no harm bringing it up just to make sure I didn?t miss something else! Thanks
 
The Full Banana said:
Crank sensor wiring is fully shielded with the drain connected only at the ecu. Ended up rewiring it separately from the rest of the harness as a test to make sure that physical proximity wasn?t the issue.

Adjusted the trim pots and it seems to have no discernible effect on the tooth logger. Also replaced the vr conditioner board to no effect.

Yep, no harm bringing it up just to make sure I didn?t miss something else! Thanks
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You know what hasn?t been brought up: crushing it sir.
 
Harlard said:
Sounds like adjusting the trim pot in the MS3X card would help you there. Concentric twisting and shielding the crank sensor harness could also be beneficial if you haven't done so already.

I'm pretty sure you knew this already, but it can't hurt to bring it up.
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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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