Dying Under Load

6

65_Stang_170

Well-known member
Howdy!

Just got everything hooked up after swapping to an 1101 and distributor from a '69 250. I think I have the timing and A/F ratio in a pretty good spot. It idles really well, but when I rev up beyond 1500 rpm it stumbles quite a bit. When I tried to drive it out of the garage, I couldn't fully release the clutch without it dying. So, now it's in the driveway while I troubleshoot... Thoughts? Maybe a vacuum leak or something?
 
I am in no way even close to an expert but I would think that it's a carburetor problem if it stumbles after a certain rpm it could be on of the fuel circuits not working right or the timing not advancing properly. Someone correct me if I'm wrong please
 
falcon_master":1v2xawup said:
...could be on of the fuel circuits not working right or the timing not advancing properly. Someone correct me if I'm wrong please
Click to expand...
no, I think ur right but w/o bein there I'd say double ck timing 1st, then onto carb if needed (also very far frm ex - spirt)...
 
At idle in neutral can you bring the rpms up to 4500 with no load?? if not hook a timing light up & see if you have a steady spark or it jumps around?? If so you may have reverse polarity.
What is your ignition system?? What is your fuel pressure??
Need more info to really pin point your problem. Bill
 
Ignition system is a stock distributor and coil from a '69 250. Mechanical fuel pump, so whatever psi that make. I don't have a gauge to test, but its pumping well/normal. I have a manual transmission, and in neutral when I press on the accelerator to bring up the RPMs it goes smooth until about 1500. I continued to press through up to 3500 RPMs and it continued to shake/stumble pretty good. When I put it in first and tried to go it cut out pretty quickly even if I really babied it.

Thanks for the help!
 
You have an ignition problem from what you describe.
However just try this, when you bring up the rpms, slightly close the choke blade to richen the mixture.
Disconnect the vacuum advance & see if that makes a difference??
 
I'd pull the top and see if all the check balls and the weight are there and in the right place. And check the float while in there.
 
wsa111":27a065hn said:
You have an ignition problem from what you describe.
However just try this, when you bring up the rpms, slightly close the choke blade to richen the mixture.
Disconnect the vacuum advance & see if that makes a difference??
Click to expand...

Thanks Bill. I'll give it a shot and see what happens.

Econoline":27a065hn said:
I'd pull the top and see if all the check balls and the weight are there and in the right place. And check the float while in there.
Click to expand...

I just rebuilt it and the check ball and weight are in the designated spot. Based on the diagram at least.
 
wsa111":kai1s2h1 said:
You have an ignition problem from what you describe.
However just try this, when you bring up the rpms, slightly close the choke blade to richen the mixture.
Disconnect the vacuum advance & see if that makes a difference??
Click to expand...

Just got a chance to try what you suggested: disconnecting the vacuum advance did not seem to change anything. However, closing the choke a bit seemingly cured the issue, and it was smooth and not stumbling up to 3500 rpm. What does this mean?

Thanks!
 
You either have a jet clogged or too lean a jet. Need to remove the top of carb & make sure each & every passage is clean. Make sure float level is correct & make sure the float drops when float bowl is empty.
Hope you don't have a major vacuum leak.
Do you have the correct pcv for your engine size? Or do you have a draft tube??
What is the # on the main jet??
 
wsa111":3qrcx9nx said:
You either have a jet clogged or too lean a jet. Need to remove the top of carb & make sure each & every passage is clean. Make sure float level is correct & make sure the float drops when float bowl is empty.
Hope you don't have a major vacuum leak.
Do you have the correct pcv for your engine size? Or do you have a draft tube??
What is the # on the main jet??
Click to expand...

I just pulled the carb apart to make sure everything was adjusted correctly. Float was adjusted when I rebuilt it, and drops as it should with fuel decrease. Current jet is a 61F. I believe I have the correct pcv size for my engine, as it was working just fine before I switched out carbs/distributor. I think I did fix a slight vacuum leak by tightening down the new adapter plate, so we're getting somewhere. I think I need to get a new hose for the PCV as it isn't sealing completely at the vacuum port. Tomorrow's project...
 
Per your carb. what is the original main jet size for your carb. ???
Put in a 68 jet & see what happens.
 
Sounds like you've gone over the carb pretty well.

Put a timing light on it and see if you're getting proper advance.
If not check the distributor springs.
 
wsa111":2jtixxi1 said:
Per your carb. what is the original main jet size for your carb. ???
Put in a 68 jet & see what happens.
Click to expand...

A 68 Jet was in it originally, but I figured smaller engine = smaller jet? I'll get it switched out tonight and see how that affects everything. Ok, two projects for tonight. New PCV hose and switch the jet.

JackFish":2jtixxi1 said:
Sounds like you've gone over the carb pretty well.

Put a timing light on it and see if you're getting proper advance.
If not check the distributor springs.
Click to expand...

How do you check how far it has advanced if the timing tab only goes to 14? I've always wondered this...
 
Other than the accelerator pump shot, a carburetor is not a fuel injector...It gets sucked in, a smaller engine means less suck and less fuel, to a point it is self adjusting...There is a lot more to it , best to use your air fuel meter.
 
Put in the 68 jet and it seems to be running much better. Got a new hose for the PCV, but I don't know if that affected anything. I was able to drive it around the block, and it felt ok. Need to make a few more adjustments, but moving in the right direction. I give a go again tomorrow, but the battery died (separate charging issue).

On a separate note (charging issue): what are the ramifications for running the car without a voltage regulator? I can't get my charging system to work: new battery, alternator tested several times, tried a few new voltage regulators. It's not giving the battery enough juice to stay charged, so it slowly drains... I accidentally left the VR unplugged, and the alt dummy light didn't light up anymore, and the battery was getting enough juice. Thoughts?
 
"...Thoughts?"
only 1 as I'm no help on electrics (or much else but...)
I've heard the VR are NOT made as well as they once were (is much?) & that many have gone thru enuff w/o gettin a good 1 so as to rebuild an old 1...
C if U can get a Motorcraft? NAPA - Elchign (spelling)?
 
You need a timing light with an advance dial to check anything over idle.
And if all you're doing is driving around the block it won't charge the battery.
 
chad":2dlyw7xz said:
"...Thoughts?"
only 1 as I'm no help on electrics (or much else but...)
I've heard the VR are NOT made as well as they once were (is much?) & that many have gone thru enuff w/o gettin a good 1 so as to rebuild an old 1...
C if U can get a Motorcraft? NAPA - Elchign (spelling)?
Click to expand...

I've tried a motorcraft/autolite mechanical VR and a few solid state VRs, and neither allow enough voltage to the battery while the car is running.

JackFish":2dlyw7xz said:
You need a timing light with an advance dial to check anything over idle.
And if all you're doing is driving around the block it won't charge the battery.
Click to expand...

Copy, need a fancy timing light. I know driving around the block won't charge the battery. I've taken it out on longer trips and have had the charging system checked while it was running. The battery wasn't getting the full 14ish volts even while holding it at a higher rpm.
 
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