[fast68]

ok got a 94 cavalier at the shop today, no start condition

wont fire on starting fluid either

plugs are pure white tipped, been runnign very lean apparently

fuel pump kicks on and primes pressure up

no spark except one time every about 10 revolutions of the engine

pulled crank sensor out of the block and it came apart completely, in two pieces, in half

they want 145 for a new one at auto zone etc which is more than the entire car is worth so we are opting for a known good sensor from a junkyard in the morning for about 40 bucks

what do you think?

probabl;y not the ignition module right?

would bad crank sensor cause no fuel injection(controls/runs the injectors)?
like the ignition module does?

some engines are like that i know.,


such as the TBI GM engines, like the 4.3L and such, they run the injectors and spark from the ignition module/sensor in the distrib...

so..

thanks

[joe_padavano]

Originally Posted by fast68

would bad crank sensor cause no fuel injection(controls/runs the injectors)?

Yes. Sequential port injection requires a crank position sensor to know when to fire the injectors. Usually, however, if the crank sensor goes bad, the system defaults to a batch fire mode and will still continue to work (though not quite as well). Have you dumped the codes, if any?

such as the TBI GM engines, like the 4.3L and such, they run the injectors and spark from the ignition module/sensor in the distrib...

Yes, because those are not sequential injection, just batch injection. Actual crank position is not required. The TBI, for example, simply alternates firing the injectors based on every spark plug firing. The original tuned port systems were the same - four injectors fired on one pulse, the other four on the next pulse, and so forth.

[fast68]

wow interestin ok good to learn thanks man

ok well we checked spark on all four wires and they are all screwy, a couple have no spark and one is weak orange and number # 1 will hit white hot spark every once in a while and then nothing again for a while

had idn module tested and the broken crank sensor tested and they actually tested fine.

fuel pump primes and has pressure

no broken ground wires anywhere on engine etc

i am baffled and confused

150 psi pressure in cylinders as well

i have no idea and no one else does either

anyone here know anything?

ign switch ?

ECM?

wow.

they said they were drivin the car and all was fine

then when they stopped somewhere for a bit and then went to start it up again it wouldnt start..

and it hasnt run since

sometimes it acts like its going to fire then backfires it caught on fire once on us around the TB unit


starter gear doesnt sound good kinda sounds like a tooth bad or something often too

130k miles

[T-bucket23]

How did you test the crank sensor. They can not be tested with a meter, you need to look at the signal with a scope. I have seen several that OHM out fine but still dont work.
You need to start by checking all power feeds and grounds. One you are sure they are all good, signals need to be looked at. A scope or a graphing scan tool is a must for no start conditions. If you dont have either you are just guessing

[fast68]

yeah i figured as much with the CS testing

i know this but i wasnt the one who took it and had it "tested"

they used ohms yes

its due to others imcompetence to understand that aspect in that case.

accordin to an above post reply it sounds like the car may still run in batch fire mode if the CS is bad but just won run very good or such,. is that still true with this particular engine?



i was thinking maybe the ECM has lost power or ground, or harness needs pulled and plugged back in, or a bad pin, etc

i wish we had a way to get a scope or such tool around here but we live out in the middle of cornfield no where and only a dealer or maybe one or two shops here might have such a thing, possibly, but highly unlikely.

but i do understand completely that even if the CS ohms out ok it doesnt mean that its operating at all or correctly.

and yeah i completely agree that we are totally guessing and hoping here, but sometimes you have no choice or other way.

suich as right now,.
these ppl dont have much money its an old beat up rusted out wrecked 94 cav and 130k miles and so we are just trying to do what we can without special testing equipment aforementioned.

haha


thanks !!

[fast68]

i checked around for hots and ground on the ECM and unplugged all three harness plugs to it and i noticed that the smallest plug with only two large wires, one is red/white stripe and other is ground

ground is fine

red/white wire is never hot at all.. key on or not..

shouldnt it be hot at some time or another ?

a couple or few of the small wires in the largest ECM harness connector are hot.

but none in either of the two smaller connectors ever are, even the biggest red one aforementioned.

CEL lights up in the dash with key in run so ECM seems to have power

maybe a fuseable link on the starter solenoid is burnt?

[T-bucket23]

Most ecm's have more than 1 power feed. You may have found the issue, try to trace it back. A wiring diagram would probably help.

[fast68]

yeah im havin a hard time finding wirin diagram for the 94 cav. can only find older ones,

hmmm


any ideas?


i think i should probe all the fuseable links at the starter next also..


thanks again!!

[joe_padavano]

Originally Posted by fast68

any ideas?

Yeah, beg, borrow, or steal a factory service manual.

[fast68]

haha yeah it would be nice.,

hmmm

this stupid small farming town has nothing

really.


maybe some day ill be so lucky as to get far away from it,


somehow hmm..

thanks!

[vettedreams2001]

I found a few wiring diagrams on Autozones site. While looking at the wires on the ECM I didn't see any red/white wires. But you can look into it more. They have basically an entire repair manual on there.

[T-bucket23]

I also checked Alldata and did not see any 2 pin connector or a red and white wire.
Are you talking about the ecm or the ignition module?

[fast68]

ECM in the cowl driver side near brake booster above it


big computer

its got three harness plugs
the smallest has a big red white wire and a big black wire

black wire is full ground good

red white wire is dead nothing ever no matter key position

thats my concern now

no diagrams show these wires at all or connector either

weird,.


thanks!

oh and lol at your signature line hehehee

i havent checked ECM fuse hmm pink black wire for it to the ECM connector

i found wiring diagrams on autrozone repair info and yeah still nothing but a single large connector and the red white wire and black wire just dont seem to exist still wow..

[fast68]

i jumped the big red white wire to direct hot and the ABS light was blinkin then,

new thing

must be ABS apparently..

hmm..


apparently i am at the wrong ECM wow. so thats my fail there, i really did not think this car could possibly have ABS,.
for some reason..

hmm..


crazy..

figures.

some cars do have the drivetrain ECM in the cowl such as the 90s ford contour etc.,

my bad....

also i need to fin dout the correct order of the coil pack towers from top to bottom

is it 1423 or 2314?

the stupid haynes manual shows them to be in an order that cant even be possible even if you swapped the coils around in any fashion. at all. no way,.



so far it is cranking over just fine and sounds like it should just fire right up but doesnt do anything, spark at each wire is random or non existent.
the injectors are not firing at all. spark plugs completely dry.

[fast68]

still wont start. has fire and will sometimes it will fire back up and out of the TB unit,.

cranks over great

out of ideas

we are about done with it and its gonna go to the shredder with another car here if it doesnt run again really soon,

thanks