352 intermittent stumbling and stalling

[MN66]

My 66 F250 4spd with a recently replaced 2bbl carb has been running perfect since I swapped carbs. I no longer need to warm it up for 10 minutes with the choke on, it pulled strong at all speeds.

On Friday morning I decided to treat her to some 91 octane non-oxygenated fuel when I filled up on my way to work, just to see if my mileage or performance improved perceptibly. About 10 miles into my commute, I felt the first brief stumble, which I had never felt before with this truck, almost like I had tapped the brakes traveling at freeway speed.

In the next several miles, the stumbling became more frequent and more pronounced, until finally it stalled when taking my exit ramp to work. The truck started immediately and I continued to the nearest gas station to buy iso-propyl alchohol. After adding it to the tank, I drove the remaining few blocks to work without a stumble.

Later, I drove it to lunch on city streets without any problems, so I assumed the iso-propyl did the trick.

On my way home, again about 10 miles into my commute, it stumbled badly again so I coasted off at the next exit. It started right up again, but it never seems to restart if I leave it in gear and and wait for the water to clear the carb.

Is there something about turning the key off, then hitting the starter that would be different than letting the transmission turn the engine over with the (pertronix) ignition left in the run position?

I'm planning to run the tank close to empty, then add sea foam and fill up with 87 octane oxygenated fuel.

Any other thoughts on what I should try?

Thanks,
Corey

[BarnieTrk]

Q1) Is there something about turning the key off, then hitting the starter that would be different than letting the transmission turn the engine over with the (pertronix) ignition left in the run position?

Q2) Any other thoughts on what I should try?

Thanks, Corey

A1) It sounds like a fuel issue - specifically, water in the fuel. I don't think the method in how you turn over the engine would effect a fuel issue.

A2) I would not wait to run the tank near empty. I would first choice recommendation would be to drain the remainder of the fuel tank into storage cans and refill with known clean fuel. If that isn't feasible, then my second choice recommendation would be to add 2-3 more bottles of ISO-PROPYL ALCOHOL to the fuel tank with the hopes it will allow you to to drive it until the fuel level is down to 1/4 tank, then refill the tank with known clean fuel...preferably with 100% gasoline....at least until you can get the water in the fuel issue cleared up.

JMHO,,, BarnieTrk

[Toyz]

Drain it out! If you still have the in-cab tank, it's a simply process to remove the flex line under the cab. Keep in mind that the alcohol is only going to absorb a very limited amount of water, and it sounds as if you got a pretty good shot of it.The alcohol water mix tends to disrupt other contaminants, so you may be feeling the results, and even changing filters/ cleaning screen for the next couple of tankfuls. There are two things which may be happening as to the restart, partially dependent on the Pertronix model you have. If your setup uses the original resistance wire or a resistor in it's place; letting the drivetrain attempt to restart may not yield enough coil output to fire the fouled mixture. The other possible factor is the decreased movement may allow the water to temporarily move away from the pick-up, allowing a re-start.
Paul

[MN66]

Thanks guys - I will drain the tank and fuel filter today and let you know what I see.

Corey

[MN66]

Hi Guys - I pulled the flex line under the cab and only a small amount from the hard line drained out. Do I need to pump it out?

Thanks,
Corey

[slickstysix]

You're better off siphoning out the gas. Waiting for it to drip out of the tube on the bottom will take forever since it has to go thru the sending unit.

[Toyz]

No flow is an indicator of a problem in the line, unless the prime has been lost somewhere by loosening components. Removing the filler cap will often aid the flow. Alcohol will break down already weakened soft lines, as well as loosen accumulated debris. Removing the pickup assembly may reveal the source, careful inspection of the tank may show the contaminates, whether water or a combination.
Paul

[ICEMAN6166]

i got 5 gallons of water in my tank one time from a gas station
made it about a 1\4 mile
made them fix the problem plus reimburse me for the cost of the gas

iso alcohol will only take up so much water

i have an electric fuel pump with a hose on each end i use for siphoning and draining my tank, best method and no gas in my mouth

if gas is not draining from the lie below the tank, ther might be a pickup tube issue

[bruceandersson]

Hmmm, did you take the gas cap off yet? Many places sell 'replacement' caps for our trucks that look right but are not vented. This could cause both the lack of flow out the tube as well as an occasional stumble as the vacuum in the tank can overtake the fuel pump.

You also could have gotten dirty fuel. Got a tank driving across the country in Chicago once. Had to clean/replace the fuel filter every tank for a while. That is why I never get gas at a station with the tanker there. The sediment in the tanks gets stirred up when they get filled.

[ICEMAN6166]

Many places sell 'replacement' caps for our trucks that look right but are not vented.

yes you need to watch out for that junk

nice to have a shiny chrome cap but definitely avoid the ones with the warning sticker on them about the pressure
ill see if i can find the one i have but do not use and write down the info on the cap.

[MN66]

I was able to drain the tank after starting the engine to re-establish prime. I drained about 3 gallons and it looked clean, though I'm not sure if you can see water in the gas. I dumped in a bottle of heat and 1/2 bottle of sea foam in the "empty" tank, then added a gallon or so of 87 octane.

I drove down the hill a mile or so from my house to refill the tank with 87 octane (with 15% ethanol) which I've been running all summer. It stalled once on the way to get gas, but restarted easily.

After filling up I drove around town and it stalled at every stop light. It stumbled quite a few times, maybe worse than before. Then I realized I hadn't drained the fuel filter on the fuel pump. I removed the filter bowl and noticed some brown crud at the bottom.

Brown crud from the fuel pump filter

download_20151012_205825.jpg (487.89 KiB) Viewed 5954 times

I take it for another drive tomorrow after work to see if anything has changed.

Thanks again for the help!

Corey

[chris401]

You may have an ignition problem also. Heat and draw will aggravate an old ignition switch and a weak coil will have the symtoms your having. You should do a bench test on the coil cold and after its hot and compare. Also while running check for a healthy blue spark by pulling coil wire 1/4" off coil. Ideal to use plastic pliers to avoid getting bit. Check starter solenoid with a known good part or you can load I terminal with a headlight, it will glow yellow, dim, flicker or go out if faulty. The resistor wire supplying voltage to coil can be loaded with a head light as well. Glow will be a little dim due to it being 9.5(?) volts.

[chris401]

Hmmm, did you take the gas cap off yet? Many places sell 'replacement' caps for our trucks that look right but are not vented. This could cause both the lack of flow out the tube as well as an occasional stumble as the vacuum in the tank can overtake the fuel pump.

You also could have gotten dirty fuel. Got a tank driving across the country in Chicago once. Had to clean/replace the fuel filter every tank for a while. That is why I never get gas at a station with the tanker there. The sediment in the tanks gets stirred up when they get filled.

Dennis Carpenter has a good locking cap.

[MN66]

I will take a look at the ignition tomorrow.

I should mention that I have a pertronix III ignition with the matching 40,000 v coil. I was wondering if the electronic ignition would typically fail intermittently, or all at once.

If this hadn't all started with a new tank of gas last week, I would have suspected it was an ignition problem, since it seems more like a loss of spark than anything else.

I'm wondering if a failing relay might cause this? I have a relay wired in so that the coil gets a full 12v rather than whatever is left over when you run through the ignition resistor wire.

Corey

[ICEMAN6166]

[quote="MN66"]I drove down the hill a mile or so from my house to refill the tank with 87 octane (with 15% ethanol) which I've been running all summer[/

sounds like the source of your problem right there

a very bad thing to do, ethanol is a carb killer

i drive out of my way to pay more for ethanol free gas or use the lucas additive i buy at the parts store or wally world

all summer is enough time to mess up a carb

learned about this nasty stuff after moving down here to the 48, there was no ethanol in any fuel in Alaska so i never worried there

its even worse in small engines like lawnmowers and chainsaws, my landlord brought his lawnmower over earlier this summer said it would not run anymore
he of course was using ethanol fuel and the inside of the carb was filled with crud.
after i cleaned and rebuilt the carb it started on the first pull and i have been using it regularly with no issues (and no ethanol)

[Toyz]

The ethanol, possibly combined with water, is likely your cause. By adding the other products, you have probably aided the E15 in breaking loose everything imaginable. I like E85 for my own purposes; I despise E15! It is pushing the raw edge of acceptability for non-flex fuel vehicles, and data-logging by myself and others has revealed the high degrees of variance in fuels labeled as E15. You may have approached the creation of that fabled "universal solvent" Don't forget to check the carb inlet screen if present. You are likely to find that any soft lines are now damaged internally, even those supposedly for use with alcohol. Better to replace now than keep changing filters and cleaning the system.
I believe the PIII is designed for full battery voltage; I would suspect a failing resistance wire triggering the relay if that is your configuration and it is partially ignition related. KISS is a pretty good description for dependable ignition systems. Your mention of inability to restart while rolling makes sense now since you mentioned your setup. I would simply eliminate the resistance wire and relay if it were a potential concern. Small voltmeters or multi-meters are a very handy tool for diagnosis. They can even be attached to suspect areas for "on the fly" diagnosis if needed. Keep in mind that "full available voltage" is just that; it seldom will be an exact 12 volts. Even with voltage drop, a running system should exceed that, while starter load may take it down well below 12 volts. If you are in fact triggering your relay via the resistor wire, you may be marginal on holding holding the relay engaged. While starting via switch, the available voltage is provided through the starter relay "I" terminal. Good luck!
Paul

[bruceandersson]

Ethanol is evil! At least to our older vehicles that came with hoses and gaskets that the ethanol dissolves. Just make sure any flex line is ethanol safe. If you had a restricted fuel line, it would run fine until the float bowl emptied. Then it would stumble or stall and you'd have to wait for it to re-fill. I have a 57 that the fuel system failed on due to ethanol. I replaced the flex line and pump and it started right away.

[MN66]

I only had time tonight to take a 12 mile ride, some in town and some at freeway speeds. Not one stutter or stumble during that drive.

I drove out to Fleet Farm to get a hand pump with the thought that I would siphon a bit of gas from the bottom of my tank to see what's down there. I won't have time until Thurs to do anything else with the truck.

I mentioned in my initial post that I had swapped carbs from the 390 that I bought a few weeks ago. I plan to go through my original carb and put it back on my truck. I assume the carb on there now should be rebuilt now that it's been drinking that universal solvent?

I have new ethanol compatible fuel line throughout, but I did not replace the hard fuel line, which I expect had some varnish built up.

btw -
I'm no fan of ethanol, and no offense intended to my farmer friends out there, but a 15% blend of ethanol is *mandated* here in the People's Republic of Mn.


Corey

[ICEMAN6166]

a 15% blend of ethanol is *mandated* here in the People's Republic of Mn.

except for these 498 listed ethanol free stations in the Republic:

http://pure-gas.org/index.jsp?stateprov=MN

[MN66]

I hear ya Iceman. You can get non-oxygenated here (sometimes they mix it with water to make it go farther) but I was under the assumption that the federal mandate for ethanol was 10%.