Jeep Engines - Oljeep

4.0L POWER TECH IN-LINE 6 (ENGINE ASSEMBLY) 2698. Reset ignition timing with vacuum advance linedisconnected. Ignition timing should be set tospecifications. Performance applications should settotal spark advance with vacuum disconnected.9. Set carburetor idle mixture adjustment (ifequipped). Adjust throttle stop screw tospecifications. Bigger camshafts require more idlefuel. Bigger jets may be required.10. Test fuel pump for pressure and vacuum.11. Air filter element should be replaced as specified in‘Lubrication and Maintenance’ section of your servicemanual. Replace more often when vehicle is driven industy or sandy areas.12. Inspect crankcase ventilation system as outlined in‘Lubrication and Maintenance’ section of yourservice manual.13. Inspect and adjust accessory drive belts.14. Road test vehicle as a final test.Basic TroubleshootingThe first step in troubleshooting is to define your problem.What does it do, when does it do it, etc? If it comes and goesor if it changes, then it can be very difficult to solve.Surprisingly, many of these apparently tough problems aresolved by simply going back to the basics. We’ll stick to thebasics because of our space limitations and let the “pros” whohave on-the-scene access to the vehicle work on the others.If a loss of performance is noticed while running theengine, ignition timing should be checked. If ignitiontiming is retarded about 16”, camshaft and accessory shafttiming with the crankshaft should be checked. The timingchain may have “jumped” a tooth. This is a nice way ofsaying check the camshaft centerline!We’d also suggest, at this point, to check TDC using theMopar Performance Parts positive stop TDC indicator tool(P4349737) and compare with the marks on the damperbeing used.Check fuel delivery system (electric pumps, etc.). Checkthe carburetor for wide open throttle and other functionsalong with vacuum leaks from hoses in the area. Also checkplug wires and wire ends.Next, run through the steps of the basic tune-up andcompare readings to initial ones. If you have no initialreadings, it is much more difficult to find a problem easily.You may want the engine leak tested to get better data.PERFORMANCE TROUBLESHOOTINGUnlike basic troubleshooting, in performance troubleshootingthere really isn’t anything “wrong.” The engine just isn’trunning as fast as it should be. Obviously, if there issomething wrong, it will make the vehicle go slow. But this isperformance troubleshooting. We are only going to concernourselves in this short discussion with the problems of usingthe wrong parts, using the right parts in the wrongapplications, or mixing the right parts for one application withthe right parts from a different application and ending up withthe wrong package. To illustrate this last point, assume thatyou install a high lift hydraulic camshaft in your standardproduction engine and use the stock valve springs. It isn’tgoing to work properl-no spring load, spring likely to gosolid, break, etc. There’s nothing wrong with the camshaft orthe springs, they just aren’t going to work together.In performance troubleshooting, the first step in finding anyproblem is to read as much about it as you can so that youbetter know what to expect. Note that defining yourproblem isn’t the first step.Refer to ‘Camshaft and Valve Gear’ section of this chapterfor camshaft and valve gear performance tips. These tipsare particularly good for finding which spring to use withvarious camshafts, and which camshaft to use for variousapplications. For many years Mopar Performance Parts hasput together parts packages for racing at variousperformance levels. These packages appear in Chapter 8,Off-Roading and Racing. All the parts needed to achieveeach level are listed by part number as they apply.Unfortunately, not all racers seem able to reach theperformance level listed when they use the parts. Then, ofcourse, the vehicle, engine, or Mopar Performance Parts isblamed. Troubleshooting race vehicles can be very difficultand, in many cases, an expert is required on the spot. Who’sthe “expert” going to be? Well, if you want to solve yourproblem without spending a lot of money and in areasonable amount of time, you’ll use this book.YEAR-END CHECKSAt the end of the race year there are several things that youshould check. Some items can change and should bechecked on all engines, while other items don’t reallychange but need to be known exactly. Any of the followingitems that you don’t know specifically, be sure to find outbefore you put the race vehicle into storage.The list is as follows: exact TDC, total timing as run (novacuum), as-installed camshaft centerline, finish line rpmas-raced, electric fuel pump delivery rate, as-raced batteryvoltage, torque converter stall speed, weight distribution.Each one should be recorded on your enginelvehicle logsheet for future reference.