Why Low injector voltage ? , injectors not firing

[scorpio12]

Just installed Megasquirt.......Ive noticed that the sparks are dry even with very high cranking pulsewidths... Injectors musn't be opening ( even though tunerstudio shows a pulsewidth)

So I tested the injector voltage on the "Relay board" and its extremely low ?

When megasquirt is "off" the Voltage difference between INJ1 pin and INJ 12V = 13 volts
When megasquirt is turned "on" this same voltage = 0 Volts ( no pulse width- makes sense)
When engine is "cranked" the voltage is irregular, sometimes hitting 7volts, sometimes staying at 1-2 volt peaks ( never hitting 12 volts) ....Without 12 Volts the injectors im guessing will never open!!

What could cause very low injector voltage on the relay board , or megasquirt ecu ...ie why wouldnt it ground the injectors properly ? ???

-Megasquirt 1 version 2 original B and G code
-Relay board

Thanks guys!

[Bernard Fife]

s12,

This could be caused by a lot of things, from having the PWM% too low, to not have 12V while cranking, to a mis-configured TPS. You might want to check the tips here: http://www.megamanual.com/v22manual/mtune.htm#howto

To get more detailed help, you might want to post your MSQ settings file, and also a datalog of a starting attempt. That will let us see what's going on.

Lance.

[trakkies]

What are you measuring the voltage with? Since the injectors are pulsed, a DVM won't give a true reading. You'll need a scope to measure the actual peak voltage of the pulse. However, a simple way is to use an LED with a 1k series resistor. This will flash even with a very short pulse duration.

[scorpio12]

hey Lance and Trakkies
I apologise some of my info was incorrect....

" When megasquirt is "off" the Voltage difference between INJ1 pin and INJ 12V = 0 volts " not 13 as i wrote

Ok so i tried using a LED 12 v test light and that was flashing indicating 12 V to injectors..... I took this one step further and used another spare injector and a pressurised fluid system( a hand pump and fluid) and hooked it up and found that the injector was indeed spraying when there was an RPM signal....

BUT

when i hooked it all back up...no love... with very high cranking PW i cant flood the cylinder while cranking..... Its not low fuel pressure ( i have an electronic AND mechanical FP gauge)...

MY GUESS-- the cranking RPM is extremely low 50-90 RPM and as such causes low amounts of fuel to be injected due to very low engine speed?
Could a low cranking RPM cause this? brand new high torque starter motor

I have 12 V to megasquirt while cranking because i used another new car battery to power megasquirt and edis as i was noticing a volatge drop when using the same battery as the cranking battery.....( engine in car but electrics connected off bench)
TPS adc count was reset so reads 0% open when its closed and 100% open at full throttle
I cant get it to kick in

[trakkies]

A slow cranking speed shouldn't much matter, unless it's dragging the battery volts down so low the MS or ignition won't work. If it's above 9v or so you should be ok.

As Lance says, the next thing to do is post a log of a starting attempt, and your MSQ.

[scorpio12]

So 50 rpm cranking isn't too slow? I'm on 2 squirts alternating, should I move to 1 squirt simaltaneous?

Any way of checking whether my vr sensor is in the right spot? Possibly a degree or two off ( 36 wheel trigger) the ms1 b and g doesn't seem to be able to tell me if its on at right spot or not? And I can't use timing light as it doesn't crank long enough ( about one spark every second while cranking for 3 seconds )

Really wish this would just fire

[trakkies]

Is there any reason why you can't post a log of an attempted start? And your MSQ file?

[scorpio12]

Just read up on msq and data log files and how to post them, will do it first thing when I get back from work

I really appreciate you guys taking the time from your schedules to help me out

[plonker]

I may be wrong on this but....

"I have 12 V to megasquirt while cranking because I used another new car battery to power megasquirt"

I think that at least the earths (battery-battery-chassis) must be connected or you'll have problems.

John

[scorpio12]

high cranking pulse.msl

low cranking pulse.msl

tune1.msq

I think that at least the earths (battery-battery-chassis) must be connected or you'll have problems.

John

Hi John- The edis and megasquirt etc all ground to the same battery negative point.... Only the starter motor has been running off a different battery, ran it off the same battery today..still no start

Hi Lance and Trakkies here are my msq file and data log of two different starting attempts... one at 88% pulse width for -40 and another at a ridiculously high pulse width of 300% recommended fuel in an attempt to flood the engine ( still no fuel soaked spark )

the kPa spikes coincided with backfires and / or "puffing" noises from the engine..... still couldnt start it.....let me know if you see anything that may gives hints...thanks again guys

[Ian]

scorpio12 ,

a quick scan over your .msq file------your ReqFuel looks amazingly low

[scorpio12]

scorpio12 ,

a quick scan over your .msq file------your ReqFuel looks amazingly low

Hi Ian I used the calculator .... Have I done something wrong here possibly?

1984 cc engine
50 lb/hr injectors at 43.5psi
4 cylinder engine

Plugging this in gives 6.3 ms?

[Ian]

No I guess with 50lb injectors it calc's right! Your'e expecting 340Hp ?
Looks like the more experienced squirters(aka 'guru's') are the ones or twos to help out here. Sorry not to be able to help!
I've no exp. with turbo'd donks.

[kjones6039]

I've no exp. with turbo'd donks.

I love learning new languages!

What's a donk?

Ken

[Ian]

he he......donk(ey......aka donkey engine....) engine!

[scorpio12]

IM SOOOOO PUMPED!!!! SHE WORKS!!!!!!

looks like there were two problems

1)- i used a testing light to see if all sparks were getting voltage during cranking....they were
But this wasnt good enough
I pulled all spark plugs...1 and 2 had no fuel on them.....3 and 4 had fuel...which told me that injectors 1 and 2 were not working...or more likely, INJ1 wasnt giving enough or any power while INJ2 was feeding injectors 2 and 3..... so my megasquirt or relay board couldnt power INJ1 and INJ2 for whatever reason.......so i switched to " Simultaneous 1 squirt" and powered both injector banks off INJ2 ....this shouldnt be an issue as on a V8 there is the same current draw across these 2 INJ 2 terminals........ The car wouldnt start but i managed to get fuel on the sparks when i pulled them out .......

2) I noticed on the datalog that whenever i had a kPa spike( attempted fire) there was an instantaneous drop in RPM...as opposed to an assistant spike in RPM....this told me that that combustion event was at that moment fighting against the rotation of the engine.....ie it was STOPPING the piston from moving at all......ignition timing must have been 180 degrees off ....so going on a hunch i completely flipped the ignition wires so that 1 and 4...swapped with 2 and 3...Completely opposite to what was marked for a 1342 engine!.....go figure???!
and VOILA!!!!

Thank you sooo much guys...its taken me a week of cranking and p[roblem solving but she starts....next step the TUNE !!!

[Ian]

excellent!