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AMC 360 runs rough and stalls when you let

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AMC 360 runs rough and stalls when you let
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Formula 40PC

Jeeper
Posts
83
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Location
Kirkwood
Vehicle(s)
'76 CJ7, 360, TH400, Quadratrac
Approx. 2 months ago I purchased a 1976 CJ7 with a AMC360 out of a old AMC Hornet. When I purchased the Jeep the PO had just installed a new holley 4 barrel on the AMC 360. When purchased the engine started ok but would take a few trys and needed a little gas to get it started, after 2-3 attempts it would start and idle ok. When driving the engine had a little sputter to it like it had bad gas or need a little tuning. I drove it a few times with the same sputter, I noticed there was no wires going to the electric choke so I installed temp wires for the choke in case that was the issue. Fast forward a few weeks, I jumped in to take it for some new wheels and tires and it did the usual started.....died.....started....died and then never started again. I started checking things and it looked like I wasnt getting fuel. SOOO, I dropped the take gas tank, everything looked great, the inside was nearly spotless, the pickup filter looked good. (While the tank was down i took the time to use a hole saw to cut an access hole for sender removal while the tank was still uninstalled. This is something AMC should have done in the beginning.)
I reinstalled the tank and then started checking the fuel pump, there were no obstructions in the fuel lines but I didnt seem to be getting fuel. I changed the fuel pump.....put it in wrong and snapped the arm....put in another fuel pump CORRECTLY and the outlet fitting was leaking fuel!!! So I hand tested the original pump and it sounded good and definitely had psi build-up. I reinstalled the original pump and installed a fuel pressure gauge between the filter and carb. Now all was good, getting decent fuel pressure, engine sounded like it wanted to start but would not. Now started checking ignition system, I checked everything wiring, coil, resistor, voltage, etc., a few plug wires didnt feel completely snapped in but they could or couldnt have been but now I was sure they were. AND somehow it started, not sure why but I wasnt out of the woods yet. It would do its usual, start, die, but then started and idled ok. I adjusted the dizzy and got it idling better. HERE IS THE ISSUE, it would idle fine and sounded good when I manually gave it throttle but once it was in gear it would run rough and once you let off the gas in gear it would die.
SOOOO, I installed a DUI HEI setup to eliminate some external components and wiring.
Engine fires right up now on the first/maybe second time and sounds good at idle but is still having the run rough and dies after you let of the gas. I have adjusted the timing every which way and still get the same issue.
Sorry for the long post but wanted to make sure I included all the details.
Any suggestions?
 
Sounds like you have gone over everything but the carb. Thats where I would have started. Starting with the float settings and checking for vac leaks. Good luck
 
Formula 40PC said:
I forgot to mention I noticed a slight-medium exhaust leak i think.
Click to expand...

I don't think that is the cause of your problem sorry. It sounds like a fuel or vac problem. Have put a vac gauge on it?
 
No. I am not very well versed in vacuum or carb issues.
I learned alot from the fuel system testing and the ignition system testing but I definitely dont know where to start on the vac or carb issues on my own.
 
I would recommend buying a vacuum gauge they inexpensive and will be the best diagnostic tool in your tool bag.
Hook it to full vacuum port
Warm engine
Set idle to 800rpm
Post your readings, or better yet, post a video of the gauge while running.
 
Look for mashed fuel hard lines and are you using a fresh clean fuel filter?
Some pictures of your carb etc would really help us here.;)
LG
 
I have attached photos of the carb and general engine in that vicinity. Excuse the wiring mess, I havent removed the old coil and wiring until I knew all was good with the new HEI.
I tested the carb vac port for the dizzy and had no vacuum so I switched the dizzy vac tube to another vac port and it idled much better, very noticable difference. But it still bogs and wants to die/almost die when given gas under load. Runs fine when throttle is manually used with no load.

So obviously the carb vac port is clogged or ???

I did some digging and ran the holley carb # and it looks like it was the same used on a late 60s ford mustang which makes a little sense since the PO was building a couple 60/70s mustangs when I bought the CJ.
I doesnt have a Ford part # but seems to be the same model # perhaps just aftermarket.
 
Like how you are using a pressure gauge on the return port of the fuel filter.:cool:
What is the open port on the front of the carb in your first picture? :confused:
Tell us about that cap on the oil filler pipe. Should be a breather filter.
Third picture, old coil-get the POS(+) lead off that terminal and secure it.
Good pictures BTW. :notworthy:
LG
 
If you are referring to the open port toward the front top of the carb that is where the dizzy vac line WAS hooked, that port has no suction so I switched to another port just for testing.

The PO put a gallon container cap on the oil filler stack so currently it is not vented, I have the correct cap ordered.
 
Never leave a port unpluged.
LG
 
There is no suction because it is a delayed port that doesn't open until the engine is off idle. The distributer vacuum line should be attached to that port. Unless there is something seriously wrong with your carb. that port will open ...... big vacuum leak there, i.e. very lean mixture leading to some very bad engine issues.
 
The vac tube is back on that port, just had it off for a sec and forgot to put it back on for the pics. The vac tube was on that port from the beginning and throughout all the problem diagnosis.
 
The PO has removed the air pump and much of the emissions control system which is fine but leaves me trying to figure out what the minimum I need is and if any of this could be causing my problem. I intend on getting some carb cleaner and spraying around the intake to diagnose any leaks. Can anyone identify or attach pics of the EGR, CTO, PCV so I know exactly what these look like on the AMC motor? Or possibly look at my pics and tell me what is there?
 
Very soapy water in a spray bottle is a great vacuum leak finder.
You'll see the bubbles pulled inside and know just where the leak is.
LG
 
Started off the day trying the soapy water trick.....got nothing. Then switched to carb cleaner.....got nothing. At this point I was almost convinced I had no vac leaks but I always second guess myself do to inexperience and so I went a bought a vac gauge. I have 17Hg at the carb and the dizzy vac increases as I give it throttle so all looked good there. Manifold vac pressure was around 15-16Hg also. So I tinkered, took out the old coil, resistor, wiring, etc.. Then I rerouted the plug wires so even if the engine wasnt running it would still look good. While I was doing this I gave a little tug to the power steering pump enough to get the dizzy a little bit further around AND now it runs and drives. After this I checked the timing and I am still spot on at TDC but it is running pretty good. Somewhere along the way someone must have broke the top half of the timing marks off so all I have is TDC and whatever is below that so not really sure where I am at there.
So now my issue is that the wiring connector on the dizzy is resting against the power steering reservoir which concerns me because of vibration. I hate to start messing with this again but I think I need to move the dizzy around a tooth or three so it isnt resting on anything. Any suggestions?
 
Easy fix on the timing marks. Harbor Freight has a very inexpensive timing light that adjusts timing for advance. Just set the light at your desired advance and adjust the distributer to "0". To find out where you are right now adjust the light until the "0" mark is set and read the dial. These lights are available in other locations at fairly reasonable prices.

Your plug wires could be shorting out on the power steering pump.
 
Anything under 5K'(ASL)altitude, that is a low reading.
I'm at 2700', and can pull 18hg with ease at 700rpm idle on my tired AMC 258 i6 / 4.2l .
LG
 
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