1990 3.1 No Injector Pulse - Intermittent

Hello I am working on a 3.1 that has an intermittent no start problem. When the car does not start there is no injector pulse. There is always spark and good fuel pressure. I have tried several other ECUs that I have lying around and the same problem exisits. Could this be an ignition module issue even though there is always spark? Please advise.

Hello I am working on a 3.1 that has an intermittent no start problem. When the car does not start there is no injector pulse. There is always spark and good fuel pressure. I have tried several other ECUs that I have lying around and the same problem exisits. Could this be an ignition module issue even though there is always spark? Please advise.


sounds more like a wiring issue
the wires from ecm(u)
to the injectors or a ground
or short
bad wires
are all the injectors losing pulse
or just one
or two

that is my guess

That is what I am thinking too but I have tried everything I can think of. I replaced the injector harness because it seemed like if I moved it around it would create a miss. That fixed the miss but didn't help the int. no start. I powered the injectors directly and ran new wires right from the ECM to the injector harness with the same on again off again no start issue. I have tried the ignition module with no help either. I checked the grounds and power to the ECM and they all seem good. Any more ideas?

That is what I am thinking too but I have tried everything I can think of. I replaced the injector harness because it seemed like if I moved it around it would create a miss. That fixed the miss but didn't help the int. no start. I powered the injectors directly and ran new wires right from the ECM to the injector harness with the same on again off again no start issue. I have tried the ignition module with no help either. I checked the grounds and power to the ECM and they all seem good. Any more ideas?

my lumina would do a similar not start thing
the car would die and not start back up
it would also drain battery
after i fried the first battery
put in a new one was fine for a while
but then went to work one day
and it turned over kind of slow again
didn't think much about it
till i got to my parents house
had my dad come out and listen
then the car would not turn over
thinking it could have been the alternator at first
but then realized that i had lights and 12 volt at the battery
then figured it was the starter

i pulled it out
had it rebuilt
worked fine ever since

if you have spark all the time its not ign mod
but it may have some thing to do with the crank sensor
it is in the back of the block near bottom middle
it a pain
have to rotate the motor to get to it
but when i replaced mine (thinking this was one of my problems only $20)
the outer plastic was cracked
this controls the timing and may tell the computer when to turn on injectors too

just a guess

Sounds like the crank sensor. If you have checked everything else, you might want to replace the crank sensor. Be very, very careful when you do. Mine was brittle and broke off when I tried to remove it. Half was in my hand and the other half was in the oil pan. Finally had to remove oil pan to retrieve it. BUMMER.

Sounds like the crank sensor. If you have checked everything else, you might want to replace the crank sensor. Be very, very careful when you do. Mine was brittle and broke off when I tried to remove it. Half was in my hand and the other half was in the oil pan. Finally had to remove oil pan to retrieve it. BUMMER.


Thank you. I just tried the crank sensor and it was cracked but the new one didn't help. Pretty frustrated at this point. To answer a question from above there is no pulse at any of the injectors. The car seems to always crank very stong. The starter appears to be recently replaced.

Thank you. I just tried the crank sensor and it was cracked but the new one didn't help. Pretty frustrated at this point. To answer a question from above there is no pulse at any of the injectors. The car seems to always crank very stong. The starter appears to be recently replaced.

is the service engine light on
or are you getting any codes

No Engine light. The only codes that I have were 32 and 33 (I think they were the numbers) Too high and too low Map Sensor readings. I think that was from when I unhooked the vac line while it was running to see if there was vac there. I have swapped the MAP out with another from the shelf with no effect. Baffeled......


Thank you. I just tried the crank sensor and it was cracked but the new one didn't help. Pretty frustrated at this point. To answer a question from above there is no pulse at any of the injectors. The car seems to always crank very stong. The starter appears to be recently replaced.

Get a scanner on it and see if you get cranking rpms when it won't start.

Yes, there is always a RPM signal when it runs and when it cranks and doesn't start. Usually around 250 to 300 when cranking w/ no start.


Get a scanner on it and see if you get cranking rpms when it won't start.

Yes, there is always a RPM signal when it runs and when it cranks and doesn't start. Usually around 250 to 300 when cranking w/ no start.

well i'm stumped
sounds like something is telling the computer to
turn off the injectors
if you changed the wire harness
and switched ecms

that is a tough one
could the computer be getting a bad reading from
the tps telling it that its flooded
and shutting of the injectors
or something like that
maybe

When this happens try tap testing the pcm, use a screw driver handle and give it a coupla moderate taps on the case, see what happens. also watch for bad connections at the ICM.

check your ECM. IF the factory number on it is 1227727, you need an ECM. These units have a very high failure rate, and combine that with being mounted under the hood exposed to the elements on your car, I would bet that is where you problem lies.

check your ECM. IF the factory number on it is 1227727, you need an ECM. These units have a very high failure rate, and combine that with being mounted under the hood exposed to the elements on your car, I would bet that is where you problem lies.


he changed out yhe ecm a couple of time i think he said
any way

that is what it sounds like to me
too

try testing the harness between the crank sensor and ignition module for continuity, maybe you have a broken wire.

I changed the ECM with two others with the exact same results. I thought about the carnk sensor wires too, but I wouldn't have spark all the time if they were bad, would I? Does anyone know exactly what inputs (and paths, ie through the Ing. Mod. then to the computer, or right to the computer, etc) the computer uses to determine the fuel timing/duration? I assume that the Crank sensor is number 1. MAP #2 and from there the IAT sensor and TPS sensor trim things out. But typically a car will run w/o the IAT and TPS, etc sensors even plugged in. I tried unplugging most of the typical sensors one at a time and all together and other combos with no help. The car only tried to start once today and has been a crank and no start the other dozen random times I tried today. :(

he changed out yhe ecm a couple of time i think he said
any way

that is what it sounds like to me
too