Narrowing down the No Start problem...Inj. Pulse.

[GS70350]

Here are the test results.
Car spins over very rapidly because of high torque starter, several hundred RPM.

Not bad starter, solenoid, ign. switch, or battery.

Car has 150psi compression each cyl.

Not timing chain.

Car has 43 psi fuel pressure at rail, holds pressure,

Not fuel pump, relay, pump voltage, etc.

Car has Spark while under compression in the cylinders, every cyl plug wire fires the timing light, so there is current travel thru the wire on compression stroke and therefore there is a spark in the combustion chamber. Spark is not intermitent.

Not coil pack or module or crank sensor.

Check the injector plug with LED light that lights up at 4 volts, no flashing. injectors dont seem to be clicking when you touch them.

TPS sensor reads .44 volts with throttle closed ign. on and operates correctly throughout the range of throttle movement.

Not clear flood from shorted TPS.

Replace cam sensor cap with known good cam sensor cap. Still wont start.

Not cam sensor cap.

Car cranked and ran suddenly and ran perfectly the other day until i shut it off again, now it has no injector pulse again. This leads me to believe that the cam sensor is still set correctly as it is not loose and hasnt moved any.

Tried different chip, one for 30lbs injectors instead of 50s. THIS should have made the injector pulse last longer, but they still arent pulsing and the plugs are bone dry.

Not computer chip.

Reset ECM several times, no difference. ECM has good data stream with no trouble codes, although the car did not crank since ECM was reset.


IS IT THE ECM??

Thanks, throw all ideas at me that you think of, going to try and crank it this weekend when i return to jacksonville (my old home town where i had to leave the car).

 

[Scott Atk]

I would crank the engine with the cam sensor cap off and verify that it is spinning. That would eliminate timing chain and bad cam sensor body. Once I broke down at the track and everything pointed to the camsensor, we changed the cap and reset it to no avail. After having it towed home I found the the screw was loose on the rotating cup in the cam sensor. I had the cap off and never noticed. Good Luck.

 

[chevyII]

module

When you crank over the engine does the ecm read rpm's. The module has different circuits for spark and fuel delivery. check all the ecm-injector fuses. do you have 12v on one side of the injector plug?ecm controlls the grounding of injectors.You probly dont have the ground from the ecm. replace the module if all above is ok

 

[Scott Atk]

interesting.... so even though he has spark, the module could still be bad?

 

[chevyII]

module

I used to trbl shoot when I was a tech. never worked on a turbo buick but if the module is inside the cap and is about a quarter of an ich thick they go bad all the time. and yes you can have one and not the other is very common.

 

[GS70350]

Scott, already checked that, it spins and is not loose and cap is tight.


Chevy II. Turbo Buicks dont have distributors with modules inside, they have a DIS ignition system with the module mounted underneath the coil pack. If it is sparking then im pretty sure the module is good.

Thanks for the tips though, keep throwing them at me.

 

[Scott Atk]

Ok, pull the harness off any injector. Now with the key on, check for voltage on one of the wires. If nothing then go to the "FP/INJ" fuse and check there. If theres voltage at the fuse but not to the injector then you have an open in that circuit (most likely the inj, harness or the large white connector). If the fuse is blown, then the inj. harness is likely burned at the EGR and shorted. Good Luck and report back.

 

[GNut]

Possible Solution

I experienced a similar problem.. ran fine one day and nothing the next. Here's what it turned out to be.. I am running an aftermarket oil press. gauge and the stock connector was cut off. Turns out two of the wires grounded out and were blowing the fuel inj fuse.. it had me puzzeled for hours and really pissed me off after I had already replaced the cam and crank sensors twice!!

 

[chevyII]

no fuel

I didnt know the 3.8 were DIS,If the ecm is reading rpm when cranking get a wiring diagram for the ecm. you can use a test light and back probe the ground wire at the ecm to see if the ecm is putting out the switched ground for the inj. I would imagne the 3.8 are sequential? The test light is not the best tool to use because it has no resistace like the inj but a set of noid lights are expensive.

 

[GS70350]

messed with injector harness connection and tugged on the wires a bit today. charged the battery, and then turned it over and boom, cranked right up. ran perfectly fine. I checked the fuses last night, none were blown. I drove it around a bit today, drove to the gas station to fill up since it was empty, and after filling up, i went to crank it and it tried to crank but wouldnt. the injectors are no longer firing and the car is stuck at the local amoco. If i dont get it running it will be towed away.

I checked the inj. fuse and it was blown, so i replaced it but it still wont start.

messed with injector harness some more but it did not help any.

I need help fast, im leaving town tommorow and car will be stuck in jacksonville for another few weeks till i get back in town, thanks.

Looks to me like the injector harness or wiring going from the fuse box to the inj. harness has a short or loose connection somewhere. thanks

 

[GS70350]

Found a injector harness wire shorted out on the EGR, insulation was burned through in several small spots anyways, dont know it that was the cause, but it could have been. It cranks up every time now, just runs really wierd, its cutting out every couple seconds and with no pattern, just cuts out for no aparent reason. Anyone got any ideas? only in drive too, idles fine. What if i got some water in the gas that i just bought? it didnt do this on the way to the gas station, but started right after i filled up. Thanks