Bad Crankposition Sensor?

I wrote a question a couple of weeks ago regarding my 99 Grandprix, 3800 II, non-supercharged V6 not starting after I had replaced the intake manifold gasket and upper plenum.

I put the car back together, but it will not fire. I read through a few threads here and I checked a few things. I have fuel and fuel pressure is good. The spark plugs smell of gas, so I believe the fuel is reaching the cylinders. There is spark to the front plugs, so I assume with the wasted spark system, there is spark to the back plugs. I noticed the MAF was cracked, but according to a thread I read here, you can unplug the MAF and it will still run, just not efficiently. I intend on replacing the MAF.

When I try to start the car acts like it wants to start, but will not sustain firing. When I turn the key off, I get a little backfire. NOT a bang, but more of a puh. Sorry, best way to describe it :)

So my question is, is it a reasonable certainty that the CKP sensor is bad? Would I even have spark, if the CKP was bad?

Thanks alot in advance for your help. I have learned a ton from this forum!!

Terry

There would be no spark if the crank sensor is bad. Change the MAF sensor first, and if it still doesn't start, let us know.

Well, I replaced the MAF, but still no success in starting it. I noticed when cranking it over that once in a while it would get a good fire, but it would never sustain it.

A mechanic friend of mine told me to do a compression check to see if there was damage done back when the intake manifold were leaking.

Any other help would be greatly appreciated!!

Thanks again,

Terry

How did you determine fuel pressure was good? Did you physically test it with a fuel pressure gauge at the Schrader valve at the fuel pressure regulator?

Was the engine firing up before you performed the intake manifold work?

Hi,

Yes, I tested the fuel pressure at the Schrader valve on the fuel pressure regulator, and we got 53psi.

I will go more into the intake replacement story. When I replace the lower intake manifold gasket I did not originally put gasket sealer at the intersections of the gaskets that rest on the head and block. So I immediately had a leak at that point after I put it back together. I tore it back down, fixed it and put it back together.

I started it, and it fired right up.... for about 30-45 seconds. It then started spewing white smoke out the back and running really rough. I thought it was a head gasket. So I replaced the front head gasket (which was not the problem) and put it back together. That is when it wouldn't fire.

I have since discovered the upper intake plenum was bad at the EGR tube and replaced that aswell. Still no fire.

Let me know if you need more info!!!

Thanks, Terry

Fuel pressure is definitely good.

Hey Rich are you going to work with this guy? We can flip a coin...lol. :lol:

Between the two of us, we'll get him squared away. I just did a upper plenum job last week, and I cannot think of anything that would affect spark. The only thing I can think of is maybe a blown fuse, or it happened when the front head was removed and a wire to the ignition module got pinched. Any thoughts Bob?

Thanks for the help guys.

Are there ways of testing the fuel injectors to see in they are bad?

I have had them unplugged, out and reinstalled several times with this project. I have cleaned them, but not extensively. It would not shock me if they "suddenly" do not work.

Also, I will probably pull the rear spark plugs and turn the engine over a couple of time to bleed out any potential anti-freeze.

Is there a method to getting the left-rear (under the alternator) spark plugs out? What a pain!!!

Terry

I had trouble finding an ohm spec the other day for 97-up GP's. The best I could find in my GM service manual was 11.6-12.2 ohms cold. Then the service manual shows a test proceedure with a tester that measures voltage drop. I wish I had a more concrete answer on injector testing, it's like it's a black art and I forgot my cauldron and wand, sheesh. The back spark plugs are a pain to reach. I have a set of ring nose pliers that work nice for getting the boots off the plugs without ripping them. Those factory heat shields around the boots make it real fun to get a grip on them.

Personally I think he would be better off running a NOID light to check the fuel injector pulse to each to verify the signal from the PCM is good.

The only other suggestions I would have is double check the wiring to the crank position sensor and ignition control module since the front cylinder head was removed. The ICM and coil packs must be removed when doing that specific cylinder head or even a valve cover gasket replacement. Whatever the problem is it is related to the work already performed which appears to be quite extensive.

On the even bank spark plugs. The one under the alternator is easy with the right tools. The one I hate is #6. I remove the 02 sensor so it doesn't get damaged plus it is in the way. Also, I remove the bracket where the 02 sensor and harness is clipped to. Two 13mm nuts holding it onto the exhaust manifold. Good luck!

Here is some additional information for you:

Did a compression check last night and here is what we have.

Back head, left to right: 140 140 140
Front head, left to right: 105 105 125

Seems a little off on the front head, but I would think it would still start and run.

Any thoughts?

I will test the fuel injectors aswell.

Thanks

Here is some additional information for you:

Did a compression check last night and here is what we have.

Back head, left to right: 140 140 140
Front head, left to right: 105 105 125

Seems a little off on the front head, but I would think it would still start and run.

Any thoughts?

I will test the fuel injectors aswell.

Thanks

It is a little off on the odd bank cylinders. 1 and 3 are marginal. 5, 2, 4, and 6 are fine. Good compression on a Series II 3800 should range from 125 - 140 psi. 100 is the minimum. Although 1 and 3 are low I don't think it will preclude an engine from starting or the cause of your problem.

Did you take all the plugs out when doing the compression test, or did you take them out one at a time and replace them after testing each cylinder?
If you had the plugs in, it is possible you have a leak between 1 and 3, causing the low reading, and compression is bleeding between the two which would cause a no start.

If you had the plugs in, it is possible you have a leak between 1 and 3, causing the low reading, and compression is bleeding between the two which would cause a no start.

I doubt it.

All the plugs were out of it when the test was done.

Terry

Ok, that eliminates the cross compression issue. Bob, I've seen on many motor jobs where 2 adjacent cylinders with equal but lower than the rest cylinder pressures have a head gasket leak between them. With the plugs out, you'd hear the air leaking out into the other cylinder, with the plugs in, you wouldn't.

Ok, that eliminates the cross compression issue. Bob, I've seen on many motor jobs where 2 adjacent cylinders with equal but lower than the rest cylinder pressures have a head gasket leak between them. With the plugs out, you'd hear the air leaking out into the other cylinder, with the plugs in, you wouldn't.

Your point is well taken. I took into account that he replaced the cylinder head gasket on that head and assumed he did it correctly. I've seen and worked on many engines where the compression was below 100 and with flaky head gaskets and I could get them to turn over. Over 30 years experience on engines from total rebuilds to modding. Plus I've done my fair share of compression testing and troubleshooting relative to compression issues.

If he wants get his problem fixed he needs to consider relevant issues and not get side tracked. Just my 2 cents. :2cents:

Ok, I understand what you were getting at and agree with you. Since he had the plugs out when he tested compression, it's a moot point anyway. I agree his issue is most likely a broken/pinched wire to the ICM (from removing the front head) or injector(s).

I will then proceed to do the NOID Light test on the injectors and let you know what I come up with.

Talk with you soon! Hopefully with good news.

O.K. guys, sorry for the delay. I did not run a NOID light test on the fuel injectors, but I did test them with my ohm meter with the key on and got a reading of 6.45 on all the injector plugins. The tester was set to 20 on the DC voltage side of the tester.

Prior to the test I removed the fuel rail to clean the injectors so the fuel lines were disconnected. When I turned the key on, obviously fuel came out of the lines, but ONLY the line feeding the back side of the fuel rail, not the front. Is this normal?

O.K. guys, sorry for the delay. I did not run a NOID light test on the fuel injectors, but I did test them with my ohm meter with the key on and got a reading of 6.45 on all the injector plugins. The tester was set to 20 on the DC voltage side of the tester.

Prior to the test I removed the fuel rail to clean the injectors so the fuel lines were disconnected. When I turned the key on, obviously fuel came out of the lines, but ONLY the line feeding the back side of the fuel rail, not the front. Is this normal?

Fuel should be in the front FI rail especially since that part has the fuel pressure regulator. With the fuel feed line hooked up do you get any fuel squirting out when the Schrader valve pin is pushed in? A total lack of fuel on the feed line is abnormal.

The NOID light is a better check. According to the GP GM service manual the voltage coming from the fuel injector line drivers should be in a range of 9 - 16 volts. The measurement is made in DC Volts (autoranging or the scale you were on should be good). The black lead should reference a good engine ground and the red lead on one of the input pins at the fuel injector connector.

I do get fuel to squirt out of the schrader valve at the fuel pressure regulator. I am having a hard time getting a hold of a HOID light, but will keep trying.

It is pretty hard to get the fuel lines switched, but the fuel comes out the line that connects to the back side of the rail. I do not get anything out of the front side connection.

Thanks.

I do get fuel to squirt out of the schrader valve at the fuel pressure regulator. I am having a hard time getting a hold of a HOID light, but will keep trying.

It is pretty hard to get the fuel lines switched, but the fuel comes out the line that connects to the back side of the rail. I do not get anything out of the front side connection.

Thanks.

Did you ever run a fuel pressure test? It is starting to sound normal to me. If the fuel pressure test is within specs you're OK.

I reviewed the fuel feed line hookup. I wouldn't switch any lines. The one on the back rail is the pressure feed and the second feed line (to front rail) is actually the return line so what you are seeing appears to be normal.

Advance and Auto-Zone both carry noid lights cheap.

I have one additional question with regard to the timing of the engine. When the lower intake manifold was removed, the top of the block is exposed.

There is a "rod" that lays on top and runs the length of the block and is centered. This "rod" has a swirl shape to it. Does this have anything to do with the timing? I remember cleaning up some water/oil residue from this and it may have turned a little bit when I cleaned it. I do not know what this piece is called.

Would this be a problem with timing?

Thanks

Hello there I have a simaliar problem with my 93 grand prix. Maybe you could help me out here. The car runs good for about ten minutes and then the tach jumps up and down then stalls. I can smell the fuel burn real rich. Any help would be appreciated

Left3field, the part you are talking about is the camshaft. It is what activates the valves. Removing the intake and cleaning or touching the camshaft couldn't mess up the timing, as it is attached to the timing chain. The cam should be difficult to move, unless the timing chain has some slop in it. Slop in the timing chain will mess with the timing, as it keeps the cam in sync with the crank.

There is a "rod" that lays on top and runs the length of the block and is centered. This "rod" has a swirl shape to it. Does this have anything to do with the timing? I remember cleaning up some water/oil residue from this and it may have turned a little bit when I cleaned it. I do not know what this piece is called.



Thats interesting. I've never heard of a camshaft described like that. :dunno:

I agree with Rich. I don't think thats your problem.

When you changed your intake, did you reinstall the old pcv and it's "O" ring into the new intake? If not you will have a massive vaccum leak and a no start.

I did not change the O-ring you describe. It is worth a shot. Thanks.

Although it is worth looking at a missing PCV o-ring (black one) will not cause your problem or a no start condition. Even if the big orange o-ring was omitted under the MAP sensor retainer it would not give you a no start condition.

I again agree with Bob. The missing o-ring can give you a false EGR flow insufficient code, but will not cause a no-start.

Although it is worth looking at a missing PCV o-ring (black one) will not cause your problem or a no start condition. Even if the big orange o-ring was omitted under the MAP sensor retainer it would not give you a no start condition.

But, a missing PCV would.

But, a missing PCV would.

I'd agree, however, he is not missing a PCV valve so it is now a moot issue.

Well I guys here is the latest update.

I had a mechanic "friend" come over last night to look at the car and here is what we discussed.

He did all the checks that we have discussed here and found nothing unsual either. He connected to a computer he brought and again nothing unusual.

He said there is a lot of gas showing up on the dipstick, so he suggests changing the oil and installing new spark plugs. He believe the original plugs are now bad due to water damage and the fuel/vapors in the cylinders from multiple attempts to start is causing bad compression mixture which will also not fire or fire poorly.

So I will attempt this tonight!

Any thoughts?

Well I guys here is the latest update.

I had a mechanic "friend" come over last night to look at the car and here is what we discussed.

He did all the checks that we have discussed here and found nothing unsual either. He connected to a computer he brought and again nothing unusual.

He said there is a lot of gas showing up on the dipstick, so he suggests changing the oil and installing new spark plugs. He believe the original plugs are now bad due to water damage and the fuel/vapors in the cylinders from multiple attempts to start is causing bad compression mixture which will also not fire or fire poorly.

So I will attempt this tonight!

Any thoughts?

Go for it. The mechanic is giving you good advice. When you encounter a situation such as yours the excess fuel due to lack of combustion will cause dilution/contamination of the motor oil requiring that it be changed. Spark plug replacement sounds good too.

Keep us posted. Good luck!

Well guys, hopefully this is the final update.

She is running!!!

The oil change and new spark plugs did the trick. AND it appears the original problem of the coolant leak is also fixed.

I let it warm up with the idle for quite a while and then took it for a 35 mile drive and all seems well.

Thanks to bnaylor3400 and richtazz for your help and all who wrote aswell.

I will continue to come here both for help and hopefully to help aswell.

Thanks!!

I have one additional question with regard to the timing of the engine. When the lower intake manifold was removed, the top of the block is exposed.

There is a "rod" that lays on top and runs the length of the block and is centered. This "rod" has a swirl shape to it. Does this have anything to do with the timing? I remember cleaning up some water/oil residue from this and it may have turned a little bit when I cleaned it. I do not know what this piece is called.

Would this be a problem with timing?

Thanks

Isn't he talking about the balance shaft and not the cam?

Isn't he talking about the balance shaft and not the cam?

Well when you remove the LIM it is exposed so I would agree with you Troy since the camshaft is not really in plain site. But it wouldn't cause the problem he had. It is used to help control vibration that the V6 puts out. All 3800s going way back have a balance shaft. I've got an old pic someplace.

He sounds good to go anyways so I guess the issue is moot. But good point. :bigthumb: