I was driving 2004 Dodge Ram 1500 5.7 Liter Hemi 4x4 Automatic and it just died on me as I was going down the road, before I could get it parked, so I put it into neutral and I tried to start it back up and it backfired...I got it towed, now when I go to try and start it it will crank over but it will not fire up and still continues to backfire. Here is a list of things that I have done to it so far...The fuel pump works, it's got fuel pressure to the engine, all of the fuses and the relays are good, it is getting spark/fire... Here is what I found that was working properly... It has low oil pressure and hardly any compression at all whatsoever...I'm completely stumped,I just don't know what to do.... If you could help me in any way whatsoever I would really appreciate it...Could it be clogged up catalytic converters, or does it need a new oil pump? Or could it be the timing, and if so is it worth fixing,if so how much is it going to cost? Would I be better off if I was to just replace the whole engine? Please help me.....
I don't think we have enough information to isolate this problem
As Paulster2 mentioned, any codes might help. Can you get us the codes? Loss of a sensor or the Engine Control Unit, ECU, the engine computer could cause it to die and just pop. It could be a crank sensor, it could be the ECU. It does not explain the low oil pressure. However, some engines will not start with low oil pressure, but usually it does this by disabling the spark and you say it has good spark and/or fuel. Most of these sensor or ECU problems will show in the OBD2 codes. A low battery will also cause ECU or injector problems. Is the battery good?
An engine needs three things to at least pop.
You already said you had hardly any compression. How do you know this, is it the sound of the starter or did you check compression? Is the compression low across all the cylinders or just some? Could you give us the compression values?
It could be a timing chain. This often causes drop in compression because of the altered cam timing. There should be a timing mark on the crankshaft. The number 1 cylinder should have both the valves completely closed on one of two revolutions. If they aren't you know the timing chain has slipped. If the valves aren't moving, then you have probably lost a timing chain, cam gear or similar.
A engine with clogged catalytic converter(s) should still have compression.
You don't say how many miles are on the engine. Eventually metal fatigue catches up with engines. It could be a catastrophic failure of the crankshaft, camshaft, flywheel, snapped oil pump shaft, etc. Check for any unusual holes in the engine, dents in the block or covers, or metallic noises when cranking the engine. Look for any unexpected oil leaks or pools of oil.