Motor turns over but will not start

Tiny
DAN-O1234
  • 1995 CHRYSLER NEW YORKER
  • 120 MILES

Motor turns over but will not start. It started with running real rough, like an injector was plugged so we ran injector cleaner through it for several tank fulls. Finely it just would not start, so I brought it into the yard and started checking things. This is what I have checked, Fuel pump turns on and pumps fuel, injectors getting a pulse signal while turning over, Spark from plugs are snappy and blue, Checked power going to Crank Shaft and Cam shaft sensors, in specs. Timing belt is good and lined up. Pulled intake manifold off and jump injectors over to battery and got a good fine spray from all injectors. Checked coil, ohm was within specs between lugs. I have read every post I could find about this, and I do not have the money to through new parts at it, so am very willing to test, test, test. I have a dig. Multi meter and a test light. Not sure if this is relevant, heater would come on full blast high heat and the control lights would go out so you could not turn it off or down, then for no reason the control lights would come back on and work fine. BCM? If so how do I test to make sure. Any help would be very helpful.

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Saturday, January 5th, 2013 AT 9:33 PM

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Tiny
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Forget the cam and crank sensors. You have spark, so they're working. If you're getting fuel spray during engine cranking, it sounds like you have bad gas, or the pressure is too low. Low fuel pressure isn't a common failure on Chryslers.

If you replace the Body Computer you must use a used one from another car that did not have the anti-theft system if your car doesn't have it. If your car does have the factory anti-theft system, you can use any Body Computer. If it doesn't have that programming, it will learn it from the Engine Computer the first time you turn on the ignition switch. If you don't have anti-theft, and you install either computer with that programming, the engine will not start until you replace both computers without that programming. What it boils down to is if you have anti-theft, you can use any computer. If you don't have anti-theft, you have to know the history of the car you're getting the used computer from. That anti-theft programming can only self-upgrade; it can not be undone.

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Sunday, January 6th, 2013 AT 12:43 AM
Tiny
DAN-O1234
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Sorry I did not get back sooner, I could not find your answer, but here I am now.
I do not have a gauge for the fuel pressure, but when I jumped the injectors, they squirted a good snappy spray and I could hear the fuel returning back to the tank.
I took the hose off of the air cleaner box and sprayed starter fluid into it while cranking over and it did not even try to start.
Replaced both Crank and Cam shaft sensor, did not see your post till after I did. Still not starting, willing to keep checking, what next. Thank you for your help, Dan-o.

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Sunday, January 13th, 2013 AT 3:07 AM
Tiny
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Pop a spark plug out and see if it's wet. You need spark, fuel, and compression, at the right time. You have spark. It sounds like you have fuel, plus you tried starting fluid. That leaves compression and timing. You think the timing belt hasn't jumped a tooth but I've been fooled before. Check the diagnostic fault codes first. If you have one related to "cam and crank sync", double-check the timing belt. I never ran into this on the "LH" cars but on the Neons, if the timing belt jumps one tooth it will set that code and the engine will run poorly and be hard to start. At two teeth off the Engine Computer will shut the engine down to protect it. You will have intermittent or no spark. At three teeth off the pistons will hit any open valves as they coast to a stop and bend them.

While you have the plug out, do a compression test on that cylinder. If the timing is off the compression will be low on all the cylinders. If the plug is wet, remove all of them to allow the cylinders to dry out, then put new ones in. We had a '94 Intrepid donated by Chrysler to my community college when they were done using it for training. Every year we were putting new plugs in it due to repeated short-trip drives of about 100 feet! For use in my Electrical classes the engine never got warmed up so the plugs fouled often. If your old plugs are wet, the spark will be shorted out and starting fluid won't work.

Also, at the dealership I used to work at, we had two cars come in two days apart that had no-start problems shortly after the owners bought gas. After spending all day on the first one, the mechanic gave up and drew out some fuel. He threw it on the shop floor and threw a lit match on it. That "fuel" snuffed out the flame. He drained and replaced the gas in both cars and they both fired right up.

Something that is probably not related, but if you had the battery disconnected or let it run dead, the Engine Computer will have to relearn "minimum throttle" before it will know when to be in control of idle speed. Until that occurs, you will have to hold the gas pedal down about 1/8" to get the engine started, you'll probably have to keep holding it down to keep it running, and you won't get the nice idle flare-up to 1500 rpm when the engine starts. If you use a "noid light" to test for injector pulses, they will show that you DO have pulses, but the length of them is not enough to allow in enough fuel to maintain idle speed. Typically that small amount of fuel vaporizes and goes out the exhaust, but you have the false impression you're getting enough fuel. Starting fluid should make that lack of fuel evident but if the Engine Computer needs to relearn minimum throttle, the automatic idle speed motor will have closed off the passage around the throttle blade and that starting fluid might be going into the engine too slowly.

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Sunday, January 13th, 2013 AT 3:46 AM
Tiny
DAN-O1234
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Pulled timing cover off and crank and camshafts were right on. Tried the 1/8" throttle and it seamed to want to try, but never started. Tomorrow I will check plugs and compression. I will get back to you with what I find and maybe able to find a gauge to check fuel pressure.
Thank you, Dan-o.

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Sunday, January 13th, 2013 AT 4:10 AM
Tiny
DAN-O1234
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Ok, installed new plugs with the correct gap. Drain some gas out into a small cup and could see a little bit of water in the bottom, if I tilt it to one side. Through the gas to the floor and lite it and it ignited. Pushed gas peddle part way and turned it over, it sputtered but still never fired up or really gave much effort that it would start. The plugs were wet when I pulled the old ones out, that is why I replaced them. Compression was at 95-100. Unable to find a gauge to check fuel pressure, but am still looking. What else do you think?
Thank you, Dan-o.

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Tuesday, January 15th, 2013 AT 1:31 AM
Tiny
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Have you checked for fault codes yet? Chrysler makes that very easy. Cycle the ignition switch from "off" to "run" three times within five seconds without cranking the engine. Wait for the Check Engine light to turn off, then when it starts flashing, count the series of flashes. There will be one group followed by a short pause, then another group representing the second digit of the code. After a longer pause the second code will flash if there is one. The last code will be "55" which just means "end of message" and can be ignored. In case you have a late production car, '96 and newer models display the codes in the odometer display.

The next thing is to connect a scanner to view live data and see what the Engine Computer is seeing. The camshaft position sensor and the crankshaft position sensor will be listed as "no" or "present". It is possible for one of the signals to be missing and not set a fault code, but then you wouldn't have spark or fuel injector pulses. Look at the MAP sensor. It has the biggest say in how much fuel goes into the engine. It can start to fail and report the wrong voltage but as long as that voltage is within the acceptable range it won't set a code. If it reports the engine is under load, way too much fuel will go in and flood the engine.

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Tuesday, January 15th, 2013 AT 3:19 AM
Tiny
DAN-O1234
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I checked the codes and what I found, I thought, was codes for when I had the intake off and I was checking for power at different places, but here is what I got.12, 42 23 24 77 32 55, now I know 12 is the start and 55 is the end. How would I check the MAP sensor, I do have a Dig, ohm meter.

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Tuesday, January 15th, 2013 AT 5:12 AM
Tiny
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I've never run into 77 and 42. 12 means the battery was disconnected recently. The rest would set if things were unplugged while the ignition switch was on.

The MAP sensors were a GM design and had a real high failure rate in the early '90s. They typically started out causing poor performance and would not set a code, but typically failed completely within a day or two. The clue was the engine would start but within a few seconds it would only stay running if you were moving the gas pedal. Didn't matter which way or how fast, as long as it was moving.

If you have reason to suspect the MAP sensor, you can unplug it, then turn on the ignition switch and try to start the engine. The Check Engine light will turn on and there will be a fault code for it, but the Engine Computer will know it can't trust its reading so it will take a pretty close guess, based on the other sensors' readings and engine operating conditions, and run off that approximate value. It won't run well, but it will run.

You can't do anything with the MAP sensor with an ohm meter because there's a lot of circuitry inside it. I did prepare a worksheet for my students to follow that involved watching the signal voltage but that was for properly-running engines. Those readings won't mean much when the engine doesn't run. When you turn on the ignition switch, that sensor measures barometric pressure. Higher pressure means more air being forced into the engine and the need to increase fuel delivery. Once the engine starts, it measures manifold vacuum as an indirect measure of engine load, and again, the need for the corresponding amount of fuel. Chrysler is the only manufacturer that has been able to make an engine run right with just that sensor. Everyone else has had to use a somewhat troublesome mass air flow sensor.

The MAP sensor is fed with 5.0 volts. Its signal voltage will always be between 0.5 and 4.5 volts, (approximately). When the voltage goes to 0 or 5.0 volts is when it sets a code related to voltage. The Engine Computer will also detect no change in voltage at engine start-up as a pneumatic problem meaning the vacuum hose is cracked or disconnected.

In the absence of a fault code, all you can do is view the data on the scanner. The signal voltage will be displayed but unless it's way off, you'll have better luck looking at the amount of vacuum. That should read "0", and the barometric pressure should be close to the actual value.

A leaking vacuum hose can cause the vacuum to appear to be low to the sensor. The Engine Computer will interpret that as the engine is under load and more fuel is needed. Beginning by the mid '90s Chrysler began plugging the sensors right into the throttle body or intake manifold to avoid leaks in the hose.

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Tuesday, January 15th, 2013 AT 7:04 AM
Tiny
DAN-O1234
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Unplugged the fuel pump relay and the motor started just for a moment, burning what gas was in the system. This is the best it has done since I started on it. So should I be looking for leaking vacuum lines or is the MAP sensor bad?

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Tuesday, January 15th, 2013 AT 12:16 PM
Tiny
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Pull the vacuum hose off the fuel pressure regulator and look inside it. If it's wet, the regulator is leaking raw fuel into the engine. That is real common on GM trucks but I've only read about it once on a Chrysler product.

Gotta go out of town. Will check back later tonight to see how you're doing.

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Tuesday, January 15th, 2013 AT 10:51 PM
Tiny
DAN-O1234
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Disconnected to MAP sensor and it STARTED, ran very rough, but it ran. Going to replace MAP sensor.
Ok replaced MAP sensor and it starts and runs. Also checked the vacuum line to the fuel pressure regulator and it is dry. I would like to thank you for all of your help. I will drive it for a few days and let you know if it stays running.
Dan-o.

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Wednesday, January 16th, 2013 AT 2:38 AM
Tiny
DAN-O1234
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Tried to start it this morning and it would not. It acked the same as it was yesterday before I replaced the MAP. I disconnected the MAP and it started, very rough. I reconnected the MAP after I ran it a little and it started and ran better. Is there somwthing else wrong?

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Thursday, January 17th, 2013 AT 12:13 AM
Tiny
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It's hard to know what's going on without having a scanner to look at. The things I would look at first are the MAP sensor voltage and the intake air temperature sensor reading. A bad connection will cause an increase in resistance in that circuit which would equate to a lower temperature. That can command more fuel, and the engine may be flooding.

Excessive fuel pressure will also cause more fuel than expected to enter the engine. A leaking vacuum hose to the fuel pressure regulator will cause the pressure to increase, AND can cause the MAP sensor to see a lower vacuum which equates to acceleration and the need for more fuel.

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Thursday, January 17th, 2013 AT 6:35 AM
Tiny
DAN-O1234
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Pulled the Air temp sensor out and wiped it off, looked kind of nasty, but not real bad. All of the vacuum hoses that pushed on real easy I took some O-rings and found the right size to fit over the outside of the female hose fitting. Once I slipped them together, I rolled the O-ring to the end to pinch it tight. It started right up and ran great. Again I will drive it a few days and get back to you here to let you know. Thank you, Dan-o.

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Thursday, January 17th, 2013 AT 7:46 PM
Tiny
DAN-O1234
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Three days and it has been running fine. But, now it is getting real bad gas mileage. Do I have to wait for awhile for everything to find its happy spot for it all to mesh and run right? Is there something else going on?

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Monday, January 21st, 2013 AT 11:52 PM
Tiny
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Fuel should straighten out right away. The Engine Computer memorizes short and long-term fuel trim data. It starts out with pre-programmed values from the factory that cover any combination of speed, load, air temperature, coolant temperature, and barometric pressure. That gets fuel metering real close, then the computer looks at the oxygen sensor readings to see how it's doing with that fuel / air mixture. It modifies the amount of fuel being delivered based on those O2 sensor readings, and it remembers how much it had to modify them. That's called the "short-term fuel trims", (STFT).

When the computer sees that it is constantly making the same corrections over a period of time, it moves those values into the long-term fuel trims, (LTFT). From then on those are the values it runs on instead of those pre-programmed values. The goal is to make the long-term numbers be so accurate that the short-term numbers are real close to "0". That means the mixture is correct and no modification is necessary.

The way to tell how the system is working is to view those numbers on the scanner. If you see a positive long-term number, that means the computer is requesting more fuel than what was programmed in at the factory. If you see a positive short-term number, that means the computer wants more fuel than what it has updated its memory to, to meet some current condition. Negative numbers means it is reducing the amount of fuel desired.

Based on the readings from the oxygen sensors, the computer can only add or subtract fuel by about ten percent. When you see numbers that high, something is usually wrong that is beyond the computer's ability to control it. Common causes are low or high fuel pressure and vacuum leaks. Also, misfires related to spark can send unburned oxygen into the exhaust where the sensors will detect it as a lean condition. You will smell unburned fuel at the tail pipe but the computer will be trying to add more fuel. No matter how much fuel it adds, it will continue to see a lean condition. That's one way it can lose control and display very high positive fuel trim numbers.

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Tuesday, January 22nd, 2013 AT 7:24 AM
Tiny
DAN-O1234
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I do smell a strong gas smell at the tail pipe and poor fuel mileage, So should I replace the O2 sensor, it is not sending a code.

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Wednesday, January 23rd, 2013 AT 2:42 AM
Tiny
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Nope, you don't replace the messenger when you don't like the message. The O2 sensors are sending out signal voltages that the computer sees as acceptable so no codes will be set. A scanner will show how the sensors are responding. You can introduce extra air by unplugging a vacuum hose, and you can introduce extra fuel by opening a propane torch near the air filter to see if the oxygen sensor voltages change.

If you see the O2 sensors are reporting lean conditions, the computer is adding fuel to try to correct that, and you're smelling that fuel at the tail pipe. If they're reporting a rich condition, which is what it appears you have, the computer has lost control and is unable to adjust the mixture enough to make it right. In that case the computer knows it's rich but can't fix it. Suspects would be fuel pressure too high, or an injector stuck open due to varnish buildup or a shorted driver circuit in the computer. Fuel pressure would affect both sides of the engine. An injector problem would affect just one side.

Take note of the catalytic converters too. Too much unburned fuel will overheat them and can make them glow orange if it's bad enough. If you see one or both are glowing, stop the engine to prevent melting the catalyst. That is how they become plugged.

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Wednesday, January 23rd, 2013 AT 4:53 AM

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