Jeep loses power

[Hunter82]

Hey,
78 Cherokee with a 360 cranks and runs great but sometimes it will just stall out and die when I hit the accelerator. I let it sit for a few minutes and crank it and it runs great. Sometimes I can run it several miles and it looses power or like today I went 100 yards and it lost power. Turned it off for a minute or two and it cranked right up so I could get it back into my shop. I know this is not much info but I don't really know where to start looking to diagnose the problem and any help would be appreciated.
Thanks

[Stuka]

Does it only "lose power" when you hit the throttle? Or can it cruise at constant throttle ok? If it only dies when you hit the throttle, it sounds like you may have a bad accelerator pump in the carburetor.

There are other things that it can be, but thats what comes to mind when you describe it dying when you hit the throttle.

[Hunter82]

Thanks for the reply. It’s a little bit of both. Sometimes does it starting out but sometimes while cruising I notice it losing power a little bit then it will accelerate back up. It just does it at random times. Other times it runs great.


Sent from my iPhone using Tapatalk

[will e]

Any fuel or ignition modifications or are you stock? (What's your setup)

Also, what gears are you running? I see in your sig you have 35's.

[Stuka]

Almost sounds like a fuel starvation issue. Have you ever checked the fuel filter?

[will e]

It might be a combination of a couple of things. I like where stuka is going with the fuel filter. But usually that wouldn't cause a problem from 'starting out'. How quickly does it happen when you 'start out'. Does it do it immediately or as you are accelerating?

What are your long term plans for the truck. Now might be a good time to get a fuel pressure gauge. Either a cheap one you can plumb in under the hood or better yet would be a in cab gauge with a remote sensor.

[Hunter82]

Hey y’all. The Jeep has only had the issue one time when starting out. I drove it 100 yards and it wouldn’t go anymore. Cranked it several times and the engine would just stall out. Tried to push it into the shop but couldn’t then I cranked it again and it pulled in fine. The other times I was cruising around the farm at 40 mph for several miles and it started surging and losing losing power again. Turned around and made it back to the house with no more issues.

It has an Edelbrock Weber carb and intake manifold. No idea what other mods it has or gear ratios. I’m new to the Jeep game. Where can I find the carb model number to know what type it is?

I would like to keep it long term and will look into the fuel pressure sensor.


Sent from my iPhone using Tapatalk

[will e]

Thanks for the updated info, that helps. The surging sounds like fuel pressure.

I don't think Edelbrock made weber carbs. Can you post up a picture? The gurus can probably identify it just by site.

I asked about the setup because of the 35" tires. You need to figure out what your axle gearing is. If it is stock it's going to make the truck a bit sluggish.

[Stuka]

Thanks for the updated info, that helps. The surging sounds like fuel pressure.

I don't think Edelbrock made weber carbs. Can you post up a picture? The gurus can probably identify it just by site.

I asked about the setup because of the 35" tires. You need to figure out what your axle gearing is. If it is stock it's going to make the truck a bit sluggish.

Weber manufactures all the edelbrock AFB style carbs, they always have, still do.

It does sound like a fuel issue. Could be water in the tank, could be a fuel filter that is plugging up.

[will e]

I was not aware of the Edelbrock/weber connection. Learn something new each day.

[Hunter82]

Tried to post these earlier from Tapatalk. Hopefully this will work.

[will e]

I can't tell by the pics which carb you have but I am not an expert.

I can tell by the pics that your engine accessory situation is modified. That is not the stock location of the alternator. This means you had a PO that did a bit of tinkering.

[Hunter82]

Interesting. Wonder why it is in a different location.
Another question I have is on the last picture there is a vacuum line that connects to the intake manifold. There is a fitting that doesn’t have anything attached to it and is open. When I am idling and I put my finger over the hole it doesn’t idle as good. What is that supposed to go to?


Sent from my iPhone using Tapatalk

[Stuka]

Interesting. Wonder why it is in a different location.
Another question I have is on the last picture there is a vacuum line that connects to the intake manifold. There is a fitting that doesn’t have anything attached to it and is open. When I am idling and I put my finger over the hole it doesn’t idle as good. What is that supposed to go to?


Sent from my iPhone using Tapatalk

Ahh, now we are getting some place. So, sounds like you have some vacuum leaks. And then the carb was adjusted to run with them there.

You need to plug the leak you found. Either find a hose that might have slipped off, or get some vacuum caps and plug it. The idle will most likely go down, this doesn't mean its worse, just lower. The vacuum leak will basically act like the throttle is partly open, but without the additional fuel.

Then, get some brake clean or starter fluid, and spray it around any vacuum lines, or the base of the carb. If the idle changes, you found another leak. Once these all get plugged, THEN we can tune the carb some if need be.

[Hunter82]

Thanks for the updated info, that helps. The surging sounds like fuel pressure.

I don't think Edelbrock made weber carbs. Can you post up a picture? The gurus can probably identify it just by site.

I asked about the setup because of the 35" tires. You need to figure out what your axle gearing is. If it is stock it's going to make the truck a bit sluggish.

I finally got back to look at the Jeep. On the carb I found the numbers 1407 0190. I am going try to find a manual on the carb to see where these vacuum lines are suppose to connect.

The did a gear ratio test and if I turn the tires 1 full turn the drive shaft rotates 4.5 turns.


Sent from my iPhone using Tapatalk

[will e]

You'll want a jeep manual, not a carb manual, to figure out the vacuum lines. I don't suppose there is a vacuum line routing sticker under the hood?

How'd you do the driveshaft test? With the tires on the ground or both off the ground or one off the ground? I am guessing with them on the ground and you have 4.54 gears which would be about the right gear to use when swapping 35" tires.

[Hunter82]

Ok. I will look in my manual to find the vacuum setup. No sticker under the hood.

I had both tires off the ground for my test.


Sent from my iPhone using Tapatalk

[letank]

Tom's site for Jeep manuals, aka TSM, there is a copy of the YM (year model) 78

https://oljeep.com/edge_parts_man.html

[will e]

Ok. I will look in my manual to find the vacuum setup. No sticker under the hood.

I had both tires off the ground for my test.


Sent from my iPhone using Tapatalk

If you had both tires off the ground for your test you most likely have 2.73 gears given the info you provided. This is a really 'steep' gear for 35" tires.
It means slow acceleration but low RPM's at highway speeds. Do you, by chance, have a tach?

[Hunter82]

I do have a tach. At 55 mph it runs about 1800 -2000 rpm.

I think I got the vacuum leaks plugged. Now when I get on the gas it wants to stall out. Is that running to rich?


Sent from my iPhone using Tapatalk