HEI 8 pin Chevrolet 350 Misfire

[drholl]

Thanks Trakkies, for the quick reply.

Since I use 100% MAP, I didn't think the TPS was important other than flood clear.
But no problem, I had to look at the LC-1 WBO2 sensor and wiring anyway.

I'll get the log to you tomorrow, as today is gone already.
Please have a good weekend.

Thanks Dave
Holl

[drholl]

OK, it's been 3 months that this car has had this RPM going to ZERO instantly resulting in the any of the following symptoms, engine stop running while on the highway for 2 seconds (it'll restart, as the engine is still spinning), a big miss or outright die. I can't find out what it is. I'll have to give up on it for now. The wife wants her car...

The main culprit seems to be; engine is running at whatever RPM, the 'squirt says the RPM instantly goes to zero and without that, no fuel, and the engine dies.

I've replaced:
ALL the relays
3 dizzy's (2 of the 8 pin HEIs, 1 mechanical/vacuum - points style - with Crane XRi points eliminator [both XTi wires to the coil] so the spark is uninterrupted). With this setup the dizzy is controlling the timing, pin 36 is not used. Yes, it doesn't make sense. Also with this setup (carb and Crane XRI points eliminator kit) and with the 'squirt datalogging, sometimes when the problem would occur - sometimes - the engine would still die. 'Squirt holding the coil (-) HIor LOW??? I only spotted this once - I think. (but at least once, to my recollection.)

When at a low idle the 'squirt beeps (reset), engine runs about one more revolution, runs out of fuel and then stops (dies). i.e. I hear the beep and the engine still runs momentarily (1 revolution), then the engine starts slowing down. In other words the ignition (Crane XRi) is still working the spark but the 'squirt doesn't read it, stopping the fuel so the engine runs on the fuel still in the manifold for 1 rev. Yeah, it doesn't make sense. I think I have the next pulse tolerance down to 20%.

4 coils (2 TBI type square coils and 2 round style Blaster coils. Increasing / decreasing dwell = no difference)
2 complete wiring harnesses
2 MS-IIs (one new and one that I pulled from another car - known good) and I put it back in the other car. It's fine.
3 Daughter cards, exchanged daughter cards in these MS-IIs.
I've wired the 'squirt and the main relay (70A) directly to the battery and then also
I've wired the (+) coil directly to the battery

Same symptoms;
The RPM reads ZERO and the fuel stops.
I can't figure out why the RPM goes to zero.
The symptoms are ALWAYS exactly the same.
The RPM reads ZERO and the fuel stops.

Guys Thanks for all the help on this one, but I've gotta get the wifes' car running.
It's been 3 months.
I'll put the old Q'Jet and the old dizzy back on it.

Thanks, I'll keep the squirt on it (in dummy mode) and try to figure out what's causing the RPM to go to zero though.
If I find out what's causing it I'll let you know. before the zero RPM started, I had managed to get 30 Miles Per Gallon out of it when cruising on the highway at a steady 60 MPH.
Now, of course, I've futzed with the MSQ but I want that back!!!
Holl

[trakkies]

Which tach input are you using on MS and how is it configured? If you loose the tach signal for whatever reason, MS stops doing anything. The fuel pump will cut as will the injectors.
If running fuel only with the tach signal from the coil, it would be normal to use the opto input. But it may need modifying 'out of the box' Can you do a pic of the opto part of the PCB?

[drholl]

Absolutely Dave. And thanks for the reply with questions.

First off, just to be clear, for all of the last 6 weeks the 350 (5.7 Liter V8) Chevrolet has had a Crane XRi on the coil, both ( + and - ). This is to run the ignition no matter what. This is what I used to prove that the ignition ran the engine for another revolution after the fuel quit, telling me that the squirt is not seeing the working ignition. The dizzy is NOT using computer control, just picking up the tach signal for injection. Today the TBI has been replaced with a Q'Jet carb, but all the wires are still there. The squirt Thinks it's controlling something, but it's not, except that I am still using it to turn on the relays and datalog ignition, AFR, MAP and minor stuff like that. OK my wife now has her car running reliably so I can live for another day! The car now has 2 fuel pumps so that I can change from a carb to Tbi in about an hour for further testing. Also the squirt datalogs on my old laptop for checking the ignition.

OK, on to the "squirts. Remember 2 different squirts.

The new MS-II (3.57) is using the HEI Mod Kit from DIY. It is otherwise untouched. I bought it just for this problem.

The older squirt is, I believe an "Extra" version for the opto-isolator, (3.0 board) which reverses the input to the MS-II processor. I used it because that left the opto-iso off most of the time. Did tat make a difference? NO, they both exhibit the exact same symptoms. But that's what I chose to do back then. And since it's not controlling ignition now, it just doesn't matter for this problem. The ignition signal just goes to zero.... And usually, 75% of the time, the engine would re-fire immediately just by cranking for less than a second. i.e. it would fire right up.

Ah, but you did mention something that I almost forgot to mention. Many times (25%) when the squirt stopped working, because it appeared to have no power (the laptop had a "greyed out screen", but it was hooked directly to the battery, no relays, so it did have power and ground) the fuel pump continued to run for at least 45 seconds, until I could get out of the car, open the hood (Bonnet), get to the wire that was connected to the CPU and pull that wire, to kill the power to the CPU, resetting it, so that the car would start again so I could get it out of the street (Most embarrassing). Also when the fuel pump continued to run, I noticed that the engine would not re-fire by cranking, until after I pulled this wire to reset the CPU.

Thanks Trakkies
Holl

[trakkies]

My feeling is you have more than one fault.

If TS greys out when the engine cuts, it could be loosing comms or it could be MS loosing power totally. So you need to be certain which it is. I'd rig up an LED fed from the MS 5 volt supply that you can site inside the car so you can see it at all times. An easy way is to get a pair of DB9 connectors and use the 5 volt supply from that. Also connect the RX and TX circuits and ground pin to pin so you can then connect your laptop to it as well. If that goes out when TS greys out you know it is a powering fault. If it stays on it is a comms thing.

If you'd like a circuit for the DB9 adaptor with LED I'll do one for you and post it here.

[drholl]

OK Dave.
It'll take a few days as the wife now takes the car to work.

I'd rig up an LED fed from the MS 5 volt supply that you can sit inside the car so you can see it at all times.

I will assume I can also use the V Ref, since the comms 5 Volts comes from the same 5 Volt regulator inside the squirt? This way I can just leave the laptop hooked up normally.

If my V Ref thoughts are correct, I probably won't need you to draw-up a schematic. Thanks for offering though.

Thanks. It'll be a few day though.
Holl

[trakkies]

Yes - V ref would be fine. Just offering an easy way without disturbing MS or its connectors.

[drholl]

Sorry to make this such a long one, but the problems are just “killin me”.
This ’71 Monte Carlo has given me trouble for over a year, so I installed a carb and Pertronixs until I got the time to replace all the ‘squirt wiring with new a harness and anything else that I could of. BTW, did you know that 15 -20 year old 7 – 8 pin HEIs lose their magnetism and don’t work anymore… That’s what started this whole fiasco. Who would think that magnetism goes away??? I’ve changed a LOT more than just the harness. But I want to keep it “stock” looking by hiding all the ‘squirt stuff, except the TBI under the stock air filter.
So now with an MSD Blaster SS PN 8207, the engine runs about a minute or two then shuts off. I give it some time, then it’ll run for 15 – 40 seconds. But I felt like it did have to wait for something to cool-off.

And the web page -
https://www.DIYAutoTune.com/tech_articl ... squirt.htm

“Bosch BIP373s have both output current limiting and thermal shutdown built in. The data sheet puts the typical current limiting at 11.5 amps with a maximum of 16 amps. The thermal shutdown range is between 185 and 210 degrees C with a typical shutdown at 195C. Basically that means the BIP373 will provide a hotter spark than a VB921, and if you configure it wrong and it gets hot, it shuts itself down instead of turning on the pyrotechnics.”

“According to the datasheet and confirmed by our tests, the BIP373s can charge up more current than a VB921s could and can do so fairly safely due to the very functional current limiting and thermal shutdown. There is however still a need to responsibly set your dwell and configure your spark output setting properly. If you let it get out of control the BIPs will not be the weak point now, they'll get hot and thermally shut themselves down and stop sparking until they cool down. You'll know something is wrong because your spark will go away and your ECU and particularly the BIPs will be HOT... but the spark will come back after they cool down. Correct the problematic setting (spark output reversed or too much dwell) and try again. Note that with the BIP373 IGBT component no longer being the weak link, the next link in the chain could be the coil itself if you overdwell it or invert the spark output. Coils can melt too. We tried really hard on our test rig and weren't able to melt one, but there are a ton of coils out there, your mileage may vary.”



This particular MS230-C has always had an issue with not reporting an accurate raw voltage. For an instant it will say 32 volts or 3 volts for no apparent reason. So not wanting to chase something that occurs as readomly as it does (it does it, in multiple cars) I just set the “Duration at voltage X” to zeros. I think that just keeps the dwell at 3ms. Runs fine that way.

Ignition Input Capture - “the 'Rising Edge' should be chosen”. Like points opening, since I use a 1000 Ohm pull-up resistor for a Pertronixs??

Cranking Trigger - “Trigger return essentially uses the module's base setting for cranking timing”. Like points opening??

Coil Charging Scheme – OK, this one’s easy. It’s either a coil or EDIS.

Spark Output - But I would like to know what Going High (inverted); really means in english… I’ve got multiple MS-IIs in multiple cars (the Monte, the old Corvette, both with HEIs). Some have RS-232 ports, some have LEDs. How do you tell the CAN enabled ones from the non CAN ones? Is there a “chip” I should look for on the daughter or main card? The two Daughter cards I have in front of me are both “V3.01 (C) 2005”. The schematic for the 3.57 shows the LEDs. And, YES, I don’t know squat about CAN… I know I want the negative side of the coil to go high for it to fire, so I chose “going High”.

I guess my question would be, since I’m using Pertronics (which work like points) on this car… What settings should I use?

It would be real nice if you also put the correct settings for a 7 or 8 pin HEI. Hint-Hint. I just want to be sure.

Oh, the hardware (dizzys, injectors, harnesses, etc.) has changed but I know you would like an MSQ. It won't be near correct but here's what I tried today.

Thanks guys you've helped me a lot over the years but this car (my wifes) has driven me crazy. And she does love it.
Holl

[drholl]

My last post may have been too detailed, long and complicated for a reasonable answer. So, 3 quick questions.
1) How do I tell if my old MS-IIs are CAN enabled?
2) With points, Crane (points eliminator) or Pertronix (points eliminator), using the BIP373. Is it correct to use “Going Hi (inverted)” for Spark output?
3) In http://www.megamanual.com/mt28.htm#ib it says “In general, use the default options and values unless you have a reason to do otherwise.” Where will I find these defaults?

So for points etc. with a BIP373 and a dizzy.
“Ignition Input capture” should be “Rising edge”.
“Cranking Trigger” should be “Trigger Return”, not “Trigger rise” which is not discussed in the documentation.
“Coil Charging Scheme“ should be “Standard coil charge”.
“Spark output” should be “Going Hi (inverted).

Thanks
Holl

[Matt Cramer]

My last post may have been too detailed, long and complicated for a reasonable answer. So, 3 quick questions.
1) How do I tell if my old MS-IIs are CAN enabled?

The no-CAN MS2 daughter boards are green, and there were only around a hundred of them made. I've only seen one of them myself in person.

2) With points, Crane (points eliminator) or Pertronix (points eliminator), using the BIP373. Is it correct to use “Going Hi (inverted)” for Spark output?

Yes.