CJN8
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Posts
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Distributor checks out and is set to spec. Also, the leak down test percentages evened out after the engine was warm, averages were about 9% to 11% which is pretty good I guess. I emailed Hesco and they said put 1/2" spacers under the CPS bracket and re-adjust my CPS to proper clearance. I did that today and it adjusted my base timing from 14* BTDC to 7* BTDC. I took it for a spin and no sign of any issues. My manifold vacuum went from about 17.5 to 16.0. I suspect this timing adjustment should make a difference in NOX production, only one way to find out. I will report back. Thanks Moses!
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So my detective work continues. Have you heard of setting fuel sync on the mpi kits and the jeep 4.0? The distributor does not adjust timing but I guess it does adjust fuel synchronization? Could this be an issue?
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Yes, percentages. My mistake. I did the tests at 90psi.
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Preliminary test while motor was not warmed up. I wanted to get my technique for finding TDC down. I used a vacuum/fuel pressure gauge so I could see exactly when the piston was at TDC. Worked like a charm Front of motor 1. 15.6 PSI (intake/exhaust manifold no hissing noise, valve cover hissing noise) 2. 12.2 PSI (intake/exhaust manifold no hissing noise, valve cover hissing noise) 3. 8.8 PSI (intake/exhaust manifold no hissing noise, valve cover hissing noise) 4. 7.7 PSI (intake/exhaust manifold no hissing noise, valve cover hissing noise) 5. 8.8 PSI (intake/exhaust manifold no hissing noise, valve cover hissing noise) 6 11.4 PSI (intake/exhaust manifold no hissing noise, valve cover hissing noise) Back of motor I am going to warm the motor to operating temp and repeat the test. Nate
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A little more diagnostics...I looked into the catch can which is between the valve cover and the intake manifold. The crankcase gases appear to have both oil and water present, probably due to the short trips I have been taking. I looked at the engine oil in the crankcase and there is no water or coolant there. I also looked at the coolant and there is no oil. I ordered a leak down tester today. The unit is made by OTC and got good reviews on amazon. I hope the test is telling. I will report back. Thanks for all the help Moses, it is much appreciated.
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From your write up on the FJ40... This engine ran sluggishly, the result of inadequate cylinder seal at the rings. The valves seated, the head casting and head gasket were fine, however, the combustion gases leaked past the rings and into the crankcase. Engines like this have a distinct "blow-by" smell in the crankcase oil. While the PCV system can recycle blow-by gases, the remnant of combustion gases remains in the oil. I have often referred to this odor, notable with the oil filler cap removed and the engine running, as the "smell of death" Bingo...this is how my oil smells, even after a change and I drive for 20 miles its there. I ordered a used oil analysis test bottle from blackstone labs on Monday to test this smell. I need to find a leakdown tester. Great help Moses. Thanks so much.
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The compression numbers offered earlier were before the rebuild. When I tested after the head rebuild I got about 135psi even across all cylinders. The shop doing the testing say it is 171, 174, 175, 174, 174, 170. I plan to test it again this weekend to verify the numbers. I am using a cheap harbor freight compression tester, maybe mine is not accurate? The real interesting thing is that I am really not getting any spark knock. I drove it home from the smog repair shop yesterday and pulled a long grade in 4th going 65mph and had no real issues with pinging. I do run 91 octane. I have the 4.2 cylinder head still. Yes I removed all spark plugs and held down the throttle during the compression test. I plan to re do the test this weekend to check my old numbers (maybe my HF tester is not as good as the shop tester). Could a small casting flashing bump cause the high NOX? I have been going through my head and I seem to remember that there was a small bump on one of the cylinders near one of the valves.
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I just recently had the head reconditioned. However, the Jeep failed NOX, roughly with the same numbers before the head was reconditioned too. The pistons were cleaned prior to the install of the reconditioned head. I have spent thousands trying to get my Jeep back on the road...my options have run out. My base timing is 14 BTDC, when I put spacers in will I see the timing drop? Will this be visible with a timing light?
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How do you space the pickup on the front of the motor down? How much spacing? Do the spacers go between the aluminum bracket and the oil pan? Regarding the head gasket I used a run of the mill felpro. Is their a better choice that is thicker?
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It has been a while since i updated the status of my NOX issue. I finally broke down and took the Jeep to a reputable emission repair facility. They smoke tested the exhaust system and found that the header collector before the catalytic converter was leaking so they replaced the flange before the catalytic converter as well as the one directly after the catalytic converter. They were able to pass the low speed test but it still failed the high speed test. They continued working through the issue by testing the fuel trims, smoke testing the intake, looking at timing, etc. etc. In the end after ruling out all other potential issues they performed a compression test and noted that all six cylinders were in the 170 to 172 psi range. They said, which I verified, that factory compression numbers should be between 120-150 psi. In the end the diagnosis was that the higher compression is creating more NOX which is no being sufficiently scrubbed by the aftermarket magnaflow catalytic converter. They recommended either the factory 1995 4.0 catalytic converter or a larger catalytic converter with the appropriate EO number. The saga continues...can you even get a factory converter anymore
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Called hesco, 14 degrees is good. Told me to check the VSS and for a plugged cat as well.
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14 degrees base timing, it hunts a little but that is where the timing mark holds the majority of the time. The slop in the timing chain is about 3 degrees when I rotate to TDC then rotate back until I feel the slack in the chain take up.
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Base timing is checked with a timing light, correct?
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Thanks for all the help Moses. I ran a manifold vacuum test and am getting 16" with a steady needle. Seems this is pointing to a timing issue? I have not run a leak down test yet but it is in my plans. The MAP test was performed using a hand vacuum pump and digital multimeter. Could a lean running MAP effect manifold vacuum? I have read that lean conditions and low normal manifold vacuum go hand in hand, true? Thanks again, Nate
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Tested the MAP sensor today. Does this explain my lean condition?? My Readings: 0" vacuum = 4.77 v (1.5% greater than below) 5" vacuum = 3.23 v (17.2% less than below) 10" vacuum = 2.38 v (20.6% less than below) 20" vacuum = .75 v (31.8% less than below) Diagnostic info from an article in Four Wheeler Magazine: 0" vacuum output should be 4.7 volts. 5" vacuum output should be 3.9 volts 10" vacuum output should be 3.0 volts 20" vacuum output should be 1.1 volts More voltage equals a richer condition, less is leaner. Even a small variance (0.2 volts) can make a big difference in air/fuel ratio and drivability. http://www.fourwheeler.com/how-to/engine/1401-driveway-diagnostics-map-sensor/