Inconsistent Injector Pulses in test mode

[Blazer79]

Hello

I have a 3.51 board with MS2. 2.92 firmware. It's installed in a 1986 camaro with TPI. It has 8 24lb/h SVO injectors in two banks.

I was able to drive this car once, just to a gas station about 5 blocks from my house. When I was returning from the gas station the car started acting up, backfiring a lot and stalling. Had to keep my foot on the gas pedal for it to not stall. I was barely able to get back home.

I replaced the cap and rotor, spark plug wires, spark plugs. The backfiring and stalling remained, until it simply wouldn't start. With some friends we checked all wiring. We tested inyectors and got a noid light. Injectors would simply not fire from megasquirt. If we grounded them manually, they would fire. The noid light would light fine with the megasquirt. After a long examination, we found out that C14 capacitor was blown up.

Today I replaced the C14 capacitor, and proceded to do the injector test from TunerStudio. I only found a 35V 4.7uf replacement capacitor, but was advised in the MS FB page that it would work fine instead of the original 25V 4.7uf cap. Did I do wrong?

So here's the problem: If I configure 10 pulses of 10 or 20ms in TunerStudio, the injectors fire fine as long as the injector test offtime is 65ms or above. If I go below this offtime, it doesn't seem to fire all 10 pulses, but about 3 or 4. Also, not all injectors are firing in each bank the all pulses, butl it seems that after a few pulses they all fire.

I have extensively checked my grounds, and even had friends help me check them. All grounds come from the same point in the engine block. What else could I check that could cause this? A friend suggests I test all diodes in the MS.

I've been struggling for years with this project and it's so frustrating. Please help.

[kjones6039]

The first thing I would suggest is to post a recent data log (msl) and the most current msq used with that log.

Ken

[DonTZ125]

Are these Hi-Z o Lo-Z injectors?

[trakkies]

Do you get the same results with both injection circuits?

[Blazer79]

Thanks for your replies guys.

These are Hi-Z Injectors. I tested each of them. They are around 15ohms each. The problem is happening in both banks. The impression I get is as if there wasn't enough current to move the injectors. Yesterday I added an extra ground to the MS. I also did the test while having the car jumped with another car so the voltage wouldn't be low, but still got the same results.

Attached you'll find the msq file when it started. and a couple datalogs from that day. Today the car doesn't start. That's why I'm trying in test mode with the injectors removed from the manifold so I can see tha actual fuel that comes out from them.

I'm sure it's gonna be a $1 part in the end. I just don't know how to find out which one.

[Matt Cramer]

Just checking, but you didn't try wiring the injectors in series, did you?

[Blazer79]

No, they are in parallel. This car was able to drive once. I think it would had never worked if they had been in series.

[kjones6039]

Although I am not certain that it has anything to do with your issue, I did notice that you are running a narrow band O2 sensor with 15% authority......
Kind of difficult to control fueling with that setup, in my experience!

Ken