Hello all! I'm a new member, but I have gained loads of knowledge as a lurker on these forums throughout the years. Thanks for the resource! Now, onto the problem:

My dad and I recently purchased a 1998 Ram 3500 V10 with 190K miles on it. The truck ran perfectly when we bought it and we drove it about 60 miles home with no issues. Pulled it into our shop to replace the front ball joints and do some general maintenance - belts, etc. One morning about two weeks ago it was cold outside, so I started the truck to warm it up a bit before leaving in it to go to work. Walked away for a few seconds and I noticed it was running erratically. Finally the truck died. Started the truck back up again and it did its usual start routine. Up to about 1200 rpm, back down to idle, die. Now the truck just won't start at all. No fire, misfire, NOTHING. Turns over fine, but no start. Now, on to the things that I have changed/checked:

1) Changed fuel pump. Whoever had it before had cut a hole in the bed above the fuel pump. The assumption was there had been a problem there before, so start with something that may be obvious. After the fuel pump change, the same issue was present. Started the truck, was able to get it to rev for a few seconds and then it died. No start at all after.
2) Checked/swapped relays and inspected all fuses in both the PDC and the in-dash fuse panel. All look fine.
3) Changed Crankshaft Position Sensor. Still no start.
4) Changed Camshaft Position Sensor. Still no start.
5) Changed MAP Sensor. Still no start.
6) Changed Throttle Position Sensor. Still no start.
7) Checked spark coming from both coil packs. Truck seems to have hot, blue spark at regular intervals.
8) Pulled three or so different spark plugs. They are soaking wet with fuel.
9) Checked fuel pressure. Fuel pump cycles on when the key is turned on, increases from about 40 lbs to 50 lbs when the starter is engaged.
10) Checked compression because I thought maybe the timing chain had either broken or skipped a tooth. Truck has at least 150 lbs of compression in each of the cylinders I tested.
10) I thought the next step may be the PCM. However, all lights in the truck come on in the dash, and the mileage displays correctly. Check engine light comes on when the key is turned on, fuel pump primes as it should when the key is turned to "run." I can connect a scan tool and it connects to the computer just fine. Displays no stored codes in the computer.

At this point, I am at a total loss for what this could be. I hope I have explained my problem sufficiently. Any/all help would be greatly appreciated because I am about to pull my hair out over here! Thanks in advance.

 

Does the truck have 2 water temp sensors? If the one for the PCM fails and reads really cold your truck will dump tons of fuel. What brand sensors did you use? The cheap ones from the parts stores don't always speak a language the PCM understands. Get Mopar sensors or Standard Motor Products if you have an Autovalue or Bumper to Bumper Store. BWD is not the same as StandardMP. It is a really cheap line manufactured by Standard. BWD= broken when delivered

 

Thanks so much for your suggestions! The crankshaft position sensor I got was a SMP from RockAuto. I thought that was going to fix the problem, because I had a similar problem on my Jeep Cherokee XJ with the crank sensor and I assumed that was going to fix it. The camshaft sensor, MAP sensor, and TPS were from AutoZone... against my wishes. At the point I changed those, I was just looking to get the truck running and finish diagnosing the problem and get a better brand after diagnosis and use the AutoZone parts as emergency on-the-roadside parts. I do believe the parts I got are working simply because the truck is getting good, regular spark. The thing I noted most was how soaked the spark plugs were when I pulled them. I turned the engine over with a couple of them out and it just seemed like waaaaaay too much fuel was shooting out of the cylinders.

To be honest, I am not sure how many temperature sensors the truck has as I had not even considered one of them being the problem. I know there is one by the water neck on the front. Would you care to point me to the other one? If the sensor you're talking about causes loads of fuel to be dumped into the cylinders, you very well could be onto something. What I can tell you is it was approximately 18 degrees F when the issue started. The truck started perfectly and idled for about a minute and then all of a sudden acted like it was flooded. Then the start semi-normal, idle down, die thing started. Now it doesn't do anything. Thanks again for your reply!

 

Just to follow up... after doing some research, are you talking about this sensor?

https://www.autozone.com/engine-mana...036/195764_0_0

If so, you may be onto something.

 

Nope, you want the engine coolant temp sensor. I do believe your truck has only one, and it should be fairly near the thermostat housing. It will be a two-wire sensor, that screws right down into the coolant passage on the intake. My guess is, yours has failed, so the PCM thinks it's something to the tune of -40 degrees outside, so it positively DUMPS fuel into the cylinders, trying to get a mixture that will burn. You can try stomping the gas pedal to the floor, and holding it there while cranking, and see if anything changes. (puts the PCM into 'clear flood' mode, and dramatically dials back the amount of fuel injected) However, depending on your plugs, they may simply be too wet to fire inside the combustion chamber. (champions were notorious for that, flood 'em out once, and they were useless.) Also, if you have some variety of 'rare-earth' plugs, (platinum, iridium, et. al.) get rid of 'em, and install some plain ol' copper plugs. (I used NGK's, work great)

Since you have a scanner, check and see what the PCM thinks engine temp is. If it's some stupid low number, and it isn't actually that cold out, there's your problem.

 

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It would be one of these. Maybe you're also having a problem with the IAC. Hey You has a V10 and knows more about the electronics. On the V8 you can clean the well under the IAC valve, I'm not sure if the V10 is similar.

 

I once had a hard miss pulling a trailer at night. Trying to diagnose it on the side of the road, I pulled the ends off of two expensive but weak Granatelli solid core wires. I carry spares and that's the only reason I did not end up sleeping in my truck. I found two cylinders with burned plugs and as it turned out later bad/warped exhaust valves. Some clown said he knew "a lot" about "those Rams" told me I could isolate the misfire by pulling injector wires. Said clown never once stuck his head under a V10 Ram hood is my guess. I needed a better way to drop cylinders. Here is what I came up with:




Took some stainless wire and bent it into a flat "S" shape, tucked it up under the coil end. Now in order to drop a cylinder I just hook my test light to ground and short one cylinder at a time. They are right about the V10 running so smooth, thank Lamborghini for the oddball firing order, crankshaft arrangement, nothing at all like a Detroit V8.

 

Check your Factory Service Manual/Wiring Diagram, if you don't have one, you are wasting your time and the time of everybody else, get one. See if you agree with this. The way I understand it, with truck powered up, the ASD relay provides constant power to the fuel pump, coils and injectors. The PCM provides the ground for each of these in the proper sequence. You said you have a flooded no start condition, spark and good fuel pressure. If the ground circuit(s) to the PCM for (some of) the injectors was shorted before getting to the PCM you might have a constant open injector(s). If intermittent ground, then a misfire. It would be worth it to find the pinout for the injector circuits, and check them end to end for continuity or intermittent loose breaks.