New-to-me 720

[CharlieW]

Hi guys, I am Charles. I recently aqcuired an 82ish standard cab 720. It has 50,000 give or take on the speedo...original miles. Picked it up for $500. It is currently all stock except for the addition of a camper shell. It is oxidized doo-doo brown. There have been some rust spots on the bedside that were repaired and primed by the previous owner.....I am the second owner. At the moment, it runs like crap, but I found an interesting write-up on the exact problem I am having here...
http://hubpages.com/...l-Wont-Tell-You

The first plan of attack was to replace ALL of the vacuum lines.....all 5000 feet. Then I replaced the fuel filter.....then the lines from the tank to the pump and filter...Still no difference. Once I check on said relay and repair if necessary, I plan on deleting all vacuum emissions lines that I can. I also plan on plugging the ports on the exhaust manifold, where the metal tubes go up to the air cleaner. I want the engine bay to be clean...and I am a little OCD about that kinda thing. Next is to remove the camper shell and sell it off. I drained all of the FRESH fuel out of the tank the other day and it was a seriously nasty orange color. Keyword....FRESH... which leads me to the main project of deleting the fuel tank underbody and mounting a 'keg style' fuel cell in the front of the bed.

I will have the lowering blocks for the rear springs this weekend as they were just taken off of a toyota pickup, and as soon as it is mobile enough to drive, I will bring it to work so I can crank on the torsion bars to get the front down. The plan is to be murdered out flat black. Don't know if that plan will hold up, but so far that is the skin of choice. I also plan on fitting cragar 'dog dish' wheels. One of the most important things I wanna do is swap from the rectangular headlights and grille to the older round style. I will need any pointers that ya'll have to offer, and let me know what you think about the project. I will get pics up as soon as the camera works!

[breadbox]

NIce. Welcome to the Forum.

[CharlieW]

whaddaya think about swapping over to the older style headlights and grille.....by the way....you have been providing me with good reading material over the past few days.....nice build you got goin on there.

[PEZi]

welcome man!

[CharlieW]

Sup PEZi.....I have been reading all of you guys posts and builds and they are awesome! Thanks for having me....let me know what you think about swapping the grille and headlights and about the fuel system.

[captainzeros]

Lowered and murderblack? Isn't that what everybody does with these trucks?

I kid, I kid, anybody who is getting one of these things running right is a friend of mine. Welcome to the forum and feel free to ask any questions you might have, sounds like you're on top of things already to me. As far as a 620 grill/headlight swap, I've never seen it done (not to say it hasn't been done, I've never looked either), I'd have to physically hold parts up to my truck to get a feel for the size/shape to see if I could make it fit or not, y'know. Fuel system shouldn't be too big of a deal (famous last words), orange in the tank sure sounds like rust to me. If you want an alternative to taking up bed space with a fuel tank, you could drop the original tank and either replace it or have it boiled out at a radiator shop then give it a good coating of POR-15, that stuff'll make it bulletproof as far as rust if you apply it right.

[Visiotech]

I took a good look @ the 620's headlight set-up... Looks like ALOT of work... The inside lines of the 620 are round and rolled into the fenders. If you have the tools and gumption to tackle it, ANYTHING can be done! If ur gonna go w/ the old school round lights might as well hit the scrapyards and find an older 74-80'ish BMW 3-series and have NICE dually rounds! I was going to do it myself but I didn't like the round fit in the square grill space.
I'm actually going to run 3 headlights. 2 on pass. side and 1 on the driver side. Taking the inside light out for intake on the D.side.. 2 hi/low beams and 1 extra high beam. I think the H4565LMP is the hi/lo that fits in the 720 bezels.

[CharlieW]

Visiotech, that sounds like an awesome idea....Just wouldn't wanna hydrolock...I guess there should be a way to stop water but keep air flowing.

[noface]

hydrolock?

wtf?

[CharlieW]

Well....if water happened to enter that air intake where the headlight used to be that Visio was talking about making.....it would then enter the carb. If it entered the carb, that would mean it would have to enter the combustion chamber......BAD.

[CharlieW]

So, a quick update from the weekend....I was tackling the running rough issue......I found a drycracked fuel supply line right at the front of the carb.....replaced.....The two lines down by the starter looked great, but I replaced them just for good measure...found another dried up vacuum line....even after I thought I replaced all of them before.....replaced it....cleaned out the filter at the bottom of the fuel pump.....cleaned out the filter at the front of the carb.....even though they both looked decent.... Now it idles like a champ....CHAMP....but under acceleration, it skips and bucks like its not getting enough fuel. I might add that I checked and resoldered the fuel pump relay that is on the passenger kick panel.

[noface]

it kicks and bucks because the afr is lean.

check to see that the carb "squirts" fuel down the throat when you mash the throttle. You can do this by looking down the barrel (engine is of course NOT running), and rotating the throttle assembly. This will ensure that the accelerator pump is functioning. If no squirt, then the accel pump needs work... if your just cruising right along and it kicks and bucks, then the jets/needles are likely restricted with varnish from old fuel sitting in the carb.

Sounds to me like you need a carb rebuild, or at least a good disassemble and cleaning, but this usually requires a rebuild kit anyway, because you'll likely need new gaskets.

As far as the hydrolock comment... he'd have do be driving 150mph in the monsoon driving sideways Forrest Gump rain to get enough water down the throat of the carb to hydrolock the motor, which is what brought on the comment/question. Unless he's mudbogging it down in Lousiana or Florida in the swamp...

[CharlieW]

I will definitely check that tonight when I get home. That will be the perfect opportunity to utilize the Droid led flashlight that I've freshly downloaded to my new Droid phone, lol. That thing would hurt Stevie Wonders eyes. Thanks for all the advice...


Not to be too argumentative, but hydrolock is easier than some may believe. I am in SC and work in parts at Benson Chrysler Dodge Jeep. I can tell you from personal experience that if you have a snorkel on a Jeep...even if it never goes offroad....will catch a ton of water without a proper separation system at the inlet. I have seen more than one Jeep come in with a hydrolocked engine that are sporting snorkels beside the windshield...grant it, sometimes we have some crazy weather here, but no hurricanes, ya know...

[noface]

I been want'in one of them Droid phones...

snorkel on a Jeep that's never offroad? yea, there's tons of em around here too...

You would probably better served if you picked up a Weber 32/36 carb and adapter.... they run SO MUCH better, and very easy to tune. Plus,,,, no can of worms vacuum lines everywhere! I had one vacuum line on my Z24, and that was to the vacuum advance on the distributor... can't get any more simple than that! Well... that is if you don't count the big vac line to the brake booster....

[CharlieW]

OK...more from last night.....drained the remaining 'fresh' fuel from the tank and its a funky brownish orange color....dad told me that it should still burn though. He said I might add a bottle of rubbing alcohol. I took all of the fuel lines off from the tank to the filter, filter to the pump, pump to the chassis lines....all were drycracked, although the cracks were barely visible, and replaced them. Replaced the fuel filter....again....
I soaked the two tubes at the front of the exhaust manifold with rust penetrant, because underneath the rust buildup I think there used to be nuts there, lol. The plan of attack is to take those tubes out and plug those holes. Then run duct from the hole left in the aircleaner over to fresh air....that should help out a bit once I delete all emissions garbage. I checked with the choke flap open so I could see down the throat of the carb....I turned the throttle linkage as to depress the accelerator pedal and fuel sprayed up into the passenger side throat of the carb.

[noface]

looks like the accelerator pump is working then.

sounds like you first need to get vacuum and fuel lines sorted out and insure no leaks to progress to the next level.

It's hard to tell any adjustments a prior owner may have made to the carb, and ignition to compensate for worn out equipment.

[CharlieW]

I wouldn't think it could have had much adjustment due to worn out equipment is because 1) the truck still has 1984 date coded plug wires....and 2) is has right around 50,000 original miles. I need as many ideas as I can get. I got the tune-up equipment at the house waiting on me, but I got youth at church tonight, so that will be a 'in the dark' project for tonight....good thing my shop has light in it, although there isn't enough room in there to pull the truck in lol...all of this going on and I still gotta find a way to keep the little lady happy....any ideas? Oh, and I picked up a filter for the bottom of the fuel pump that I am gonna throw on tonight as well....Wish me luck.

[noface]

even if it only has 50k on the odo, it's till a 25+ year old truck. I'd likely suspect the seals to be shot in the carb.

Get your tune-up stuff done and all the vacuum hoses replaced or checked for leaks. Old hoses can leak the whole length of the hose from dry rot. Replace one at a time so you lessen the chance of getting mixed up.

Rebuild the carb, or have someone do it that you KNOW has the expertise if you don't. Or simply buy a reman carb from a parts store. Better yet, replace it with a Weber 32/26.

Once you get these done, I think you'll be in good shape.

[CharlieW]

I will definitely get one of the mechanics that works with me here to help me on the carb rebuild.....I think I could do it, but I would rather have the expertise watching over. All of the fuel and vacuum lines have been replaced, and I have a schematic so I am gonna check it again to make sure they are all going to the right places. I didn't get the chance to do the tuneup last night....church went a little longer than planned. I won't have the kids tonight, so as soon as I get off, I will be able to start right on it. I also have two more bolts to get out of the compressor and all of that will be cleaned out.

[breadbox]

you should make a write up when you build the carb. like the set of instructions you used and problems you encountered or tips you have picked up throughout the build and take some pictures.

[CharlieW]

For sure....I will definitely do that. I am gonna tackle the tune-up and fuel pump filter tonight and see if that helps.

[CharlieW]

So, I did the tuneup last night and slipped the new fuel filter into the bottom of the fuel pump....threw my shirt back on and decided to ride to the store to get some gas because I drained all of the orangish brown fuel from the tank.....didn't realize that payday was long gone and I was out of cash....oh well. I get paid today, so maybe off to the gas station tonight. I will update you guys on the running situation as soon as I get her fired off. I can tell you that the plugs looked to be in decent shape, although the wires cap and rotor looked terrible. I know for a fact that the wires had never been changed as they were date coded 1984. It also looked as if the cap and rotor were the originals. Hopefully that will do the trick and the carb won't have to come apart...Only time will tell. Oh, and I almost forgot, I finally got the rest of the A/C stuff off....the compressor and the idler pulley were a bit of a terd as they had to come off through the bottom, but they are off now and the engine bay is much cleaner. It is amazing how just the little things help a lot. I guess next will be the vacuum line delete, but I would like to get it running good before I do that.

[CharlieW]

Also looking at replacing the ignition coils....they look like standard GM units....can I use accel GM coils, or is there something else I need?

[Visiotech]

replace them w/ stock 720 coils is the safest route.
If I can get the net @ work today I will post u some napa #'s for stock and upgraded coils
.

[CharlieW]

awesome....thx dude!

[CharlieW]

[Rev_D21]

Good looking truck. Don't do the headlights, they won't look right on such a square body.

[CharlieW]

ok... where do I start? so I get up this morning and slip outside to go get some fuel. get back and I put about five gallons of fresh fuel mixed with a half bottle of seafoam. I figured the tune up yesterday did the trick... walk around the truck and got the ignition and it idles great, but still runs like crap under a load. so back to the drawing board. in the meantime, I made a new coolant jug from an oil tank on a moped...works great! Running through my head is the fact that the little truck has all new fuel lines, vacuum lines, and a fresh tune up...all new filters,etc. So my next thought is that all the emissions garbage is so old that some of it may be bad. So I go ahead and delete all the vacuum lines and emissions equipment. After that's done I head back to the key switch to see if it made a difference. I hit the switch once again and...NOTHING happens...not even a click. I go back out under the Hood..extremely frustrated... and notice a wire going to the positive terminal on the battery that's been spliced into. The tape is frayed so I start to fix it. When I grabbed the wiring I heard the ignition dinger go off...so I thought that wire may have been the ignition switch feed or something. So I go grab my soldering iron and heatshrink to fix my problem. When I get back, I tug on the wire a little bit and the positive battery terminal comes right off the post. It was broken in 2 places. The only thing holding it to the battery was the rubber cover that goes over it. So, I put a new positive battery terminal on it and fixed the broken wire and voila....truck runs like a champ. My assumption is that the battery wasn't getting a good enough connection to produce enough fire to the coils when the engine was under a load.....go figure.

[86 720]

Replace all those battery cables with at least 2 ga.

It'll be a huge difference!

[Rev_D21]

Glad you found the problem. I was beginning to think the distributor or timing chain were off a tooth. Glad it was something so simple.