Timeless Posted October 18, 2013 Share Posted October 18, 2013 I have searched numerous boards for some answers and unfortunately, I think it has only created more questions. When I bought my 1987 Comanche last August the motor sounded great when it was cold. After the test drive I noticed it was a bit noisy, but nothing too alarming. Once I started to drive the truck home, I realized the engine was making a ruckus. A year later, I am finally ready to try to diagnose and rectify whatever the problem is. When cold, the engine purrs. Seriously, its extremely quiet. Once it is warm, it sounds like a diesel. It sounds like the valve train is the source of the noise and when driving, at least one of the valves has a very audible tick. When the engine see's higher than 3000rpm, the valve noise is very loud...I would liken it to a box of marbles. The previous owner supposedly replaced the lower end with a low mileage late model xj block. I do not know how to confirm or disprove this. When he supposedly swapped blocks, he used all of the RENIX components including the head, intake/exhaust manifold, etc., and replaced the intake/exhaust manifold gasket. I suppose the question is, are there any ways to better diagnose if the intake/exhaust manifold is shot or whether there is something worse going on with this engine? how about to confirm the year of the block? I have no real issue with putting a new motor in the truck, but I don't want to do it unless it is necessary. Thanks in advance. Link to comment Share on other sites More sharing options...
ParadiseMJ Posted October 18, 2013 Share Posted October 18, 2013 One way to find a manifold leak is to seafoam the intake...a leak will be apparent and present itself as smoke INSIDE the engine bay. Link to comment Share on other sites More sharing options...
cruiser54 Posted October 19, 2013 Share Posted October 19, 2013 Which engine? Link to comment Share on other sites More sharing options...
Timeless Posted October 19, 2013 Author Share Posted October 19, 2013 Wow....after I posted I thought "I hope I didn't leave out any important and otherwise relevant information" and then re-read my post. Fail on my part. Its a 4.0. Link to comment Share on other sites More sharing options...
cruiser54 Posted October 19, 2013 Share Posted October 19, 2013 Wow....after I posted I thought "I hope I didn't leave out any important and otherwise relevant information" and then re-read my post. Fail on my part. Its a 4.0. Exhaust leaks are worse when cold and diminish with heat/warming. So does piston slap. Link to comment Share on other sites More sharing options...
Timeless Posted October 20, 2013 Author Share Posted October 20, 2013 The noise is not piston slap. Its certainly coming from the valve train. After doing some homework, the PO put in: mopar performance springs pn P4876062 mopar retainers pn P4452032 mopar locks pn P4529218 comp cams timing chain comp cams lifters comp cams 68-232-4 cam My fear is that something was buggered up when he did the install, but my understanding is that he was an army mechanic. Thoughts? Link to comment Share on other sites More sharing options...
Oyaji Posted October 21, 2013 Share Posted October 21, 2013 Could be the stamped-steel rocker arms. There is no adjustment on them; presumably the hydraulic lifters are supposed to do the job, but they seem to have small limit for how much they can compensate for wear. . On my 4.0 HO the rockers were the culprit - when I changed them out the valvetrain noise went away. Link to comment Share on other sites More sharing options...
Timeless Posted October 21, 2013 Author Share Posted October 21, 2013 Thanks for the help. Any idea how I can better diagnose the culprit of the noise? I have no problem opening up the valve train, but I don't want to do it without some specifics to start looking for. Link to comment Share on other sites More sharing options...
cruiser54 Posted October 21, 2013 Share Posted October 21, 2013 Buy a mechanic's stethoscope.......... Link to comment Share on other sites More sharing options...
Timeless Posted October 22, 2013 Author Share Posted October 22, 2013 Cruiser, thanks, already have one actually. Its not much help at this time simply because the valve train makes so much noise. Oyaji, thanks for the tip. I figure I will have to pop off the valve cover soon so I will check them out. They are cheap enough to replace too. There is certainly more noise coming from the exhaust manifold side which leads me to believe there may very well be a leak, but it is likely not the only cause of the valve noise. I'm changing the oil today and will be adding a quart of Marvel Mystery Oil to clean/free things up and I'll see what happens. I recorded a few videos last night that might be helpful but I cannot get them to upload to imageshack. Link to comment Share on other sites More sharing options...
Timeless Posted October 23, 2013 Author Share Posted October 23, 2013 After the oil change today I checked various points on the head and valve cover. There is a pronounced tap from the front most portion of the head (assuming the first set of valves) on the drivers side. This tap can actually be felt when I put a screw driver on the valve cover or head, its that pronounced. Already ordered the valve cover gasket and expect that i will be ordering some other parts once I figure out what is going on with this thing. Once I get the valve cover off, can anyone offer some advice with how to best diagnose if I am dealing with a collapsed lifter, worn rocker, etc? Thanks! Link to comment Share on other sites More sharing options...
cruiser54 Posted October 23, 2013 Share Posted October 23, 2013 Rotate the engine to #1 TDC and see if the rockers feel loose . Setting Your 4.0 at #1 TDC With #1 spark plug removed, turn the engine over clockwise using the 3/4" front crankshaft bolt. You will see the degree marks on your front cover. Mark the 0 with chalk or white-out.You will see the timing mark on the balancer. Mark it with chalk or white-out. While turning the engine over, put your finger/thumb over #1 spark plug hole. As the mark on the balancer approaches the marks on the front cover, if you are coming up on #1 TDC, pressure in the cylinder will push on your finger. If there's no pressure, you're at #6 TDC and need to crank the engine over until you see the marks coming together and you get pressure. Set the mark on the balancer to the 0 mark on the front cover. Link to comment Share on other sites More sharing options...
Timeless Posted October 23, 2013 Author Share Posted October 23, 2013 Cruiser, you're the best! Link to comment Share on other sites More sharing options...
cruiser54 Posted October 23, 2013 Share Posted October 23, 2013 Let us know what you find. Link to comment Share on other sites More sharing options...
Oyaji Posted October 23, 2013 Share Posted October 23, 2013 Rotate the engine to #1 TDC and see if the rockers feel loose . Setting Your 4.0 at #1 TDC With #1 spark plug removed, turn the engine over clockwise using the 3/4" front crankshaft bolt. You will see the degree marks on your front cover. Mark the 0 with chalk or white-out.You will see the timing mark on the balancer. Mark it with chalk or white-out. While turning the engine over, put your finger/thumb over #1 spark plug hole. As the mark on the balancer approaches the marks on the front cover, if you are coming up on #1 TDC, pressure in the cylinder will push on your finger. If there's no pressure, you're at #6 TDC and need to crank the engine over until you see the marks coming together and you get pressure. Set the mark on the balancer to the 0 mark on the front cover. . That will just get both valves closed for #1 - you will need to repeat this 5 times (each 120 degrees of crankshaft rotation past #1 TDC) to get each of the other cylinders to top dead center on compression stroke. This is to ensure that both valves for each cylinder are closed and thus that their rockers are maximally slack when you check them. . I guess that you could use how slack the rockers are for #1 as a general indicator of how worn the others are, but since you have the valve cover off, may as well check them all. Link to comment Share on other sites More sharing options...
Timeless Posted October 23, 2013 Author Share Posted October 23, 2013 Thanks guys. Oyaji, great advice and will do. I am hoping this is rocker arm related because it seems most of the other upper end parts were replaced. Seems the high performance springs could be causing a problem with the factory rocker arms too. I will be getting to this sometime next week. Link to comment Share on other sites More sharing options...
Timeless Posted October 28, 2013 Author Share Posted October 28, 2013 I pulled the valve cover this evening to take a look at the valve train. Nothing blatantly obvious was wrong and the valve train is very clean and sludge free. The rockers in cylinder 1 were no better or worse appearing than the others despite a lot of ticking coming from this area. Most, if not all, of the rocker arms will move forward and back (parallel with the axis of the bridges). There is no apparent lash in any of the rockers even at TDC. I did find what I can only describe as "wobble" on a few. The arms had some play if rotated perpendicular to the bridge axis (parallel with front axle center line). I don't know if this could be causing the noisy valve train or not. I'm figuring that I will replace the arms and bridges just to eliminate them as the culprit as they are reasonably inexpensive. Link to comment Share on other sites More sharing options...
Timeless Posted October 31, 2013 Author Share Posted October 31, 2013 Got the new rockers, pivots and bridges in. Disconnected the coil to get some oil flowing and cranked the engine over a few times. Reconnected the coil...and the truck will not start. I'm getting fuel, the plugs are wet with gas, but I'm not getting any spark. I know I need to check the CPS. If it checks out, how can I check the coil and ICM? Link to comment Share on other sites More sharing options...
Timeless Posted November 1, 2013 Author Share Posted November 1, 2013 I tested the CPS and the resistance checked out fine. The voltage reading when cranking was low so I replaced it with my new spare. The engine still would not fire. Resistance through the CPS was again fine and the voltage when cranking was no different. I'm not sure what this means. All fuses under the dash are fine. Distributor cap, rotor and plugs were replaced in the spring. ICM contacts were cleaned about a month ago. Grounds were refreshed and C101 was cleaned in the spring. My understanding is that the ICM cannot be tested. So the last thing I can check is the coil before I have to start throwing parts at this thing. Any other tips? Link to comment Share on other sites More sharing options...
cruiser54 Posted November 1, 2013 Share Posted November 1, 2013 Test the CPS AV voltage output. Renix CPS Testing and Adjusting Renix CPSs have to put out a strong enough signal to the ECU so that it will provide spark. Most tests for the CPS suggest checking it for an ohms value. This is unreliable and can cause some wasted time and aggravation in your diagnosis of a no-start issue as the CPS will test good when in fact it is bad. The problem with the ohms test is you can have the correct amount of resistance through the CPS but it isn’t generating enough voltage to trigger the ECU to provide spark. Unplug the harness connector from the CPS. Using your voltmeter set on AC volts and probing both wires in the connector going to the CPS, crank the engine over. It won’t start with the CPS disconnected. You should get a reading of .5 AC volts. If you are down in the .35 AC volts range or lower on your meter reading, you can have intermittent crank/no-start conditions from your Renix Jeep. Some NEW CPSs (from the big box parts stores) have registered only .2 AC volts while reading the proper resistance!! That’s a definite no-start condition. Best to buy your CPS from Napa or the dealer. Sometimes on a manual transmission equipped Renix Jeep there is an accumulation of debris on the tip of the CPS. It’s worn off clutch material and since the CPS is a magnet, the metal sticks to the tip of the CPS causing a reduced voltage signal. You MAY get by with cleaning the tip of the CPS off. A little trick for increasing the output of your CPS is to drill out the upper mounting hole to 3/8" from the stock 5/16", or slot it so the CPS bracket rests on the bell housing when pushed down. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts. Revised 01-26-2013 Clean the ICM contacts: Renix Jeep ICU/Coil contact refreshing The contacts between the coil and the ICU on your Renix Jeep can become corroded and loose causing a complete or intermittent no-start condition. I recommend the following procedure as a maintenance precaution to insure this is eliminated as a possible cause now and in the future. The coil is attached to the ICU by two T20 Torx bolts. Remove these two bolts and lift the coil up off the ICU. You will see 2 pins and 2 sets of contacts. Clean both the pins and springy contact pieces with a good electronics cleaner and some fine sandpaper. Squeeze the springy contacts closer together with some needlenose pliers. Bolt the coil back on to the ICU. While you’re right there, unplug the connectors from the ICU and inspect the pins in the harness connector. Make sure the pins are not retracted into the connector. Spray out the connector and the receptacle of the ICU with the same good electronics cleaner you used earlier. I feel this procedure should be performed at least once in the lifetime of a Renix Jeep. Revised 04-04-2013 Link to comment Share on other sites More sharing options...
Timeless Posted November 1, 2013 Author Share Posted November 1, 2013 Cruiser, CPS voltage for the old CPS tested out to about .1V. So I thought that was the problem. After I got the new CPS in, it too tested out to .1V. Either I got a super dud CPS, my multimeter sucks, or its not the problem. I don't have a fully charged battery anymore from all the attempted starts the past few days, so that may be causing the low voltage read. Hopefully i will be able to charge it tomorrow. ICM/Coil contacts were recently cleaned. Link to comment Share on other sites More sharing options...
cruiser54 Posted November 1, 2013 Share Posted November 1, 2013 Yeah. Charge the battery. Link to comment Share on other sites More sharing options...
Timeless Posted November 1, 2013 Author Share Posted November 1, 2013 Charged the battery this morning. Will not start. Measured CPS voltage and its still at .1Vac. This is the same as the old CPS which I replaced. Is there a sender on the flywheel that could have gotten screwed up? The truck was running fine (except for an intermittent long start time) prior to me pulling the valve cover and replacing the rocker arms so I'm at a loss on what happened here. Link to comment Share on other sites More sharing options...
carnuck Posted November 1, 2013 Share Posted November 1, 2013 Rockers may be too tight and holding the valves open. Before you pull it apart, try a spoonful of fresh gas in the throttlebody and see if it tries to fire up. Link to comment Share on other sites More sharing options...
Timeless Posted November 1, 2013 Author Share Posted November 1, 2013 I am getting no spark at all and plenty of fuel. Link to comment Share on other sites More sharing options...
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