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#11
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oilyspill wrote:
> > My info says the p300 code is usually caused by a lean condition. Too > much air, maybe a vacuum leak or not enough gas. If you have the cfi > fuel system, they are noted for problems. > > If you think it is an ignition issue, I have heard of using a > timing-lite to see the misfire, I've never tried it, I guess the timing > pulse will act-up. Using a timing light to find a miss is deceiving. I have been caught by 3 cylinders not showing a pulse so we thought electrical. We started there. Nope. It was one of the carb barrels not working so 3 cylinders weren't getting near enough gas. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's |
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#12
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My P0300 was caused by a bad fuel pressure regulator. It was leaking
gas into the intake manifold and also causing too much gas to go thru injectors, making it run too rich and misfire. It was not fun to replace. |
#13
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It seems to me that a no fuel condition wouldn't have anything to do
with the spark. To me, ignition means spark. If three cylinders were dead because of lack of fuel, there still should be a spark? If the plug gap was bridged, then the timing-lite pulse may be deceiving. I believe there would still be a timing pulse even though the cylinder wouldn't ignite. I used a cheap inductive spark tester not a timing lite, on a DIS system once, the lite was so irregular, I guess because of the exhaust spark, I didn't like it at all, took it back and got the old regular spark tester, where you could see the spark itself. I've never used that on DIS ignition. If you used a regular spark tester, the kind where you unplug the boot and put it on the tester, on a DIS ignition system, would the companion plug still fire? I'm going to try it one day, just out of curiousity. It is interesting. |
#14
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On 2 Mar 2005 14:00:37 -0800, "oilyspill" > wrote:
<snip> >If you used a regular spark tester, the kind where you unplug the boot >and put it on the tester, on a DIS ignition system, would the companion >plug still fire? I'm going to try it one day, just out of curiousity. >It is interesting. Yes it would |
#15
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In article
.com>, "oilyspill" > wrote: > If you used a regular spark tester, the kind where you unplug the boot > and put it on the tester, on a DIS ignition system, would the companion > plug still fire? I'm going to try it one day, just out of curiousity. > It is interesting. If you had a plug wire long enough, you could clip the spark tester onto the block of another car, (start the first car of course) and it would fire. |
#16
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If you were doing a cylinder balance test on a vehicle with DIS
ignition, pulling one plug-wire would kill two cylinders? But, as long as you used a spark tester, the companion cylinder would still fire. I guess you would have to kill the engine everytime you changed plug wires and restart. I wouldn't want to handle the wire with the engine running, I tried that before, that stuff has a bite to it. I was even holding an insulated screwdriver handle, still got me. I was dancing a jig hollering at the helper to turn the key off. The vehicle was OBD1. thanks |
#17
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In article
.com>, "oilyspill" > wrote: > If you were doing a cylinder balance test on a vehicle with DIS > ignition, pulling one plug-wire would kill two cylinders? You don't want to be pulling wires off if the engine is running. The voltage is going to go somewhere, odds are, it will arc across the coil winding causing damage or find it's way to the ignition module causing damage. > But, as long as you used a spark tester, the companion cylinder would > still fire. For these purposes of discussion, the coil doesn't care whether the spark occurs inside the combustion chamber or outside of it. > I guess you would have to kill the engine everytime you changed plug > wires and restart. I wouldn't want to handle the wire with the engine > running, I tried that before, that stuff has a bite to it. I was even > holding an insulated screwdriver handle, still got me. I was dancing a > jig hollering at the helper to turn the key off. The vehicle was OBD1. > thanks Much easier and safer to cut a piece of vacuum hose for each cylinder, install the vacuum hose in between the plug wire and; the plug or the coil tower (which ever is easier), start the engine and short the spark at the piece of vacuum hose with a grounding probe or a test light connected to ground. of course, you want to disable the idle control and disconnect the O2 sensor (force open loop) for accurate readings. If you must poke, probe or mess around with the plug wires with the engine running, connect a ground wire to the tool your using so if the spark arcs to the tool, it will be shunted to ground instead of zapping you. |
#18
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Thanks for the reply, I've heard of using pieces of vacuum hose. I've also heard of using a piece of coaxe-cable, like you use on your tv. Ground one end to the engine block, strip the insulation back off the other end far enough so you can backprobe the plug boot and short the spark to that cylinder. When I was using the screwdriver, I was trying to see if the spark would jump to engine ground. The insulation on the handle may have been cracked or the handle was greasy, maybe, don't know. thanks |
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