Was running great.... now won't start

[Syclone1452]

I did some more surfing, and found this thread:

http://www.camaros.net/forums/showthread.php?t=103811

his problems sound just like mine...

I pulled the Ignition Control Module and coils. I drug them to Autozone. They tested the ICM. It is okay... drat!

The only test they did for the coils was to measure the resistance across the two plug wire studs. Is there any other way to test the coils?

The service manual mentions a 3X crank sensor. How do I test that?

I noticed that the SES light stays on while cranking, but I didn't see any codes in TunerPro, but I'm not sure I had communication with the car all the time.

What scan tools are available for the '95 Camaro?

[1988GTU]

You can have a bad coil or ICM even after a meter test that shows good results.

[Tbay99Venture]

Sparks & sensors

The service manual mentions a 3X crank sensor. How do I test that?

That's not the 7x sensor? I thought the senors for DIS were one for the cam and 2 for the crank -- a 7x and a 24x. You can check the 7x with an ohmmeter but I don't have the value handy

Here's an interesting article about how the ICM utilizes the 7x sensor alone and the PCM is using the other two:

http://www.mastertechmag.com/mtwp/2009/April/image/pdf/MT_Online_200904_toothfairy.pdf

Short story is a busted cam resulted in a rebuild. Apparently the first shop broke the extra tooth off of the crank and therefore the ICM never could sense the special double-peak signal for #1 cylinder and wouldn't generate a spark. It might give you some pointers on what ails the spark.

[Syclone1452]

I was able to spend some quality time with Sydni's car today.

My reading told me that during starting of the car, the ICM only looks at the sensor in the side of the block [FSM calls it 3x] sensor. After the car is running, the sensor on the crankshaft is used to fine-tune the timing.

I am able to get the car to fire sometimes when I crank it. If I disconnected the crank sensor that plugs into the ICM, the engine doesn't fire at all. That is sort of telling me that the crank sensor in the side of the block is okay... I hope.

I then took out my spark tester... one of these:

http://www.amazon.com/OEM-25069-Adjustable-Ignition-Tester/dp/B0014WDFLY

I adjusted it to 35-40 on the little gauge ... the setting for DIS cars.

When I checked 2, 4 and 6, the spark jumped/snapped for every firing cycle.
When I checked 1, 3, and 5, the spark on 3 was pretty consistent, but the sparks
for 1 and 5 only snapped every 4 or 5 cycles.

I then moved the wire for 3 that was sparking well over to the coil post for 5.
Wire 3 then started missing most of the sparks. That eliminates the wire, right?

So...

Can coils go bad on one end?
Or do I have an ICM that is bad?

Confused in TX...

[Syclone1452]

I just did another experiment...

I exchanged a couple coils on the ICM.
The no-spark followed the coil...

[pocket-rocket]

The no-spark followed the coil...

I think you found your culprit.

[Syclone1452]

I give up...

I found my wife's Silhouette in the driveway... just sittin' there...
I looked on the AutoZone site... it said the replacement coils and ICM were the same parts as Sydni's Camaro.
I "borrowed" the coils and ICM from the Olds
I installed fresh plugs in the Camaro.
It *still* won't start... it fires and coughs, but won't start...

I did a compression test... 2,4,5, and 6 all have about 90 psi on a stone-cold engine
3 has about 120, and one has about 60.

Would those number prevent the engine from starting? I would think they may prevent it from making 200 hp, but not from starting.

Should I borrow the crank sensor from the Olds?

VERY confused in TX....

[Tbay99Venture]

I give up...

I found my wife's Silhouette in the driveway... just sittin' there...
I looked on the AutoZone site... it said the replacement coils and ICM were the same parts as Sydni's Camaro.
I "borrowed" the coils and ICM from the Olds

I installed fresh plugs in the Camaro.
It *still* won't start... it fires and coughs, but won't start...

I did a compression test... 2,4,5, and 6 all have about 90 psi on a stone-cold engine
3 has about 120, and one has about 60.

Would those number prevent the engine from starting? I would think they may prevent it from making 200 hp, but not from starting.

Should I borrow the crank sensor from the Olds?

VERY confused in TX....

Brave man; pinching parts from your woman's machine!

I would have bet the original coils were all-or-nothing functiion since they fire on compression & exhaust. But maybe it's a center-tapped winding or dual secondaries? No matter, hete's my 3400 comp readings that confirmed the dancing temp needle was a failing head gasket:

#1; 120, 150, 180 190
#2: 85, 120, 150, 160
#3: 110 150, 180, 190
#4: 135, 150, 170, 185
#5: 120, 160, 180, 190
#6: 120, 140, 170, 195

The van was running fine otherwise, 160,000 miles.

Seems to me if you can visually confirm spark at the end of each wire the ICM is not the problem and fuel of ratio must be it.

[bszopi]

Have you inspected the 3x sensor wire to the ICM? If it is shorting out anywhere, it may not be getting an accurate signal to the ICM and thus causing erratic spark. But the fact that the miss is following the coils makes me think a coil is at least on its way out...

[86FieroSEv6]

You should consider pulling the fuel pump fuse for a bit. Those comp. readings look like you are starting to wash down the cylinders, I believe this motor has a 110psi minimum for cranking pressure. If she's getting injector pulse, then the crank and cam sensors are okay. If you are getting spark from all three coils then the ICM is okay as far as starting goes. Spark from one side of the coil only means bad coil. If you ever run across no spark on either side of one coil, you can put your test light across the coil primary terminals on the ICM with the coil removed and check for the test light to flash as you crank, that confirms if it is coil or ICM when you have no spark at all.

[douglasfalde]

the ignition control module that the coils mount on likes to go bad. i've had this problem with 2 cars now. your best to just replace all the coils at the same time, use dielectric grease, and if the electrical system is pushing 20 now, get ready for fuel injectors closely followed by the pressure regulator, throttle body gaskets (cleaning), and the fuel pump.

[Syclone1452]

In today's episode of "How to waste your life away working on someone else's car"...

I removed the fuel rail and injectors.... hooked everything up and placed the injectors on a piece of clean cardboard.

The injectors didn't leak... actually, they didn't do anything.

I plugged-in all the wires to the Ignition Control Module, and connected all the plug wires. The last thing I needed was an open spark <yikes!>

This time, all six injectors started firing... nice little spray patterns. I was sort of hoping to find a few injectors leaking like a garden hose... <bummer>

I mashed the gas pedal to the floor and cranked it over a few times.... no fuel. That is good. It tells me the PCM is not totally stupid.

I put it all back together and it still wouldn't start <sigh>

I pushed the car into my shop and put it on the lift. I removed the 3x crank sensor and checked all its wiring. Everything looked okay. I put it all back together and it still wouldn't start.... big surprise

It sure seems like a flood condition to me. It wants to start in "clear-flood" mode, but it appears to be hosing-down the spark when the injectors are running.... drives me nuts.

I found two more fuel pressure gauges....

One reads between 40 and 45 psi while cranking, and the other two read between 50 and 55 psi while cranking.... hmm.. interesting.

I connected a vacuum pump to the FP regulator and pulled it down 20 inHg. It held steady for several minutes, so I know the diaphram isn't damaged. When cranking with the 20 inHg, one of the 50-55 psi guages now reads 40-45.... but the car won't start.... probably flooded from before.

I think my problem may be fuel pressure... but that's odd, because the car drove fine for a couple thousand miles with this fuel pump. I wonder if the return line has a restriction.

The pump I put in there is the Walbro F20000169. It drops right in that silly module. Only problem is that pump is a 255 ltr/hr pump at 40 psi. I wonder if it's too much fuel for that rail/regulator to be able to return the extra fuel to the tank. I know the LT1 cars don't have trouble with that pump, but they have different fuel rails and regulators...

I really don't want to have to drop that tank and replace that pump, again...

... and the bad dream continues....

[60dgrzbelow0]

On the subject of the Unholy Three of the camshaft and crankshaft sensors and all the weird problems that can arise when they misbehave...have look at this interesting article that ... while involving a 3100 engine... may still have some relevance here, since the discussion also includes the possible involvement of the Fuel Pump (pay close attention to the aspect of the level of fuel inside the gas tank in correlation with the failure to start):

http://www.flatrater.com/sample/sample.htm

Also... it may make some sense to consider replacing the PCM... eBay has the two flavors for both Automatic and Manual Xnsmishuns:

Automatic

http://cgi.ebay.com/ebaymotors/Firebird-3-4L-1994-1995-Engine-Computer-ECM-16184737_W0QQcmdZViewItemQQhashZitem483a2aac78QQitemZ310213520504QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

5 Speed

http://cgi.ebay.com/ebaymotors/CAMARO-ECM-FIREBIRD-95-94-ENGINE-COMPUTER-3-4L-5SPD_W0QQcmdZViewItemQQhashZitem563583f2aaQQitemZ370265027242QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

Replacing the Crank Sensor makes good sense at this point...

[86FieroSEv6]

What is the engine coolant temp sensor reading? If you don't have a scanner handy, a DVOM (digital volt/ohm meter) on DC volt scale backprobed at the yellow wire should read about 3 volts or so for a cold engine (roughly a half volt for a warmed up engine). Also, a MAF screw up can cause this as well. Try unplugging the MAF to force backup fuel and spark control and see what happens.

[60dgrzbelow0]

Have you inspected the 3x sensor wire to the ICM? If it is shorting out anywhere, it may not be getting an accurate signal to the ICM and thus causing erratic spark. But the fact that the miss is following the coils makes me think a coil is at least on its way out...

Brad... wasn't there some blurb a while back about somebody accidentally "untwisting" the 3X pigtail-wire...or repairing one without the requisite number of turns in it necessary to prevent EMF interference...and essentially nullifying its signal quality?