Non-jeep Tech help needed for my 74 Ford

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Dr. Marneaus
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Non-jeep Tech help needed for my 74 Ford

Postby Dr. Marneaus » Tue Jul 31, 2018 9:19 am

Okay, we all own these old things and are pretty knowledgeable. I have some weird stuff going on on a 74 ford.

Its a duraspark truck, but running pertronix.
Running an edelbrock 600CFM Carb
Ford 390, stock.

I was having some vapor lock issues it seemed, but truck was running great 95% of the time. My fuel filter failed and let a bunch of crud into the Holley carb that was on the truck, so i replaced the filter, and removed the carb, opened it up, cleaned everything out, and put it back on. At that point, it idled poorly, and after heating up and driving a bit, it died on me and wouldnt stay running. Sometimes it would idle in park but as soon as i went into gear it died. Sometimes it wouldnt idle in park unless i had my foot on the gas. Pretty much any time i tried to gas it, it would almost die.

Flash forward, i threw on an edelbrock because i dont understand holleys. It expressed a similar issue. It would ONLY RUN WTH THE CHOKE CLOSED, which indicated a lean condition requiring choking to make it rich. SoI opened up the eddy, cleaned it out, now when I try to start the truck, it fires up INSTANTLY, and it idles smooth and clean. Idles perfect with choke closed, and choke open now.

However, the following issues still exist:
1. If I give it gas even SLIGHTLY quickly in neutral, it will try to stall out. If i SLOOOWWWLLLYYYYY apply throttle, it'll gain RPM smoothly and happily.
2. If I put it in gear, it'll die. It doesn't shut off INSTANTLY, but will peter out over 3 or 4 seconds and shut down. If I put it back in park and hit the key, it fires instantly and idles perfectly in neutral/park.

This morning I fired it up, threw it in gear, and it ran fine. I moved it back and forth a bit in my driveway, it idled fine in gear. I'm assuming the choke was closed, and maybe that was enriching the mixture enough to keep it running in gear? I even held it in place with the brake and gave it gas, applying a bunch of load, and it idled fine. I didnt let it warm up I was just testing if it ran.

Things i have done:
-Checked fuel filter.
-Checked fuel pressure, getting 8psi at carb from factory mech pump.
-Checked all damn vacuum lines and ports, sprayed with carb cleaner. No leaks detected.
-Removed one at a time each vacuum accessory, no change in idle or vac leaks detected.
-Replaced carb caskets and carb spacer with a spare i had, no leaks detected.
-Tried two different carbs, precisely similar issue exists (holley and edelbrock).

so to summarize, it wont idle under load when warmed up it seems, and when hot or cold, if i gas it, it'll try to stall.

Sounds like a vac leak right? But i cant find it. Maybe its just running way too lean?
Well it ain't just the smoke and the traffic jam that makes me the bitter fool I am But this four-wheel buggy is A-dollaring me to death.
For gas and oils and fluids and grease, And wires and tires and anti freeze....And them accessories, Well honey, that's something else.

bigun
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Re: Non-jeep Tech help needed for my 74 Ford

Postby bigun » Tue Jul 31, 2018 10:36 am

Something I have run into with todays fuel, because of the alcohol will partially vapor lock in older engines when it is hot.

letank
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Re: Non-jeep Tech help needed for my 74 Ford

Postby letank » Wed Aug 01, 2018 12:34 pm

It sounds like I can offer $500 for that old truck.... to relieve your headache... short version of below: add external clear fuel filter before the fuel pump.

Otherwise you have realized that junks got into your idle circuit, you have cleaned and cleaned and cleaned and even he eddy had shown similar issues, dirt in the idle circuit, or charcoal canister is you have one releasing bits...

I had the same with a friend's old motorbike, poor idle but running well with throttle opened at any speed... when the gas tank started to release rust, we cleaned, and cleaned... every 3 months my friend was coming for a carb clean up, for some reason he has not installed a fuel filter that I gave him, the tank could not be coated, and no tanks on ebay...

As Bigun said it could be gas, my bike sometimes cut off at idle, regardless of gas tank fill level... a pain... and here in SF, no vapor lock.... it is always 60ishF...
Michel
74 wag (349 Kmiles... parked, next step is a rust free body)
85 Gwag (226 Kmiles... the running test lab)
See Engine bits and Fuel and brake lines, and Body work

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Dr. Marneaus
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Re: Non-jeep Tech help needed for my 74 Ford

Postby Dr. Marneaus » Wed Aug 01, 2018 4:04 pm

Keep in mind, the issue is the opposite now. I have a fuiel filter before the pump.

The truck idles wonderfully, when you give it gas to come off idle in neutral it tries to stall, or when you shift into gear, it stalls.

If you sloooowly open the throttle, it'll run fine all the way up to several thousand RPM. But, if you try to open the throttle too quickly, it'll stall.
Well it ain't just the smoke and the traffic jam that makes me the bitter fool I am But this four-wheel buggy is A-dollaring me to death.
For gas and oils and fluids and grease, And wires and tires and anti freeze....And them accessories, Well honey, that's something else.

letank
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Re: Non-jeep Tech help needed for my 74 Ford

Postby letank » Wed Aug 01, 2018 5:42 pm

Dr. Marneaus wrote:Keep in mind, the issue is the opposite now. I have a fuiel filter before the pump.

The truck idles wonderfully, when you give it gas to come off idle in neutral it tries to stall, or when you shift into gear, it stalls.

If you sloooowly open the throttle, it'll run fine all the way up to several thousand RPM. But, if you try to open the throttle too quickly, it'll stall.


sounds like the accelerator pump circuit of the motorcraft 21xx series, but I am uncultured for the eddy carb. IIRC they use springs!!!
Michel
74 wag (349 Kmiles... parked, next step is a rust free body)
85 Gwag (226 Kmiles... the running test lab)
See Engine bits and Fuel and brake lines, and Body work

BCRAWLER
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Re: Non-jeep Tech help needed for my 74 Ford

Postby BCRAWLER » Wed Aug 01, 2018 6:29 pm

I allow myself one dumb question per year so here it goes. Is it possible something else has gone amiss such as timing chain jumping one tooth?
1980 Cherokee,360/727/208, propane powered,unknown lift,31' Adventuro's on Chevy rims,Warn winch
1980 J10,360/standard/208, stepside

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tgreese
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Re: Non-jeep Tech help needed for my 74 Ford

Postby tgreese » Thu Aug 02, 2018 6:13 am

The symptoms point to too lean on acceleration.

A carburetor needs an accelerator circuit. When the throttle is at one place, the main jets (or idle circuit) supply the fuel needed. Vacuum is high, and the carburetor is powered by vacuum. The vacuum does the work to meter the fuel and make the proper mixture. When you open the throttle plates, the engine is going the same speed and the volume of air has increased. Vacuum falls, and does not pick up again until the motor speeds up.

The Holley has two circuits that assist with this transition. First is the accelerator pump, which converts the throttle pedal motion into a shot of gas that overcomes this immediate loss of vacuum, adding a big slug of liquid gas to the larger volume of air. This is controlled by a plastic cam on the side of the carburetor that you can change to adjust the pump shot.

Second is the power valve. The power valve is in the float bowl, and is held shut by the vacuum. So when vacuum falls, more gas can come by gravity into the engine. It basically increases your main jet size at low vacuum.

All of these things point to a too-lean condition at all times except when the engine is running at a constant speed. At a constant speed is the time when the engine will run and keep running on the leanest mixture. If you don't have a base gasket leak or another hole that's adding extra air and leaning out the mixture, the carb is simply set up too lean to transition from constant to increasing speed.

Note that too lean will also make the engine run hot.

All this stuff is very accessible on a Holley. This could be a problem (the PO messed with the carb trying for better economy) or an advantage in it's pretty easy to increase the pump shot or fit a higher number power valve. In the day, you could go to your local speed shop and buy everything you need to tune a Holley. Holley has instructions on their site for picking a power valve based on vacuum readings. The pump cams come in a kit. You pick the cam for the largest shot and keep changing the size down until you notice a hesitation. Then back to the next larger shot.

You should also look at your spark plugs to get an idea of the main jet size. Main jets for Holleys are easy to change and widely available. All of this should have some analogous adjustement for a Carter/Edelbrock.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 FCA Jeep Cherokee KL Trailhawk, ECO Green

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Dr. Marneaus
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Re: Non-jeep Tech help needed for my 74 Ford

Postby Dr. Marneaus » Thu Aug 02, 2018 1:47 pm

Sooo, I didn't do anything and it runs perfect now.

All i can figure is the edelbrock was a little gummed up inside. I pulled it apart partially to clean some stuff out, and then reassembled. At that point, as mentioned in my first post, it idled great in neutral, but was still dying under load or quick throttle opening.

Well, i guess getting it good and hot and letting it sit over night must have dissolved some other varnish that was in some passage somewhere, as yesterday it fired right up, and its idling and running perfect again. I let it get good and hot sitting still then romped it around my neighborhood. good response and everything. No weirdness whatsoever.
Well it ain't just the smoke and the traffic jam that makes me the bitter fool I am But this four-wheel buggy is A-dollaring me to death.
For gas and oils and fluids and grease, And wires and tires and anti freeze....And them accessories, Well honey, that's something else.

SJTD
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Re: Non-jeep Tech help needed for my 74 Ford

Postby SJTD » Thu Aug 02, 2018 8:34 pm

This is why I like Diesels.
Sic friatur crustulum

'84 GW with Nissan SD33T, early Chev NV4500, 300, narrowed Ford reverse 44, narrowed Ford 60, SOA/reversed shackle in fornt, lowered mount/flipped shackle in rear.

rocklaurence
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Re: Non-jeep Tech help needed for my 74 Ford

Postby rocklaurence » Fri Aug 03, 2018 6:31 am

I was going to say "Check Vacuum". The engine at idle should have >-12 and knowing your vacuum will allow you to chosse the correct Power Valves etc.

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Stuka
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Re: Non-jeep Tech help needed for my 74 Ford

Postby Stuka » Sun Aug 05, 2018 10:13 am

It’s running fine now, but was also going to ask if you had a vacuum gauge.

At your altitude you should be in the -17hg range.
1981 J10 AMC 258 with HEI and Weber 32/36 DGEV Carb, T176, NP208, D44/M23 with 4.56 gears and Detroit Locker, 6" lift, 33x12.50 Cooper STT's, BJ's Offroad Rear Dozer Bumper.
2017 JKU Rubicon Lifted
Pevious Jeeps: 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ

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Re: Non-jeep Tech help needed for my 74 Ford

Postby rocklaurence » Mon Aug 06, 2018 3:15 pm

Stuka wrote:It’s running fine now, but was also going to ask if you had a vacuum gauge.

At your altitude you should be in the -17hg range.


Yep, I agree and I use a 8-9 power valves.

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Dr. Marneaus
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Re: Non-jeep Tech help needed for my 74 Ford

Postby Dr. Marneaus » Tue Aug 07, 2018 9:15 am

Its pulling a pretty steady 16" of vac at idle.

So it ISNT better. It BEEP the bed on me on sunday. I had driven it to the parts store in the AM, then driven it up and down the highway to home depot and back. About an hour after that we hopped in to take a trailer back to a friend and it started running like crap. Same thing, any time i got on the gas it would start to choke out and sputter and it would die if i kept trying to go.

The whole time, it would still idle in neutral 100% perfect and I could rev it 100% fine, unless it was in gear. I limped it home.

When i got home, i let it sit for a minute then went to check fuel pressure. When i pulled the carb hose off, while the engine was off, it was spurting out of the fuel line in surges, with air/vapor coming out between the spurts of gas, like it was bubbling out.

It wasnt burning hot or anything, and the fuel line from the fuel pump to the top of the intake is insulated. I could hold my fingers on the fuel pump, so it was hot but not super hot.

I checked fuel pressure and was getting 7psi at the carb.

So, i dont know, seems like maybe its sucking air somewhere? There shouldnt have been bubbles in the line right? There's no way it should be boiling IN the line either right?

Everything is 100% Factory on this except the carb. The issue happens on either gas tank. This got me thinking maybe its the selector valve, or something from the selector valve forward. I HAVE seen the selector valve oozing slightly in the past?

So yesterday I bypassed the tank selector valve, and ran straight from the aux tank. I replaced the last section of old hose ( about 6" from steel line to fuel pump). I think there is one last piece of old rubber on the tank itself, but we'll see. I filled the tank, and let the truck get hot idling, and then romped it up and down some good hills for a while, and couldnt get the issue to appear. So, i'll keep driving it a bit on one gas tank with the selector bypassed, and see what happens.
Well it ain't just the smoke and the traffic jam that makes me the bitter fool I am But this four-wheel buggy is A-dollaring me to death.
For gas and oils and fluids and grease, And wires and tires and anti freeze....And them accessories, Well honey, that's something else.

letank
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Re: Non-jeep Tech help needed for my 74 Ford

Postby letank » Tue Aug 07, 2018 11:36 am

sometimes we wander if we could add some chemicals to make the fuel less volatile, it was recommended to add oil -2 stroke engine oil has less ashes) to the gas... or MMO. Did I try? Yes, did it work, not really, because I created a heating trap when I decided to turn the undercarriage to a smoother surface with a sheet of metal (oil drip oil pan) , first It did not increase the mpg, second it prevented cooling of the cat and muffler, increasing the heat of the gas... it took me to Ouray a few years ago... and I had many issues which were vapor locking, even with a E pump... drip pan is off, no vapor locking yet...
Michel
74 wag (349 Kmiles... parked, next step is a rust free body)
85 Gwag (226 Kmiles... the running test lab)
See Engine bits and Fuel and brake lines, and Body work

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Dr. Marneaus
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Re: Non-jeep Tech help needed for my 74 Ford

Postby Dr. Marneaus » Tue Aug 07, 2018 12:34 pm

I should probably note that when i bought the truck, the rear tank had been abandoned. The truck was running directly from the front tank, to a filter, then into the steel line that feeds the fuel pump. The selector valve and rear tank were capped off and disconnected at the selector.

My buddy who sold it to me did not do that, it was that way before he bought it. He did, however, replace the fuel pump. He said he never had any issues and used it hard. He towed bobcats and stuff with it.

My thoughts are that the rear tank was abandoned for SOME good reason.

The sending unit works. The fuel gauge works. The seals are all fine and it doesnt leak. Why was it abandoned? Maybe because it was causing issues like the ones I'm having. But why wasn't the front tank abandoned instead of the rear? Why didnt they just leave the selector set to the aux tank?

All of this makes me think these issues have come from the fuel delivery system.

So, I have returned the truck to the way it was when i got it from him. This will at least eliminate the selector, and the rear tank/fuel lines. I'll know if its from the front tank to the carb. So, i've eliminated half of the fuel system.
Well it ain't just the smoke and the traffic jam that makes me the bitter fool I am But this four-wheel buggy is A-dollaring me to death.
For gas and oils and fluids and grease, And wires and tires and anti freeze....And them accessories, Well honey, that's something else.

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Stuka
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Re: Non-jeep Tech help needed for my 74 Ford

Postby Stuka » Tue Aug 07, 2018 1:22 pm

Did both tanks have fuel in them? I have seen where a selector can "leak" to one tank or another. If both have fuel, not a big deal. If one is very low/empty, it can suck air from that tank.
1981 J10 AMC 258 with HEI and Weber 32/36 DGEV Carb, T176, NP208, D44/M23 with 4.56 gears and Detroit Locker, 6" lift, 33x12.50 Cooper STT's, BJ's Offroad Rear Dozer Bumper.
2017 JKU Rubicon Lifted
Pevious Jeeps: 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ

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Dr. Marneaus
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Re: Non-jeep Tech help needed for my 74 Ford

Postby Dr. Marneaus » Tue Aug 07, 2018 4:21 pm

Stuka wrote:Did both tanks have fuel in them? I have seen where a selector can "leak" to one tank or another. If both have fuel, not a big deal. If one is very low/empty, it can suck air from that tank.


The front tank had a good amount. 13-14 gallons id say. I do not know how much is in the rear, as i didnt try to fill it up yesterday.

The selector in this truck is a simple 3 way brass valve. "main" "aux" and "off" I have noticed it slightly oozing from the selector knob though, b ut it wasnt doing it actively. so i'm not sure if it was just from the heat or of it was actively leaking fuel or what.
Well it ain't just the smoke and the traffic jam that makes me the bitter fool I am But this four-wheel buggy is A-dollaring me to death.
For gas and oils and fluids and grease, And wires and tires and anti freeze....And them accessories, Well honey, that's something else.

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tgreese
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Re: Non-jeep Tech help needed for my 74 Ford

Postby tgreese » Thu Aug 09, 2018 8:23 am

These valves are pretty cheap and widely available. Just a quick example - https://bcbroncos.com/shop/fuel/fuel-ta ... ly-bronco/
Boat supply places have them too.

Assuming you are still running the Edelbrock - sorry for the long-winded post about Holleys. Don't know anything about the AFB/Edelbrock.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 FCA Jeep Cherokee KL Trailhawk, ECO Green

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Dr. Marneaus
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Re: Non-jeep Tech help needed for my 74 Ford

Postby Dr. Marneaus » Fri Aug 10, 2018 1:15 pm

So.

I got it good and hot. It started acting up. I let it soak in it’s heat for a few minutes, and got it acting up real good.

Then I switched coils to a spare I had laying around s

No more acting up. Here’s to hoping it was just that stupid Accel coil acting up when it was hot. It was too hot to hold.
Well it ain't just the smoke and the traffic jam that makes me the bitter fool I am But this four-wheel buggy is A-dollaring me to death.
For gas and oils and fluids and grease, And wires and tires and anti freeze....And them accessories, Well honey, that's something else.

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Stuka
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Re: Non-jeep Tech help needed for my 74 Ford

Postby Stuka » Fri Aug 10, 2018 1:50 pm

Out of curiosity, if you measure its resistance, what do you get? Wondering if it was starting to fail, or if its just getting too hot.

Also, this is a major advantage of moving over to a TFI coil. The oil filled ones are very susceptible to heat soak.
1981 J10 AMC 258 with HEI and Weber 32/36 DGEV Carb, T176, NP208, D44/M23 with 4.56 gears and Detroit Locker, 6" lift, 33x12.50 Cooper STT's, BJ's Offroad Rear Dozer Bumper.
2017 JKU Rubicon Lifted
Pevious Jeeps: 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ


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