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[IrishKenCJ7]

Right , this is doing my head in for 12 months. I only get a hour or 2 every week or so.

I have a cj7 that will start but only stay running if i keep my foot on the gas and the revs over 1500. Once I go under 1500 it jumps like hell and will cut out if i go below 1000 rpm.  I'm doing this as its in my drive. Not able to drive it in this contidion.  I cant do anything under the hood with the engine running unless I put a block on the pedal or something.


It woldnt start the last could of weeks and I cleaned the carb(1bbl carter) and go a bit better but would not start. I put in new plugs and now it starts but as I mention I must keep the pedal flowing.

Is there anything wrong if the engine is jumping like crazy at low revs. I have oil in it.


When I took the plugs out they were carbon all over but they were dry. I was running rich I believe from the interweb.
When I cleaned the carb the piston was stuck in the auto choke and I freed it up. I dont think I adjusted any screws. I cleaned the whole carb 3 time and know it inside out and dont think thats the issue.

Could I now be running to lean and this is whats causing the jumping.

The next thing i will try is take off the distributor cap and check for corrosion.
I had took the spark plug  leads off and cleaned them up. Good bit of blue corrosion from sitting idle for last year outside. The leads are back in the correct firing order.

After that I will try adjust the idle screw and give her a small bit more juice (or less depending).

I pretty much have to get this sorted myself as every mechanic around here is up the walls and the one guy I know that does vintage is 20 miles away.

Is it a vacumme leak. I dont hear hissing or anything and I've see guys with the engine running with the air cleaner taken off and wouldn't that be a vacume leak in itself if I understand correctly. If not then I may have vacume hoses wired incorrectly (They are all new hoses).

Another thing I have smoke coming from the input manifold meets the engine. Probably a gasket leak there so is there anywhere I can get new input manifold for a 258. This one is rusted a good bit but seems solid.

Thanks for reading this far.
Any help appreciated.

Ken (non mechanical but this bitch wont get the better of me)

[Nosebolt]

might be a silly question but you got the firing order right or maybe the dizzy 180° out?

[Dave69]

Have you lookd at these sites

http://www.4x4wire.com/jeep/tech/electrical/jn-ignition99/

http://www.jeeptech.com/engine/carter.html

http://home.sprynet.com/~dale02/list.htm

[IrishCJ6]

Ken

Sounds like timing to me, have you adjusted it lately? Try undoing the distributor fixing bolt and rotating the casing a small bit, go only one way to start with. Try small bits at a time and see if it improves. If you get it running, then try small adjustments whilst it is running. Keep adjusting until the engine try's to die, then go the other way, the RPM's will start to rise and then it will die again, between the two is the sweet spot. Once you have this point, try increasing the rpm (2000 - 2200) and listen carefully for any pinging nosies, if you hear this you need to back off the timing slightly (turn the distributor) until it doesn't do it anymore. Its just trial and error unless you have a timing light. I prefer to do it by ear and then check with timing light afterwards. If you were closer I would come and help. Hope this helps.

If you still think there is a vacuum leak, get hold of some carb cleaners from the motor factors and when the engine is running spray the cleaner at all the hose connections points, the engine will try to stall if there is a leak. If there is no attempt at stalling then you won't have a leak.

To check and see if the distributor is in the correct way, remove sparkplug No.1, rotate the crank till you find TDC on No.1 (you can put a screw driver in plug hole and watch it rise/fall) careful not to get it jammed at full lift (between top of piston and plug wall), there is two points at which the piston will be at the top (firing stroke or exhaust stroke) to determine the firing stoke hold your finger over the sparkplug hole and you will feel pressure against it. Check and see that the TDC marks on the crank pulley line up with the marks on the block. Once you have TDC then remove the distributor cap and see if the rotor is pointing towards the No. 1 sparkplug wire then ensure that the other wires are in the correct order.

[eastryjeep]

My '77 CJ7 can play about like you describe and you said that the Jeep had been standing for some time.
Have you checked your fuel pump is actually doing what it's supposed to at low revs?
Try disconnecting the carb inlet pipe, stick it in a milk bottle (or similar) and just crank the engine, if little or no fuel, then pump be knackered.
The engine either fires on what's in the carb bowl or on a slug of juice down it's gullet but if my foot wasnt planted the thing would just die, and revving the nuts off a cold motor is never a good thing as you've got no oil pressure to protect anything.
If you suspect you have a vacuum leak then block the vac hose up close to the carb and let it run on mechanical advance only, it wont be as peppy as if the hoses were all attached but it's a start.
Go back to basics and problem solve from there.

[Dave69]

manual timing is 8 degrees BTDC with dizzy vacuum blanked
auto is 10 degrees BTCD

[IrishKenCJ7]

Thanks guys I'll give it another go on Friday at lunch when I'm back. I have a feeling its the distributor also. It hasnt been moved since the last service and it ran fine after than but Im sure these things get out of whack.  Andrew thanks for the PM, I'll give you a call if I'm still stuck.

Ken

[eastryjeep]

If you've not moved the dizzy since it ran fine, then don't shift it about just for fun.
I'm assuming you still have the electronic ignition fitted, but if some twerp has changed it to points that could be an issue.
If so just change the condenser, without disturbing the points, except to clean them and that may help.
Also check for condensation in the distributor cap and make sure its not cracked (points or electronic).
Oh, and make sure you have a good connection at each end of your HT leads, and that they are within spec. too much resistance or burned out inside and it will only ever run like a bag-o-nails!

[Bubba]

hope I am wrong but could be a near flat cam I have seen this

[eastryjeep]

  He's got a point there.
Remove the oil filler cap and have someone crank the engine so you can see if Cyl. #1 rockers are moving.
Also the seals in the hydraulic cam followers may have failed, (though I doubt it), if the followers don't hold pressure the cam just shoves them up their bore and that's where they sit. Fat, dumb and useless because the push rods can't shove them back down again.
But as I said, that is really unlikely, and would be extremely bad luck.

Worth checking but hopefully not your problem, is that the arm on the mechanical fuel pump can wear a groove in the camshaft, so that the pump arm has no lift. Just take the pump off the side of the block and have a squint with a mirror in the hole to make sure the arm is still running on a lobed section of camshaft.
If it's all worn and knackered just rivet a couple of plates on either side of the existing pump arm to widen it up so it spans the groove nicely, or bend the bludger over 1/4 inch.

[IrishKenCJ7]

Thanks I ll have a look into the first cylinder.
In relation to the fuel pump the PO installed an electric pump. This is working as when I floor the pedal I can keep it going. However could that be the issue at low revs... I still havnt gotten to check the dizzy. Will do tomorrow.

[eastryjeep]

Electric pumps generally put out a much higher pressure than the original mechanical unit.
If you don't have a fuel pressure regulator in there you could quite easily be over fueling it, that will cause poor idling every time.