Idles fine, dies in gear

[Handegard 10]

Help me make a troubledhooting checklist.

 

Had the carb rebuilt over a year ago, and have problems for over six months.

 

Car woud start, run, and randomly start to stumble and die at stoplights on my comute, and recently it has failed to run at all.

 

I took the carb to the carb shop and they tore it apart and cleaned it (said the imulsion tube was clogged) and I put it back on.

 

It fired up, it had a obvious vacum leak and idled HIGH. I moved it a few feet and turned it off.

 

Today, I replaced the base gasket (below the spacer) and put it all back together. It fired up and idled pretty good (maybe a tad high, but it was on choke and I don't have a tach)

 

Then, I put it in gear, and it stumbled again. I tried to move it, and it just stumbled and died.

 

I do have a new fuel pump, fuel filter, just put good gas in it, fresh air filter. I have also checked over all the vacum lines, and don't believe I have a leak. Last time I checked vacum, I it was wonderfull, I think it was steady 18", also has good compression. Any other suggestions?

 

I'm going to have to go dig out my tools and check the gap and timing again, but that was checked over and over and over again last time I tried to troubleshoot this...

Edited March 27, 2011 by Handegard

[SM69Mach 68]

Not saying this is the same as what you have, but I had a similar issue last year. I checked the carb, vacum, plugs, timing etc. Everything always seem to be fine, at idle, in Park or Neutral it was fine. As soon as I put it in gear it would immediately shut off. After working through a couple of things, it ended up being a bad Torque Converter. Once I changed that out, problem solved.

[Rcodenewf 44]

What sort of carb do you have? What is timing set at?

 

And are you saying that it idles ok with the choke partially on?

 

Maybe a little more info and hopefully we can help you out.

 

As stated earlier i have also seen the torque convertors pack it in and do just that....John

[LoneWolf2U 136]

Not knowing where the carb shop placed the settings at you need to do a baseline set first.

I use the mixture screws set at 1 1/2 turns out from closed.

A 1 1/2 turn in on the idle screw from first touching the throttle plate.

Then warm eng to operating temps and adjust carb to eng and test.

Also I do a quick vac leak test with starting fliud while it is running to warm up by spraying around carb base and lines. If there is any varying in rpm there is a leak.

[StephenC 10]

I had a problem similar to your awhile ago on my 351W to where it would start right up and idle normal in park and nuetral but one you put it into drive you would have to give it gas to keep it running. Turned out that there was a vacuum leak in both valleys of the intake manifold.

[Handegard 10]

Torque Converter is going to be my absolutely last guess. For now, I'll go along pretending that it's fine, until all other options have been exhausted.

 

I don't think it's a manifold vacuum leak either (though I know I have one after the carb was off!). When this problem first started, I put a vacuum gauge on it, and had a almost perfect 18" of vacuum, with nary a hiccup in the needle.

 

Last week, it wouldn't start, or would start for only a few moments. Then, I pulled the carb off, took it to the rebuilders, and they found a clogged emulsion tube (?)

 

I put it back on, and it reved HIGH. So I replaced the lower carb gasket, and it started (with choke) at 1800rpm. Idled fine, after it sat a minute, choke came off, idled some more. I turned it off, it fired right back up a minute later, I put it in gear, and it stumbled immediately, and died.

 

I checked timing today, and it's good, and I set the points yesterday (to 0.021 I believe)

 

I talked to the carb shop today while buying a new gasket, and they suggested the coil. I happen to have a new coil sitting in the car I had meant to install, so I'll try that.

[buening 63]

Did you check your vacuum line going to and from the vacuum modulator on the trans?

[SM69Mach 68]

When it goes into gear is does it engage hard or is it a smooth transition from Park to Drive?

[foothilltom 33]

Hi Chris, here are a few thoughts based on my experience (such that it is):

 

Don't lump together idle behavior and "running" behavior. These are different animals entirely and most likely have unrelated causes.

 

I'd suggest getting your idle circuit working "just so" before tackling any other problem so you don't chase your tail. If you can't get your idle circuit dialed in, there's obviously a problem that needs to be found.

 

It's great that you've brought a vac gauge into the mix. Your car should comfortably idle in the 600-900 range at maximum vacuum. Make sure the engine is warm and the choke off entirely. If you get tired of waiting, just manually disengage the choke. The choke just introduces another variable you don't want.

 

As somebody suggested, get your idle-mixture screw baseline set. Turn them all the way in (both sides) and back out 1.5-2 turns (as a starting point). Adjust until you get to max vacuum and lowest idle.

 

If you can't get 'er to idle correctly, it's time to start diagnosing possible causes. Vac leaks are an obvious concern though it sounds like you don't suspect that. Anywho, get your idle circuit right before you press on. This way you're dealing with fewer variables as you move on to the "power circuit".

 

When I read your post, my first thought was "power valve". I don't believe you've answered the "what kind of carb" question, but if it's a holley, you have a power valve (PV). The PV is supposed to open (to deliver more fuel) when vacuum drops to a certain level (depending on the rating of the PV). If the PV doesn't open at the right moment, the engine would stumble and possibly die upon wider throttle.

 

Does your engine die only under a load? Or can you reproduce the stumble/die by just quickly opening the throttle in neutral?

 

One other thought is your vac advance. If you don't have one, borrow a vacuum tester (one that creates vacuum, not one that measures it) and see if your vac advance is leaking or broken. Your vac advance could also explain a stumble/die condition under load.

 

In summary, take it one step at a time: diagnose/fix idle behavior before moving on.

 

Best of luck!

Tom

Edited March 30, 2011 by foothilltom

[Rcodenewf 44]

When you say your timing is "good" ...what is it set at?

 

Disconnect vacuum advance and plug and record the timing.

 

Try this: Back the timing off a few degrees and then of course turn the curb idle screw up to get back to your original idle.

 

If putting it in gear improves or solves it, it may mean that there wasn't sufficent fuel flowing through the idle/transition circuit when load increased. An engine can idle away happily on a very lean condition but by putting it in gear it comes under load and the lean fuel mixture isn't sufficent to keep it running.

 

Try it and see and get back to us.....regards...John

[Handegard 10]

To add- The car is all stock, factory 2bbl.

 

Did you check your vacuum line going to and from the vacuum modulator on the trans?

 

No, I haven't, but I will. Tonight, I'm going to remove all the vacuum lines, and just plug the tee on the manifold during troubleshooting.

 

When it goes into gear is does it engage hard or is it a smooth transition from Park to Drive?

 

This car has always had a "thunk" when going into any forward gear (not reverse though) but it was almost non-existant after the carb shop tuned it all up and adjusted the idle.

[Handegard 10]

The carb shop suggested I try a new coil, so I tossed one on (BWD E70, supposed to be direct replacement) and the car behaved exactly the same.

 

This time, I managed to keep a fresh impression of it's behavior in my head and get straight to the computer!

 

So heres what happens.

 

Cranks, fires, idle seems to skyrocket for just a instant, then falls to what I feel is a good smooth chocked idle (sounds/feels normal). Keep in mind, I have no tach.

 

Idles a moment, I put it in reverse, it immediately stumbles, stumbles, dies.

 

After it dies, it didn't just fire back up. I had to crank and crank, pause, and try again. After I cranked it a bit, it eventually got that little "pop........pop......pop....pop...pop..pop.fire" fire feeling like it was trying real hard, just not quiet catching. It then idled poorly for a moment, and died again.

 

At that point, I shut the hood and posted here. I'm now going outside to cap all the vacuum points on the manifold, and change the upper carb gasket (and possibly the lower, again, depending on what it looks like)

 

I will also check the gap again, and the timing again if I have the tools here.

 

Vacuum will have to wait till another day, the car is at home and all the tools are at work.

[Handegard 10]

Don't lump together idle behavior and "running" behavior. These are different animals entirely and most likely have unrelated causes.

 

I'd suggest getting your idle circuit working "just so" before tackling any other problem so you don't chase your tail. If you can't get your idle circuit dialed in, there's obviously a problem that needs to be found.

 

Currently, the car idles just fine. I had it dialed in last summer by Carb Conn and it ran great for awhile, then this happened. Right now, when I fire it up, it idles just as good as it did then.

 

 

It's great that you've brought a vac gauge into the mix. Your car should comfortably idle in the 600-900 range at maximum vacuum. Make sure the engine is warm and the choke off entirely. If you get tired of waiting, just manually disengage the choke. The choke just introduces another variable you don't want.

 

Cold and on choke it idles at 1250 when I first start it, after I let it warm up, it drops down a bit, I'd guess it's smack in the middle of that range. I can toss the timing light on it again tomorrow and check it's warm idle rpm. I get off early tomorrow, and want to work on it....

 

As somebody suggested, get your idle-mixture screw baseline set. Turn them all the way in (both sides) and back out 1.5-2 turns (as a starting point). Adjust until you get to max vacuum and lowest idle.

 

I'm not really wanting to play with anything here... My knowledge of carburetion is scant (I work on new european cars all day after all!) but I'm guessing that if none of this has been touched since the car ran perfectly, it shouldn't need to be touched again?

 

If you can't get 'er to idle correctly, it's time to start diagnosing possible causes. Vac leaks are an obvious concern though it sounds like you don't suspect that. Anywho, get your idle circuit right before you press on. This way you're dealing with fewer variables as you move on to the "power circuit".

 

I'm not going to rule anything out. At this point, I haven't found anything wrong with the car, so I'm willing to start back over. I didn't get to work on it this evening, but tomorow I will plug every vacuum line on the car, and rule them out. I might even dig up my vacuum gauge, just to re-check. I have a Mityvac I can use to test the advance unit, but I've had 4 distributors in the car in the last 6 months, each with the same symptoms, so I doubt it's bad.

 

When I read your post, my first thought was "power valve". I don't believe you've answered the "what kind of carb" question, but if it's a holley, you have a power valve (PV). The PV is supposed to open (to deliver more fuel) when vacuum drops to a certain level (depending on the rating of the PV). If the PV doesn't open at the right moment, the engine would stumble and possibly die upon wider throttle.

 

Factory Autolite 2bbl.

 

Does your engine die only under a load? Or can you reproduce the stumble/die by just quickly opening the throttle in neutral?

 

When I start it, it runs fine. Idles for awhile even. But when I put it in drive/reverse it dies.

 

After this, when I restart it, it'll die again on it's own.

 

One other thought is your vac advance. If you don't have one, borrow a vacuum tester (one that creates vacuum, not one that measures it) and see if your vac advance is leaking or broken. Your vac advance could also explain a stumble/die condition under load.

 

I will put a vacuum on it to see if it hold. But again, I've had 4 distributors in it in the last 6 months for various reasons.

 

When you say your timing is "good" ...what is it set at?

 

I checked it against the manual at the time. If someone wants to chime in as to what the timing should be, I'll go set it again.

 

Disconnect vacuum advance and plug and record the timing.

 

I'll check again tomorrow.

 

Try this: Back the timing off a few degrees and then of course turn the curb idle screw up to get back to your original idle.

 

I've rebuilt engines, automatic transmissions, I've done the heads on a bi-turbo Audi A4 V6, but the one thing I freely admit to knowing nothing about is carburetors. And yeah, I know it's easy, but believe me, I've tried. I have zero luck anytime in the past I've touched one, and I honestly just don't want to. It's the one part of my car or boat I'm content to just pay someone else to touch. I know it's stupid, but I'm just not going to go there unless everything else is possibly ruled out. I don't have money to pay the carb shop to undo all my mistakes again.

 

If putting it in gear improves or solves it, it may mean that there wasn't sufficient fuel flowing through the idle/transition circuit when load increased. An engine can idle away happily on a very lean condition but by putting it in gear it comes under load and the lean fuel mixture isn't sufficent to keep it running.

 

Something like this is what my gut is saying. I've got 5 years of experience, and it may not be with older cars, but for whatever reason, my nagging feeling is saying "fuel delivery"

[Handegard 10]

And hell, maybe someone just needs to teach me to set points.

 

The reason I've had 4 distributors (well, 3/4 of them), is that over the course of troubleshooting for the last 6 months, I swear to you the gap is wrong EVERY time I check! I'll set it, it's right, and by-god the next time I look it's off again. I know there are two screws to tighten, and I'm familiar with a screwdriver, so I just don't get it.

 

I rotate the engine until the cam in the disty is holding the points open on the highest point, then adjust the gap to have light drag at .021" (actual spec is not in my memory) and recheck after I tighten the screws, right?

[foothilltom 33]

Hey Chris, most of us feel your pain on the breaker points. Getting them just right is a PITA to say the least and proper setting is crucial for timing/dwell. If you're in the mood to spend $99, consider upgrading to a Pertronix Ignition Module to eliminate the points entirely.

 

There's going to be a simple reason for your problem, but it usually takes "starting from scratch" to find it. I suggest building up from the basics.

 

Timing. Factory is 6-8B (more or less) though many of the fellers seem to advance as far as she'll go w/out pinging. I'm not good enough to play this by feel, so I break out the timing light and set it precisely. Note that your point setting will affect timing. Get your Dwell meter fired up and get the dwell angle set properly (i forget the exact value, but I want to say 29 degrees). You can look it up easy enough. It's *really* hard to get this right, so plan on pulling that distrib cap many times and farting around with those points (do I need to say Petronix again?).

 

Make sure you disconnect and plug the line to the vac advance to set the timing and work at a consistent idle. Once timing/dwell are verified, you can cross that off the list more or less.

 

Idle-mixture doesn't sound like your problem. Signs are pointing to the power circuit (aka fuel delivery). That stock autolite could be your problem. My son's 302/2V ran like crap and we played all the games I'm describing to you. We eventually threw up our hands, swapped out the autolite for a friend's 2V holley he had laying around, and OUILA! it ran awesome. Carbs are intricate animals and there could be any number of issues with clogged passages, baffle incorrectly seating, etc. Maybe the carb shop you patronize would let you borrow one for an experiment?

 

Another basic item is the fuel mixture. The symptoms you're describing could fit an overly rich mixture problem. This is not the same as your idle-mixture. Does your exhaust smell "gassy" or any "oily" exhaust? Since your car has trouble starting after it initially dies, I'm wondering if your plugs are getting fouled by the rich mixture. Your autolite should have a sight screw that you can remove to check the fuel level in the bowl. The fuel should just trickle out if the floats are set properly. If the fuel pours out, you are running rich. This could be an improper float setting or your fuel pump is overwhelming your carb. Hell, it could be improper jetting. Anywho, a rich mixture can wreak havoc on how your engine runs.

 

I need to run now, but I have additional thoughts for later. You'll get this licked...just be open to starting from scratch and re-checking these settings over and over as you change stuff up.

 

Tom

Edited April 1, 2011 by foothilltom

[Handegard 10]

Well guys, this one was a great experiance.

 

I talked to the carb shop, talked to the owners of a local shop that do lots of classics, talked to my old boss (most skilled tech I've ever met) and I've asked about this in a few forums over the last six months, and on the suggeston of a old co-worker who "hates chinese parts for Fords" asked me to humor him and replace my brand new condensor......

 

 

And the car runs great.

 

Six months, and it turned out to be the condensor? I guess that pertronix kit I purchased is going in now ;)

[buening 63]

Its always the simplest things we overlook. Glad you got it figured out!

[Pakrat 1,043]

LOL, wow, and that is pretty much the cheapest part in the whole system too. That's a perfect example of why the shotgun approach of just replacing parts is such an inefficient way of diagnosing a problem. Now we will all know to suggest that first the next time this issue comes up, it certainly would not have been the first on my list to check but I also went to Pertronix at my very first point regap too.

 

The late great Superdave of the Stangnet forums always said "NEW PARTS" means nothing, always verify before you install. Not sure how you can verify a condensor but he hated import replacement parts also.

 

I hope you buy this guy a beer and a shot!