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Derek Werner
Derek Werner, Dodge Technician
Category: Dodge
Satisfied Customers: 137
Experience:  ASE Master Technician, L1 Advanced level specialist
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I have compression....I 't have a pulse....4.7L 2003 dodge

Customer Question

I have compression....I don't have a pulse....4.7L 2003 dodge ram 1500 4x4 no start
Submitted: 1 year ago.
Category: Dodge
Expert:  Derek Werner replied 1 year ago.

Hello and welcome!

Do you have a scan tool that can read data?

Are there any fault codes in the system.

The most common causes for this concern is a failed crankshaft position sensor. While cranking the engine you should have a rpm reading. It is somewhat common for the pcm to fail also, a no buss message will be displayed in the cluster and the check engine light will not turn on when cycling the key.

Thanks

William

Customer: replied 1 year ago.
No check engine light , no codes...this is a replaced motor ...I replaced the camshaft sensor...there is no distributor on this motor
Customer: replied 1 year ago.
Basically I'm not getting a pulse spark to the plugs....I'm getting power to the coils
Expert:  Derek Werner replied 1 year ago.

Did you install a OEM crankshaft sensor? Aftermarket sensors are know for failure even if they are new.

The pcm ground each coil individuality to control spark.

Expert:  Derek Werner replied 1 year ago.

what engine is in your truck?

Customer: replied 1 year ago.
it was a stock sensor I used
Customer: replied 1 year ago.
4.7
Expert:  Derek Werner replied 1 year ago.

Check the year of the engine. The VIN is on the right hand side of the block just ahead of the motor mount.

Expert:  Derek Werner replied 1 year ago.

10th digit in the VIN

Expert:  Derek Werner replied 1 year ago.

There is a early/ late design crankshaft position sensor tone rings that can cause a no start. They should be checked to match up

Customer: replied 1 year ago.
Motor is an 02 truck is 03
Customer: replied 1 year ago.
Where is the crankshaft location if there is no distributor?
Expert:  Derek Werner replied 1 year ago.

The Crankshaft Position sensor is mounted into the right rear side of the cylinder block. It is positioned and bolted into a machined hole.

Engine speed and crankshaft position are provided through the crankshaft position sensor. The sensor generates pulses that are the input sent to the powertrain control module. The PCM interprets the sensor input to determine the crankshaft position. The PCM then uses this position, along with other inputs, to determine injector sequence and ignition timing.

a tonewheel is bolted to the engine crankshaft. This tonewheel has sets of notches at its outer edge.

The notches cause a pulse to be generated when they pass under the sensor. The pulses are the input to the PCM.

Expert:  Derek Werner replied 1 year ago.

If the engine is a 02 it could have the wrong style tone ring as this was a cross over year, and the correct year of engine will need to be installed. Do you know how many connectors the pcm had going to it on the vehicle the engine came out of?

Customer: replied 1 year ago.
That information I don't have....The truck was exactly the same as mine just a year older....So then where is the camshaft sensor....I may have the two confused....
Expert:  Derek Werner replied 1 year ago.

If the engine is the same year, 10th digit on the both engine blocks are the same you should be ok there. If the engine installed is from a Durango it could be the split year.

The Camshaft Position Sensor on this engine is bolted to the right-front side of the right cylinder head.
The CMP sensor on this contains a hall effect device called a sync signal generator to generate a fuel sync signal. This sync signal generator detects notches located on a tonewheel. The tone-wheel is located at the front of the camshaft for the right cylinder head. As the tonewheel rotates, the notches pass through the sync signal generator. The pattern of the notches (viewed counter-clockwise from front of engine) is: 1 notch, 2 notches, 3 notches, 3 notches, 2 notches 1 notch, 3 notches and 1 notch. The signal from the CMP sensor is used in conjunction with the crankshaft position sensor to differentiate between fuel injection and spark events. It is also used to synchronize the fuel injectors with their respective cylinders.

Customer: replied 1 year ago.
Ok I will have to check the cmp sensor as well...so what exactly can cause there to be no pulse going to the spark plug....just to recap
Thank you
Expert:  Derek Werner replied 1 year ago.

No problem at all, Thank You!

A failed ECM, No ckp signal, if there is no cmp the engine should still start but will have a long crank time.

Also injector pulse should be checked this will verify proper operation of the ecm and ckp.

A security system or theft light on could cause the concern.

Expert:  Derek Werner replied 1 year ago.

Did the old engine run before the swap was done?

Customer: replied 1 year ago.
the old engine fired up no problem...it was blown from over heating....(previous owner) I picked up the truck really cheap and found a motor cheap so...here we are...after testing all the volts and fuel pressure and compressions everything at proper levels...but no start, I took off the cmp sensor from the working motor and put the one from the previous motor and still no start. ..no pulse to the plugs
Expert:  Derek Werner replied 1 year ago.

do you have a test light to check for injector pulse. Or a Noid light can be used. The only problem that can really cause this is a missing ckp signal to the pcm, if the engine did run its likely not a pcm failure.

Try installing the ckp from the old engine, you will need to remove the starter to gain access.

Customer: replied 1 year ago.
Ok I will check that out tomorrow. ...it must be the ckp signal.....it agree the pcm should be ok...possibly the wiring harness?? And possibly the factory alarm?
Expert:  Derek Werner replied 1 year ago.

A theft light would be illuminated in the dash and the engine should start up for a few seconds and die with a fault in the security system.

And if the wiring harness was not damaged in the engine swap and installed correctly a wire harness problem is not very likely, a fault code should show up on the scan tool if a wire was open or shorted.

I would start with the ckp this is a easy part to change.

Customer: replied 1 year ago.
those points all.make sense...thank youI will have to look into the ckp sensor....which is located here the tranny bolts up? On the top or bottom?? You said I had to remove the starter?
Expert:  Derek Werner replied 1 year ago.

Yes the easiest way is to remove the starter, the sensor is hidden between the engine block and the starter.

By looking at the picture it looks like you wont have to remove the starter and it does not mention it in the service manual. Just be aware i normally have to take the starter out on the 4.7l .

Expert:  Derek Werner replied 1 year ago.

I could be wrong on having to remove the starter but i hope the picture helps out.

Customer: replied 1 year ago.
Ok I will check it out and get back to you tomorrow. ..
Customer: replied 1 year ago.
Thing is tho....if it were the ckp wouldn't a could show up?
Expert:  Derek Werner replied 1 year ago.

not always if the signal is weak or erratic it may not set a code. If the signal circuit was shorted to ground or power yes. Testing the CKP signal with a oscilloscope is the best way to do this.

Customer: replied 1 year ago.
Ya don't have one of those testers....I may purchase a new ckp tomorrow and try that....other than the ckp I'm lost with this situation
Expert:  Derek Werner replied 1 year ago.

P1391 is a Intermittent loss of cmp or ckp. This is the code that should set if the engine installed is the wrong year.

Expert:  Derek Werner replied 1 year ago.

or a wiring or sensor fault

Customer: replied 1 year ago.
Omg so then maybe it's not the ckp either? Since I'm getting no codes
Expert:  Derek Werner replied 1 year ago.

what type of scan tool are you using? not all aftermarket scan tools can read all of the codes stored in the pcm.

and 95% of the time a problem with the ckp is the cause for no spark, and no injector pulse.

But the only way to know for sure is to perform the proper tests, and have the tools to do this. I can not guarantee that replacing the ckp is your silver bullet, but at this point it is the best chance you have to getting your truck running. I am here to help i am sorry this is frustrating diagnosing electrical faults can be very difficult for any technician. I am just trying to give you the most information that i can.

Customer: replied 1 year ago.
I know and I appreciate it, your answers make alot of sense and are definitely pointing me in the right directions ...I unfortunately don't have all the testing tools but after trying the ckp sensor and I still.habe the same problem I will have my friend come.over with his testing tools and give it all a try!
Expert:  Derek Werner replied 1 year ago.

Not a problem, if you need help with any tests or anything at all please let me know. A test light is a cheap tool and can be used to check signal to the injectors.

I am going to call it a night i will be back on tomorrow to follow up with any other questions.

Thanks

William

Customer: replied 1 year ago.
Thank you and same here!
Expert:  Derek Werner replied 1 year ago.

Hi! any luck with getting your truck running?

Customer: replied 1 year ago.
Well I discovered that after pulling the motor a few wires got damaged at the plug....so I'm in the process of repairing these wires....I'm hoping this is the cause but with no fault codes coming up makes me wonder
Expert:  Derek Werner replied 1 year ago.

what does the plug go to? On your year of truck wiring faults do not always set a code repair the wires and re test.

Customer: replied 1 year ago.
Truck is back in the same boat...no spark to the plugs
Expert:  Derek Werner replied 1 year ago.

i am sorry to hear that, Does the check engine light turn on when you cycle the key?

I am thinking you have the wrong engine installed for your truck with the old style crankshaft position sensor tone ring. this will not set codes and cause a no start condition.

Customer: replied 1 year ago.
I think your right about the wrong engine installed...the engine is a 2002 dodge ram with a 3 pin hookup to the ecm while my truck is an 03 ram with 4 pin...Would that be the problem? If so what's your best idea solution? I have the old motor still so can I drop the crankshaft and swap tone wheels or is that a disaster of a job to do? Better off to find another motor and sell this one??
Expert:  Derek Werner replied 1 year ago.

Yes If the replacement engine had a 3 connector ecm then it will not work with your truck. The 4 connector ecm uses a different tone ring, this is the cause for your no start i have seen this before.

I would not recommend trying to swap the crankshafts as the bearing clearances of the crank could be different. With the time and labor to swap the parts would be more then just finding and installing the correct engine. For a long term repair i would just find the correct engine and sell the one that does not work.

Customer: replied 1 year ago.
Ya that's what I figured...and changing the pcm is not recommended? How come?
Expert:  Derek Werner replied 1 year ago.

The pcm is a updated design and has different software and the pins and connectors will not be the same.

You might get it to work by replacing the engine wire harness but then you run into software issues and security system faults. And the other ECM will likely not be compatible with the other modules in the vehicle.

I have a good friend that is a dodge expert and aftermarket changes i will ask him what he thinks.