Help needed with a 7MGE-T

[toddm]

Oops! I did count wrong on the delay teeth! i didn't realize the first tooth was 0.. I have tried to start it at a delay setting of 0, but it wouldn't work. thats when I had the bright idea of setting it to 11.

So i didn't screw up on cutting the distributor....thats a relief! I guess i'll go back and make sure i didn't make any other dumb mistakes in the setup.

one question though. if the MS2 picks up on the wrong missing tooth won't it fire the coil on the exhaust stroke instead of the Compression?

Thanks,

Todd

[grippo]

one question though. if the MS2 picks up on the wrong missing tooth won't it fire the coil on the exhaust stroke instead of the Compression?

Todd

If it fires on the exhaust stroke, it won't be because it picks up the "wrong" missing tooth. It will be because things were aligned so that when you reached the missing tooth, the next cylinder to fire (as determined by the dizzy) was on the exhaust stroke. If this is the case, it will also be true when you get to the next missing tooth, just on a different cylinder. You need to look at your crank damper and bring the engine to where no. 1 cylinder is at TDC of the compression stroke. Now look at the wheel inside the dizzy, in particular, the missing tooth that is closest to the position sensor, but has gone past it. This should be within a few teeth of the sensor. and the number of teeth past the sensor is the Delay_Teeth. So the processor senses the missing tooth, waits Delay_Teeth, and then you should be right near TDC of the compression stroke and it will fir based on the timing you put in relative to that. Now the teeth are pretty coarse - each is 30 deg at the crank, so you will have to eyeball or measure the exact degrees from the edge of the nearest tooth to thte sensor and put this into the trigger offset value.

That said, you may have other problems. I say this because the processor has no way of knowing how everything is aligned and regardless of how it is, it should get an input on every tooth and should fire every 4 teeth regardless of where the piston is, and this fire should show up on the timing light. Of course if the piston is in the wrong place your engine or starter may not be too happy. When you ran the dizzy with a drill, did MT show a constant rpm - no quick drops to 0 on the guage. If so, but it does show rpm dropouts when you are in the car, then you may have a noisy tach input.

[toddm]

With the #1 piston @ TDC the Missing tooth that just passed the sensor is 10 teeth away. the next missing tooth is 1 tooth from passing the sensor. the sensor is actually halfway between tooth 10 and 11. That means i should set the Delay_teeth to 10 so it will start on the 11th tooth after the missing tooth right? or would it be easier to set it to 0 like you first suggested?

With the drill the rpm was nice and steady on the gage in Megatune and the signal looked nice and clean on the scope. while cranking the rpm jumps to 98 then Zero and back again. Also the Cranking /Not cranking indicator at the bottom of the screen is switching back and forth. I'll hook the scope up to it tomorrow and probably run a longer shielded twisted pair if it looks ugly. The factory Distributor wires were shielded but not long enough to reach the MS2

Looks like you found my problem! Thanks Mr. Grippo!

Todd

[grippo]

I count a delay of 9 teeth. The 1st tooth after the missing one is numbered tooth 1 and counts as 0 Delay. So you want to start the first tach pulse at tooth 10 (Delay_Teeth = 9). Assuming leading edge triggering, and 50% duty cycle teeth, this would put the sensor at about 23 deg from the leading edge of tooth 10, so the trigger offset would be would be 23 BTDC. This is where the first tach pulse should arrive. Once the car is running, you can tune the trigger offset to match the reading on the timing light.

[toddm]

I set the Delay_teeth=9. It made no difference in starting it however. I ran a new VR wire from the distributor to the MS and provided a good ground for the shield. the signal going into the VR conditioner had a little noise on it but the signal after the conditioner looked really clean. I took a picture of it. The square wave looks quite good. I get eleven pulses then the obvious gap for the missing tooth. I'm guessing that this should be adequate for the MS to use. I also did a few datalogs while i was cranking..the RPM is zero for most of the time and every once in a while it will jump up into the 200's for a few samples then back to zero. I'm attaching a pic of the signal at TSEL/VROUT.

[grippo]

If those are the input pulses directly into the processor, then the scope pulses look good, but if you expand the scale so that you only see about 4 - 6 pulses and you stare at it a bit, do you see occasional flashes at the top or bottom that indicate a missing or added pulse ? Also, after you put in the shielded wire, did you run the dizzy on the drill - everything being the same except the drill driving things instead of the engine, do you get no cases of 0 rpm (the rpm guage in MT never flips to 0). The reason I ask is that you said that you did this earlier before the new wire and with Delay = 10 and it all worked perfectly. If this is still the case with the new wire and Delay =9 then I am at a loss. There must be engine noise getting into the system somewhere for the rpm to be lost when the engine is running, but not when the dizzy is run by a drill.

I also noticed the pulses look like avery high duty cycle and the spacing may be a bit uneven - can't really tell without blowing up the scale. But use a starting PulseTol of 70% to be sure that isn't the problem.

[toddm]

the pulses were are a little different in width one to the next.. Could this have anything to do with unstable cranking RPM, just the mechanical variance as the engine turns over? I have finally gotten a good RPM reading on the Megatune Gage. it is about 220 +/-5 RPM while crankning. Still won't start but the ECU is now at least reading the triger wheel. The fix was to unwind the VR wires from amongst the high tension plug wires and the coil wire. I had them all laying together at one point. I'll need to find a different routing for the VR wire once I clean everything up. Once i verify the ignition timing and get some known good fuel in the tank, I think it will start.

Thanks,

Todd

[toddm]

It RUNS!! once I set the distributor to TDC instead of BDC it fired right up. Thanks for all the help! I'm sure i'll be back with more questions once I get to tuning.

Todd