98 LeSabre won't start - Help!

[onetruerick]

My 98 LeSabre (3800) won't start. It had overheated when the radiator cracked, but ran fine after it was replaced. Today, I was driving it and it started running rough and lost power. Thinking it might be hot (even though the gauge was below 160), I pulled off the road and turned it off. The radiator wasn't particularly hot (yes, it has a brad-new thermostat) but it was about a half-gallon low. It won't start at all now. It cranks over fast but doesn't sound like it is firing at all.

I once had a 92 with the 2.5 four cylinder, and it's Ignition Control Module went out and it did the same thing. But a new for this car is nearly $300, and I can't buy a new one unless I am sure it will fix it.

Can the Ignition Control Module be checked?

Can anyone help?

Thanks,
Rick

[bobc455]

When you say that it cranks over "fast", do you mean that it cranks faster than usual? That might mean you have some valves which stay open (maybe a timing chain problem or something).

How often have you flushed the antifreeze? (Yes, I'm asking for a reason...)

-Bob C.

[onetruerick]

Thanks for posting, Bob. It seems to crank over at normal speed, and it had been well-maintained, although I don't know how many times the radiator had been flushed (I just got the car).
Since my last post, I had the ignition control module checked and it is good. The fuel pump is working and the fuel filter is not clogged. The spark plugs are firing, but when I try to start it, I can hear a slight backfire into the plenum, as though the timing is off. So, I suspected a bad crankshaft position sensor, but I used an ODB II scanner, and it says "0 Codes" (the Check Engine light was NOT on prior to this trouble).

So, could it be a bad crank sensor, even though there are no codes, or is it probably the timing chain?

Any help you could give me would be greatly appreciated.

[bobc455]

As far as I know (and I could be wrong), if the crank sensor is bad then the engine has to be running before the computer will set that code.

If it was the timing chain, then the engine would be cranking extra fast and you would be able to hear it not compressing. But the timing chains usually don't fail on these motors anyhow.

So I'm kinda leaning toward the crank sensor (or maybe cam sensor), so there are a few things to check. If the computer doesn't see the engine cranking, then it won't fire the injectors or spark. I have a thing called a "noid light" which shows whether injectors are firing, these are pretty commonly available.

One other possibility is bad fuel. My brother had a tank of BAD gas once, and we went crazy diagnosing everything we could think of! The engine was getting spark, fuel, but wouldn't catch. If we sprayed starting fluid in the intake then the engine would run fine for a few seconds then die. So that's one other thing to consider.

If you want to bring it to a garage, they can use computers to see how the crank & cam sensors are acting. If you want to do some trial & error troubleshooting, then I'd start with the crank sensor.

-BC

[onetruerick]

Thanks again Bob - Actually, I have tried starting fluid. It still just backfires and doesn't start.
I will look at the crank sensor (not sure if there is a cam sensor, but I will check). This car might have a water leak (can't tell at the moment because I can't start it up and get it warm), but if so, the leak is at the water pump. And if the water pump has been leaking, it could have affected the crank sensor due to where it is located. Have you ever seen this happen?

I will check the fuel first, but since it won't start on starting fluid, I am pretty sure I will be quickly proceeding to the sensors(s).

Thanks again, Bob.

[bobc455]

I believe there is a cam sensor, and I guess it could be either one. But I'm thinking (my psychic side is working here), I'd go for the crank sensor first.

Be sure that you get a real set of instructions for this, because if I remember correctly there is a special way to insert the sensor to the correct depth (without going too deep and smashing things, or going too shallow and not getting a reading).

-BC

[onetruerick]

You're right, there is a cam sensor. The crank sensor is behind the harmonic balancer, and I think it is more likely the culprit, especially if, as I suspect, the water pump has leaked. And if it did leak, it would leak directly onto the crank sensor. I know that a little water shouldn't hurt it, but if it was failing, a shot of hot water could have finished it off.
Just a guess. Both sensors are $25.99 at Auto Zone, so either way it isn't a whole lot of money.
After I check out the crank sensor I will let you know what happens.
Thanks,
Rick

[bobc455]

Any progress?

-Bob C.

[onetruerick]

Hi Bob - I replaced the crankshaft position sensor, and it made no difference at all. Would you recommend replacing the camshaft position sensor now? I guess I am becoming a bit pessimistic about the chances for success on this thing, wondering if maybe I missed something simple.

At this point, I am not seeing the benefit of a distributorless ignition. It seems that there are considerably more points of failure than a distributor ignition. Just my opinion.

What do you think, Bob?
Thanks again,

Rick

[onetruerick]

Okay, I replaced the camshaft position sensor, and it did no good at all. I took the intake hose loose and sprayed some starter fluid in it, and tried to start it. Got a nice "Boom" from the intake, then nothing. So, it is firing, but still seems to be at the wrong times. But it could be something else, I don't know.

I am going to see if there is any OBD code while cranking, but I am doubtful.

Let me know what you think.
Thanks,
Rick