Mystery problem... please help diagnose.

My problem is that when driving, let's say on a flat, in second gear, I cannot accelerate more than about 29 miles an hour. This doesn't change when going uphill, or down. I know that I wouldn't want to go much more than say 32, but there is a definite hesitation, like a restrictor or governer, that isn't a loss of power as much as a wall, and plenty of throttle left, but engine won't go

This also happens in 3rd at about 46 miles per hour, up, down, flat, whatever.

My suspicions are that it is the timing, fuel, compression, or vacuum.

 

I guess i should give the other info that everyone is going to ask anyway.

f134
new
fuel pump
oil pump
msd ignition
very good rebuild on carb
points
coil
condensor


I just cleaned fuel lines, vacuum lines, pcv valve?, oil bath filter.

I think that covers it.

 

guessing
sounds like retarded timing issue
or no advance

 

How about fuel filter, just a thought.

 

That is kind of what it sounds and feels like. At higher rpms or speeds, if feels like i go down to 2 cylinders or something. I have kept messing with my timing, thinking that was the problem, and can tell a small degree, when I change the timing a touch, but no solution. Is there the possiblity that a manifold vacuum leak could cause the advance to not take place?

 

I thought about fuel filter, but it isn't apparent where it is, as I suppose it is inside the fule pump or such. I will look tomorrow.

 

BTW, there is no distrubitor vacuum line to carb.

 

but you don't have a manifold to leak....
you can check for vac at idle with a vac gauge
at sea level you should have 16-18" of vac, higher where you are a little less
at mid to full throttle, you won't have any vac to the advance, which is normal
maybe the centrifugal advance weights inside the distributor or sticking/frozen up.

 

now your going too far! What the hell are the centrifufal advance weights inside the distrutor, and what do they look like? btw, did I mention this was a 61?

 

Well, first thing to check is whatever you did most recently - but that is a long list of "new" stuff.

Sounds like it could well be retarded ignition timing but if you tried advancing it it then maybe the points gap is off spec.

Fuel starvation is possible but would become worse under load, such as going uphill.

 

I am with jpflat2a on checking the distributor advance weights and inspecting it for broken springs etc, the reluctor ( the part the points rub on ) could also be stuck to the dist shaft this could certainly be a contributing factor if the vehicle has been sitting for some time. As he mentioned if they are stuck power will quickly fade at higher rpm.

Can you take the dist cap off and rotate the rotor against the advance weight springs?

 

2x on the mechanical advance. You may have adjusted the initial timing, but only a few degrees. Mechanical advance will advance timing on the order of 20-25 degrees.

 

msd ignition doensn't need a specific gap on the points just an operable gap, as far as i understand. It keeps coming back to timing, but I have adjusted it as much as possible both directions, with no improvement.

 

Does your MSD have a rev limiter?

 

Show us a picture of your engine. One from the radiator on the carburetor side and one from the radiator on the spark plug side.
You may have one of the old engine speed governors mounted on the spark plug side that won't let you go over a certain speed in each gear.

 

I guess that I should mention that this is a newer developement, and that I have had the jeep up to 65 of so going on a slight downhill. This was a couple of years ago, and I think that the only thing that I have made any changes to since in the ignition.

 

Make sure you're getting full travel on the throttle linkage. Had that on my f-head, where carb could not go WOT due to interference. Once that was cured, was like I had an extra 20 hp!
Easy things first.

 

This was on cj3b page about distributor installation:

Scott Blystone commented on the Bulletin Board: "Nice writeup -- your info is correct from my personal experience. I would add however that even if you do not perform the one tooth offset on installation, there is just enough adjustment to set timing correctly (but only if everything else is mostly up to correct specs). Someone put the wrong distributor in my F-head during a prior rebuild and I could never get the timing where I wanted it -- never had that top end power it should have. As I fixed other problems (valve lap, new points, plugs and wires, etc.) I was able to get the timing right -- but my distributor is turned all the way to the stop in order to do so. I suspect there may quite a few Jeeps suffering problems like this. I know I have seen a lot of vacuum advances on flat fender Jeeps over the years. I am sure they were replaced because people thought they would work better."


I am more thoroughly reading the page about distributor installation, to make sure mine is correct and not off by 36 degrees due to the oil pump. Seems unlikely that that would be the problem due to the fact that I have never messed with the oil pump, and it ran well before.

 

I messed with the timing further, and was able to rotate the distributor freely, and am confident that timing is not an issue.

The msd 6a does not have a rev limiter function.

The throttle linkage travels freely, and hits the high end just fine.

The feeling does happen at half throttle, but at certain speeds. It is like there isn't enough gas travelling from the pump, or not enough spark for the gas, I can't tell.

This was on the msd website. I have basic plug wires, and havn't ever upgraded since installing the msd.

SPARKPLUGSAND WIRES
[FONT=Swis721 BT,Swis721 BT][FONT=Swis721 BT,Swis721 BT]Spark plug wires are very important to the operation of your ignition system. A good quality, helically wound wire and proper routing are required to get the best performance from your ignition, such as the MSD Heli-Core or 8.5mm Super Conductor Wire.
[/FONT][/FONT][FONT=Swis721 BT,Swis721 BT][FONT=Swis721 BT,Swis721 BT]Note: [/FONT][/FONT][FONT=Swis721 BT,Swis721 BT][FONT=Swis721 BT,Swis721 BT]Solid Core spark plug wires cannot be used with an MSD Ignition.
A helically, or spiral wound wire must be used. This style wire provides a good path for the spark to follow while keeping Electro Magnetic Interference (EMI) to a minimum. Excessive EMI, such as the amount that solid core wires produce, will interfere with the operation of the MSD.


could it be the wires, or more likely, I need to test the fuel pump?[/FONT][/FONT]