Please listen. Does it sound choked a little when revved. Just doesn't sound right. The gauge is manifold vacuum. The carb has been rebuilt. I've tested the ignition 7 ways til Sunday. It bogs a little with throttle tip in. Thoughts? Time to swap the TPI?
When is the last time you put fresh plugs in it.
I chased an off idle stumble for months before an old guy asked if I had tried new plugs. A fresh set of plugs cleared it up instantly. Now it's SOP at my shop to start all carb diagnostics with new, properly gapped plugs.
That sounds like it may need a little larger accelerator shot. How does it behave under load.
New plugs last week.
It misses and hesitates under load. I rebuilt the carb last week as well.
In reply to vwcorvette (Forum Supporter) :
I assume the issues were present before the rebuild, and remain unchanged? Was this combination ever running well before this?
In reply to Shavarsh :
It all began with a drive in heavy rain. So I pulled the cap and found a ton of moisture inside. It has been a while since it and the rotor had been replaced so I swapped them and the module for new. It ran so so after that then got worse and ultimately stopped running. I replaced the coil and plugs. No change. Carb had not been addressed in 20 years so I rebuilt it. After installing I attempted to check and set the timing, but no amount of fidgeting could make it right. I'm ready to toss the TPI unit I just got on it
Based on your video the ignition sounds retarded, and a late spark will definitely make the engine lazy so that it won't want to accelerate and sounds "choked off" for lack of a better word.
I also have a carbureted car and chased this issue for several months as well, convinced that the carb was the culprit until a friend suggested I just try advancing the distributor, which cleaned it right up. I also had issues with plugs fouling and misfiring, and the engine ran hot than normal, in case you're seeing those issues too.
I'll add that my engine is tired and due for a rebuild so I'm guessing the timing chain is worn out as well. In the end I had to advance the timing even more than the mark on the balancer would indicate. If you have an older motor this is one of those things you may end up setting by feel rather than relying on a timing light.
In reply to jerrysarcastic (dork in training) :
+1 on the worn timing chain and setting by ear vs light.
Engine was built for the Soccer Mom Challenge. When was that? Prepandemic, right?
I will advance it a bit more and see how things go.
A friend is bringing over another carb to try as well.
vwcorvette (Forum Supporter) said:In reply to Shavarsh :
It all began with a drive in heavy rain. So I pulled the cap and found a ton of moisture inside. It has been a while since it and the rotor had been replaced so I swapped them and the module for new. It ran so so after that then got worse and ultimately stopped running. I replaced the coil and plugs. No change. Carb had not been addressed in 20 years so I rebuilt it. After installing I attempted to check and set the timing, but no amount of fidgeting could make it right. I'm ready to toss the TPI unit I just got on it
Go back to the basics. 1-8-4-3-6-5-7-2. I see you have two different brands of wires on there. Check those. Clean off the timing tab and mark the balancer with some yellow or white paint on the timing mark. Did you adjust the timing with the vacuum advance hooked up or disconnected? Did you set the advance with total timing at 3000rpm or base timing at idle?
Check to verify all the spark plug wires are in their proper place per the timing order. ( I assume with a carburetor you also have a distributor)
Noddaz said:vwcorvette (Forum Supporter) said:In reply to Shavarsh :
It all began with a drive in heavy rain. So I pulled the cap and found a ton of moisture inside. It has been a while since it and the rotor had been replaced so I swapped them and the module for new. It ran so so after that then got worse and ultimately stopped running. I replaced the coil and plugs. No change. Carb had not been addressed in 20 years so I rebuilt it. After installing I attempted to check and set the timing, but no amount of fidgeting could make it right. I'm ready to toss the TPI unit I just got on it
Go back to the basics. 1-8-4-3-6-5-7-2. I see you have two different brands of wires on there. Check those. Clean off the timing tab and mark the balancer with some yellow or white paint on the timing mark. Did you adjust the timing with the vacuum advance hooked up or disconnected? Did you set the advance with total timing at 3000rpm or base timing at idle?
I did just that and screwed something up. I decided to reset the distributor so it wasn't 180 out and moved the wires accordingly. I marked the balancer and cleaned off the tab as you suggested. I put my leak down tester in the number one cylinder to verify I was on the compression stroke. The tab and balancer lined up perfectly. The distributor was off about a quarter inch. A friend suggested turning the oil pump drive a bit and realigning the distributor. So I did that too. And it would't fire up. No spark. Checked spark with the timing light. No flash. Turned the distributor back to the origianl spot and it popped through the carb, with spark, but wouldn't fire up. I need to start over again.
Remember back in school when the math teacher would say if you get stuck on a problem to move on to the next and come back to this one later. Yeah, it may be time to move on to another thing.
Okay, so I verified TDC one more time. Set the Distributor and wires in the correct orientation and order. Got it fired up and running. Idles okay. Timing at 15 degrees at idle (vacuum advance hooked up) and all in at 3000 rpm (35 degrees). Snap throttle response is good. Test drive. Womp womp. Will not take throttle under medium load. Bogs down and dies. Occasionally with a back fire (mighty spectacularly with the air filter off and the dog house removed). I live up a hill (about a 500 foot incline over about a half a mile). Couldn't get beyond 10 mph. Had to be REAL gentle on the throttle or it would die. Pull in the driveway. Let it idle for a minute. Snap the throttle. No problem.
Perhaps my carb rebuilding skills aren't so good?
How long did you let the carb soak in cleaner?
Did you blow out / through all of the orifices?
Did you check the float for a leak?
L5wolvesf said:How long did you let the carb soak in cleaner?
Did you blow out / through all of the orifices?
Did you check the float for a leak?
I soaked it for two night in Pine-Sol/water mix. I blew out all orifices and passageways with shop air and carb cleaner. I did not check the floats for leaks.
vwcorvette (Forum Supporter) said:L5wolvesf said:How long did you let the carb soak in cleaner?
Did you blow out / through all of the orifices?
Did you check the float for a leak?
I soaked it for two night in Pine-Sol/water mix. I blew out all orifices and passageways with shop air and carb cleaner. I did not check the floats for leaks.
I’ve never heard of using Pine-sol on a carb. A quick search says PS is not recommended for copper or aluminum. Good news is – it probably smells good.
vwcorvette (Forum Supporter) said:Timing at 15 degrees at idle (vacuum advance hooked up) and all in at 3000 rpm (35 degrees).
Should this say vacuum advance was disconnected? If you have 15 degrees of timing at idle with the vacuum advance hooked up, then thats the problem.
When you say it won't take throttle at medium load, does that mean it does above and below that?
To me, that would suggest a clogged passage. I believe there's probably a sort of intermediate/transitional passage after idle and before main?
A friend is letting borrow a carb tomorrow to try out.
Shavarsh said:vwcorvette (Forum Supporter) said:Timing at 15 degrees at idle (vacuum advance hooked up) and all in at 3000 rpm (35 degrees).
Should this say vacuum advance was disconnected? If you have 15 degrees of timing at idle with the vacuum advance hooked up, then thats the problem.
What should it be then?
I found the pinesol recommendation online so it must be okay, right? Lol
I cleaned it after with carb cleaner and shop air.
Jesse Ransom said:When you say it won't take throttle at medium load, does that mean it does above and below that?
To me, that would suggest a clogged passage. I believe there's probably a sort of intermediate/transitional passage after idle and before main?
So long as I don't push too hard the van will run but it doesn't like any throttle at this point.
I should stick to water-cooled VWs.
In reply to vwcorvette (Forum Supporter) :
12-15 degrees at idle, 34-36 all in above 3-4k rpm. The important part is that this is done with the vacuum advance disconnected, and the vacuum line on the intake manifold/carb should be plugged. (So there isn't a vacuum leak)
The advance at idle with the vacuum canister hooked up should read much higher, like 40-50 degrees. The "all in" measurement with the vacuum canister hooked up isn't of much use.
Edit: You got this!
In reply to Shavarsh :
Good advice, but be aware of ported vs. manifold vacuum. Working correctly, ported vacuum will be 15ish at idle and 30+ just off idle. What you're describing is Manifold vacuum.
Ported vacuum comes from a little port just above the throttle blades, an is only active above idle.
I don't know how your distributor is set up, but if it's stock, my guess would be it set up for ported vacuum. Check your carb and see which port is what, and hook it up accordingly.
Additionally, when you have the carb off, flip it upside down and check the transfer slot exposure. It should be a little square. If not, turn the idle screw down until it is. Idle screw adjustment shouldn't move too far of of that. If you need to turn it down a bunch to get it the idle down, you've got a vacuum leak somewhere.
You're on the right track, keep at it!
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