Slant 6-- New Carburetor and loss of power

carhunter · Sep 23, 2014

Hello there, I have a mysterious problem that has developed with my 1962 Plymouth Belvedere. I have installed a new (exactly the same) single barrel BBS carburetor on its slant 6. Before doing so the car ran fine, however, the old carburetor had an irreparable accelerator pump. The car had severe difficulty starting only after the new carb was installed.

After adjusting and playing with fuel mixture screw and no results, I figured I would check the "quality of build" the remanufactured carb came with. After disassembly, I noticed the float looked as if it had been stepped on. I then took it upon myself to take the float from the old carb and without adjusting it, installed it into the new carb. I also decided to swap the metering jet. The old had a 130 jet and the new came with a 160 jet. I have an idea of how these operate and figured since the carbs were the same, I'd put what I knew worked into the new carb. The new carb is currently using the old 130 jet.

Now to the problem. When I am going down the road, It feels as if something pulls on my back bumper intermittently, in other words, the car seems to lose engine power in spurts. When I make an attempt to accelerate it is like the car is not getting enough fuel and tries to die. Not all together, but bogging in and out.

I thought maybe the fuel pump was bad. So I 'dangerously' pulled the fuel hose off
(after disconnecting the coil wire) and cranked the motor. Fuel shot half way across the yard. To heck with the grass.

I figure the pump is ok. I also feel that the carburetor bowl keeps enough fuel for the car to run (maybe).

Is there a chance the old rubber fuel lines could be getting vapor locked?

I have a see through fuel filter hanging horizontally above the valve cover. When the car is finally started and running, only a small amount of fuel dribbles into the almost empty filter. Is this a significant fuel pump problem or is the float and needle doing their job in the carb?

Any help is appreciated

Thanks,
Marvin

emore · Sep 23, 2014

There's a chance that the filter that's on the tank end of the fuel line(filter sock) is clogged, especially if it hasn't been replaced before. The weak fuel pump would have a hard time sucking the gas through it.

747mopar · Sep 23, 2014

You said you didn't adjust the float? Any difference in height or length of the new seat or needle will change the float level so I'd rule that out first by checking it. If it ran before with the old carb then I'd focus on what was changed first.

carhunter · Sep 23, 2014

747mopar said:
You said you didn't adjust the float? Any difference in height or length of the new seat or needle will change the float level so I'd rule that out first by checking it. If it ran before with the old carb then I'd focus on what was changed first.

I'll begin by adjusting the float to allow for a higher fuel level in the bowl.
I still won't discount the possibly clogged fuel sock in the tank.

747mopar · Sep 23, 2014

I'm not familiar with your carb but usually you can get the specs on the level. You usually adjust them by holding the float assembly (top of carb) upside down and measuring from the gasket surface to the float and then just tweak the tab until you get it right.

Photon440 · Sep 23, 2014

Another idea that won't cost anything is to try it with the 160 jet that it came with.

mopar 3 B · Sep 23, 2014

While you have the top cover off to check float level make sure the gasket surface is flat. They are notorious worppers.

nm9stheham · Sep 24, 2014

Some other things to check that are fuel related:
1. The rubber line from the top of the fuel tank to the fuel line back under the car will age and crack and will suck in air.
2. If this only happens when hot, the fuel may be vaporizing in the line from the pump (newer fuels). You can try to see if there is non-alcohol fuel available in your area. Also, try some premium as an alternative. Some folks have routed the fuel line from the pump over the top of the valve cover to keep it cooler, but I have not found this necessary on my '62 Dart /6.
3. Your description of the nearly empty fuel filter is concerning; I suspect that the pump is not doing its job and has a bad valve at either input output. The air ought to eventually purge out of the filter, at least most if not all.
4. Tee in a fuel pressure guage and check; your test with no back pressure is no gurantee of a good pump. Should be 3.5 to 5 psi at low idle. Stop the engine and see if the pressure bleeds off very, very slowly or not at all. if it drops the instant the engine stops, then there is a pump valve issue.

Moparsmitty · Sep 24, 2014

I know that you checked the fuel flow, but I've been fooled by this before. Check the fuel pressure too. Change all of the rubber lines and the filter in the fuel system before you go any further. Even if it isn't causing this particular problem, it should be changed anyway. And make sure that you don't have water in the fuel system. Adding new fuel with ethanol to an old car can cause all kinds of weird troubles. After you've done that then you can concentrate on the carburetor.

miller · Sep 25, 2014

Are there ANY signs of trash, or dirt, in the bowl of that 're-manufactured' carb?

Years ago I got my hands on one, a four-barrel. The re-manufacturers had sand blasted the body halves, you know, to make it look good. Carb had sand in all the fuel, and air ports. Real piece of work.

Might want to look that thing over real good...

carhunter · Sep 29, 2014

Well... I replaced all the rubber fuel hoses and installed a brand new fuel pump. There is still the same problem. Despite the fact that I fooled with the carburetor to the point of it spraying fuel out of the accelerator pump linkage.

I had the car idling for a bit (before I messed up the carb) and decided to put it in gear, hold the brake and push on the gas pedal. As soon as I put a "load" on the motor, it sputtered and died. It is in fact getting fuel.

I also noticed "NO vacuum" at the carb where the distributor vacuum line attaches. When I pulled the line off, the car was not affected. Could the timing advance inside the distributor be the culprit of all my problems?

- - - Updated - - -

miller said:
Are there ANY signs of trash, or dirt, in the bowl of that 're-manufactured' carb?

Years ago I got my hands on one, a four-barrel. The re-manufacturers had sand blasted the body halves, you know, to make it look good. Carb had sand in all the fuel, and air ports. Real piece of work.

Might want to look that thing over real good...

Hi miller. I'm pretty sure the carb is clean. However, I noticed that the pump that adjusts the metering jet height had a corroded spring underneath. It was also missing the small "bb" that I guess should have been under the spring. I took the "bb" from the old one and dropped it in there and put the metering pump back in place. I figured it would be ok since the carbs are the same. I'm not the best with carburetors, I just try to do my best.

miller · Sep 30, 2014

Understand, carhunter...

You say no vacuum at the advance port? That could very easily be a wrong gasket in the carb, a hole missing or the sort. I'm no 'expert' at carbs, either, but I've overhauled my share of them. By "bb", you mean a check ball?
Anyway, even a single-barrel like your's, have both air and fuel 'ports' in them, most very small, and anything can block them. Not saying that's it, but could be part of the prob, besides the basic 'overhaul' that was done to it. Missing (like that bb) or wrong parts can cause probs, too.

Might consider getting a new overhaul 'kit', use your old carb as a guide, and completely go through the one you want to use. Make sure that ALL ports are open, and start fresh. The kit will also give you all the needed adjustments.

Crummy deal when you have to overhaul a 'overhauled' carb. Must be a sign of the times. Good luck with it!

Doesn't matter how 'clean' it looks. If any of those ports are loaded with junk, your flogging a dead horse.

Badvert65 · Sep 30, 2014

carhunter said:
However, I noticed that the pump that adjusts the metering jet height had a corroded spring underneath. It was also missing the small "bb" that I guess should have been under the spring. I took the "bb" from the old one and dropped it in there and put the metering pump back in place. I figured it would be ok since the carbs are the same. I'm not the best with carburetors, I just try to do my best.

That 'BB' is important. It is a check valve and without it, carb will definitely have problems. Make certain the one is under the Accelerator pump as well.

70bigblockdodge · Sep 30, 2014

I had a fuel problem with my Challenger turned out to be half clogged fuel line and sucking air anything below 2/3 of a tank my clear fuel filter would not have any fuel visible running at idle then other times be full, this combo of problems drove me nuts. I had to start at tank and work my way forward checking and replacing.

coloradodave · Sep 30, 2014

I would take a different approach. You say you installed a 'new' carburetor and yet when you took it apart the float was crushed. I would return the carburetor to the shop where you bought it and ask for another 'new' one. Then I would go home and pull the carb apart and check the float level and drop. Also take the needle and seat and mixture screw out and blow through all the passages. The carb may very well not be the problem, but when you pay good money for a part you should at least get a good one...

carhunter · Oct 1, 2014

coloradodave said:
I would take a different approach. You say you installed a 'new' carburetor and yet when you took it apart the float was crushed. I would return the carburetor to the shop where you bought it and ask for another 'new' one. Then I would go home and pull the carb apart and check the float level and drop. Also take the needle and seat and mixture screw out and blow through all the passages. The carb may very well not be the problem, but when you pay good money for a part you should at least get a good one...

I'll look in to it. Although, it took an act of God for carquest to get there hands on one for me. If I took it back, I might face even more difficulty obtaining one that is better than the crap I already have

- - - Updated - - -

I just made absolutely sure my timing was good. I had to make a new mark on the harmonic balancer. It had slipped on its rubber grommet. I took vacuum line to distributor loose and set it to 0 degrees TDC. I also noticed that when the timing light lit up the mark I made, it was steady as a rock where I adjusted it (with engine running of course). I reattached the vacuum line to distributor advance and revved the car. The new timing mark steadily advanced to higher degrees. I would imagine this rules out the timing issue.

I have a feeling that the little "bb" that goes in the bottom of the finger size cylinder below the metering jet pump could be causing an issue? It fits into a little hole under the spring. The old carb had it in there and the new one was missing it. Maybe the new carb was designed slightly different? I have had it apart maybe 15 times already. This pic is of the old carb to give an idea. What would a "bb" be in there for?

I would like to post a video of the car's problem but don't know how...yet.

Paul_G · Oct 1, 2014

Is it possible to put all the borrowed parts from the original carb back on it, reassemble it. Then put it back on the car and see how it reacts. If the starting problem goes away and your original problem returns, your rebult carb is lame. I would take it back and try another.

Photon440 · Oct 1, 2014

'bb' or check-balls are generally in there to act as a one way valve.

miller · Oct 2, 2014

I feel your pain, carhunter, even if it's only a simple one-barrel. Think it would be that hard to return? Unreal that you have to pay for junk like that. Of course, it's your call, since it's you there. When you saw the mess-up float, that was a red flag. If your stuck, turn it around, and make it good. Simple deal.

On the original carb, you say the accelerator pump was trashed? In what way? In the carb body, or the pump itself?

Unless you can return, and replace the 'new' one, other option would be to repair your old carb, robbing parts off the new one as needed. Never messed with a single barrel, but overhaul kit can't be that much.
Deal is...if you want it done right, do it yourself. Learned that the hard way.
Main thing on a carb is, needs to be clean, and all adjustments right for the particular carb. Anyone can do it!

carhunter · Oct 2, 2014

Hey guys, the check ball that I added to the rebuilt carb's jet pump had been causing the problem (I removed it). I also noticed that the old carb actually had a place for the check ball to rest in the bottom. The new one allowed the ball to roll into the hole with little resistance.

Anyway, the car will run down the road fine. Although I feel that some fine tuning that I'm mentally incapable of, would get rid of sluggish power. The accelerator pump has a "dead spot" in which it immediately is too much gas, then the motor catches up.
It is also absolute hell to get it started in the morning. The choke is not hooked up. However, I don't think that is the whole issue. I hsd to pour gas down the carb. I also used a machinists gauge and made sure the float was exactly 1/4 inch from top rim of bowl.

I have a 1bbl rochester monojet in good condition but the car refused to start with it. I'm beginning to think that this car has a mind of its own and is extremely picky about what it wants. Maybe it is my lack of knowledge in this field. I feel bad that it is causing more stress than enjoyment. I just didn't want a crusher to get it. I greatly appreciate all of ya'll giving good advice. I'll continue to hammer away at the issues.

Slant 6-- New Carburetor and loss of power

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