258 Ignition timing help please.

Hi everyone.

I finished rebuilding my 258 a few weekends ago, and after some cursing and fighting got the engine and trans and frame to all play nicely together. I got the engine to about 8degrees BTDC and got the distributor in. A little gas and it fired right up. I did not want to mess with it much and just ran the engine for about 10-15 minutes, then shut it down and restarted a few times. Mechanically the engine is great normal temp, normal oil pressure.

I took it for a short drive about 20 minutes and was going easy on it. It was doing great. Then I decided to take it over a large dirt pile to see check the low end torque. Driver error and a bad shift on my part stalled the motor. And so my adventure began.

No more spark. I had forgotten to connect the ground wire to the frame and the ignition module had burned out. $25 for the new part and an hour to go home get the big truck and tow the jeep back later I tried to start it again. It sparked but it was weak and intermittent.

Keep in mind I never had a chance to tune the motor in the first place. I did put a vacuum guage on it while trying to crank (not running) 0 mm HG. I started to mess with the distributor position eventually pulled the distributor messed with it, the coil, the distributor pickup ect. Much fun with the multimeter, but in the end parts are cheaper than my time in a cold NY garrage.

Currently. 83 cj-7 stock carb(all vacuum and emmission controls are plugged except for brake booster and distributor advance)(carb ran ok by carter standards on previous motor), new ignition control module, new ignition coil, new magnetic pickup coil, of course new plugs and wires, engine, body and frame are grounded with less than 2 ohm resistance.

Engine has been moved to 8 BTDC using the timming marks and the finger in plug 1 test multiple times.

First question, I seldom have help any better tricks for finding piston 1 position with out a second person?

Question 2 I know the timming is way off. any tips to get it right. I've started from scratch 1/2 a dozen times or more. There is spark intermittently, and I believe its problem is mechanical position of the distributor, but working alone is not going so well.

FYI if the distributor gets vacuum it does advance normally. Diaphram is fine. I'm not sure why I have vacuum problems from the engine. It did not run long enough to test, but ether spray did not find any leaks around the intake manifold or the carb base, or the plugges emmission hoses. Also I chose 8 degrees because its in the middle. Engine seemed to run best at 16 degrees BTDC. I figgure it should at least start at 8. I don't know what the factory calls for, but I plan to use the tune by ear method to start.

So the real question is how do I get this thing running long enough to figure out if it has other problems and eventually tuned right. Especially while working alone.???


And yes it does have a good supply of fuel as far as I can tell. Engine cranks and tries to sputter but never starts. ocassionally it will blow back through the carb. Spark is visible on the number 1 plug when the plug is grounded to the block, but it still seems to be intermittent. Again I suspect mechanical position of the distributor more than electronic failure at this point.


Thanks for your help!!!!

-Mike

 

I'm running late so I will just drop you a quick answer for now...The position of the distributor will have nothing to do with spark. As long as it is turning and everything is hooked up...it will spark. You can take it out of the engine and as long as everything is hooked up...you can make it spark by spinning it by hand.

 

You said it was a rebuild so everything is tight. But could it have jumped time. Did you look at the drive gear on the dissy? Just went through this on my 360. Thought it jumped time so tore down the front. That was fine. Looked at the drive gear on dizzy and it was chewed up.

 

This worked well for me when I was installing my HEI.....

Finding 0° TDC on the compression stroke:
Remove your spark plugs. Place a wine cork (or the finger of a second person) in the #1 spark plug hole. Don't force the cork into the hole, we want it to be able to come out when the piston compresses. Place a (3/4"?) wrench or socket on the vibration damper's bolt, rotate clockwise until the wine cork pops out so you now know this is the compression stroke. Note: Always rotate the engine in a "clockwise" direction as you look at the vibration damper. Continue turning until the timing mark shows 0° TDC. Make sure you have not made a complete 360° turn. If you did, this will be the exhaust stroke and you will need to start over.

 

Thanks for the cork tip. The rest of the finger method is what I have been using. The wine might come in handy if the engine still won't start.

As for the distributer gear. That is fine. Tried a second distributor as well. If the timming chain slipped I think I might need the wine again. That would not be good. I really do not want to open the front of the engine.

Any simpler thoughts, like what does the computer under the glove box control. Does that have anything to do with the spark? If so can I bypass it?

Maybe the carb is not mixing fuel well. I did have problems with the stepper motor ocasionally.

Thanks.

 

Computer? Mine had 3 fuses. Thats as close as I have to a computer.

I know it sounds dumb, check wiring order. Then go for setting the timing again. Check the dizzy bolt. It could be loose allowing the dizzy to rotate. I backfire through the carb is a timing issue. Sounds like 180 off.

 

I don't know much about the fancy new CJ's with the computer controlled carb. But I read this in the lobby of the Holiday Inn one time...That little box can certainly have an effect. I do know if you pull the smog stuff, and alter the stock setup on the carb, and do not do something called the "Nutter Bypass" (google is your friend, here) the motor at best will run really rich in the "limp home mode". The BBD carb from the stepper motor era is also well known for being a PITA, something about clogging idle tubes.

You are gonna have to find someone who has experience with this stuff. Early and intermediate jeeps have no computers. I know there are other websites out there that deal more with your year than Ecj5, I don't know if I'm allowed to post a link. Maybe others will chime in.

 

I downloaded the nutter bypass the day after I bought the jeep. Never needed it untill now.

After thinking about it, I think the thinking box under the dash may be part of my problems. I have not decided how I want to procede. Its cold and I'm busy this weekend, but motorcraft 2100 carb may get ordered. No idea what I want to do for spark though. I'm not buying a computer unless a cheap one pops up somewhere, and I don't completely love the Gm ignition idea. Up untill recently I always liked ford ignition parts.

I agree on the possible 180 out, I have used an assistant and a long thin screw driver in the plug hole to verify piston 1 position on a ford v8 before but that won't work so well on a straigh 6. Best case i get a bent screw driver. worst case bad things happen to my new motor.

I'll try the cork or wait for an extra person to use the finger method I suppose.


btw how does a 70's AMC generate spark with out computer. ( I don't mean points, ect. That would be replaced with a pertronix pickup anyway. But I am not sure I am completely understanding the ignition process.

I'll be looking that up on line in a minute.

But key switches 12 vdc to ignition module, coil, and distributor pickup coil. In "start" the starter relay is also given 12 volt and opens the relay to provide 12VDC high current to starter.

The ignition coil runs the positive side polarity current through the coil and ramps up voltage from 12vdc to 10K VDC. The high voltage is carried through the coil wire to the distributor center.

Meanwhile the starter begins to rotate the engine and the distributor acts like a rotating switch sending 10k+ vdc to each plug wire in turn. What's the magnetic pick up coil in the distributor actually doing? to the circuit? Just acting as a passive buffer to transfer high voltage with out burning out contacts on the distributor cab or is there more to it?

Anyway as the switch rotates high voltage is transfered to each plug wire, then through the plug to the electrode. The outside of the plug is grounded to the block so the high voltage jumps the plug gap and goes to ground causing a hot spark. Gasoline explodes and engine moves 1 revolution further and restarts the cycle in the next cylinder.

What is the ignition module actually doing? How is the computer under the dash involved in this process. I can see the purple wire from the ignition module goes to the computer and then to coil negative and the distributor as Nutter describes so the computer has to control the ignition coil voltage and i assume the field voltage in the distributor pick up coil.

Its these little missing or flawed details that currently confuse me. Oh well its late but it will give me something to figure out in the morning.

Tell me again does anyone actually drive a jeep or do you all just repair them piece by piece one dollar at a time as I seem to be doing? Oh the joy of jeeping.

Thanks again for the help.

-mike

 

By far the best performance upgrade for my 258 was #1 the motorcraft 2100 carb. Wow! Next would be the HEI dizzy. I don't know if you could lose the computer if you replaced your carb and dizzy. Replacing both would be a performance boost especially with a new rebuilt motor.

Both can be sourced at your local bone yard, ebay or catalogs. Lots of post here about sourcing and installing. The good thing about HEI, you lose all the wires in the engine compartment. Just a 12v and tach to the dizzy.

 

The GM style HEI is far superior to any other stock distributor style ign...period. That's not a loosely based opinion, that is a fact that has been proven time and time again in my line of work. Try it...you won't believe the difference until you do.

 

I agree 100%. This was THE best bang for the buck for my 75 258. Eliminates a lot of the stock components (which were very troublesome), and is extremely reliable, inexpensive, simple and parts are easy to get anywhere.

Sine installing a couple of years ago, I have had zero issues with ignition.

 

Okay....my timing issue now.

I installed my HEI ignition distributor today. Timing is way off. It runs okay without the vaccum line attached but, if I attach the vaccum or step on the skinny pedal, it dies. If I try to adjust the timing, it dies.

Any suggestions would be appreciated. I pulled the plugs and re-set to TDC....still no good.

 

A few things come to mind:

Did you re-gap sparkplugs ? Gap needs to be .045-.050.......

Did you change wires ? HEI requires special wires (8 mm, I believe)

Are you sure your not out 180 degrees on your #1 plug ?

Is your HEI a rebuild or new ?

 

Agree... HEI is drop in, set timing and forget about it.

Check firing order, the vacuum you are pulling is ported and set your time at idle with the vacuum hose disconnected.

Mine is at 13 btdc give or take.

 

Your timing is retarded AND...you have the vacuum line hooked to the wrong port. At idle...you should not feel any vacuum coming from the port...but if you just slightly crack the throttle...then you will feel vacuum. Advance it...alot...don't worry, your not going to hurt anything by advancing it too far while it's sitting in your shop. If after you have advanced it...it has trouble turning over (sounds like a weak battery) then you advanced it too far, back it up a little. That will a least get you up and running.

 

So it was a warm 40 degrees this afternoon and back to the jeep I went.

I did the nutter bypass and learned that you can completely remove the jeep ecm computer, all the emissions controls and actually get the jeep running rather easily.

For those that one day have the same issues.

Disconnect the computer if you like you can cut every wire out of that harness. (assuming you are not going for emmisions. In my case most parts were old broken or just shot anyway.

Next do the bypass. In short. Red and white from the first connector of the module go through the fire wall to the ignition switch. I did not trace them. They seem to work well.

The second connector is purple, orange green and black.
Purple needs a jumper wire to go to the purple wire of the distributor pickup coil. Orange used to go to the ECM then to the distributor, cut the computer out and orange from the ignition module goes to orange of the distributor. Black goes to black and green goes to the tack and negative of ignition coil.



Ok so the jeep starts and drives. I still have issues getting the stepper motor valves in the correcct position??

I still have no vacuum advance and everything on the carb is plugged. A full can of either was sprayed around the intake and all old seal vacuum fittings with no change in RPM. I can't find the vacuum leak yet if there is one. I am still assuming its stepper motor related.

Problem two is still ignition timming. By ear the engine runs fairly well, but the timming light is not even close to giving me a timming mark I can read. Its way way out.

I have not had a chance to drive it yet. I plan to figure out what the stepper motor needle valves are supposed to be this evening. I am also going to ponder the possibility of the motorcraft 2100 carb.

Any chance I am still 180 out? Any thoughts on the lack of vacuum?

Thanks again.

 

Question about the reply above.... Jeeps don't produce vaccum at idle?

As for ports. I have the brake booster in the driver side large port at the base of the carb/ top of intake manifold.

The distributor advance is connected to the passenger side port bottom middle of carb. I swap the vacuum guage in its place when setting the timming with the light.

There is a vacuum line at the back of the carb going to the choke diaphram. (for now going manual choke later)

All other ports on the carb are blocked and sealed with silicone and a screw in a short piece of rubber.

All emmisions controls are removed, and the PCV is vented to air with a breather cap.

I am assiming with the engine at idle I should read about 20 mm hg vacuum at the distributor port of the carb. Am I wrong?

It seems to be running really well. Starts on first turn of key idles well and reves to 4k plus with no sputtering. I would like to see vacuum and a correct timming mark to make me feel better before driving it.

Thanks

-Mike

 

It won't run 180 off.
Are you 100% certain you have the light hooked to number 1?

 

Absolutely light is clamped to the number one wire with no chance of cross talk.

Distributor is currently alligned so vacuum diaphram port is almost parallel to the engine with the port facing the radiator.

Cap is new position 1 is almost perpendicular to the engine give or take a few degrees.

All plugs and wire are in the correct order. Plugs are bosch 4x platnium tips. No way to gap them but with 4 leads they don't change gap easily either.

By ear the engine sounds good and the exhaust smell/view the engine is currently running very well. Its got plenty of power sitting in the garrage and around the block. Its also not bogging down when the throttle is wide open. It starts normally. I can adjust the timming and it will stall or act like a dead battery with hard starts. Currently I've got it in " its happy place" At least by ear.

I will try to actually drive it later in the week or next weekend and of course learn alot more. I will also try to convince a friend to follow me around with my f350 just in case the jeep gets a little lazy.

As for the timming light. with the distributor vacuum on or off the carb currently there is no change in the timming marks. The vac guage reads 0 so that is to be expected, I don't hear a vacuum leak and I don't think I'm running lean. If anything I'm running just slightly rich, but its cold and the choke is closed.

When the engine was first cranked (post nutter bypass) the distriibutor was mechanically at 8 degrees btdc. It fired up with a little encouragment, but I had to rotate the distributor almost immediatly to keep it running. Now that it runs well by ear, The light is flashing, but the timming mark is no where in site.

I know the first time it ran (3 weeks ago) the light was putting the engine at 15-16 degrees Before. Assuming I moved the distributor in a similar direction I would think I am around 20-22 degrees before tdc now. That would put the timming mark somewhere under the water pump close to the 12 or 1 oclock position, and out of my sight. That seems odd to me...?

I'm thinking I'm a distributor tooth off Maybe two. To be honest i'm not sure. The jeep is trying to drive me crazy. Oh well I'm slowly learning from mistakes.


Thanks everyone for all the help.