antonov225

So, here goes nothing.
I've replaced a lot on this motor. Rotor, cap, wires, plugs, fuel pump, ECU, TPS. The car has strong spark, and the mobile mechanic that came out said the timing (on the distributor) was right. Regarding the ignition system, the only thing I haven't replaced is the ICM. However, the spark is still very strong. The mechanic said he couldn't smell fuel on the spark plug when it was cranked over, but I checked the wiring using a NOID, and the injectors are getting pulse. The fuel pressure is also up to spec. It does have good compression, as evidenced by how hard it was to turn over by hand. I'm completely at a loss at this point. The mechanic mentioned that the camshaft could've jumped timing, but wouldn't that also mess up the distributor?

Turbok9

Ignition timing is measured off your harmonic balancer, thus is related to crankshaft rotation. If your cam jumped time, that won't change the relationship between the dizzy and the crank.

If you pull your dizzy cap and mark the location of point 1, pull your dr side valve cover, and turn her over by hand, when the dizzy is pointing to #1 the lifter shoul be just about all the way up for intake on cyl 1 and the timing mark should be at about 6-8* (keep in mind you may have to go around twice to get the lifter there). If you jumped you may be able to tell without pulling the timing cover.

antonov225

So even then, if that was the case and the cam slipped timing, would it still pop on a few cylinders when turning over?

zed-028

a dead ICM will cause exactly this problem

if you really want to check your timing, pull plug one, put your finger over the hole and have a friend turn the engine by hand until your finger gets pressure to blow it off, stick a pen or a dowel or something in there, turn the engine by hand back and forth very slightly until the most dowel is showing. check then timing groove, should be about TDC

antonov225

So a dead ICM would only throw off the timing for the spark, not stop it completely?

zed-028

a dead ICM acts as a kill switch in the sense that it wont send the signal to the ECM that the car needs to run.

The EST spark timing circuit controls the advance etc from the initial setting, but without that signal being sent to the ECM youll have a complete no running condition.

antonov225

So the car will inject fuel and still spark but somehow not start still? Sorry, just trying to understand this fully so I don't have to keep throwing parts at it

zed-028

I do recall something else but someone might need to back me up on this one but from memory injectors wont actually fire anything with a dead icm either. even with pressure to the rail. but it think thats only for TBI engines.

antonov225

So can the injectors receive pulses, and still not fire anything? I checked with a NOID light, and both banks are receiving a pulse.

Turbok9

I've never heard of getting spark with a dead ICM? I thought a dead ICM caused a no-spark thus no-run condition?

Turbok9

Maybe, maybe not. Depends on how far out. Are you sure your dizzy is not 180* out? You can't tell that with a timing light, you have to know you are on the compression and not exhaust strokes when you set / check time. Cyl 1 should be building pressure as it comes up on rotation, pull the plug as was already suggested and follow his directions to check..

zed-028

Thats thing, ive had one which caused no spark and one which caused a no run condition.

The one that caused no spark was a fully dead ICM
The one that caused no run was tested 5 times by an auto electrician, Passed/Passed/Failed/Passed/Failed
A mate of mine had one that would fail when it got hot, causing no spark situations

I hate these little units with a passion.

Turbok9

lol thats crazy. never heard of that but im taking your word for it. I've had stranger things happen with these cars.....

zed-028

Try with starter fluid, if it fires at all then youre looking in the fuel region

If it doesnt fire on starter fluid youre looking somewhere else

redneckjoe

best advice IMO.

antonov225

Yup. Tried it before. Still didn't fire. I'll try one more time tomorrow, and go ahead and order an ICM, just to err on the side of caution (and hopefully cheap fix)
I've checked, there's no way to get the dizzy on backwards on this car (luckily). I'm almost positive it's right, since it seems to occasionally fire on a few cylinders.

zed-028

I would rebut that with its ENTIRELY possible to get it 180 out. Just because the cap is facing roughly the way it was doesnt mean that the dist gear itself it sitting on the cam gear in the right spot.

Thing is, if its off you will probably get a couple of things, youll either get 1 crank and nothing, or you will get some decent easy cranking with occasional noise that might sound like firing. the reason for this would be an incorrect firing order. If it did fire and fire hard on the wrong cylinder, youll send a rod through the block. Game over

Id just check it on #1 to be sure.

Turbok9