monte-ss

I was out driving around and stopped at my storage shed, when I went to get back in the car it wont start, so I started to test everything, and it points to the ECM, good spark, fuel pressure in the rail reading like 50 somewhere PSI, I have a harness/injector tester, you can hear the injectors clicking and watch the fuel oress drop when you fire them, placed a noid light on the harness and no flashes, my GM service man says
1. key on harness unplugges get pos voltage from each side of the harness,
2. then with harness plugged in and ECM disc get voltage ad D15&16
I have all this then says ecm is the prob, this ecm is maybe 5 years old.
car has been running great since I fixed the charging probs I had, last weekend I went home 4 hours each way on the highway no probs then all of a sudden just craps out
any ideas why?

monte-ss

allright I checked some more and had already bought the new ecm but thats not the problem, I missed one check on the list of things to look at, one of them said to disc all the injectors, and test for voltage at one of them on the ecm side, all the ecm wires on the drivers side show volts, and their not supposed to somehow, the pass side shows no volts, and this is all with the ecm plugged in and the key on.
Now my question is, where do all the wires from the ecm side of the injectors tie intogether at? somewhere between the injectors and the ecm its shorting out to hot so Im cornfused! Im ready to rip out all the wiring and put a painless kit in it, but no place to do the work at right now so I have to make this work, arggggggghhhhhhh!!

Guest

Stock harness? They tie in where the AC box starts, so thats just above the passenger side head. The tie in from R-L is in the ecm itself.

BTW they are easy to spot in the harness, they are both twisted pairs (the wires are wrapped around one another.)

u r sofa king we tah did

there are two fuses "INJ" and "INJ2/F.P."

one for each side of injectors. check the fuses first. easiest and cheapest.

Swapmaster

With the key on, an ignition lead feeds two fuses, one for each
side through pink/black wires. These wires will be HOT with the
key on. If one of these wires is not hot, you have a bad fuse, bad
wire or the connector needs cleaned or replaced. Make repairs to
assure both sides are hot.

One bank of injectors returns to the ECM with a black/pink wire
to ECM pin D15 and the other bank returns with a black/ LT green
wire to ECM pin D16. The driver pulses these wires to ground to
fire the injectors.

Use your noid light with one wire connected to BAT+ and probe
ground side of the harnesses (black/pink and black/light green)
and crank the engine to verify the ECM.

I the noid light does not flash on one side or the other, recheck
with the noid light taped in at D15 and D16 of the ECM. If no light
on one of the pins the ECM is bad. If both do light then you have
a broken wire between the ECM and the engine. Thats where the
fun begins.

Good luck.

RCR

Two questions: How did you verify spark? What's a noid light? If it's what I think it is, your injector pulse width could be short enough that you'll never see the lamp light up. (I think)

monte-ss

checked for spark 2 ways, when using the tool to fire the injectors it will supply enough fuel to get the engine to fire off then die.
pulled one plug wire did the old screwdriver in the plug and crank watching the spark jump from the screwdriver to ground.

if the injector pulse is too short aside from reprogramming a prom how do I fix this, I have tested the injector wiring with this light before same computer/prom and could see the flash no problem.

I dont think the higher rated injectors cause any problems since people have used these before and I cant find anything related to it in a search. Besides since I have gotten this thing put together it has run great this just died without any warning.

RCR

Well, if you have spark, and you have fuel, then it's along the injector drive (obviously). The injector drive should be tied to battery on one side (mentioned). With all injectors disconnected (I remember how tuf some of those were to get off/on), you should have 12v on one side only. Check for continuity to ground on the other side. If it's tied to ground (car off), it's bad. How's fuel pressure when it tries to start? Does it drop?

monte-ss

I didnt know about checking the ecm side of the harness to ground with the car off, Ill have to try that and yes one of those plugs on each side is a real PIA! haha but I got one to come off without any real trouble but one on the drivers side I had to "modify" the plug to be able to get it out.

The fuel pressure stays up since nothing is coming out, and after you crank the engine a little you can hear the fuel pump relay click off, and the guage reads a constant 50something PSI

RCR

Have you come up with anything new???

monte-ss

https://www.thirdgen.org/techbb2/sho...814#post812814

monte-ss

ok got it all together with the new ign module, rechecked the timing, and took off, the timing was a couple degrees off, no big deal, but either that old module just wasnt up to doing much anymore or the few degrees off made a whole lot of difference, but WOW!!! couldnt get the thing to do a burnout before and after I got the thing put together I took off and nailed it, left a nice long streak down the street, I just figured it was the dirt on that road was aiding in the loss of traction, well saw a friend of mine on the street and was playin around he said smoke it, I thought it wouldnt do it but lets try, and next thing I know is its coming up to 6 grand on the tach and smoke everywhere! Im not a big fan of drawing attention that way but it was nice to know it has gotten all its pep back