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| Sprocket timing | Rating: 
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| Posted: 08-01-2015 08:22 pm |
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1st Post |
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Frank Schwartz Member
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I just put a new belt on a JH and now I cannot get the engine to run but when it does fire, it backfires. I tried moving the park plug wires on the distributor cap around to all positions and no luck. Is it possible, that I need to rotate the crankshaft 360 with the cams set where they are to get things back to normal??? I am really stuck here and this is the only thing I think it would be..
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| Posted: 08-02-2015 05:33 am |
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2nd Post |
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answerman Member
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Frank, somehow I think I'm telling you what you already know, but... Have you checked to be sure that #1 is at TDC when you have the marks aligned? You should be able to tell by pulling the plug. Once you've established that, pull the distributor cap and see which wire the rotor is pointing at. That will tell you which one is #1. Then, counter clockwise from that one, they should be #3, #4, and #2.
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| Posted: 08-02-2015 06:34 am |
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3rd Post |
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Frank Schwartz Member
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Yes...and this is crazy...#1 is at TDC..the mark on the crank pulley is lined up with 0 TDC and the cam markings match that is, 110 to 110...and I have tried the plug wires at all four positions on the cap...that is I moved them around 360 degrees, actually 90 degrees each time and It ony back fired....I am really stumped.
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| Posted: 08-02-2015 02:57 pm |
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4th Post |
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Brett Gibson JH5 20497 Member
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Frank, if things were aligned as you say then look at the distributor, make sure it is snugly seated in it's slot, then again align everything and look at the dizzy rotor to make sure it is pointed at the #1, if your still getting a backfire put a timing light on and see just were things are firing. Brett
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| Posted: 08-02-2015 11:50 pm |
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5th Post |
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Arvin Appelman Member
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You might try static timing. Set the crank at TDC or the advance you want at idle. Attach a test light to the Neg post of the coil. Turn the switch on and slowly rotate the dizzy until the light comes on. Lock done the dizzy and remove the test light. The timing should be close enough to start and adjust with a timing light.
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| Posted: 08-04-2015 01:57 am |
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6th Post |
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LambandAndy Member 
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Frank, The best way I know to be sure you are not 360 degrees out is to remove the valve covers (I know, on a 907 we all hate to do that), and make sure that when you are at TDC that the inlet and exhaust valves have free play. If they are tight or partially open you are 360 degrees out. If this is correct then your problem is somewhere else. However, if you already rotated your plug wires, this should have taken care of it. Remember, the crank doesn't care which stroke it is on, it is the sychronization of the cams and the distributor that counts. I also remember that I screwed up the timing marks on the pullies one time with the same effect (think I confused the inlet and exhaust marks) and another time screwed up the firing order (1342). Just some suggestions, Andy
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| Posted: 08-04-2015 09:33 am |
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7th Post |
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Tim Murphy Member 
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When one changes the timing belt the distributor timing gear can freely rotate and cause large changes in the spark timing. IMO, moving the spark plug wires around may only confuse the issue. Re set everything back to its basic setting as you have started to do. 1. 110 IN lined up with 110 EX on cam gears: done 2. Engine Crank mark lined up with TDC: done 3. Rotor centered on distributor socket for cylinder 1: You may have to loosen the timing belt and rotate the distributor gear by hand a few notches to get the rotor positioned correctly. 4. Points open (or electric ignition equivalent) so high voltage current sent to cylinder one spark plug. 5. Plug wires in distributor installed in proper firing order 6. Plug wires well separated to avoid cross firing, the spark current jumping from one wire into another. As Andy said, we all have gone thru this. Good luck and please tell us what the problem was when you get it worked out. Take care Tim Last edited on 08-04-2015 12:20 pm by Tim Murphy |
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| Posted: 08-04-2015 04:22 pm |
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8th Post |
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Jensen Healey Super Moderator 
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Hi Frank, I experienced the same symptoms once and it turns out I had installed the plug wires in the wrong order due to the backwards thinking required by the rear facing distributor. A simple mistake that ended up causing brake booster failure from the backfire. Cheers, Kurt
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| Posted: 08-05-2015 05:17 am |
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9th Post |
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answerman Member
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Any luck yet, Frank?
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| Posted: 08-05-2015 06:12 am |
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10th Post |
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Frank Schwartz Member
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No luck yet. I have all the marks lined up as per the manual and I have done this a dozen times in the past. I fire up the engine and it runs still at about 60 degrees advance..if I try to retard it, it speeds up..amazing...and if I try to advance it, for sake of argument, it slows down backfires and quits. When this car was brought to me it was running at 40 degrees and the weights were stuck in the distributor. I replaced the distributor and I still am too far advanced. I wonder...could the cam gears be put on front to back..or are the markings the same if the cam gears are reversed..that is turned around. Also a professional told me it could not run at 2000 rpm as it does without getting fuel and air.I blocked off the line going to the brake booster with no change. The fuel pump is putting out 4 pounds of pressure...now, I am removing the carburetors...again...arrrrggghhhh....and making sure the butterfly valves are completely closed...tomorrow I will have a go at it again.... The only change is that I removed the points and put in a Pertronics ignition...and yes, the points ran at 40 degrees advance and with the Pertronics, I am even running at more advance....I am ready to shoot the car and find a deep hole for it...
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| Posted: 08-05-2015 10:28 am |
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11th Post |
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UKJames Member
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If you want to sanity check the relative positions of the sprockets and timing marks there is a good image here http://www.jensenhealey.com/forums/attachment.php?id=69 Although if you have 110IN visible on the left sprocket and 110EX on the right sprocket they are probably fine Jim
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| Posted: 08-05-2015 06:27 pm |
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12th Post |
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Frank Schwartz Member
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Yes, all timing marks are correct....so now I am checking fuel and air...no air leaks, removing carbs to make sure butterfly valves are completely closed...then start up and see...fuel pump is putting out 4 pounds so no problem there...will push on and see what happens...getting the carbs on and off is a chore due to the nut on the bottom of each carb which is hard to reach...making a tool to do that..hope that works....
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| Posted: 08-06-2015 05:02 am |
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13th Post |
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Frank Schwartz Member
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Well, talk about a combination of errors...mainly throttle cable hanging and a bad tachometer...things now back to normal...idle at 10 degrees, but have to change the tach to get a good idle reading...and timing belt too tight..whines..can fix that, too...so things are getting back to normal in Jensenland
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| Posted: 08-07-2015 07:09 pm |
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14th Post |
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Jensen Healey Super Moderator
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Hi Frank, can you explain how a hanging throttle cable and bad tach caused your symptoms? I'm confused. Kurt
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| Posted: 08-08-2015 05:53 am |
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15th Post |
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Frank Schwartz Member
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Kurt: If I knew the answer, I'd write it up. Now that things are back to "normal" with 0 degrees static, it idles at 10 degrees and revs up to about 20 plus...suddenly is as tame as a kitten...I need another tach..know anyone with a good used one for sale or trade??
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