1995 Cavalier 2.3L DOHC.
Car cranks but does not start. Not even a hint of catching even with starter fluid sprayed into the air intake. Plugs are good and not flooded. Tested all 4 coil outputs and they all spark. Fuel pump goes on (can hear it) and in any case i smell fuel and even with starter fluid not even a hint of catching. Brought cylinder #1 to TDC and the mark on the crank pulley is vertical so don't suspect timing chain problem (I replaced the chain, tensioner and guides 4 months ago after repairing the cracked head). I think i can rule out the cam and crank position sensors cause i get spark. Engine has compression although weak on cylinder 3. Shouldn't be fuel related either because no hint of catching with starter fluid. BTW, no codes (car is equipped OBDII).
Wasn't sure if spark was too weak so i replaced one coil pack and still the same.
I wonder if there is a simple way to determine if the t-chain slipped. I have 120-140psi on three cylinders so would that be ruled out? I have spark, fuel and compression so what's wrong? thanks
if the timing chain snapped you would no it, the motor would crank over exremely fast its possible it slipped but not really likely. you need 4 things to make an engine run.... air, fuel, compression and spark. start looking into each one. air is simple enough, make sure the air filter isn't clogged (I've seen an engine not run cause a squierel filled up the air cleaner with dog food
) the air part is simple enough. for fuel spraying starter fluid isn't good enough, pull the fule line off and turn the key on, the pump should prime and shot gas out of the line crank it and make sure it kept pumping for a few seconds (the line your friend is standing there holding aiming into an empty 1 or 2 littler pop bottle so you don't make a mess and spray fuel all over) if thats working check the fuel pressure regulator, make sure the diaphram isn't torn sucking in gas through the vacum line, if you can get a hold of one plug in a noid light to make sure the injectors are getting the signal to fire, is the pressure high enough, if the filter clogged, make sure the injectors spray. you said you did a compression check and you have some compression, even with bad/low compressin the motor should still fire up. what about theat 4th cylinder you only mentioned 3? For ignition knowing the coils are firing is a good start, make sure the spark is making it to the plug and actually firing.
My first thought was crank sensor, no crank sensor no start, I don't know if that will stop the coils from firing or not.... unplug the sensor and see if the coils fire, quick easy check.
My second thought was fuel problem, you said you pulled the plugs and said it wasn't "flooded" if you crank it over and its getting fuel its gonna spray it into the cylinder, if its not starting the the plugs should be wet with gas right after turning it over, if they aren't then your not getting fuel.
How are you testing for spark? Ok lets say your getting spark all the way to the plugs.
Now if your plugs are not wet that says to me that there is no fuel injected in. Or else the car would be running.
Your fuel pump works, you say. Are you getting fuel pressure?
If you have fuel pressure, then your injectors arent firing.
Now the injectors are told to fire by the ignition module and the ecm.
The ignition mod can be tested at a parts store but not the ecm. Have them test the ignition module, If its good get a used ecm (computer) its under the passenger side headlight.
A quick way to check for a fuel related problem is to put some gas in a dish soap bottle and squirt it in the throttle body while cranking the engine. If It starts you have isolated the problem.
Throw that starting fluid away, I have some at work that I use to clean parts, Its good for that.
01 cav w/01 3400 gam gt 4t45e
Thank you, great info. Will test this fuel issue out as soon as I can next week and will report back. I test for spark by lifting off the coil pack assembly and attaching a spark tester to each coil output and I get spark. I assume this means the crank position sensor is working but will disconnect it and test for spark again in case it is the culprit even though I get spark. Most importantly i will test the injectors with a noid light and will test for fuel delivery by disconnecting the fuel line and placing it in a bottle while cranking.
I did not have time to test the crank pos sensor and fuel delivery yet but my friend who is a mechanic took a look and reporting this back to me:
He sprayed fuel into the throttle body and the car backfired into the intake. He claims that the timing chain slipped or a cam is broken. Unless you tell me otherwise i will ignore this info and test as you suggested.
Have your ICM checked at a local parts store. sounds like its firing on the wrong cylinder at the wrong time. Its either that or the coil tower housing has a couple of cracks in it causing the spark to either jump to ground or jump to the wrong plug. If I would have to bet money , my money would be on the coil tower. Very common problem.
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Thank you for providing your valuable diagnostic. I did take a look at the coil tower when i replaced one of the coils, maybe i need to look more carefully again for cracks. I will take the ICM into the local Autozone to test it. Is it obvious by visual inspection when the tower is cracked, should I take out the coils and inspect in that part of the tower.
While I'm at it I'll see if I have the correct noid light for an injector test and maybe even a fuel pump pressure and volume test if all else appears OK.
Thanks again, I really hope you're right because it would sure beat tearing down into the timing chain and cams as my mechanic friend claims I must do!
I brought the ICM to Autozone, they had the proper test leads. We ran the test 4 times and it past each time.
I removed the two coil packs from the coil tower. Tested the coils and they ohm out fine both primary and secondary. in any case i know i'm getting spark.
I carefully inspected the coil tower (inside and out) and there are no cracks or burn marks indicating a short to ground. I'm pretty bummed out cause I really wanted to find a problem there.
I put a noid light on an injector lead and the light pulsed when cranking the engine.
Could not find a port on the fuel rail to hook up a fuel gage. not even sure if there is a convenient spot to disconnect the fuel line from the rail. i hear the fuel pump go on with the ignition switch for a few seconds as expected. I did squirt fuel into the throttle with the throttle plate open while cranking and nothing fired! I was not able to get it even to backfire as my mechanic friend claimed.
In my first post I wrote "Brought cylinder #1 to TDC and the mark on the crank pulley is vertical so don't suspect timing chain problem" but that doesn't proove anything about the mechanical timing. What I really would have liked to know is if the two cam are in the correct positions when the #1 piston is at TDC.
If the crank position sensor failed i wouldn't be getting spark and/or the noid light to flash on the injector lead.
Please help, what should I do next?
from the sounds of it i first thought it was your cps...like mentioned all you need is air fuel and spark..you know you have air..and if your spraying fuel into the throttle that kinda rules out that so then that leaves spark..but you said your positive you have spark..but if so then it should fire..in some form lol
Is there a way to determine if my mechanical timing is off without digging into the engine. I want to verify that the cams are in the correct position in relation to the crankshaft position. I hate this engine!
I know i have spark when i pull off the entire coil pack and tower assembly and run a spark tester off the tower. Unfortunately i don't know how to test for spark with the tower mounted on the engine, nor to determine if the spark is getting to the plug at the right time.
Please help,
thanks
Your not going to see any visual cracks in the coil housing when it is bad. What appears to happen is that the spark will jump internally across the spark leads that are molded in to the cap. Which causes the spark to go to the output of the cap but to the wrong cylinder. If spark is applied to the engine at the wrong time then you wont have a running engine. Just because you have spark in this design of engine doesnt mean that it will run. There are ways to isolate this problem but requires a timing light and 4 spark plug wires. the 4 wires are used so you can apply spark to the plugs with the ignition assembly removed . the timing light is attached to cyl. 1 , then crank the engine and watch the timing mark on the crank pulley. Now , you asked how to test the cams. well the only way that I can think of without tearing anything down is to do a cylinder compression test. your going to need a compression gauge for that. should be around 150 psi, some wear may cause a little drop to around 135-140.
I would still have to recommend that you replace the coil housing to fix your problem. If your hesitant on changing it because of the cost, you will be happy to know that you will be able to return it if it isnt bad because it isnt an electronic component. (unlike the ICM which isnt returnable)
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Joe,
thank you so much for your advise. will change it and report back. The car ran great one day and then one day would not even give a hint of starting. i would think i'd at least get something from a cylinder or two or even poor running before failure. Will try with new coil housing and cross fingers. If doesn't work will maybe try to hook up spark wires on the fly and check #1 with timing light.
elliot
Joe,
thank you so much for your advise. will change it and report back. The car ran great one day and then one day would not even give a hint of starting. i would think i'd at least get something from a cylinder or two or even poor running before failure. Will try with new coil housing and cross fingers. If doesn't work will maybe try to hook up spark wires on the fly and check #1 with timing light.
Would also want to test for fuel but can't find a place to connect in a fuel gage. Fuel lines are steel and connect right into the rail.
elliot
^ Don't listen to him.
There's no plug wire on a 2.3. And you CAN'T miss match the boot.
Gilles
2.3 Ho
I put in a new coil tower but still doesn't start. The problem is not the coil tower. I then ran spark plug wires on the fly betwwen the housing and the spark plugs. With a timing light I detected spark at each of the 4 cylinders.
Unable to see a usuable timing mark on the crank pulley. There are no provisions for checking the timing on this engine.
Do i have no choice but to open up the timing cover to see what is wrong?
I have air, spark, fuel and compression (good on three cylinders and poor on one). It seems that i don't have correct timing or else the engine would fire up.
120-140psi is not good compression. Good compression on a Lo is 175-195psi.
Gilles
2.3 Ho
So if that's no good is it possible that the timing (mechanical btwn crank and cams) are off?
How many miles are on it?
It almost has to be the timing chain, You said that the compression was poor on one, how poor are we talking. What was the max for the other 3.
Looks like your going to have to pull the timing cover.
See if there is excessive slop in the chain and that all of the guide plates have their nylon wear bars on them.
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