1998 Dodge Ram no start

First of all, stop replacing random parts. You're going to add a whole bunch of variables and turn it into a mess. You had the battery disconnected. That means idle speed is going to be too low. You'll have to hold the accelerator pedal down 1/4" for the engine to start and stay running. Have you tried that?

When you replaced the crankshaft position sensor, was there a spacer on the end to set the critical air gap?

What year truck did the engine come from? Which flex plate did you use, the original one from the truck or the one from the donor truck?

I can't find the picture in the service manual, so the first thing I would do is remove the inspection cover from in front of the transmission, and turn the crankshaft by hand while watching the square holes in the flex plate. There are different hole numbers and configurations and you probably have the wrong flex plate. Some of them have four sets of three holes to identify each cylinder, and some have three holes, three holes, three holes, then four holes, as I recall. The set of four holes identifies cylinder number one. You might also do a search for the flex plate part numbers. If they're different between the two years, you're going to have to use the one made for a '98.

The next thing is to remove the crankshaft position sensor to see if it's broken. A new one from the dealer will have a thick paper spacer stuck on the end to set the air gap. You need to install a new spacer when you reinstall those. A lot of aftermarket sensors have a thin plastic rib molded on the end instead. When you reuse one of those you're supposed to cut off the remaining part of the rib, then use a new paper spacer.

The next thing is to see if the automatic shutdown relay is turning on during cranking. Don't go by fuel pressure because the ASD relay is going to turn on for one second after you turn on the ignition switch. The fuel pump will run for that one second so pressure is going to be up. You want to see if that relay turns on again during cranking. The easiest way to do that is to measure the voltage on the feed wire for the ignition coil, any injector, or either small terminal on the back of the alternator. That wire is usually dark green / orange. The Engine Computer turns the ASD relay on when it gets pulses from the crankshaft position sensor and from the camshaft position sensor in the distributor.

If the ASD relay is not turning on during cranking, check for diagnostic fault codes. You might get lucky and one set indicating which sensor signal is missing.

Did you notice there's two different flex plates and they have different holes? One has eight individual holes, (which I don't remember), and one has the groups of holes. What you're describing is exactly what happens when the wrong flex plate is used, so I strongly suggest checking that first. If you can't see the holes through the inspection cover, you'll have to remove the starter, then look through there.

There's no timing to set. The camshaft position sensor in the distributor synchronizes the firing of the injectors. Ignition timing is set by the crankshaft position sensor.

Are you saying you had a 360 but now it's a 318? I know there are a few engine sizes you can change on Chrysler products but you're getting into a complicated area when there's too many new variables. I don't know what the ramifications are for fuel metering. The 360 is going to need more fuel per cylinder, and that has to be done either by holding the injectors open longer or they must have a larger flow rate. I know you can go from a 2.7L in the Intrepids to the better 3.5L with no other changes needed. You even keep the same Engine Computer. That tells me the injectors have to be bigger because the computer is going to hold them open for the same amount of time each time they fire. Unfortunately for your project, you really can't go by part numbers on the computers because any time one is rebuilt, or when a design change is made, they get a new part number. The only thing you can do is if you see a listing that says that computer is for either engine, you'll know you can use the one you have with the new engine.

The other thing you have to consider is the 340 and 360 from the early '70s were externally balanced. There are weights added to the vibration damper and torque converter. If you mix those up you'll have an irritating vibration. I don't know if that still applies to the '90s engines. The way to tell is to look at the vibration dampers. The 318's will be symmetrical all the way around. If the 360's is externally balanced, it will have added material in just one section inside the outer ring.

Did you check the holes all the way around? Are there eight individual holes spaced equally all the way around. Was that the same as on the original one?

The next thing would be to connect a scanner to look at live data and see what the camshaft position sensor and crankshaft position sensor are saying. I use Chrysler's DRB3 scanner. It lists both sensors as "no" or "present" during cranking. It will also show if the Engine Computer is turning on the automatic shutdown (ASD) relay when it gets those two signals. If the crankshaft position sensor is shown as a steady "present", we'll know the flex plate and sensor spacing are okay.

Sorry to leave you hanging. I had a house fire Feb. 28.

I can't read that huge sentence with no punctuation. I'm having a hard time understanding what you're saying. The ASD relay is turning on, but you think it's the cause of the problem? "The timing is set perfectly". How did you check that? Ignition timing is not adjustable. It is set by the crankshaft position sensor and is not adjustable. Turning the distributor just changes when the injectors are fired, and you'll never notice those changes. There's no such thing as an "upgraded" Engine Computer. It runs the injectors, ignition coil, and other things. There will be improvements made for reliability when one is sent in to be rebuilt, but other than that, they all do the same things. It IS very possible the 318 and 360 can use the same computer, but this is where the year of the engine and computer must match the notches in the flex plate. I don't know what the ramifications are when switching years. I DO know if both flex plates are the same, everything else should be the same, but if the flex plates are different, and you need a different computer, I don't know if the wiring harnesses will be the same.

If you do have spark, you should have injector pulses too. Spark indicates the computer is reading the flex plate notches and is turning on the ASD relay. Try using starting fluid to be sure.