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2003 Dodge Ram 1500

Hi all,

I’ve been having misfiring issues with my parent’s pickup and wanted to see if you all could provide some feedback. Since this isn’t my vehicle please bear with me with the sketchy maintanance history since I didn’t maintain it.

The vehicle has a had a history of misfiring which prompted a replacement of two ignition coil packs. Recently the truck just stalled on the highway and we were able to coax it back to the house. I borrowed a scan tool from a friend and after several scans, clearing the computer and rescanning, the codes that kept coming up were P303, P305, and P307. These were misfiring codes on cylinders 3, 5 and 7.

In order to try and isolate the problem more I moved the ignition coil packs from cylinders 3, 5 and 7 over to 2, 6 and 8 to see if the codes would follow the packs. Instead I got P300 which is random misfires.

I then went ahead and started to disconnect the coil packs one by one to see if the truck would idle differently, it didn’t on 4 coil packs so I went ahead and ordered 4 replacement packs for them.

The new coil packs came in, I tried to start the truck before doing any work to see if the truck would still start and it did idle. I then changed the four packs and tried starting the truck again and now it only cranks over but won’t start up.

I then checked fuses, all good. Then checked to see if there was pressure on the fuel rail, it was about 50psi. Then started doing a compression check on the cylinders. Turns out I was able to check 6 out of the 8 cylinders, which they read 135psi, the other turn seem to have been threaded in incorrectly. I wasn’t even able to get them out with a cheater bar. In trying to perform a compression test though I noticed that some fluid squirted out of the spark plug hole on cylinder 5. At first I thought it was gasoline but it seems to be more like coolant. I looked at the dipstick and noticed that the oil viscosity was light and had a caramel color to it. I drained the oil and the viscosity did look thin but I seemed to also get a sense of gasoline smell with the oil. I’m at a loss now on what might be the issue with this truck not starting up.

Any help or direction would be greatly appreciated.

You’re describing coolant contaminating the oil.

So there’s either an intake manifold or a head gasket leak. And if enough coolant gets into the cylinders the engine won’t fire.


The gasoline odor from the oil suggests blowby. Low compression readings suggest the same.
In short, it sounds like the engine has seen better days.

I’d suggest changing the oil and getting an overall picture of what the oil looks like, not just what was on the dipstick. It seems that the misfires were all on one side of the engine (all odd cylinders) unless I’m misunderstanding how the engine is labeled. Look for a vacuum leak on that side of the engine. Of course a failed head gasket or intake gasket could cause this. I’d suspect the intake before the head gasket, as these engines aren’t really known for blowing head gaskets, but since your oil seems contaminated, it’s certainly possible. What does the coolant look like?