I'm bout ready to burn this car as I have never seen a vehicle with so many problems. anywho

1991 Camaro 3.1L

The car intermitently will not start and I notice the tach does not move when cranking and I have no injector pulse.

Car will start with staring fluid so I know it has spark,, and the car drove to my house just fine,, started up twice and then no start???

I have verified that its defiently a no injector pulse condition. and the ignition module was just replaced recently (its not when the probs started though)

Injectors and new ford bosch units and they are all fine.

Does anyone have a wiring schematic or idea what would cause no pulse/tach?

Thanks,
Brad M

There are a couple things that will cause a no-pulse condition on the injectors. First off, Check the wiring harness from the distributor to the ECM. If that harness has become disconnected somehow, then they ECM will not have a pulse reference from the distributor in order to fire the injectors.

Also, make sure that you actually have power to the injectors, there are 2 fuses that supply them, so make sure they are not blown.

Not knowing about the Ford injectors, they may be a lower resistance and may have caused a high current draw and blown the fuses. I assume they are the same electrical load rating though.

I've checked the harness but I havent dont a continuity check on it yet.. I dont see anything out of the ordinary.

The injectors are the same ohm and lb rating as the gm units and yes I have +12v on both sides so its not blown.

I'm just not getting a negative trigger form the computer..

Is there a damn crank trigger on this engine? one schematic says yes and the other says no.. since it has a dizzy I would assume no and being that it runs with ether I would also assume the hall effect/pickup sensor is good.

As far as the VATS system doesnt that turn off the injectors? and if i remember correctly I thought if the vats was tripped it would fire for about 1 sec then die,, mine doesnt do this but is this correct.

Also does the tach get its signal from the ECM or direct from the coil?

I'm wondering if I have a prob with the PROM in the car has become loose so I guess the computer is gonna have to come out for a check.

The pickup for the ignition/injector trigger is inside the distributor. if you have spark, then there isn't a problem with that.

The tach signal comes direct from the coil on the white wire.

when a alternator goes bad and your battery gets low you gauges will start acting up and the car will start to miss fire. I wounder if you have a low voltage problem, maybe one of the wires running from the starter to inside of car.

I have to throw my 2-cents in ,since I just replaced my computer in mine.Make sure your getting a reference pulse to the ECM via-scanner and make sure all the grounds out of the ECM are good,including the ones like the ground strap at the back of the pass. head etc..If those check out then try a known good computer.When I pulled mine out it was hot like it just came out of the oven(hard starting hot/cold issues)..electronics dont like heat.Expansion and contraction of the board can break a circuit or create an awesome ride into a big pile of crap.

I'll learn more tommorow when I tear it apart,, is the ref signal strictly a RPM pulse like the tach?

Brad

Check the 20 amp fuse that is mounted to the inside of the fender above the battery. There is a red wire that runs from the battery to the fuse and an orange wire that runs from the fuse to the ECM. I searched all over on line and could not find an answer so I found a schematic and checked for battery voltage at pin C16 (orange wire) of the ECM. There was no voltage so I checked the fuse at the battery as shown on the attachment and discovered that the fuse was bad. I changed the fuse and the engine fired right up.


ECM Pinouts.pdf

Check the wiring in the GRAY ignition coil connector... Even if the ECM isn't seeing DRPs, the tach should still move. If not, there could be some sort of power loss to the ignition coil, which means no power to the ignition module, which means no DRPs to the ECM. The PINK wire should have power with the key on. Check for a broken wire at or near the connector (I've had that happen before ).

:edit: Necroposting hurts...