Projects Truck Quit on me! Thinking it's the carb...

Alright gents, I'm sitting at work thinking about why my truck won't run, so you're all part of my process now, welcome to the madness.

I've been driving my truck around the last week or so, having sorted out most of the issues. It's been running good! On the freeway I have been able to cruise at 75-80 pretty steady at about 2200-2300 RPM, temp stays under 205 for the most part at the higher RPMs, and drops to 180-185 as soon as I lighten my foot. I have one (1) Holley 94 on it with 51 jets and a 6.5 power valve. Idles around 450.

Usually I can start it right up with a little choke and a pump of the throttle and she'll warm up and be ready to go pretty quick. So on to the problem!

Yesterday it was bucking a little on the highway on the way to work, and it seems like it's from a rich-mixture bog, but I'm not certain.

In the afternoon I went to go home and had a huge problem just trying to get it started, and it began to smell of fuel/flooding. I managed to get it started with lots of throttle and lots of foot pumping while messing with the choke, but I couldn't go anywhere. As soon as I let off the gas, it would die. Trying to keep the choke out and drive resulted in lots of bucking and little motion.

Personally, I'm thinking blown power valve, but I'm curious what others might think. All comers welcome to chime in!

Thanks in advance,
Mike

 

Status of gas tank?

 

sounds like an ignition issue....

 

What engine, distributor do you have??????

 

You may be correct on the power valve. It only takes one backfire to ruin it.

 

Is it in time?
Does it have spark?
Does it have fuel?

Have no pre- conceived notions. Start with the basics. Let the engine tell you what's wrong. Start with the basics. It does not matter how good it ran last week.
Look for dumb stuff like almost broken wires... loose connections..... blocked fuel lines....
Fuel
Fire
Time....

 

I am with squirrel on ignition, is what I was smelling while reading your symptoms.
You can smell gas so I assume you have fuel, what about good spark? do you have a spare condenser to throw at it?

 

80 % of carb problems are ignition related.

 

A test is worth a 1000 guesses!

First part of the test. Take off the aircleaner, and, using a squeeze mustard or ketchup bottle which you have emptied and washed, try to fill the bowl of the carburetor through the vent. If you can, it is not the power (economizer) valve. If you cannot, rebuild the carb and replace the power valve.

Second part of the test. Disconnect the fuel pump and plug the line. Now, will the engine start and run for several seconds with the carb you just filled with gasoline? If yes, check fuel delivery system. If no, its in the ignition.

My guess is on the ignition, BUT: a test is worth a 1000 guesses.

Jon.

 

Ethenol eat up your Fuel pump diaphragm. That's just a guess but I'd check it out first.
The Wizzard

 

I love the thought process on the HAMB. Keeps me honest.

Brand new. And full. Valid point though.

Could very well be Jim, could very well be. Out of curiosity, how would you go about checking the timing? Personally, I'm thinking some ticker tape on the crank pulley somewhere and a wire tuned to TDC, but that might be harder than I think.

59A with a crab distributor. Just rebuilt the distributor a month or so ago, so I'm not saying it's not the issue, but it's plausible.

Seems like it has spark, as it fires, but may not be in time... will check for sure.
Fuel it has, 100%. Bypassed the mechanical pump in favor of electrical (which I keep on the firewall for emergencies right now) and it's definitely pushing fuel.

I don't have a spare, but I can get one I'm sure. Thinking about it, definitely could be the culprit....

Interesting, I hadn't thought about that check, but definitely a good one worth trying!

I swapped over to an electric fuel pump to eliminate just this issue. One thing checked off the list.


Thanks for the input, and keep 'em coming if you have more! I'll check on these tonight/tomorrow for sure.

 

Moisture under the distributor cap?

 

This one has bitten me in the past. HRP

 

If it's hard to start and in a too rich, flooded, "raw gas smell" condition, DO NOT try to start the engine by pumping the throttle or closing the choke. You'll only make matters worse by adding even more fuel to the cylinders and flooding it even worse. Instead, open the choke fully and hold the throttle fully open without pumping the accelerator. Crank the engine over for a couple seconds and pause, with the throttle held open, for 5 0r 10 seconds. This will allow some of the excess liquid fuel to evaporate. Repeat the process, with the throttle still held open, a few more times and often the engine will eventually start. By going in short bursts like this you reduce the chances of overheating the starter and/or grinding down the battery.

This process also assumes that the carb doesn't have a sunk float or a needle and seat that won't fully close. In which case it's going to keep dumping more fuel into already too-rich engine. And depending on how badly it was flooded, check your oil for an over-full condition and see if it also smells noticeably of raw fuel contamination.

 

Two of the easiest things to check is both connections on the coil, and make sure they are tight.

My 34 was running intermittently and I couldn't figure it out for the life of me. It would run fine for a bit, then sputter, choke, cough, and either go back to running or die. Didn't see it till it was getting dark, started it up, but noticed a sparking at the positive side of the coil. Tightened it up and it ran great after that. Couldn't really tell cause it looked good with the wire sitting there, but seen the sparking once it got dark outside.

Not saying that is what it is, but you definitely want to start by checking the easy things that don't cost any money 1st.

 

Flooding?

Sent from my LG-TP450 using The H.A.M.B. mobile app

 

I found cheapo aftermarket male plug at distributor had lost its memory and was not making contact occasionally causing starting and stalling issues. Bent the prongs and was good for a couple years until i had time to put a quality plug on

 

Too much fuel pressure with electric pump?

Mick

 

My first thought as well, most electric pumps put out too much pressure for carbs, unless it’s got a regulator? Need all the pieces of the puzzle to venture a guess. I would tend to say it sounds like an ignition problem as well.


Sent from my iPhone using H.A.M.B.

 

Don't forget about the condenser. These can be bad out of the box. Sometimes they work, sometimes they dont. Sometimes thier lives are measured in minutes.

 

So what’s changed ? Or is likely to have changed ?
My thoughts, from similar experiences,
Blown power valve, blocked fuel lines,

I don’t know enough about this to understand why others think it is a timing issue, unless something has rattled loose, so I am watching with interest to learn more.

Just for curiosity, what motor, car is it.
Thanks.

 

See, learnt something right here, didn’t know that you could do that.
After my car has been sitting for a while, I remove the top of carb to fill the bowl.
This sounds easier.
Thanks !

 

Most engines will run at least 30 seconds on the gas in the float bowls alone and some will run longer. That's why you can drive about half a block with a car with an electric pump when you forget to turn the pump on.
Here I am going to side with those who say too much gas or a blown power valve.
The too much gas could be due to the electric pump putting out more pressure than the carb can handle or it it could be because there is a piece of dirt keeping the needle from seating.

 

Sounds like ignition; however, you should make sure your are under 3psi in the fuel pressure department.

Old 94's can get a little drippy if over-pressured.

 

As we have all stated it could be a number of issues . If I remember correctly .doesn’t the power valve screw into the pass side rear of the carb on the outside ? My suggestion is , if the power valve is located on the outside of the carb, just remove the old and screw in a known working power valve . These can go to junk rather fast as stated with today’s gas . Nothing is as it was in the good old days . If it be gas , or the product the power valve is made from , the bastards are always going bad in today’s world . Just remember this is a pretty simple animal your dealing with , take a few moments to determine what door Murphy opened on you and you will back in the fun business before you know it .

 

Its the condenser. Its always the condenser. For some weird reason most people want to blame the carburetor but 90% of carburetor problems are electrical. For those slow to catch on, thats humor. Replace the condenser

 

That would be the "spark control valve"; the power (economizer) valve is located inside the bowl.

Jon.

 

I laughed at this. The more I've been thinking about it, the more I think you're right, BUT I'm also thinking it's points. New points, and I just set up the distributor not long ago, so barring a loose fastener, I don't see that being the issue. I do think that it might have something to do with the frost we had that morning though, and possibly a distributor cap that isn't sealed from the elements as well as it should be... Checking it out today and I'll report back!

 

It is getting harder and harder to find good condensers these days.

That's why I leave them on the shelf.

 

X5 or 6