Okay guys since my truck I am working on I have gotten a new Dakota for a work truck. Got it for 1100 with 139,000 miles. It's 4wd ext cab with a 318 Auto. I bought it and they told me sometimes on a hill it would stall out and die and would have to sit for awhile before it would start back up they said they were told by a mechanic that it had air in the fuel but that's all I know. I have tested fuel pressure and when I start it up with it being completely cold it's running about 39 psi at an idle. Doesn't really change with throttle. If I come to start the truck when it's completely cold it will fire right up. You let it run a few mins and shut it off it will just crank and not start when u try to fire it back up. Let it sit till it's cold again or for about 15 mins it fires right up.

 

Did some more testing and the truck can seem to be running smoothly holding about 37 psi and then u shut it off and try to start back and it turns over either many times and sputters to life or it just cranks with no start. I also checked the notorious splice under the fuse box. and it appears to be perfectly fine. I can also hear the fuel pump kicking on. Also showing no check engine light. Looked down into the plenum and it appears to be a little stained oil colored after all these years of running but it doesn't look any different to me then my 3.9 did and it ran fine. When cranking and running the fuel pressure gauge when u watch it bounces fast by like maybe 2 to 3 psi.

 

Need to know what's missing when it won't start. Check and verify you are getting good spark.

 

 

How are you testing for spark?

 

According to service manual holding spark plug 1/2 inch from ground. And observing for a steady strong spark.

 

Spark plug wire? (I just use a spare plug I have layin' about....)

Try testing with the coil wire. If you still are getting a weak spark, may be a dying coil.

 

I pulled one of the spark plugs out of the engine and stuck it in the spark plug boot to test. I also tested from coil itself and its definitely Stronger than from the spark from the plug wires but not sure how intense it should look. Coil ohms out for the correct resistance according to the service manual so it's in spec.

 

It may be in spec, but, that doesn't necessarily imply that it's "good".

Should get a nice fat spark from the coil wire. Ideally, it should be blue, and you should be able to hear it SNAP quite clearly. The spark will get weaker with age..... so, if you get a snap you can hear, and the spark looks nice, color isn't the complete deciding factor. If it looks consistently weak, replace the coil.

 

I don't hear a snap from it so that's possible it could be bad. But would it sometimes work and sometimes not work when it is getting weak bc the truck will start when it's cold