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bucking slant six, timing issues, diesels sometimes
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Author:  86slant [ Mon Nov 10, 2003 3:28 pm ]
Post subject:  bucking slant six, timing issues, diesels sometimes
1986 Dodge ram d100, 126,000 miles. It stumbles, bucks cuts out around 70 diesels when i shut it off. These problems are not all the time. I back the timing down, it doesn't diesel as bad, but runs really badly when driving. also runs hotter. If I advance it runs greats, but the valves ping under load and diesels real bad at shut off. Timing mark is all over the place. The timing is so far advanced it is almost off the degree indicator tab. I would hate to think the timing chain is that bad. After all it is a slant 6 and I never heard of a timing chain going bad on one. So I am thinking it is the computer on the fender messing with the timing and causing the stumble while driving. Has anyone had any dealings with this. I know the newer computers is a form of the "lean Burn" used in the 70s early 80s. I don't see a conversion kit to go back to the old system of the mid 70s for the slant six. I know it exists for the v-8s.
Any advice input is appreciated.
Gary
Author:  Pierre [ Mon Nov 10, 2003 3:37 pm ]
Post subject: 
If you don't care about emmisions regulations, I'd suggest retrofitting to either a mopar electronic ignition or msd based system.

There are no kits anymore as you pointed out for the /6, but all the parts (ignition box, ballast, coil, magnetic pickup distributor) are availible from local stores or your friendly junkyard. The only thing you'd have to rig up would be the harness, of which the diagrams are availble off the articles link at the homepage of this forum.

You could also try a pertronix ignitor setup. What this does is replace the points in your distributor and you connect it directly to the coil, effectively bypassing the whole computer system.

Try turning your car off in gear if you are that annoyed by the dieseling ;)
Author:  86slant [ Mon Nov 10, 2003 4:51 pm ]
Post subject: 
I've done the shut off in gear, it doesn't like that too well. I found an old mopar part number for the slant six. The stealer may could locate me one. The emissions are already unhooked. Looks like this may be the route i take. The stealer can get me a new computer for it, but why when i think old is better.

Gary
Author:  Craig [ Mon Nov 10, 2003 8:08 pm ]
Post subject: 
Do you have an automatic or manual transmissoin? There are some slight differences between the ESA (electronic spark advance) systems depending on the transmission.
I have a 1987 with automatic trans. The 1986 and 87 systems are exatly the same with the same part number computers. Long distance trouble shooting is difficult.
Wandering timing? Strange. Worn out plastic gear on the distributor? Might want to check that out.
If you junk the computer please send it to me.
I saw one in the junk yard where someone removed the engine temp sensor for the computer and installed a sender for a after market temp gauge in the hole. The computer will never work correctly that way.
Author:  86slant [ Tue Nov 11, 2003 4:07 pm ]
Post subject: 
it is an 86 manual tranny.

Gary
Author:  Super6 [ Wed Nov 12, 2003 10:46 am ]
Post subject: 
As craig said, you should have an SCC behind the battery under the driver front fender. This computer has a vacuum pod on it that controls the timing advance as a vacuum advance dist would. My '87 also had the wandering timing issue--even with a brand new timing set. (wandered about 7-8* )

First I would check the timing chain for slack, and replace the timing set if needed. If the chain is OK, either you have a vacuum leak between the vac advance port on the carb and the vacuum pod on the computer, the vacuum pod is bad, or the computer is going south. (could also be a bad input from somewhere else, almost everything runs through that computer)

Second, as craig said, check the dist for excessive play. You should not be able to 'wiggle' the rotor much.

I just finished removing all the wiring associated with that computer on my '87 D150...there is a lot of usless wiring in your harness if you change over to electronic ignition. I converted mine using a 70's single pickup, vac advance dist and an MSD ignition. Timing was rock solid after relieving the computer of ignition duties.

If you decide to convert your ignition let me know.

Craig--I have the SCC out of my '87 sitting on a shelf. Do you need one or is it something to play with? I am pretty sure mine has a bad vac pod on it, but I never checked it so I do not know for sure.

-S/6
Author:  86slant [ Wed Nov 12, 2003 2:49 pm ]
Post subject: 
Distributor has not slop. I do want to check the chain as soon as I get a socket big enough to fit on the bolt on the crank. Like I had mentioned earlier I never heard of a chain going bad on a slant 6 and being a long stroke motor and their reputation for durability I doubt it would be bad, then to you never know. The problem isn't consistent.

Gary
Author:  Super6 [ Wed Nov 12, 2003 5:16 pm ]
Post subject: 
Actually, if your slant still has the factory original timing chain, it is probably a nylon-toothed gear; which after 126k miles is likely worn out and/or missing teeth :shock: New, all-metal timing sets are a fairly inexpensive item at most parts stores. Getting the timing chain cover to re-seal w/o any leaks is the toughest part of the job IMHO. If you do not already have one, you will need a puller to get the dampener off. It will not come off w/o taking the crank bolt off, but the bolt does not really hold the dampener on, it is a very tight press fit.

You can check your timing chain for wear before you disassemble anything. Since your dist is tight, pull the cap so you can see the rotor. Turn the motor over slowly by hand at the crank bolt (taking the spark plugs out makes this much easier) If the rotor does not begin to move when the crank starts to move, your timing set is loose/worn.

Good luck.

-S/6
Author:  86slant [ Wed Nov 12, 2003 5:41 pm ]
Post subject: 
Ah. So they were still putting those junky timing chains in them. Dad had a 318 in 81 it went at 50k. I do plan to check that before I start any kind of conversion. Thanx

Gary
Author:  Craig [ Wed Nov 12, 2003 8:04 pm ]
Post subject: 
Quote:
Craig--I have the SCC out of my '87 sitting on a shelf. Do you need one or is it something to play with? I am pretty sure mine has a bad vac pod on it, but I never checked it so I do not know for sure.

-S/6
I was just looking for something to play with. My truck is auto tranny. The comptuer controls the lock-up torque converter too so I imagine the manual tranny computer does not have an output for that. I'm not sure why I want one to play with but they are just neat-o to me. :) I just wish I could tamper with and tweak the thing! The manual tranny comptuer uses 12º base timing instead of 16º like the auto tranny version. That might work better for my dual-fuel propane/gasoline conversion (so I can use larger idle speed throttle opening) and I can add a toggle switch in the cab for the lock-up converter. See, I like to "play". 8)
Author:  Craig [ Wed Nov 12, 2003 8:24 pm ]
Post subject: 
Hey 86Slant,
Some more things to check.... but would be easier for a knowledgeable person peson who knows the ESA system to be there to check it in person... Too bad I'm not your neighbor.

Jumping timing... In addition to timing chain, Check for endplay in the distributor shaft. Bouncing shaft will cause shaft to advance/retard because of the helix of the gears. Add shim washers under plastic gear as required.

Missing.... check inside of distributor cap. Mine gets some strange coating/condensation in it every now and then. I need to remove it and wash and dry it.

Oh yes... the ESA computer controls the lock-up torque converter in your automatic transmission. If you remove the computer your torque converter will no longer lock up. If you install other ignition system I do not know if that part of computer will work by it self. I have not tried it. Right now I am doubtful. If you disconnect too much the computer will not go onto warmed-up engine mode to make the lock-up work.

There are lots of other checks you can do. I can't remember them all right now since mine has been working and I have not been playing with it lately.
Post back with what you find and we'll go on from there.
Author:  86slant [ Thu Nov 13, 2003 2:59 pm ]
Post subject: 
It is a manual. I am going to go over it with a fine toothed comb this weekend.

Gary
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