So I bought a 620...

[KlassicMotion]

It sat for a couple weeks while I was doing the brakes and all the fuel seems to have run out of the pump, fuel filter, lines etc.  Is that normal when not driving every day?  Is there something to prevent flow back?  I couldn't get it started even after a lot of cranking, until I disconnected the rubber fuel line and stuck it in a jar of gas to prime the pump and get it going.  After I hooked the fuel lines back up it sputtered and took a while to get good fuel flow and a good idle going.

 

 

Try this (I have one on my '76 Bronco):

 

1/4"

http://www.ebay.com/itm/One-way-Check-valve-for-Gas-or-Diesel-fuel-1-4-Bio-/151136157802?pt=Motors_Car_Truck_Parts_Accessories&hash=item23306ac06a&vxp=mtr

 

5/16"

http://www.ebay.com/itm/One-way-Check-valve-for-Gas-or-Diesel-fuel-5-16-Bio-/151134105263?pt=Motors_Car_Truck_Parts_Accessories&hash=item23304b6eaf&vxp=mtr

[c4ck4]

I finished up the brake lines, balanced the brake adjusters till it stopped straight and then the brakes seemed fine.

 

Then after some distractions, some months later I changed out the water pump, radiator, coolant hoses, thermostat...pretty much the whole coolant system.

 

I'm pleased to report that now it doesn't seem to ever overheat anymore, and I feel like I can actually drive it places.  I've been driving it to work the last few weeks daily even during our cold snap which was in the ~20-30s with a low of around 10 degrees.  Much colder than we're used to in Portland.  I had to warm it up for a good 10 minutes or so and it wouldn't idle without some help from the pedal for some time, but then it seemed to run and drive okay.

 

However it still feels choked when I drive it and the revs sound awfully high for the amount of power i'm getting and speed that I'm traveling at.  After going about 100 miles and using almost 9 gallons to get there...I'm getting 9-10mpg if I'm lucky.  I need to figure out what's wrong with my mpg.

 

I know very little about carburetors in general so this stuff is the trickiest for me compared to the other stuff I've had experience with.  I don't know what to check and in what order.

Am I supposed to set the timing first?

Or the valve lash, or the choke, or the idle mixture?

Put on a new carb kit?

Solve my fuel drain-back problem?

Figure out which pieces of emissions are active and which aren't and attempt to understand my vacuum lines?

 

I keep running across bits and pieces of info on all this stuff but I have no idea where to start and how to systematically improve the performance. 

[datzenmike]

...I'm getting 9-10mpg if I'm lucky.  I need to figure out what's wrong with my mpg.

 

I know very little about carburetors in general so this stuff is the trickiest for me compared to the other stuff I've had experience with.  I don't know what to check and in what order.

Am I supposed to set the timing first?

Or the valve lash, or the choke, or the idle mixture?

Put on a new carb kit?

Solve my fuel drain-back problem?

Figure out which pieces of emissions are active and which aren't and attempt to understand my vacuum lines?

 

I keep running across bits and pieces of info on all this stuff but I have no idea where to start and how to systematically improve the performance. 

.

Fuel cannot drain back from the carb into the tank. If your carb is empty or the line empty the next time you go to start it ... it's likely leaking,

[KlassicMotion]

I know very little about carburetors in general so this stuff is the trickiest for me compared to the other stuff I've had experience with.  I don't know what to check and in what order.

Am I supposed to set the timing first?

Or the valve lash, or the choke, or the idle mixture?

Put on a new carb kit?

Solve my fuel drain-back problem?

Figure out which pieces of emissions are active and which aren't and attempt to understand my vacuum lines?

 

I keep running across bits and pieces of info on all this stuff but I have no idea where to start and how to systematically improve the performance. 

 

 

Check the timing, check valve lash, check for vacuum leaks, check choke, set idle mix with vacuum gauge.  Check for fuel leak...... 

 

 

Is your fuel pump good? 

There is another member on here that is having terrible time with Autozone fuel pumps coming apart on him.  He is on his third pump, but he doesn't have the money to give up the lifetime warranty and switch to a different brand.... Just a thought.

[c4ck4]

Fuel cannot drain back from the carb into the tank. If your carb is empty or the line empty the next time you go to start it ... it's likely leaking,

Well that's good to know I guess, but I'm not sure how to tell where it's leaking. I haven't seen any signs of leaking anywhere along the lines, I have no clue where it could be coming from. It takes about 3 days for the carb, pump, fuel filter and line to empty. I guess I could wrap a paper towel or something around each connection from soft to hard line to see if it's seeping out slowly?

 

Is your fuel pump good?

It pumps enough for me to drive around so its clearly pumping, but how do I diagnose if it's pumping "well enough"?

[KlassicMotion]

To test a fuel pump, you can hook a pressure gauge up to it, and read the pressure.

Stock Hitachi carb, right?  If your float bowl is empty, check the seal around the float bowl, or the seal on the main jets under the float bowl..... An unnoticeable leak there though, doesn't explain 10mpg... Remind me, have you swapped the trans, or rear diff, or wheels/tires, speedometer?  I'm just curious if your calculations are off because the readings are off.

[c4ck4]

An unnoticeable leak there though, doesn't explain 10mpg... Remind me, have you swapped the trans, or rear diff, or wheels/tires, speedometer? I'm just curious if your calculations are off because the readings are off.

I bought it in September and have only recently started driving it. Everything appeared to be stock, the hitachi carb, air cleaner cover etc. Based on that and general appearance I'd guess the rear diff, trans and everything else are stock.

 

I drove 96mi on the odometer on a full tank (and I'd guess that much based on real distance around town) and then put in 8.89gal at the pump, equalling ~10.79 mpg

 

I've been busy running errands before christmas when not working, and haven't been able to look at the carb, timing, choke or anything yet. I may not have time until after christmas unfortunately, I really want to figure this thing out.

 

Additional symptoms are very slow warm up, it won't keep idling by itself until several minutes of gentle revving warm it up. Slow acceleration, lack of power. Rarely over the last couple weeks it has backfired relatively quietly. Sometimes it seems to run on when turning off the key. I believe the fuel shut off solenoid is functioning.

 

I'm hoping it's mostly timing, but I can't find my timing light, let alone that I've never actually used one. I feel like this might be obvious to somebody more experienced. I don't clearly understand the details and relationships of the parts of carburation and engine electrics/timing systems well enough for this to be obvious to me from the symptoms.

[KlassicMotion]

Time it, and buy a Weber!! :thumbup:


Truthfully, a Weber isn't a bad idea, but only spend the money if you can't get the Hitachi tuned.

Timing; do it once, and you won't forget how. Hook the power cable(s) to the battery, pick-up cable to #1 plug wire, make sure cables are away from the the fan. Familiarize yourself with the timing marks (Pointer on the block with checks for 20 15 10 5 0 -5, and one mark on the crank pulley). I like to paint the crank pulley mark white or yellow, and like wise, the 10* mark on the timing indicator (just makes it easier to see). Turn engine on, make sure RPM is set to around 800 (if automatic, put trans in drive with foot on pedal to set idle speed).  Vacuum lines should be unplugged and capped off...  Point timing light at timing marks and see where the mark on the crank pulley is in relation to the timing marks. If not on 10*, then loosen distributor hold down bolt (there are two bolts, I don't believe it matters which bolt, I use the bottom bolt when setting the first time...), and turn distributor until the timing marks line up, tighten dist. hold down bolt.

 

Did I forget anything?

 

 

Have you set the valves?.... I don't remember....

Have you checked the plug gap, wires, cap, rotor... ?

 

 

[Eagle_Adam]

sweet little truck man! 

[c4ck4]

Thank you Klassic, very helpful information....now if I can just find my timing light.

 

Turn engine on, make sure RPM is set to around 800

I don't know how to make sure the engine is idling around 800. I could just completely guess based on the sound of other engines I've heard, but that's the best I'd know how to do and I'm not sure that'd be very accurate. So I should set the idle first then do the timing.

 

Have you set the valves?.... I don't remember....

Have you checked the plug gap, wires, cap, rotor... ?

I haven't checked the valve lash yet, but it's on the list. I also haven't checked plug gap or point gap, haven't replaced spark plugs (but bought them) DID replace plug wires, one of them was arcing to the heater hose actually.

[c4ck4]

sweet little truck man!

Thanks! You might actually see me driving around, I drive through Beaverton all the time. I live in Garden Home area

[KlassicMotion]

Three options to find RPM:

 

One,  Install a Tach.

 

Two,  Buy the least expensive Tach you can, and crimp some alligator clamps on to the end of the wires and use it as a diagnostic tool.

 

Three,  Buy a dwell meter.  A dwell meter will give you the diagnostic ability to tell RPM, Dwell and Voltmeter.