Need Some Help Guys

[TNCJ7]

First post here guys. I searched the forum but couldn't find a post to match my problem...hard to search for the exact match. Sorry for the lengthy post but want to give you the full story.

I've had this '77 CJ7 for about 7 years..it's got a AMC 304 in it and no problems up to now. I had the engine pulled to repaint it AMC blue and the guy I picked to do it took his sweet time. It basically sat for almost a year..had to literally threaten the guy to put it back together but that's a whole other story!

This is where all my problems started. It didn't run that well after I got it back and then one day, it wouldn't crank at all. As a result, I ended up replacing:

Plugs
Wires
Starter
Distributor along with cap and rotor
Ignition Module
Rebuilt Motorcraft 2100 carb

After all this, I was having a problem with the engine turning over very slow when cranking and once cranked, fuel loading up in the carb. Checked the timing and it was advanced real bad. Timing is good now and cranks up fine...no fuel issues like before.

Well...took it out for a drive yesterday and was gone about 30 mins when I got into some severe stop and go traffic for at least 20 mins. btw..it was about 80 degrees here yesterday. It was idling through all this traffic fine. Got to the point where I could put some throttle into it and it sputtered and died. Couldn't crank it again. Sat for 30 mins with it..still wouldn't crank. Put some fuel in the carb and it fired up...drove another 5-10 mins and it died again. Left it for 3 hours...came back and it fired up and ran fine. Seems like something is getting hot and not allowing proper fuel delivery. Perhaps vapor lock?

Couple of things I noticed yesterday..when we were setting the timing, I noticed there is no vacuum at all. Put a gauge on the hose and nothing. Vacuum port in carb could be clogged? Also, the fuel line is running directly under the header with no insulation. I've never had this problem before and the line has always been there though. I had a shop put an electric fuel pump on it about 3 years ago but it could be a cheap one. I'm at a loss here. Any ideas?

 

[Torxhead]

Part of your many issues could be from poor fuel delivery and the fuel could be too warm going into the carb. An externally mounted electrical fuel pump has to be set up correctly as the fuel from the tank has to be siphoned to it. My first two recommendations would be to convert back to the mechanical pump and move the fuel inlet line out into a cooler location.

 

[Lumpy Grits]

Ck fuel pump psi.
How old is the gas?
When was the last time the fuel filter was changed?
LG

 

[Bent]

The timing port shouldn't have any vacuum with the throttle closed. But hard cranking/sputtering/no vacuum sounds like a timing chain that's one tooth off. If you don't find a problem with fuel delivery it might be worth pulling the balancer and cover and recount the pins. Someone with more v8 experience can correct me if I'm wrong, but I think it's 20 pins between the timing marks with the cam gear mark at 3 and the crank gear mark at 12.

 

[Hedgehog]

Does anybody else have difficulty with the word "Crank"? It has or could have so many different meanings. For some "crank" means to turn over either by hand or with the starter, I'm of this group. For others "crank" evidently means to start or run, not necessarily well. I think the OP's description of the problem is well written, but I get a little lost on the word "crank".

 

[hdgapeach]

Does anybody else have difficulty with the word "Crank"? It has or could have so many different meanings. For some "crank" means to turn over either by hand or with the starter, I'm of this group. For others "crank" evidently means to start or run, not necessarily well. I think the OP's description of the problem is well written, but I get a little lost on the word "crank".

I'm with you. To me "crank" means to spin it over with the starter to get it to "start" and then "run".

After re-reading the original post, the "wouldn't crank at all" would mean pretty much a dead battery (my interpretation)!!

The next iffy understanding for me is "when cranking and once cranked". Does "cranked" indicate the engine started or did it finally begin to turn over.

Where's a grammar teacher when you need one???

 

[JR74CJ5]

Could be vape-lock... could just be lack of fuel...

What kind of filter do you have? Some people have to run a 1 in 2 out filter type. I never have personally.

You said newly rebuild carb, triple check float and needle settings.

I would then check the entire fuel line system, including the pick up in the tank for blockage, or cracks... Even if no gas coming out, air can be sucked in instead.

For the Vac issue. Remember there are 2 types of vac. Ported and Manifold.

If you're not running a CTO switch, you need to make sure you're running the right one.

Manifold Vs Ported Vacuum - JeepForum.com

At one time I knew this to explain it better, but basically one of them has high vac at idle that drops off as you increase throttle, and the other is opposite.

The Post from other forum above is pretty detailed, and good info even if it's not what you were after


~ Jr

 

[hdgapeach]

On a more serious note;
You very well may have a vapor lock issue.
What Torx said about going back to the manual pump would be a step in the right direction.
Did you blow out all of the passages in the carb with compressed air when you rebuilt it?
Is there a functioning fuel return line in your set up?
After sitting for that long, was the fuel tank dropped out and cleaned? Old fuel and crud build up will drive you nuts!

Man, I have more questions than answers