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Ron
Ron, ASE Certified Technician
Category: Dodge
Satisfied Customers: 33392
Experience:  ASE Certs
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Dodge Dakota 3.9L Auto: ***** ***** with no start condition after

Customer Question

95 Dakota with no start condition after extensive overhaul. Suspecting that the problem is the pcm.
Submitted: 1 year ago.
Category: Dodge
Expert:  Ron replied 1 year ago.
Hello, my name is ***** ***** I am a professional here at Just Answer. I have noticed that your question was not getting a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.
In order for the engine to start and run you need good spark, injector pulse, proper fuel pressure as well as compression. If you can check each one of these for me and post back with which one you are lacking I will try and help you determine the cause. Check these for me and post back with the results and we can work from there.
Customer: replied 1 year ago.

I get a weak spark at the coil. When I checked the spark at the spark plug, I only saw it spark once. The coil is new.

When I checked the injector pulse with a NOID light, I gave it a good crank but only saw it flash one time. Not sure if that's normal.

Pressure is good. I changed the fuel pump, and its getting proper fuel pressure to the rail. Compression is also good and even on all cylinders.

Expert:  Ron replied 1 year ago.
The injectors should cause the NOID to flash consistently as long as you are cranking as well as the spark, are you sure your getting a good signal from the CKP (crankshaft position) sensor?
Customer: replied 1 year ago.

What do you mean with a good signal? I bought a new CKP sensor and CMP sensor as well.

Expert:  Ron replied 1 year ago.
The computer needs a good signal from the CKP to fire the injectors as well as the coil. If your sure the CKP is okay then I would be looking at the connection to it from the CKP to the PCM (computer). Has the computer been scanned for codes.
Customer: replied 1 year ago.

No. I only did the on-off-on method with the key to check for trouble codes.

Expert:  Ron replied 1 year ago.
Well it sure sounds like you are loosing the signal from the CKP either due to a wiring and or connection concern and or a wiring problem from the sensor to the PCM, or the PCM is faulty. I would suspect a wiring issue.
Customer: replied 1 year ago.

Ok, I will check the wiring connections from the CKP to the PCM. Will let you know how it goes

Customer: replied 1 year ago.

Alright, I looked for continuity on all 3 of the crankshaft sensor's cables. From the sensor to the pcm. They all have continuity.

What else should I check? Should I check for power or ground? Thanks.

Expert:  Ron replied 1 year ago.
Yes I would check all ground to the engine since you had the engine out as well as power and ground to the PCM.
Customer: replied 1 year ago.

I checked for power to the pcm (pins 3 & 9) and they do register the battery voltage. I also tested the power grounds on the pcm (pins 11 & 12) they are good too.

For the CKP sensor, I got positive results on the 8v input, the ground, and the switching 5v signal which I checked by turning the engine by hand. Wires from the CKP sensor seem to be functioning correctly.

There's a ground cable that goes from the right cylinder head to the firewall which was a bit loose, so I fixed it up and placed a new one.

What else do you suggest checking? Did I miss a power or ground that I should be testing?

Expert:  Ron replied 1 year ago.
It sounds like you have a CKP signal at the CKP , did you check it at the PCM as well ? It sounds like you did the right testing. If you have a good signal and power and grounds at the PCM it should fire the injector. In most cases that would mean the PCM is bad but I find that kind of hard to believe if it was working before the engine was removed.
Customer: replied 1 year ago.

Sorry, I wasn't home today so I didn't read your message until now.

What other tests can I do to be 100% sure it's the PCM?

Also, I read somewhere that if the truck has a factory installed alarm and it is activated it will tell the computer to shut down the ignition system. I also read that there is a way to reset the alarm system by putting the key on the door and then connecting the battery. I did that but saw no difference. I have a little LED light close to the drivers side door that looks like an alarm, but I'm not really sure if I have alarm or not. When I purchased the truck I didn't get a remote key.

Any other ideas of possible causes?

Expert:  Ron replied 1 year ago.
If you have an alarm it will shut the injectors down and not the ignition. About the only way to check the PCM would be to replace it with a known good one. That being said, I'm not convinced the PCM is bad if it was working before you removed the engine.
Customer: replied 1 year ago.

I feel the same way as you. The tests we have done doesn't seem that the PCM is not working.

The problem I see is that the injectors are not pulsing like they should.

What can cause the problem of low pulses at both the injector and the spark cables if the CKP is working ok?

..Update.. While I was waiting on your response I checked the injectors. I pulled out the rail with the injectors connected on and I put a plastic bag on each injector, with the harness connected. The results are:

1. When I turned the key to the 'on' position, the injector #2 sprayed gas.

2. When I cranked the engine various times, the injectors spurted out gas alternating.

3. When I checked with the NOID light I would see it light up at the beginning and then after 3 cranks, no more light coming on.

I don't get why the injectors are not pulsing as they should if they are doing their job with spraying the gas.

Expert:  Ron replied 1 year ago.
The injector and the spark plugs get there pulse signal from the signal from the CKP to the PCM. The injectors need to pulse as long as the engine is cranking and or running. Are you sure you do not have wiring and or ground issue?
Customer: replied 1 year ago.

Yesterday I was checking one of my grounds. The one that is bolted close to the power steering (which goes to the negative terminal post) and another smaller ground cable that is bolted very close to the battery. I found that the larger cable had some corrosion. I will buy a new cable and will let you know how it goes.

I was also checking pin #3 from the pcm to see if it had power, and I also checked the ASD and Fuel Pump relays by checking to see if they had B+ on their terminal 30 using a test light. They all checked good with B+, BUT without the key switch in the "on" position.

Is this correct or should it have power only when it's in the on position?

Expert:  Ron replied 1 year ago.
The red/white wire at the relay needs to be hot at all time with power from the Fuse D in the power distribution center.
Customer: replied 1 year ago.

I sent you a short video of how the engine sounds. The very first time we tried (This afternoon) it sounded like the engine was about to start. But I didn't record that.

VIDEO: http://youtu.be/6U2ArbnnfUc

Tomorrow I'll recharge my battery to give another try. I changed the ground cable that goes to the battery and the ground cable that goes to the relays.

When I didn't get pulse on the injectors and spark plug cables I checked the resistance on my engine coil on the secondary it was a bit off the specs and I bought another one. But was a very cheap one, I don't know if it might affect my performance because when I checked the spark color I didn't see a blue or white light. Instead It was a red and yellowish color.

One thing that I have noticed since the first time that we tried to start the engine is that the light indicator with the figure of an oil lamp has never turned off. All the dashboard indicator lights like abs, check engine, brakes, gas, ect.. appear and then go off with the exception of the oil lamp figure.

I also checked for computer codes but it didn't show any.

Let me know what you think.

Thanks

Expert:  Ron replied 1 year ago.
Nella, Are you sure you have your timing set correctly, from listing to your video it sounds like the timing is off.
Customer: replied 1 year ago.

The timing is set correctly. The timing chain used to be very loose and off. But I added a new tensioner and adjusted the timing.

Expert:  Ron replied 1 year ago.
It sure seems to crank like it the timing is advanced don't you think?
Customer: replied 1 year ago.

I have the timing right at 0 TDC. Maybe it could be that the distributor rotor is 180 degrees off, I don't know.

Expert:  Ron replied 1 year ago.
I would not think it a 180 out but perhaps a tooth or you have it to far advanced because in the video you sent it sounds like its kicking back.
Customer: replied 1 year ago.

I'm not sure if you are able to hear it clearly, but in the video I sent you there is a loud bang that sounds like a metallic-like noise. It's heard every time I crank the engine as it wants to start up.

Expert:  Ron replied 1 year ago.
I did not hear a loud bang but I did hear the engine kicking back.
Customer: replied 1 year ago.

Since I am getting the low oil pressure gauge, I am going to remove the oil pan in order to check the oil pump and see if everything is ok.

About the timing, are you saying that I would have to remove everything in order to get to the timing chain just to move it a tooth?

Expert:  Ron replied 1 year ago.
If the timing is off then yes you would have to remove the cover to change it and or even check it for proper alignment. Have you ran a compression test, usually if timing is off it will affect the compression.
Customer: replied 1 year ago.

I while back I measured the compression which was even between all cylinders. The TDC is at 0. But I have the measurements on the pulley for -5, 5, 10, etc. as well.

Expert:  Ron replied 1 year ago.
Well something is sure missing here and I'm not sure how to advise you at this point. If you have good spark, compression , injector pulse and proper fuel pressure the damn thing should start.