MicroSquirt.com read only forum (Jan.15,2018)

Well, here's what I've been working with. I have a basicly stock TBI 4.3L V6 from a 1989 Astro van. MS-II controlling the ignition, V3.0 board, IAC control etc. etc. Here's where stuff gets hairy. I had an overly large fuse in there, because I'd been blowing it every so often and I hadn't gotten any more fuses. I changed my number of squirts per cycle from 6 to 3, hoping that I could get more precise control of the idle. Well, I start it and it runs real rough, before I know what was happening I see smoke coming out of my MS box. I crack the case, and the .5 ohm 20W resistor is cracked right down the middle. I also know I have at least one injector that doesn't seem to spray right, and one that is totally dead. I suspect this is an ongoing event and I merely finished the job. I've included the last conf file below, which is basicly identical to the previous one except I had 6 squirts a cycle instead of 3. I've also included one of my logs. I'm wanting to fix my MS and get it put back on, but am not willing to smoke another set of injectors until I've at least tried to figure out what's wrong.

are you running low z or high z injectors ? i see your msq is configured for hig-z injectors. if you have low z injectors that would explain the smoke from the ms unit.

so whats the resistance of a single injector ? how many you run ? how are they wired (i.e. all share one common power and ground or half use one and other half used different set uf grounds) ?

exacly which resistor blew ? (ms component name plz)

what kind of ignition you run ? is it direct coil control and idzzy ? if yes, whats the primary coil resistance ?

mops wrote:are you running low z or high z injectors ? i see your msq is configured for hig-z injectors. if you have low z injectors that would explain the smoke from the ms unit.

so whats the resistance of a single injector ? how many you run ? how are they wired (i.e. all share one common power and ground or half use one and other half used different set uf grounds) ?

exacly which resistor blew ? (ms component name plz)

what kind of ignition you run ? is it direct coil control and idzzy ? if yes, whats the primary coil resistance ?

The injectors used are a pair of low-Z units, I'd thought I'd set parameters in the ECM for low-Z.

(mega-manual, setting up PWM injectors section, low impedance injectors)
1. Start with:
* PWM Time Threshold = 1.0 millisecond, and
* PWM Current Limit (%) = 30% on a V3 main board (if you have the active flyback circuit installed).

your's PWM Time Treshold is 25.5ms, which is the defaul for high-z injectors and should be about 1ms in your case. 25.5ms = no current limiting for injectors, hence burn I presume....

did you had trouble cranking engine, like... it's hard to crank (because injectors are drawing so much current that there's not enough juice for sterter ?

.....

Yeah, getting the thing started in the morning wasn't fun, and I realized while it's been starting easier it's been running progressively worse. I'd had that part of the table very lean, do you think I should re-configure it? I'd also been having issues with very "jumpy" O2 voltage readings, as shown in that file. Do you think the proper PWM will help me out with that at all.

Heya...


yes, i'm pretty sure that running low-z injectors on high-z settings was the cause of the burned components on MS board. hard starting could very possibly be caused by the same setting -as i said before, with your wrong seting injectors were consuming abnormal amounts of power - and that *might* be responsible for varying sensor readaings aswell.


reread the section of manual re pwm injectors. replace injectors, preferably you want to get a set, bot just 1 or 2, as they might cleaner/dirtier than what you have therefore making tuning even more difficult. fix your ms board. try again and post back