Severe bogging, surging under load...

[effinrich]

This is my first time posting, so I'll try to do this right.

I recently replaced the mag. pickup coil in the dizzy. I was sloppy about the dizzy reinstall and knocked the timing way off. Over the next few weeks, after getting a timing light and researching, I was able to get the timing straight. The fuel pump was bad, so I switched that out at the same time.

Upon driving the first time after all of the work, the truck started out pretty good. After driving it for roughly twenty minutes it started boggin down, surging, and lunging on even the slightest incline. The gas pedal looses pressure, the RPM's jump back and forth from 3000 to 3500 just to get it up to 40 mph. There's also a steady clicking or tapping noise coming from the engine during all of this. Sounds like a card in bicycle spokes.

I thought the timing was still off, so I set it again and again with the same bad results.

I've adjusted the carburetor which seems to effect it to some degree, but nothing dramatic enough to make it drive well.

Thought is may be the ignition control module, so I changed that out, as well as got new plugs and wires.

I'm going nuts trying to figure this out. Any thoughts would be extremely appreciated.

The truck: 1965 GMC 1000, HEI dizzy, 350 crate, Edelbrock 1406 carb, 63 amp internally regulated alternator.

Recent work: New alternator a cpl months ago, replaced the dizzy pickup coil as the magnet on the original cracked, new ignition control module, new plugs, new plug wires, new fuel pump, new sending unit.

thanks!

[gimmy 64]

was the truck sitting for any length of time? sounds like it's starving for fuel. check fuel filter or change it.

[Corts60]

I agree with gimmy. The ticking noise you are hearing is more than likely an exhaust leak which I guess could be mistaken for a card in a bicycle wheel.

Change your fuel filter before doing anything else. If that doesn't cure it, the 1406 carbs have two little filter screens inside of them. If the carb has been sitting awhile, it couldn't hurt to grab a cheap rebuild kit and go through it. Those carbs are super easy to rebuild. Also ensure that you do not have sediment in your tank that is clogging up your system.

Not sure how you are noticing the gas pedal losing pressure. It should have a return spring that keeps it a contstant tension.

Oh and Welcome!

[effinrich]

It was sitting for roughly two weeks while I was working on it. Forgot to mention I replaced the filter as well, and it's clean. Could the electric choke adjustment cause this?
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[effinrich]

I'll pick up a carb tuning kit regardless of the cause. I hadn't thought of the internal filters.

So I adjusted the choke to lean it out a bit and it definitely drove better for 20 minutes or so. I idle was too high (1500 rpm's), so I adjusted the idel screw down to 1000 rpm's or so. When I drove off the awful lurching, lunging came back. I'm not sure if that's a coincidence or what. It definitely seems to start giving me trouble after the engine has reached operating temp.

Also, when I stopped and turned the truck off, the engine kept turning for a couple of seconds; kind of jerking and sputtering.

[brokenspoke]

Vacum leak?

[awbrown]

make sure the choke is completely open when the vehicle is warmed up ,is it blowing black smoke from the tailpipes??? if it runs good cold but not hot it sounds like a choke problem ... if it is electric make sure it has power and a good ground ...

[effinrich]

A vacuum leak had occurred to me. What's the best way to test for a leak? Seem to remember a trick with carb cleaner or something.

Brokenspoke, there's no black smoke, but it does run better cold. Initially getting through the gears runs high rpm's either way however. I'm putting the screen/filter back on the fuel sender right now. It had fallen off. Maybe sucking too much fuel, or dirty fuel?

On an unrelated note, the headlights went out at random last night, so now there's that.
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[awbrown]

a vacuum leak will run better cold because normally the choke is on .. if it is a leak spray carb cleaner at areas the you might suspect,base of carb , intake gaskets etc..

[neto]

Like mentioned before make sure the chock is opening completely. My sons 1406 on his mustang did the same thing. The ground wire was not making good contact. Is the ticking sound there when cold also? If so then check for a broken rocker or check you compression.

[brokenspoke]

I use a propaine (sp) torch (do not light) My truck had simular symptions as yours and I found a vacum leak at base of carb

[effinrich]

Ok, so I was derailed temporarily. The alternator burned up my battery, the voltage meter read 18+ just beforehand. After fresh wires and a spare battery I had in the garage, it's going again and the volts are reading steadily a little over 12.

I haven't had time to get a carb rebuild kit, but I did change out the new sending unit for my old one, and the gauge started working immediately. On the way to work today I noticed that the apparent fuel delivery issue (lunging, surging, having to floor it just to get up a hill at 30mph) started right as I went over a hump in the road. Also the fuel gauge seemed to fluctuate with how badly it was boggin and surging.

I have to fix the headlight situation before driving home from work tonight, as they went out completely this morning. Old wiring issue I assume? I'm picking up a carb rebuild kit for the weekend and will check for vacuum leaks as well.

[61_FL_Apache]

does the dist have vacuum advance?

[ozzyman]

If it runs good cold and gets worse at it warms up I would suspect a over rich condition. This could easily be the choke causing issues. Also the fuel gauge will bounce when the truck bounces and surges because the fuel in the tank is sloshing.

Have you pulled your plugs to check for a lean or rich reading?




Good luck!

Mike

[effinrich]

It does have vacuum advance, and it's quite old.

The plugs indicate rich, at least according to the attached reference image. They are grayish white on the tip, then sooty below that.

After installing the new fuel pump last week I followed the Edelbrock video instructions as to how to set the choke, which was considerably richer than my setting. Regardless, I did as the video instructed, which was to turn it clockwise (richer). If that's the sole cause of this issue, I'll be simultaneously relieved for the easy solution and embarrassed for being a moron.

Bye the way, thanks for all the help everyone.

[ozzyman]

Originally Posted by effinrich

It does have vacuum advance, and it's quite old.

The plugs indicate rich, at least according to the attached reference image. They are grayish white on the tip, then sooty below that.

After installing the new fuel pump last week I followed the Edelbrock video instructions as to how to set the choke, which was considerably richer than my setting. Regardless, I did as the video instructed, which was to turn it clockwise (richer). If that's the sole cause of this issue, I'll be simultaneously relieved for the easy solution and embarrassed for being a moron.

Bye the way, thanks for all the help everyone.

If your plugs indicate rich, and the fact it gets worse as the engine warms indicates rich my prime suspect would be the choke set too rich or not turning off as the engine warms up. Can you disable it completely to eliminate any interference at operating temperature?
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[effinrich]

I could Remove the hot wire, which should do the trick. I'll try it in the next hour and give you an update.

[ozzyman]

Well I'm headed off for the night but i was reading through your orignal post and noticed you had fresh plugs in there. If they are already showing signs of running rich it's either weak spark or a carb tuning issue. Also are all plugs indicating rich or only certain ones?

Does it only surge at certain RPMS? Only while accelerating? Only while cruising (steady rpms)? if it's running rich enough and you have a exhaust leak the "card in a bicycle" tire sound could be simply extra fuel burning off after the exhaust stroke.

Once the engine is warm, if you blip the throttle quickly does the engine hang, return to idle or bog down slightly and then return to idle? if the engine hangs you have a lean condition or vacuum leak, if it bogs down slightly before returning to idle it is running rich, which could be float levels, choke or jetting.


Hope you figure it out soon, will check in tomorrow to see where your at.


~Mike

[effinrich]

Hi Mike,

It appeared as though the driver's side plugs were richer than the passenger's side, but I'll check all of them again in a bit and get back to you. I also changed most of the plug wires, so I'll double check those connections.

The surging/bogging issue starts around 60mph, between 2000 and 3000 rpm's. By the time I get to work - 40 minute drive - I'm pushing 3500 rpm just to get up a hill at 40mph. The issue doesn't right itself after exiting the highway and slowing down, only after it cools off, then the whole cycle starts again.

The issue is only when accelerating. When my foot's off the gas, it's fine.

When I blip the throttle once the engine is warm, it bogs then returns to idle.

I leaned the choke out considerably last night, and it seemed better until I was up to operating temp. and higher rpm's.

After getting home last night I checked the tranny fluid while the engine was hot. It was dry as a bone, so I added a couple of pints.

I also noticed a hissing noise coming from the area of the break master cylinder/booster. That may have always been there, I'm extremely suspect of every noise at this point.

Just to add to the list, I found a lose hose connected to a steel line at the back passenger's side of the tranny, which leads to the engine compartment. I'm not very knowledgable regarding transmission specifics, so I apologize for the vague description.

[hopped up]

im thinking ignition/timing problem? loosing spark at the upper rpms?
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[ozzyman]

could be a multiple problem situation. The transmission fluid level could have caused problems with a hot transmission, the fact it only seems to happen at operating temperature and in the higher RPM range could be float levels off or maybe even a clogged jet. Seems like you got your choke adjusted properly.

The hissing sound from the booster could be a vacuum leak. either from the diaphram or a cracked/loose hose

the loose hose off your transmission could have been a cooler line, which would be why your fluid level was low.

is it an auto trans? does the fluid smell burnt and apear brownish in color?

Wish i was still down in SoCal, was just there in ventura last week, could have offered more hands on help

~Mike

[gofastnut]

I was thinking the line going towards the trans might be for the vacuum modulator. If that was off, it would shift hard and late. If it was a cooler line, there'd be fluid all over. Hitting a bump and having it happen says there might be cr@p in the carb. How much rubber line do you have between tank and pump? Between pump and carb? Check the rubber hoses to make sure they're not cracked and you're sucking air.

[gimmy 64]

the hissing sound from the master and the line going to tranny-modulator are 2 very bad vacume leaks that could be your problem

[effinrich]

Pardon the late reply, guys. Work's been nuts

Hopped up: dealing with the timing was the beginning of all of this, and it's still a concern. My first attempt was too far advanced, and it was definitely missing. Could it now be retarded too much?

Mike: It's an auto trans, and I changed the fluid about six weeks ago, but I'll take a look at the color. Hands on help would be a godsend, bye the way.

Gofastnut: there's about a 18" of hose under the truck and 12" to carb. Under the truck is definitely suspect.

Gimmy 64: I'll replace the tranny hose, and check the booster hose. Not sure where to find a replacement for that. Any ideas?
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[gofastnut]

effinrich, check the grommet and the check valve that the hose goes into at the booster. The hose is specific due to it's high vacuum nature. Most NON box type parts stores carry it. the trans vacuum line you should use vacuum tubing again.
I'd love to give you a hand, but that's quite a drive.
Good luck!