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  #1  
Old 06-29-2003, 09:10 PM
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Default RPM does not drop when plug wire removed

Im still collecting parts for the 400 stroker. In the mean time.......

While drive the Challenger last weekend after about a 60 mile trip, I pulled into my dads driveway and started to put it in park. Before I could get it in park, the car cut off/choked down.

I adjusted the idle a little (Holly carb) and went about my way. After getting back to the garuage, I thought I might have a dead cylinder. I pulled the plug wire off the first plug (front of the motor,drivers side) the motor almost cut off because the rpm dropped so low. I moved to the next plug (still drivers side) pulled the plug wire and there was no change in the rpm. Checked the plug for spark and there was spark on the wire without the plug. I took out the plug, stuck it in the boot and there was fire on the plug.
A friend suggested a compression test. Following the instructions included with the test, I found no compression leak in either of the cylinders previousley mentioned.
Maybe I got some plug wires mixed up a while back so I looked up the fireing order in my factory manual and things seemed ok.........I even checked the timing with the flashing light hooked to plug one (front plug drivers side) until I tried some other cylinders.

This is when I found that I could remove FOUR plug wires from the distributer cap-every other one-and there was NO DROP IN RPM!!!!!!
i mean that all four wired were off at the same time and the car cranked up just like always and idled ok!

Is this correct?

I cant believe the car runs as good as it does and i am only running on four cylinders!

any suggestions to correct my problem or information to educate me (as you can tell from my previous posts i dont know alot about what I am doing but I am learning) will be very welcome.


thanks

Chris

1970 dodge challenger
318 2bbl-now 4bbl
automatic on the colum 904 tranny
ittybitty rearend
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  #2  
Old 06-29-2003, 10:00 PM
mtrv8n mtrv8n is offline
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I think Chrysler is engineering this into the next generation of cars to save fuel..

You are idling well on 4 cylinders???

We did a post a while back on the timing sequence v. distributor postions, and it was noted that the distributor can be 180 degrees off, and still kinda work..


My alignment method is to turn the dist so that the #1 cylinder is lined up closest to the post on the the dist that feeds it.

The #1 hole is the driver side , closest to the front of the car.

the dist terminal that feeds it should be the closest terminal to that cylinder.
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Old 06-29-2003, 10:51 PM
sixpackgut sixpackgut is offline
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bambam,
i have no clue if mtrv8n is right about this but i think what hes trying to say is pop off the distributer cap, pull your dist out and turn it 180 degrees around, put it back in and put your dist cap back on and see if you could get it to fire. i dont think this will work or if its your problem but i think i would have tried it already if i went through what you described.
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Old 06-30-2003, 12:39 AM
jelsr jelsr is offline
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Not electrical, it's the idle circuit in the carb. The stock manifold is a 180 deg type and each side feeds every other cylinder. When it is revved above idle speed the carb comes off the idle circuit and runs on all 8. If you look at the manifold runners carefully you will note that the 2 end cylinder runners go to the 2 center cylinders on the opposite bank which is every other one in the firing order. You can tell which side by adjusting the idle screws, one will change idle quality, and the other will have no effect even if you screw it closed. Probably some dirt or the like in the one side. Remove the offending screw and give the hole a shot of carb cleaner (no compressed air!). May have to remove the carb for a good cleaning.
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Old 06-30-2003, 02:52 AM
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well... thats the damndest thing i ever heard, jelsr, but it kinda makes sense. i never paid any attention to manifold runners. but DISTRIBUTOR POSITION DOES NOT MATTER!!!! as long as the ignition timing is correct and the firing order is right, it will work and work well. call it an esoteric thing... i dunno... put #1 cyl on TDC comrpession stroke, find where the rotor points on the dist cap, and call that tower #1. firing order on all mopar v8s is 1-8-4-3-6-5-7-2... clockwise direction for the small blocks... counterwise for the big blocks. wire accordingly. be careful and double check your work. if #5 and #7 get crossed up, the car will start. it will run. it WONT run right. it WONT run well. but the damned distributor could care less how it is installed!!!
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Old 06-30-2003, 07:12 AM
Tomasso B Cuda Tomasso B Cuda is offline
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No change in rpm when the plug wire is removed more than likely indicates you have a cylinder missing most of its compression. A stock 318 will idle fine on 6 cylinders...personal experience...try a compression test before chasing tail any further.....
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Old 06-30-2003, 12:19 PM
jelsr jelsr is offline
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Yeah creative1, sounds a little far fetched, but it's a fact. All the dual plane manifolds are 180 deg and each side feeds 4 cyl's. The plenum is divided, 1 side shallow, 1 side deep. When 1 side of the idle circuit gets plugged it has a very distinct sound, not uneven, but noticeably different, and of course slower. Pittsburg huh, thats about as far from here as you can get and still be in Ks.
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Old 06-30-2003, 12:38 PM
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I will double check the fireing order and then check the adjustment on the carb-clean it out- and so on.

if that is the problem and I correct it, will I notice a drop in RPM when ANY plug boot is pulled from the plug while the motor is at idle?

Thanks for ALL the input.

chris
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  #9  
Old 06-30-2003, 02:10 PM
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Quote:
Originally posted by jelsr
Not electrical, it's the idle circuit in the carb. The stock manifold is a 180 deg type and each side feeds every other cylinder. Probably some dirt or the like in the one side. Remove the offending screw and give the hole a shot of carb cleaner (no compressed air!). May have to remove the carb for a good cleaning.
Damn jelsr, I thought no one could learn me anything anymore, I learned something new today! You the man--thanks!
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Old 06-30-2003, 02:58 PM
jelsr jelsr is offline
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Yes bambam, if the cylinder is working you will notice a drop in RPM and usually a little shake when you remove the ignition source. If you have access to a tach note the RPM drop for each cylinder as you do them. The weaker cylinders will not cause as much drop in RPM.
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  #11  
Old 06-30-2003, 08:00 PM
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jelser-
thanks
i took the pin out and shot the carb cleaner into the hole on the passenger side of the carb. the motor seemed to like the carb cleanen (rpms went up) but there was no change in the the pistons that seemed not to be working to start with.

what i mean is after reinstalling the pin, the simptoms when pulling off the plug boots were the same. 2 cylinders on the drivers side caused low rpm and shake and the other 2 showed no change. Same thing on the other side. No change in rpm even with all 4 pulled off at the same time (2 on one side and 2 on the other)

guess its time to tear down that carb.

time for some more ojt!

thanks
chris
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  #12  
Old 06-30-2003, 10:22 PM
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Since you will be down a while why not run a dry compression ck and a wet compression ck and a leak down test? Will give you more info to work with. The more knowledge you have the better armed you are to fix the problem w/o T&E
just my $00.02
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  #13  
Old 07-01-2003, 12:29 AM
jelsr jelsr is offline
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For whatever the reason you are not getting fuel to the idle circuit on that side. It picks up speed for a short time using the cleaner for fuel then goes right back to the same as before so the problem is delivery to that circuit. Get that cleared up and you're back in business.
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  #14  
Old 07-01-2003, 01:01 AM
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things i would look for include crud in the bowl of the carb, jets (some carbs get their fuel for the idle circuit after it goes through the jets), and anything that may be blocking the passages from the bowl to the needle valve, and anything that may be blocking the passage from the needle valve to the idle port. this includes the needle valve itself, as i have seen the tip broken off in its seat. this could happen if the needle valve has been overtightened. i dont know of any case where the casting has been distorted so badly (from overtightening the needle valve) that the passage(s) actually are blocked by the damaged metal itself, but i would guess it could happen. the needles should be carefully inspected. they should appear the same. no areas of depression from overtightening, no broken needles. they should be evenly tapered almost to a point. if you decide to disassemble, clean, and rebuild the carb, i would suggest B-9 chem-dip carburator cleaner and parts dip from berryman to clean the carb. you should be able to get it at any parts store. not real expensive... i think the gallon i have cost me about $11 or $12 a couple of years ago. read the label thoroughly first, though, and get a small turkey pan or a 9" cake pan for the large parts. it has a basket inside the can for the small stuff. do not clean any plastic or rubber parts. dont even think about those... they will go bye-bye! lol. anything metal is ok. no smoking around this stuff, and no flames or sparks. using it in the house is probably a no-no, cause it will eat carpet, vinyl, paint (including polyurethane) or almost any floor covering. it will, however, make that carb look new, and get rid of any foriegn gunk in the carb passages. i use the spray carb cleaner to rinse the parts after soaking them overnight. save the used cleaner for another day, cause it is good for many cleanings. oh... and dont put your hands in it ... it will eat those, too... lol... just wash them with soap and water if you get any on them.
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Old 07-01-2003, 08:09 AM
Tomasso B Cuda Tomasso B Cuda is offline
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Basics Basics Basics!!!! Standard Basic Troubleshooting !!!!We still don't know if all 8 cylinders have equal cylinder pressure.
Compression test time!!. If all 8 are working you typically see over a 50 rpm drop when you pull a plug wire. If you have good compression readings then proceed to look elsewhere. You need a solid baseline to proceed. It starts with the "air pump". If you pull a plug wire and there is no change in rpm and you have spark/fuel present there is a problem with that cylinder of the "air pump". An internal combustion engine is an air pump......nothing more
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  #16  
Old 07-01-2003, 11:18 AM
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compression test showed all cylinders to be within 10 lbs of each other
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Old 07-01-2003, 12:15 PM
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Quote:
Originally posted by Tomasso B Cuda
If you pull a plug wire and there is no change in rpm and you have spark/fuel present there is a problem with that cylinder of the "air pump". An internal combustion engine is an air pump......nothing more
Yes but what jelsr is saying is that there is no fuel present at idle in those cylinders due to the circuit being blocked.
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  #18  
Old 07-01-2003, 12:24 PM
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Take those wires off, and run the engine for 5-10 min. Then take those plugs out to see if they are wet or damp with fuel.
Pull the valve covers off and see if all the valves are opening the full amount.
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  #19  
Old 07-01-2003, 03:35 PM
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Default amxauto-x

glad to see you weighing in

I have taken a look at the rocker arms with and they seem to all be opening fine.

what you suggested about checking the sparkplugs sounds eaiser than pulling the carb apart so I will check that first.

I still fear it is going to be a carb problem.

well, at least I dont have to have new heads! (I dont think)
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  #20  
Old 07-02-2003, 07:42 AM
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Why are you so hung up on what this engine does while its idling?? I think it would be more important to know what goes on going down the road under power. I have not seen it mentioned what this runs like under power. I'm quite sure if its only running on 4 or 5 cylinders you would notice.
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Old 07-02-2003, 09:03 AM
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Quote:
Originally posted by Mopardad
Why are you so hung up on what this engine does while its idling?? I think it would be more important to know what goes on going down the road under power. I have not seen it mentioned what this runs like under power. I'm quite sure if its only running on 4 or 5 cylinders you would notice.
Because some problems show up better at idle. For example. My van wouldn't run for beans at an idle. Quite rough. At speed/cruise it would run just fine. So, what do you think the problem was? Can't check the plugs at 50 mph on the hwy. You have to do it in the driveway/garage, at an idle. So anyway it was a bad exhaust valve, 50lbs cylinder pressure. At higher rpms it'd seal off and run fine. That's why you should be concerned what it's doing at an idle. Besides, they do a lot of idleing at the stoplights.
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Old 07-02-2003, 09:27 AM
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quote from amxauto-x

"Besides, they do a lot of idleing at the stoplights."


This is how this whole thing started. I pulled into a drive way and the motor cut off before I could put it in park. I have a standard 904 tranny. On the way home, when I came to a stop I had to put it neutral and idle up high to keep it from cutting off. When the light turned green i had to slam it into drive and bark the tires to keep from chokeing down. Barking the tires once in a while is ok with me but not at every light thru town on Sunday while others are in the church i am beside. I must respect their rights to their quiet time! anyway thats off subject---

Thats part of what caused me to check out what was going on under the hood.

The car is staying at a friends house and I havent had time to check the sparkplugs as amxauto-x suggested or dig into the carb as jelsr deduced.

hopefully over the next 2 or 3 days-if it ever stops raining here!

chris
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Old 07-04-2003, 03:11 PM
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running fine now-thank you all!

Got out the carb cleaner this morning and wet that baby down GOOD while it was still on the motor. Let it soak for a few minutes while I transfered tools and such from the truck to the Challenger. Soaked it down again-inside and out. Lots of attention to the jet area. Front and rear.
fired it up and with a shot of flames and gurgle, it fired to life.

and to my joyful amazement, , when i pull off any plug wire , the rpms dropped!

Carb trouble it was!

And once again, I must thank you all for your suggestions and 2cents worth.
I learned something from everyone.

Thanks to in no order-


amxauto-x, Mopardad,
MOPARMANJAMES, Tomasso B Cuda,
creative1, jelsr, 23T, mtrv8n, and sixpackgut.
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  #24  
Old 07-04-2003, 03:20 PM
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youre welcome!
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Old 07-04-2003, 03:26 PM
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Glad to hear it! Didn't mention it before but I had my speakers on and I could hear the funny idle sound!
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Old 07-04-2003, 08:12 PM
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you found the and got your engine back in shape without a lot of & $$
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