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4.0 l jeep motor please tell me how to set the timing with out a light.
What is the firing order? just in case I get a timming light what wire should I hook it to? and what should the timming be set at? And how do you ste it by ear exactly? thanks
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You can't set or change the timing on a Cherokee 4.0 liter. The distributor does nothing but sent the spark to the proper cylinder. The actual timing is dictated by the ECM, which recieves it's signal from a cam and crank position sensor. Turning the distributor will just change how far the spark has to jump inside the cap to get from the rotor to a terminal on the cap.
I used to have one of those things. I hated it. I wanted to flip that thing sooo badly. Or centerpunch a phone pole. Anyway, I have a J-20 now. 401, D44/D60, T-18, NP 208. MUCH better.
[This message has been edited by Tom 400 CFI (edited November 12, 2001).]
The firing order for a late 70's 4.0 is
153624. It porbably hasn't changed since then. I don't know how it is with jeeps but with every other fuel injected motor i had you still had to set the base timing even if the ecm was controlling it. Hook the timing light up to #1 cylendar (its the one closest to the front. Your goint to have to find which wire to disconnect to bypas the ecm's controll of the spark b 4 you set the timing. Under the hood there should be an emission sticker to tell you what the base timing should be
[This message has been edited by thatsme (edited November 12, 2001).]
<font face="Verdana, Arial" size="2">Originally posted by thatsme: I don't know how it is with jeeps but with every other fuel injected motor i had you still had to set the base timing even if the ecm was controlling it. </font>
That's because in some other FI engines, the DISTRIBUTOR is what generates the ignition signal AND distributes it to the proper cylinder. In the Jeep, there is a crank position sensor on the rear of the block, getting it's signal from reluctor wheel cast into the fly wheel. THAT generates the signal the ECM uses as basic information on spark timing. To alter the timing, you would need to either change the flywheel's position relative to the crank (tough to do!), or move the crank position sensor (also tough to do). Think of it like this; the crank paosition sensor does a similar function as the magnetic pickup in a conventional distributor. If you hook a timing light to the Jeep, and rotate the dist. while the engine is running, the timing will not change, because the timing signal does not originate from the distributor.
It always killed me that a late model SFI engine took 7 times more cranks that the old two barrel 401 in my J-20. I knew why, but I thought it was another pathetic aspect of that fine vehicle...
I have a 92 jeep I put a long block in, after farting with it for 8 hours I did some heavy research. You need an old dist cap with the side of ti cut away around # 1 wire lead. find TDC for #1 cylinder by pulling the spark plug and ratating the engine till the cylinder produces pressure,set the timing mark on zero. Now with the rotor on and the dist. cap on you need to put the distributor in so the rotor is just comming up to the #1 tit on the cap. about .005" gap between the rotor and the tit on the cap. After I found out how I got it on the first try.40,000 miles later its still running great. good luck
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91 Firebird TA
5.7 TPI
WS6 performance package
700 R4 W/O 3rd & 4th
soon to be replaced
