Dies under acceleration

TxSlick66 · Post by **TxSlick66** » February 21, 2010, 3:22 pm

A muffler that is clogged up can do that. Chased those exact symptoms on a MACH I I rebuilt the engine in. Turned out the original exhaust tubing was double walled adn the inside collapsed and clogged the flow. New pipes and mufflers and it ran like a bat out of hell

stevechaos13 · Post by **stevechaos13** » February 22, 2010, 10:20 am

Well, she completely tanked on me yesterday and I had to have her towed home.
I reset the distributor, got her timed in much better and gassed her up. She was ready to run it would seem. Took her for a few jogs around the neighborhood, and she ran great. She was roaring and ready to go it would seem. So I decided that I was going to take her home, so I could mess with her everyday and get her dialed in and get a few more things done. Bad idea.
The trek started out just fine, she was running pretty good and then something happened. I was cruising along doing about 55 when I started to notice that she was lagging. RPM’s were steady at around 2.5K, but all of a sudden it just seemed like the power was draining. Speed started dropping, and if I tried to give it more gas, you could feel it start to struggle. The wife was following behind me and said that she could tell something was wrong because when I would start to sputter, I would start throwing out a little black smoke. Then she died. I sat there for a minute and decided to take her back home. Fired her again, she fired right up and took off like everything was just fine. Made it about another mile down the road and the exact same thing happened again. Acceleration started winding off, and she sputtered, smoked and died. At this point, I’m just trying to get her to run long enough to find a place to turn around. But it was a constant cycle. She’s die, then restart, go a little further and then die out again. Everytime except the last one that is. She finally just flat out killed and I didn’t even try to restart. Got out and called the tow and waited. Opened the hood, and didn’t see much. The fuel filter up to going to the carb was once again completely full of fuel, but other than that nothing seemed odd. By the time I got her home on the wrecker it was too dark to see anything, so it’ll have to wait until this weekend.
I’m kind of at wits end here. I have no clue what’s she’s doing. I’m fearing the worst I’ve gotta say. Something just isn’t right. Does any of this sound familiar to anyone? I’m about ready to start tearing this motor down, but at this point, I’m not even sure if that would help me out. Any suggestions?

slick4x4 · Post by **slick4x4** » February 22, 2010, 10:49 am

sounds like fuel to me...
vented cap / fuel line collapsed / weak fuel pump / filters
sounds like it runs fine after it sits for a bit...
i would look for fuel problems, my

TxSlick66 · Post by **TxSlick66** » February 22, 2010, 11:00 am

A vaccuum gauge is your friend here...

Connect Vaccum Gauge to intake, Leave All Vaccum Hoses Connected.
Normal Engine at Idle When the engine is warmed up and working correctly, at idle the needle of the gauge should be steady and within the range of 17 – 22 inches of vaccum. Normal Engine operation when Throttle Snapped Open and Closed Vacuum should drop to 3 and then gradual climb to 25 – 28 before settling back at the previous value. This indicates that the valves and rings are OK. Poor Rings or blow-by at Idle The needle will be steady but the reading will be lower than normal. Poor Rings or blow-by when Throttle Snapped Open and Closed Vacuum will drop to near zero and then gradual climb to about 22 before settling back to previous value. If you have a Valve hanging open The needle will drop occasionally about 4 inches of vaccum from its normal idling reading. Burnt Valve The needle will regularly drop by a greater amount than with a sticky valve ,If showing 6 inches of vaccum you.have a Leaky Valve The needle rapidly drops two or more inches each time the valve should be closed. May also indicate a Lean misfire. Loose Valve Guides Fast vibration of the needle between 14 and 19 inches of vaccum.If you have a Weak Valve Springs When revving the engine hard, needle varies between 14 – 22 inches of vaccum. As rpm increases, a wider variation occurs in needle movement. Leaky Intake System Needle reads low ( below 5 inches of vaccum)and idle will be rough and unstable.. May also indicate late ignition timing or incorrect camshaft timing. Leaky Head Gasket Between Cylinders Needle floats regularly between 5 and 19 inches of vaccum. May also indicate intake manifold gasket leak at an intake port or a faulty injector. Blocked Exhaust High reading at first but will normaly stay under 3 inches of vaccum.Also motor will be very flat, no power. Clogged PCV or Intake Manifold vaccum Needle moves slowly through a wide range of readings. Also check idle air/fuel ratio. Conclusion Obviously vacuum gauge readings cannot pinpoint all problems, but they can save you a lot of time and money in chasing down major issues. Altitude Factor If looking at the readings, it’s important that you remember that the vacuum readings will decrease as your altitude increases. So if you live X amount of feet above sea level, remember to drop 1 inch of vacuum for each 1000 feet you are above sea level.

stevechaos13 · Post by **stevechaos13** » February 22, 2010, 11:20 am

Thanks TXslick, I actually have a vacuum pump/gauge that I’ve only used to bleed my brakes. I knew that I could use it for diagnostics too, but I forgot all about it. Sounds like a good idea. I see that you’ve highlighted the exhaust part of your post, so it would seem to me that you are leaning heavily on that? I can honestly say, that is something I’ve never checked out. I’ve got dual flowmaster that are dumped right behind the cab, so you normally don’t even see all the smoke until it starts to dissipate. After it’s been sitting for awhile I crank it up, after a few minutes of idling it will normally throw out a some white smoke, which I was told was actually water vapor that accumulates. It doesn’t do it for very long, and as the engine warms up, it stops completely. I’ve never seen it blow black smoke before, but the wife said that everytime I would start to loose power and it would start sputtering, it would start belching out black smoke. Those flowmasters are on my list of things to remove already, even more so if that could be part of my issue.
Slick 4x4, fuel was always my original thought too, but aside from the carb, it all seems fine up until that point. Like I said before, I have one clear filter below the fuel pump, and one after, on the line that goes into the carb. When the truck is running like it should, neither one of them usually fill up more than half way. If you’re standing there watching it run you can actually see the fuel cycle through the filter. Open up the throttle and rev it up and it will suck fuel out of the top filter, but it never empties it. Whatever it draws out, is replaced immediately, or else I would suspect the pump. The lines are all steel, with the exception of the upper line going from the filter into the carb, and it is not kinked I know for a fact, because I’ve had to route it to accommodate for the bigger HEI distributor. It’s just strange to me that everytime she dies on me that top fuel filter is completely full. Like it’s sending the fuel faster than the engine can take it. Or the carb isn’t working right, or there just isn’t any combustion…
I don’t really know, but I know I want to solve the problem so I can get her back out on the road.

TxSlick66 · Post by **TxSlick66** » February 22, 2010, 11:32 am

Remote possibility, clooged exhaust, but your symptoms are exactly like those experienced in the past with that problem. Just someting else to check.

stevechaos13 · Post by **stevechaos13** » February 22, 2010, 12:12 pm

TxSlick66 wrote:Remote possibility, clooged exhaust, but your symptoms are exactly like those experienced in the past with that problem. Just someting else to check.

It does seem likely. I have had this problem before on one of my rides, but it was due to the 25 year old catalytic converter. A couple of good whacks and it blew free.
What could cause such an issue, and what are the remedies?

Obsa · Post by **Obsa** » February 22, 2010, 12:38 pm

One outside possibility, are you sure that the carburetor float vent is clear? If it is clogged it is possible that it is only barely allowing enough fuel to pass through the carb.

I have seen this problem only twice once on a Honda 750 shadow where the owner had rerouted the float bow vent hoses incorrectly so they were pinched shut. The bike would idle and rev without a load, but would not pull in gear.

The other time I bought an old mid sixty chevy pickup that had been setting fora year or so. It would crank and die. My dad and I towed it home and when I started to clean the carburetor I noticed that "dirt dauber" wasps had fillen in the vent tube. I cleared the tube and it cured the problem

TxSlick66 · Post by **TxSlick66** » February 22, 2010, 1:26 pm

Vacuum gauge will tell you right away, especially if you can run a hose and plaec it where you can see it while driving.

I also had a 67 bumpside with a 240 I-6 that would try to die out on left hand corners. After a year of C&R (chasing and replacing) it turned out to be the float was bad in the carb. That truck ran perfect going straight at any speed or when turning right...

stevechaos13 · Post by **stevechaos13** » February 22, 2010, 1:58 pm

Okay, I'm going to hook my vacuum gauge up and run through a few things and see what I find out.
I've been researching it and it looks like the exhaust being backed up could be key. From all I've read, the symptoms are identical, and there are even a few that I had forgotten to mention.
I'm thinking I'm going to chop my flowmasters off this weekend, and see what difference it makes. I've got a set of headers on the way, so chopping those off was going to happen anyways, but I'm cusios to see what kind of impact it makes given my current situation.
The carb has always been a point of interest too. It's a Holley 4bbl with an electronic choke that's not hooked up, and there are at least 2 maybe 3 ports that are plugged up for some reason, and could probably use a good rebuild. So I guess now would be a good time to start.
Sounds like a plan?

TxSlick66 · Post by **TxSlick66** » February 22, 2010, 2:55 pm

If the pipes between the engine manifolds and the mufflers are original, they are prone to collapse internally even though they still look fine externally.

Once you cut the flowmasters loose you still have potential for clog. Only way I know to be sure is to pull at the manifold.

Or, if all else fails, READ THE VACUUM GAUGE~!

stevechaos13 · Post by **stevechaos13** » February 22, 2010, 3:18 pm

TxSlick66 wrote:If the pipes between the engine manifolds and the mufflers are original, they are prone to collapse internally even though they still look fine externally.

Once you cut the flowmasters loose you still have potential for clog. Only way I know to be sure is to pull at the manifold.

Or, if all else fails, READ THE VACUUM GAUGE~!

Haha, don't worry, I'm going to use my vaccum gauge!
Colapse internally? How does that happen?

TxSlick66 · Post by **TxSlick66** » February 22, 2010, 4:32 pm

Ford used some tubing that had a double wall. The inside one rusts and collapses and clogs up the works. I found this out the hard way after spending two weeks trying to figure out why a nice 351W I built would not get out of its own way.

stevechaos13 · Post by **stevechaos13** » February 22, 2010, 4:48 pm

TxSlick66 wrote:Ford used some tubing that had a double wall. The inside one rusts and collapses and clogs up the works. I found this out the hard way after spending two weeks trying to figure out why a nice 351W I built would not get out of its own way.

Okay, that makes a lot of sense.
Once I cut the mufflers off though I should be able to see this though right? Maybe the exhaust will blow it out once the mufflers aren't in the way?

Obsa · Post by **Obsa** » February 22, 2010, 6:30 pm

stevechaos13 wrote:Okay, I'm going to hook my vacuum gauge up and run through a few things and see what I find out.
I've been researching it and it looks like the exhaust being backed up could be key. From all I've read, the symptoms are identical, and there are even a few that I had forgotten to mention.
I'm thinking I'm going to chop my flowmasters off this weekend, and see what difference it makes. I've got a set of headers on the way, so chopping those off was going to happen anyways, but I'm cusios to see what kind of impact it makes given my

situation.
The carb has always been a point of interest too. It's a Holley 4bbl with an electronic choke that's not hooked up, and there are at least 2 maybe 3 ports that are plugged up for some reason, and could probably use a good rebuild. So I guess now would be a good time to start.
Sounds like a plan?

With a Holley you have an excellent source of information on tunng from holley.com

http://www.holley.com/division/Holley.asp#64

The electric choke not being hooked up would only be a problem on cold starts, unless it is so far out of qdjustment that the choke plate is always closed.