rabino34

I have an '83 Dodge Ram Van Prospector with the 225 c.i. slant-six engine. It was missing (misfiring consistently...I determined it to be so by an evenly spaced puff sound coming from the tail pipe at idle, and under load). I could also just feel it with a slight vibration at idle, and under load.

I replaced the plugs, wires, rotor, cap, PCV valve, and adjusted the timing. Still, it's missing.

I was thinking of replacing the coil...should I? I'm told "either it's working or it's not, and if the engine runs at all, then the coil is good and doesn't need to be replaced." That sounds suspect.

I can't figure out why this darn thing is missing!

The engine only has 105,000 miles on it. The head was out and redone at some point. I don't know if they did the valves, but I assume so. I checked all the compression in the cylinders...all good, all even.

Wouldn't that good and even compression that rule out a burnt valve being the culprit for the engine missing anyway? I also don't hear any bad valve sounds or taps.

I disconnected the #6 spark plug wire, and ran the engine....it feels the same!! Just a little rough, but the same amount of roughness. I reconnected #6, and then disconnected the next one toward the front of the van. It's the same feeling...still clearly missing, but felt almost identical to having the #6 unplugged. The missing is apparent anywhere, but it's most apparent by the huff...revolution....huff....revolution...huff...s ound coming from the tail pipe.

I triple-checked the firing order. It's correct.

I replaced all the new plugs with another set of new plugs, thinking that could be the problem. Nope, still the same problem....still rough.

I am extremely frustrated. If I know the engine's getting spark on all cylinders, the firing order is correct, it's probably not a burnt valve because I have compression on all cylinders, what else could it be that's causing it to miss?

Could it be the carburetor? It has a one-barrel remanufactured Holley (I think it's a Holley copy). I can't find a name on it, or even any numbers on it other than 480640, 40160, and 0977 and it says "remanufactured."' But why would a bad carb cause the engine to miss on what seems like only one cylinder? The carb does look suspect -- the fast idle actuator is not connected electrically and that is the first thing that makes me lose confidence in it. Secondly, although I can see the vacuum operated choke trying to work, it doesn't actually close the choke when I need it to. Thirdly, near the vacuum amplifier hockey puck looking thing, there is a small plastic box about 1"x1"x1" square that has vacuum lines coming in and out of it, but there are flat connectors on it that connect to nothing! What does that do, or should it be doing? Is that the culprit?

I noticed the canister that goes into the electronic ignition module that has a vacuum line going into it from the carb is a little broken on the right-side mounting point but mostly stays in place...but I think that's still pretty much working to advance the timing, and I don't think that would cause it to miss on only one cylinder at idle. Right?

Sometimes in between the prominent and consistently regular huff/miss sound coming out of the exhaust pipe, there are a couple of other misses/misfires...seemingly coming from other cylinders. Kind of like a buh, du, dum, dumm....smooth, huff, smooth, huff, smooth, huff....buh, du, dumm, dumm....smooth, huff, smooth, huff....etc.

I don't understand how the "vacuum amplifier" hockey puck thing can work because it just has vacuum going into it and then coming out of it....how does it get amplified? There's nothing electric connected to it. could something be wrong with that thing?

ANY HELP WOULD BE HUGELY APPRECIATED!!!!!!!!!!!!!!!!

rabino34

Haven't taken the distributor out yet. Where would I get a new gear? Chrysler dealer? Or buy a whole new distributor?

To the other replies: I was going to order a a rebuilt carb from Autozone, and I will buy the temp tester from Harbor Freight.

Any other ideas?!?!

richinny

check those vacuum leaks first. a lean mixture can cause a misfire.

the distributor gear is available at auto parts stores. it is not on my list of suspected items.

the choke vacuum unit opens the choke, not close it.

do you have the first set of old plugs? if one was different looking it would help identify the problem. a lean mixture makes the plug very white.

rabino34

I do have the old plugs. One was darker (not oily...just a bit more carbon). I did the digital temperature check on each exhaust cylinder's exhaust manifold flange just now. #6 is definitely colder than the rest, but so is #1, but less so. Those outer flanges would dissipate heat more quickly though, so it's still not clear whether #1 is the culprit. In fact, I charted it...the numbers on the right with the colors indicate cylinder number....#1 is closest to the firewall, #6 is closest to the rear of the van. Readings (T1, T2, etc.) were taken about 1 minute apart.



Clearly it looks like #6 is significantly colder than the others. Does anyone have any opinion about whether #6's valve(s) could be burned, despite having good compression? Could it be that the intake valve is not opening?

Could a vacuum leak cause a single cylinder to miss, but not the others?

richinny

i don't know if leaner or richer will burn cooler. while the intake runners are pretty close in length, the end runners tend to get a bit less fuel.

have you checked the egr valve? if you remove it the gasket might break due to the high heat. a piece of aluminum can makes a good test plate when put between the vlve and the manifold but will soon burn through. i pooply seating valve or a blocked on for that matter, can give a rough idle.

rabino34

EGR valve is fine. Unfortunately it's missing at every RPM, not just idle. I haven't removed the valve cover yet as someone asked, but would a bent rod be visible just be removing the cover? And wouldn't I hear a strange sound while the engine was running if a rod were bent?

rabino34

You didn't hear the valve doing something funky (clanking, tapping, etc.) before the valve cover was removed?

rabino34

Thanks! I wish I could make the engine run as well as I can quickly make a cool chart, but, alas, I cannot. :-(

Anyway, following are two pictures of the #6 plug as well as multiple pictures of the carburetor. From the carbon on it, it looks like #6 is firing, at least to an extent. I ordered a new carburetor at Autozone to replace this, and it raises another question. Even though there were several carburetors (Carter BBD, Holley 1bbl, 2bbl, various model #s) one could have had from the Dodge factory originally installed, Autozone/Advance, etc., only carry one for non-Canada, non-California '83 B150 6-cyl vans. This van originally had the "electronic feedback" one from the factory, that had not only a vacuum line going to a transducer (plunger with sensor for how much vacuum) on the under-the-hood electronic ignition computer, but also had wires going from that computer back to the carburetor to adjust lean-rich air-fuel mixture. The only one that Advance/Autozone carry is one with nothing elecctronic on it....it's the basic Holley 1945. When the previous owner replaced the carburetor with this one on it now that has a remanufactured sticker on it, that's probably what he got. So, maybe the mixture is not being controlled at all, and that's why the engine is missing. When you look a the picture of the #6 plug that has only 60 minutes of use on it since new, it looks carboned up quite a bit. So maybe without the electronic feedback carburetor the mixture can never be correct. What do you think?

Maybe one of you gurus will have a look at the pictures of the plug and the carburetor below and see something obviously wrong with the carburetor...like vac line X or Y is missing, or that nipple on the side shouldn't be capped. Any of the photos can be enlarged by going to the following link, which shows a grid and then clicking on any one of them: http://s216.photobucket.com/albums/c...albumview=grid






Is there any way to lean this carb out without touching the black hole of the electronic ignition? Can I eliminate that electronic ignition that looks so suspicious and "upgrade" to a points distributor? It would be less of a whole set of unknowns that way.
Regarding the vacuum lines..it seems like there's plenty of vacuum, and if I disconnect one of then from the carb it does stall the engine. I was saying before that the hockey puck vac amplifier is connected to nothing electrically, and that 1"x1"x1" box is also connected to nothing. There is one tube on the carb that is capped off. Should it be? Rich in NY posted that I should check the vacuum lines for leakage because that will cause it to misfire...but how can I check them for that? They all look fine :-) I don't know if they are routed properly, and the sticker under the hood is not helpful because this is a remanufactured carb from the previous owner...not all the options on it are connected.

richinny

if you have no input to the lb computer, it's not going to run right but i don't think it's your main problem. going to the basic carb may drop gas mileage but will simplify things.

btw, when i worked at a dealer i found that while many items had 12 different part numbers when new, most of the numbers seemed to super cede to one or two part numbers.

can the air mixture on the current carb be adjusted?

is the vac advance working on the computer?

putting a point distributor in is a big step backwards but ok if you like adjusting points every few thousand miles.

if that vac amplifier isn't working i don't think the egr can work.

the fact that 1 & 6 are both having problems is a hint but my theory is too dusty to troubleshoot that info.
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1 and 6 are on the same cycle.

when you pull the plug wires you said 6 made no difference. was the spark as strong from 6 as the others?

oh and folks, when chacking spark, don't use the edge of any openings on the valve covers. i did that once and ignited a lot of raw gas in the crankcase. my eyebrows have since grown back.

rabino34

Rich, I don't know any of the 3 answers...I don't see any adjustment for mixture, but maybe I'm missing it. With the vac advance, the engine pings when revved up over load, but maybe the fuel has too low of octane. I was hoping someone would know if the mixture is adjustable from the pictures! I didn't notice if #6 was as strong of a spark as the others -- I will retest. I am using the inline $5 light from Harbor Freight; hopefully that light flashes brighter when the spark is stronger. I am not sure what you mean by pistons 1 and 6 being on the same "cycle" -- it's not a V6...it's an inline slant-6.

rabino34

Whatever problem this is, it's either far too complicated for any of the 3 mechanics I tried in Daytona to figure out, or they are scared by the unknowns of the rudimentary factory electronic ignition working with the replacement non-electronic feedback carburetor. Initially I had thought about doing what I am doing now with y'all anyway, but before tackling this on my own I had decided to go to a mechanic because my schedule was too tight although money was too tight to make doing that comfortable. But ultimately none of the three could figure it out or wanted to figure it out, so now I'm committed for the time being to figuring it out on my own. Next steps...compare all sparks 1-6 for consistentcy, then pull the valve cover and check for valve lash, verify valve geometry.

Maybe these mechanics in Daytona just aren't very good, despite (or because of?) their proximity to NASCAR, or maybe that makes them wannabe race mechanics and they fail miserably being quite the opposite. I am going to continue to try to solve this problem on my own, but can someone recommend a Mopar specialist anywhere in Florida (hopefully not far from Central Florida, best would be in Daytona) who would really know these engines inside and out anyway? I'm just looking for a backup plan...I really want this engine to be running properly. Backup plan #3 is to convert to throttle body injection from junk yard parts.

rabino34

I've always thought that leaner runs hotter, although the Chilton's manual says in an unrelated section, "watch out for choke stuck in closed position because the engine will run very RICH, and will thus get very HOT." First time I've heard that.

rabino34

Does anyone know whether a '94 Ram Van engine would fit in this '83 B150 like a glove, or whether it'd be taxing to get it in there?

rabino34

For the cost of a rebuilt Autozone carburetor for this slant-6, I could get a running '94 Ram Van and put the engine in the Prospector. (IF it would work!!)

richinny

from a mechanic's view you have the proverbial pandora's box. so far i think you have:
disconnected vacuum lines
emissions stuff not working
possible mismatched carb

...and the miss.

there could be many more problems. a shop would have to go step by step to verify that the fuel and electric are working properly. i'd be curious as to how loose the timing chain is.

an engine scope would take some of the guesswork out of the ignition ststem.
a gas analyzer would tell you about the fuel air/fuel ratio.

if you swap engines you still have to transfer all the ignition and electrical stuff.

you have a tough nut to crack.

richinny

hot or cold a lean fuel mixture will leave the plug pretty white.

i don't think the light will tell you how strong a spark you have. an easy test is to loosen the wire before starting the engine, hold the end with insulated pliers about 3/4" away from something grounded and look at the spark. it should be visible in dim light and have a sharp snapping sound.

rabino34

Not on any illicit drugs, but the Dodge Brothers or Lee Iacocca's engineers' work are making me frustrated enough to think about trying some....joke. Why are Chrysler products so "weird?" :-) Maybe I should just put it back together, put the engine cover back on (I wish it had more sound insulation...the engineers couldn't think of that?), and just drive it for a while to see if it stops missing. Maybe the missing is just from lack of use/sitting -- it'll be fun to try all the gas additives the parts stores sell, especially those that claim they solve every problem. I need one that says cleans injectors/carbs, fixes knocks, pings, misfiring, loss of fuel economy, leaking tires, dead batteries, frozen AC compressors, uncomfortable seats. :-)

Seriously though folks, because of the dynamics/size of this engine, it doesn't shake wildly when it misses (I just hear it from the exhaust pipe, and feel the lack of top speed, and feel the loss of fuel econ in my wallet), and I am sure it's either not just one cylinder missing OR if it is that elusive #6 low temp cylinder, that it's not consistently missing.

Maybe all the valves are slightly off, and lot of everything else is a little off too, and by running around with it and trying the additives it'll just work!