[Izzy46]

OK, I went ahead a desoldered each resistor and low and behold they all tested perfectly at 99.9k.

I also desoldered the Q2 mosfet and it tested out fine. I used the method below.
https://youtu.be/IF740E5bm84

Other than excess soldering paste causing a short I can't come up with reasons why the mosfet is getting hot.....

[apollard]

Did the other resistors have similar resistance from injector to injector?

Also, try with a different MEGA. Possible the output pin got damaged, especially since R16 reads different from the others in circuit.

[Izzy46]

Did the other resistors have similar resistance from injector to injector?

Yes, I desoldered all of the resistors and they all came back with the same resistance.

Also, try with a different MEGA. Possible the output pin got damaged, especially since R16 reads different from the others in circuit.

When I was originally testing the resistors I had the board disconnected from the Mega. Unfortunately I don't have a spare MEGA to play with. Living out here in Qatar it takes 1-2 weeks to order one online.

[PSIG]

If I read you right, and if they read different resistances in the circuits but test properly when out (Mega off), then it's probably a "board" issue of PCB, components, or solder. It would help to to find where the change in resistance is, or pathway it is using the change resistances. I would use an Ohm-meter, and probe from a GND point to each side of a resistor, then repeat from a 5V source point and again from a 12V source (power off). Work your probing towards the resistor and nearby points, looking for the path. Referencing the schematics, some will be proper and any others, not.

Inspect everything. For example, residue on the board can goof things. After soldering, I use plenty of alcohol and an old toothbrush to clean it very well. Some put their boards into the dishwasher. Air blast it off or let it dry overnight. Check the Mega for correct insertion, as it is easy to be 1 pin offset. Check all directional components for proper orientation. If testing does not reveal anything obvious, I might question the board source (assuming they were all the same seller). Stuff like that.

At some point, you may want to just purchase a pre-assembled and tested unit, so you can get to tuning. Your issues are not "Speeduino". Consider all your options. You're so close! Good luck!

[apollard]

I would add just one point to PSIG's information above. After reassembly, plug in the mega and power it vis USB. Measure the voltages on the gate of each mosfet. If they are different (and the resistances measured were the same before the mega was installed), it indicates a problem with the mega itself. That may be what he meant by 5V testing, but wanted to make sure since you don't have a spare.

[Izzy46]

I follow your advice PSIG and went over the injector circuits connection by connection. I was unable to find any issues so I went ahead and washed the PCB in the dishwasher. After it was all cleaned up I put it on the boat and was able to power up the Speeduino without the injector 3 mosfet heating up.

While everything seemed to be working well, I did notice the injectors clicking after the engine finished cranking. Each time I finish cranking I could hear about 4 injector clicks in quick succession.

I cranked over the engine a few times without anything interesting happening. Then I got my wife to crank the motor over and move the throttle while I sprayed some 'Start Ya Bastard' into the throttle body. Pretty quickly she came to life, if only momentarily. I didn't get a chance to experiment with the settings as my computer had run out of charger and the charger was left at work.

I'm guessing the main issue now is getting the fuel / air mixture right so I can get a working base tune. At the moment I'm working with the attached tune. Where is the best place to start when trying to get a decent base tune?

After reassembly, plug in the mega and power it vis USB. Measure the voltages on the gate of each mosfet. If they are different (and the resistances measured were the same before the mega was installed), it indicates a problem with the mega itself.

Thanks Apollard, I will go back and do this in the morning and see what comes up just to be sure.

[apollard]

That is good news-

Here is what I see from a quick review of your tune and my experience getting mine to crank and run:

Cranking enrichment seems to be pulling fuel very early, I would run at 100% or better until 10C from operating temp.

Cranking timing seems low, I would start with 10*. Then make sure to verify it with a timing light while cranking. Better yet, lock the timing ( spark settings dialog) and verify it. You may need to adjust. If cranking timing is retarded, it will be very hard to crank and run. Remember to unlock it to allow speedy to control timing.

I would increase priming pulsewidth, try tripling it for now. If you have to flood clear, you can back down, but these engines like a lot of fuel to startup.

Warm up enrichment seems OK to start, but if it keeps cranking and needing throttle to keep running (or you have to start it at 1800 rpm or so for a while), increase it. I had to increase mine a lot. After start (for warm starts) might need some more too, but I would try what you have now.

Spark timing at idle seems high, might want to lower it. Then use the idle advance to accomplish something similar (I can't help much here, I need to tune that setting myself).

VE in the 40-60 MAP range at idle (5-800 rpm) seems low (and not smooth from the values near it). I would think something in the low-mid 20 VE is more likely. Too low here will severely lean your mixture and give symptoms similar to what you are seeing.

Before I had this all tuned, I had to cut the key on and off several times to prime it a lot, then start at a throttle setting off idle, and run it 1800 or so for a while. You can try that also just to get it going.

I have attached my current tune for reference. Use it to see what worked on mine and consider if yours might need changes (ie, not as exact numbers).

[LPG2CV]

Set the injector prime to 2.1. The idea is the prime happens after the FP is up to pressure, and the system purged

Any enrichmments are based on the current VE value. So when cranking, enrichment will be the VE shown in by the pointer in the VE table.

When cranking, the rpm will not get out of the first column in the VE table. there will not be much vacuum (zero with the throttle open) when cranking, so the pointer will always be near the top of the column.

Change the values from 9, to nearer 100.

Then you will get a decent cranking enrichment

[apollard]

Change the values from 9, to nearer 100.

Then you will get a decent cranking enrichment

Good catch, I didn't notice that

[LPG2CV]

Yes, as @apollard suggests, also increase the cranking enrichment table. Set 0*C around 40-50

It's about giving the engine what it wants