English Guy
Well-known member
Hi folks,can anyone tell me where the crankshaft sensor is on l98 and any way of testing it to make sure it's working ok?Many thanks
Question: crankshaft sensor
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vetteboy86
Well-known member
Hi folks,can anyone tell me where the crankshaft sensor is on l98 and any way of testing it to make sure it's working ok?Many thanks
What issues are you experiencing?
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English Guy
Well-known member
Thanks for putting me straight ex-x-fire,i feel like a right muppet lol.
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- #5
English Guy
Well-known member
Hi vetteboy86 thanks for the reply, my c4 fires up on first turn of key and promply dies.Can't figure it out and am trying everything i can to get it sorted.
boomdriver
Well-known member
You've been on this for quite some time now....perhaps its time to take a break and recap.
Firing right away and immediately dying tells something. It says that there IS spark and at least some fuel present.
Spark is fairly simple, if its hot enough to lite up a stone cold motor, it's probably enough to keep it running. Usually a weak spark won;t fire anything. You might want to look at a plug firing just to see the blue arc across the tip of the plug. A spark plug test lite that clips on the plug wire will flash each pulse and confirm that each is firing.
All thats left is fuel. Either too much or too little, or contaminated. This is where all the sensors come into play. They regulate the fuel and insure precision. Although a perfect 14.7 to 1 ratio is the goal, anywhere close will allow the engine to run. So, the list of possible things that can interrupt this are:
fuel pressure/flow is low from bad pump or plugged tank screen or inline filter.
mass air monitoring, whether it be mass air flow or manifold pressure sensor.
throttle position.
fuel regulator.
injector signals or shorted injectors. ( use a noid lite to test)
EGR stuck open.
ECM or prom defect. (flash display would show issues with the base 12 code pulse)
I know you;ve already done most of this, but sometimes it helps to revue everything from a different perspective.
What became of the white smoke issues? if that was never resolved, that would have something to do with the inability to keep running. White exhaust smoke is a clear sign of water in the combustion. A cracked head or bad gasket will do that.
I hope you find some answers soon, its aggrevating for sure.
Firing right away and immediately dying tells something. It says that there IS spark and at least some fuel present.
Spark is fairly simple, if its hot enough to lite up a stone cold motor, it's probably enough to keep it running. Usually a weak spark won;t fire anything. You might want to look at a plug firing just to see the blue arc across the tip of the plug. A spark plug test lite that clips on the plug wire will flash each pulse and confirm that each is firing.
All thats left is fuel. Either too much or too little, or contaminated. This is where all the sensors come into play. They regulate the fuel and insure precision. Although a perfect 14.7 to 1 ratio is the goal, anywhere close will allow the engine to run. So, the list of possible things that can interrupt this are:
fuel pressure/flow is low from bad pump or plugged tank screen or inline filter.
mass air monitoring, whether it be mass air flow or manifold pressure sensor.
throttle position.
fuel regulator.
injector signals or shorted injectors. ( use a noid lite to test)
EGR stuck open.
ECM or prom defect. (flash display would show issues with the base 12 code pulse)
I know you;ve already done most of this, but sometimes it helps to revue everything from a different perspective.
What became of the white smoke issues? if that was never resolved, that would have something to do with the inability to keep running. White exhaust smoke is a clear sign of water in the combustion. A cracked head or bad gasket will do that.
I hope you find some answers soon, its aggrevating for sure.
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- #7
English Guy
Well-known member
Hi Boomdriver your right it is time for a recap.this is the present situation as it stands,There is no more white smoke/steam.
The coolant is at correct level as is the oil and neither show any signs of contamination.
distributor cap nearly new(coil is not),injectors ohm tested and fine.
Spark plug lite shows plugs sparking but plugs were black and stank of gas on inspection but i cleaned them and checked gap was ok.
when ign on but not cranking there is no voltage to plugs connecting to injectors
plenty of gas in tank and gas filter changed every 12 months.
Compression test shows 150psi on cylinders.
this is wierd tho, when i crank engine brake light warning lights up on center console and has never done that before:confused.when cranking stops light goes out regardless of engine firing up for a couple of seconds or not.
checked fuse panel and no fuses blown.
I have not touched the maf stuff as i am pretty clueless as how it works.
Ihope what i have written might give you a better idea of what is wrong with my poor old car,as ever i am very grateful for your time and advice,many thanks
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- #8
English Guy
Well-known member
Btw Boomdriver how does base 12code work?Ihave shorted the 2 terminals on top right hand side of diagnostic plug and all that happens is "CHECK ENGINE" light flashs in bursts of 3 until i remove paper clip short,is this right?Thanks
brian
brian
Hib Halverson
Technical Writer for Internet & Print Media
Btw Boomdriver how does base 12code work?Ihave shorted the 2 terminals on top right hand side of diagnostic plug and all that happens is "CHECK ENGINE" light flashs in bursts of 3 until i remove paper clip short,is this right?Thanks
brian
Actually, that is Code 12. When you key-up with the engine off then short the diagnostic pin to ground and you see the check engine light repeating: flash (pause) flash-flash, that's a 12. That means the ECM has no stored codes and the engine controls are not where the problem is that prevents the engine from starting.
I suggest you order the Factory Service manual from Zip Products, here in the States, then follow the instructions Section 6E covering: cranks but won't run.
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- #10
English Guy
Well-known member
Thanks for info Hib,I'll be ordering one a.s.a.p.I have a chiltern manual but it's as much use as a chocolate teapot:L
boomdriver
Well-known member
you are correct on the code 12 flash. How that works is like this...
The ECM goes into diagnostic mode when you jump the ALCL plug with the paper clip or wire jumper. The ECM when good, shows the 1...1-2 pulse, or (12) twelve. After 3 times, any stored codes will be displayed in the same way, so you have to pay close attention and watch the pulse count. 1-2-3 then 1-2-3-4 is a code 34.( thirty-four)
When all stored codes have been displayed, the ECM will again show code 12, three times or the 1 then 1-2 pulse to show that the memory has been run. Then it will repeat the whole process. ANY code is always flashed 3 times then it moves to the next until there is nothing left, then it repeats. 12 twelve is the ok code for the ECM.
Now the symptoms...
You will not see any injector signal until the motor is cranked over. Thats what a noid-lite is for. Thats a little inexpensive test lite that shows the injector is getting a signal but you say the plugs were wet with gas, so lets move on to something else for now......
Did you actually watch a plug fire or just use a test lite? I'd like to know that the spark is blue and nothing less. If the plugs are only producing a red arc, then thats not enough to maintain ignition. That is a sign of either a bad coil, or a bad ignition module inside the distributor.
MAF or the air metering system will make the car run like tired old crap, burping and spitting, but it will run and after some seconds go by it should cycle the ECM into a pre-programmed mode refered to as "limp home mode". This is the ECM's backup in case of sensor failure and it works very well. The MAF sensor is fairly delicate but usually last a very long time unless abused or damaged. It works by measuring the resistance differences in a hot wire inside the bore....the amount of electricity needed to keep the wire hot at a set amount changes with air speed. The difference is transmitted as a signal to the ECM as a measurement of how much air the engine is getting in real time. If that were the issue, it would run poorly, but it would run.
If it were me, I'd want to see that blue spark from a spark plug. And if that were good at a couple different plugs, then I'd go back and make sure the fuel system was all in good working order.
As easy as it is to get an engine to run, it's much easier to disable one and prevent it from running on its own. I have always found a good reason why it would not run when it happened to my L98 motors.
Be sure to get any codes off the memory. Those will not say "the problem is there" but they are a way of seeing what the ECM sees and then you can go to the malfunctioning system and diagnose it.
The ECM goes into diagnostic mode when you jump the ALCL plug with the paper clip or wire jumper. The ECM when good, shows the 1...1-2 pulse, or (12) twelve. After 3 times, any stored codes will be displayed in the same way, so you have to pay close attention and watch the pulse count. 1-2-3 then 1-2-3-4 is a code 34.( thirty-four)
When all stored codes have been displayed, the ECM will again show code 12, three times or the 1 then 1-2 pulse to show that the memory has been run. Then it will repeat the whole process. ANY code is always flashed 3 times then it moves to the next until there is nothing left, then it repeats. 12 twelve is the ok code for the ECM.
Now the symptoms...
You will not see any injector signal until the motor is cranked over. Thats what a noid-lite is for. Thats a little inexpensive test lite that shows the injector is getting a signal but you say the plugs were wet with gas, so lets move on to something else for now......
Did you actually watch a plug fire or just use a test lite? I'd like to know that the spark is blue and nothing less. If the plugs are only producing a red arc, then thats not enough to maintain ignition. That is a sign of either a bad coil, or a bad ignition module inside the distributor.
MAF or the air metering system will make the car run like tired old crap, burping and spitting, but it will run and after some seconds go by it should cycle the ECM into a pre-programmed mode refered to as "limp home mode". This is the ECM's backup in case of sensor failure and it works very well. The MAF sensor is fairly delicate but usually last a very long time unless abused or damaged. It works by measuring the resistance differences in a hot wire inside the bore....the amount of electricity needed to keep the wire hot at a set amount changes with air speed. The difference is transmitted as a signal to the ECM as a measurement of how much air the engine is getting in real time. If that were the issue, it would run poorly, but it would run.
If it were me, I'd want to see that blue spark from a spark plug. And if that were good at a couple different plugs, then I'd go back and make sure the fuel system was all in good working order.
As easy as it is to get an engine to run, it's much easier to disable one and prevent it from running on its own. I have always found a good reason why it would not run when it happened to my L98 motors.
Be sure to get any codes off the memory. Those will not say "the problem is there" but they are a way of seeing what the ECM sees and then you can go to the malfunctioning system and diagnose it.
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- #12
English Guy
Well-known member
Hi Boomdriver just to let you know i've got my vette running again,in the end i found a bad connection on the V.A.T.S system all is good
thanks for all the help
bri
thanks for all the helpbri
boomdriver
Well-known member
Cool!
A bad connection on a VATS connection? weird....I would have thought that something like that would have not even allowed it to crank over !
I wish that I could have helped more, sooner. The up-side is that going into the unknown attempting to solve a mystery is also known as education. Now, everybody that participated in this has a better one. I know that I learned something.
Good Luck to you and your car !
A bad connection on a VATS connection? weird....I would have thought that something like that would have not even allowed it to crank over !
I wish that I could have helped more, sooner. The up-side is that going into the unknown attempting to solve a mystery is also known as education. Now, everybody that participated in this has a better one. I know that I learned something.
Good Luck to you and your car !
So Bay Vetter
Well-known member
Just out of curiosity, where was the bad connection?
Vanity Plate Bob
Well-known member
Had a stop go adventure with a Cavalier.
Recall Hib? Ended up with an ignition switch. Switch was as only receiving 6 volts at times.
Shaft sensor and fuel pump replaced 1st. YUK $$$$$$$$.
Recall Hib? Ended up with an ignition switch. Switch was as only receiving 6 volts at times.
Shaft sensor and fuel pump replaced 1st. YUK $$$$$$$$.
vetteoz
Well-known member
VATS module itself has two components; starter enable and injector enable. If the injector enable is not working you will get crank ; no fire . A lot of guys don't understand this so if it cranks they disregard the possibilty of it still being VATS related as the most common VATS problem is the input signal ( key resistor reading) to the module ; not the output signal ( injector enable)
boomdriver
Well-known member
yeah, I understand what you;re saying. English stated that it would fire, and run but die almost immediately. Thats curious in regards to VATS. The injector side of the system perhaps?
His symptoms included good fuel pressure, and spark. And it would crank over. Would a VATS fault in the injector circuit allow all that but just stop the injectors from actually firing?
If so, that would mean that his engine was firing off of "leak-down" fuel in the intake with nothing after that to keep it running. That scenario makes sense....but I'd sure like to know where this bad contact was. Odd but interesting.
His symptoms included good fuel pressure, and spark. And it would crank over. Would a VATS fault in the injector circuit allow all that but just stop the injectors from actually firing?
If so, that would mean that his engine was firing off of "leak-down" fuel in the intake with nothing after that to keep it running. That scenario makes sense....but I'd sure like to know where this bad contact was. Odd but interesting.
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- #18
English Guy
Well-known member
where the blade fuse slots in.
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- #19
English Guy
Well-known member
i had been using easystart spray(25%ETHER I THINK)when trying to get car going also according to guy i bought the car from the vats was by passed with diode when he owed it.Does this make any sense?
boomdriver
Well-known member
Yes,
I suppose there could be a way of bypassing in the VATS starter enable circuit with a diode. Otherwise, the starter should not have worked. Appearantly the injectors are still protected by the VATS. Thats a good thing.
I can relate to the loose fuse. I had one for the exterior marker lites/tail-lites actually melt the plastic from the arcing in the loose contacts.
I suppose there could be a way of bypassing in the VATS starter enable circuit with a diode. Otherwise, the starter should not have worked. Appearantly the injectors are still protected by the VATS. Thats a good thing.
I can relate to the loose fuse. I had one for the exterior marker lites/tail-lites actually melt the plastic from the arcing in the loose contacts.
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