Need help with my "new" '72 F-100 Sport Custom!

[thetommyboy2k]

Hey everyone!

Almost two weeks ago, I traded for a '72 F-100 Sport Custom. It's a great truck, but it has one problem that's puzzling me. It idles well in park and neutral, but whenever I put it into reverse or drive, it will barely run and most times shuts off. When I can get it to run in reverse or drive (one foot on brake, other on gas to keep it going), it runs strong, but still doesn't feel right. My Dad had a '79 F-100 Custom Explorer, and I know from that one this one is not running right.

A member on one of the FB F-100 groups offered to help me fix it if I could get it to his house, which is an hour away. I was able to make it. He did everything he could think of. He sprayed carb cleaner around the carb and intake, hooked up a vacuum gauge or pump and no vacuum leaks, replaced points and condenser (points were completely shot and not even set anywhere near right according to the guy who was helping me), adjusted timing and adjusted idle/mixture screws and idle rpm screw. No matter what he tried, it didn't help it. He tried taking the hose off the vacuum advance, and it shut off while in park.

The guy who had the truck previously told me the carb had been cleaned, as the guy who helped me remarked at how clean it was when he took the top off the carb. He told me the gasket between the top and bottom of the carb needed to be replaced as it was leaking. He said the diaphram looked good. He advised me to replace the carb on it (Autolite 2100) with a Holley 2 or 4 bbl. He said the Autolite 2100 carbs are junk in his opinion. I've had people tell me to rebuild the 2100.

I did find out before I took it to him that the in-line plastic clear fuel filter is leaking. Not horribly, but enough to notice. I asked the guy if that on its own be enough to cause the dying in gear problem and he said no, but that it was part of the problem. I've had some people tell me to completely get rid of the in-line filter while others have said it doesn't hurt to have it on there.

I found out the motor (302) was rebuilt. I've had people tell me it could be the cable that goes from the carb to the modulator on the tranny might not be adjusted right. I've had people tell me it could be the modulator itself or a vacuum leak to the modulator. More than a few people have mentioned the torque converter could be locked up.

I'm trying to figure out where a good starting point is and that's why I'm posting. I live in the Upstate of South Carolina in Spartanburg County. I would really appreciate any help. I really need to get this truck up and running as it will be a work truck and also one for hauling.

Thanks in advance!
Tommy

[basketcase0302]

Tommy,
to and please stop by the welcome mat and say hi to everyone when you get a chance.
http://www.fordification.com/forum/viewforum.php?f=1

Lot of good info here to help folks help you, (wish most guys could offer this much as it really narrows it down).
I believe you might actually have two different mechanical issues at play here...

"A member on one of the FB F-100 groups offered to help me fix it if I could get it to his house, which is an hour away. I was able to make it. He did everything he could think of. He sprayed carb cleaner around the carb and intake, hooked up a vacuum gauge or pump and no vacuum leaks, replaced points and condenser (points were completely shot and not even set anywhere near right according to the guy who was helping me), adjusted timing and adjusted idle/mixture screws and idle rpm screw. No matter what he tried, it didn't help it. He tried taking the hose off the vacuum advance, and it shut off while in park. " This sends a big red flag to me for one issue as the engine RPM's should usually increase when the vacuum line is unhooked from the dizzy-not kill the engine. WHAT WAS THE INCHES OF VACUUM/MEASUREMENT THE ENGINE WAS PULLING AT IDLE? The 302's are bad about intake vacuum leaks at the rear gasket surface where it mates to the engine block, (which is also one of the hardest places to try to spray to find a vacuum leak. Try spraying that area, (I love starter fluid as it doesn't leave a residue like carb cleaner does) with the engine off then quickly start the engine and listen for any RPM changes.

"The guy who had the truck previously told me the carb had been cleaned, as the guy who helped me remarked at how clean it was when he took the top off the carb. He told me the gasket between the top and bottom of the carb needed to be replaced as it was leaking. He said the diaphram looked good. He advised me to replace the carb on it (Autolite 2100) with a Holley 2 or 4 bbl. He said the Autolite 2100 carbs are junk in his opinion. I've had people tell me to rebuild the 2100." Regardless which carb you decide on it sounds like it does need addrssing, (or at least change the gaskets to rule out that being the issue, (the gaskets should have stuck out like a sore thumb when sprayed with carb cleaner). I'm a huge fan of For'd Motorcraft 2150 as they are a proven die hard carb-I'll never buy another Holley as long as I live-Eldebrock rocks-but you'll get a 1000 answers here on which carb you choose LOL!

"I did find out before I took it to him that the in-line plastic clear fuel filter is leaking. Not horribly, but enough to notice. I asked the guy if that on its own be enough to cause the dying in gear problem and he said no, but that it was part of the problem. I've had some people tell me to completely get rid of the in-line filter while others have said it doesn't hurt to have it on there." If this inline fuel filter is before the fuel pump itself this could be one of your problems. Guys have tended to install them in this location, (which should never be done-the fuel filters on our engines should always be placed "downstream" from the pump itself). Remove it if it is before the fuel pump as it could be causing loss of suction to the fuel pump, (a test of your fuel pressure would be good to conform this but you might not get a good reading if there is a leak at that filter).

"I found out the motor (302) was rebuilt. I've had people tell me it could be the cable that goes from the carb to the modulator on the tranny might not be adjusted right. I've had people tell me it could be the modulator itself or a vacuum leak to the modulator. More than a few people have mentioned the torque converter could be locked up." There would not be a "cable" connecting the engine to the C-4 transmission, (it would be a steel vacuum line with short rubber hoses at each end terminating the connection at the intake manifold and the modulator valve on the transmission. I firmly believe from your troubleshooting you've done this will be one of the places you'll find the issue on as to why the engine dies when put in gear. Either the short rubber hoses on each end is cracked and leaking vacuum-or the modulator valve itself is leaking vacuum. Try unhooking the vacuum line that runs down to the transmission which is usually at the rear of the intake manifold-and plug it then start the engine and put it into gear to see it it makes a difference or not.

There's a few things to get started on and I'm sure someone else can chime in here for other clues to help.

[sargentrs]

The Autolite 2100/2150 are among the simplest, most reliable carbs ever made, IMHO. If you choose to replace it, call Guaranteed Carburetors. https://guaranteedcarburetors.com/X6-244_p_328.html. I've bought 3 carbs, 2 Autolite 2100's and a 1bbl and all 3 have been bolt on and go. Lifetime warranty and fantastic customer service. Add an electric choke and you'll be set.

[thetommyboy2k]

I took some pics yesterday if this will help narrow things either...

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[thetommyboy2k]

Here's more pics...

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[thetommyboy2k]

Some more pics...

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[thetommyboy2k]

Last two pics...

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[basketcase0302]

Yes it looks to me like that clear fuel filter is on the suction side of the pump Tommy. Is the discharge side of the fuel pump all steel line that runs from the pump up to the carburetor? Keep in mind there is a fuel filter inside that canister hanging down below the fuel pump, (so you should not need the extra fuel filter). My guess is the previous owner was having issues with trash in the gas tank like most of us have had on our bumps.

I see a leaking front oil pan gasket and a few other things but can't really diagnose the vcuum lines or modulator valve on the transmission from here.
This is what it looks like and is on the side of the transmission just above where the pan attaches to the transmission.