84YotaBuck

Have a weird problem I've been fighting for a few weeks now. Truck idles and runs great around town, but when I get on the freeway, after 10-15 mins it starts to stutter like it's not getting enough fuel. Had a similar problem years ago after wheeling when I kicked up a bunch of crud from the tank and it plugged the fuel filter. I've changed the fuel filter twice, checked the weber 32/36 internal filter, and changed the fuel pump. Fuel pressure set at 3.5, pulled and checked jets for crud and re-adjusted the carb but nothing helps, any ideas? Possibly not fuel related? Stumped at the moment, going to order a weber gasket set and check the float level next.

Thadrickbecker

I vaguely remember someone saying there was a filter inside the tank also?

Thadrickbecker

In school they taught us that the easiest way to check fuel delivery is to pull the fuel line off the carb and run it into a can. Then pull the coil wire and hit the starter for 15 seconds. Should be more than a cup of fuel in the can after 15 seconds. assuming youve got a manual fuel pump.

84YotaBuck

That was on my mind as well that maybe there is a screen on the pick up in the tank and it's clogged? Anyone know for sure if there is a screen on the pick up? 30 year old truck so wouldn't surprise me if it's plugged up. I seem to remember something about a sock filter being in there.

84YotaBuck

Checked some more things, found a few suspect plugs on some not used vacuum ports that I replaced but didn't help anything. Timing is at 5 BTDC, but when I rev the engine it almost instantly jumps to the left probably 3 inches so off the gauge, how much vacuum advance should there be when revving the engine? I'm thinking not that much.

84YotaBuck

Found the page in the FSM on vacuum advance, page A-8 if anyone is interested. Vacuum advance should top out at 13 degrees at 2400 RPM, but I'm wondering that since with a Weber on the truck you plug one of the vacuum ports on the distributor so would that cause the large advance that I'm seeing?

84YotaBuck

Have a partial fix for this problem after doing a bunch of other things. So far, in addition to what I posted above I've changed out the soft lines coming out of the gas tank, adjusted the carb float, replaced my 7 year old Optima Red Top that wasn't holding a charge anymore, ordered and received the filter for inside the tank but havn't had time to replace it yet, replaced the crappy Weber spacer plate with a LC engineering spacer, replaced all the caps for unused vacuum ports and swore and cursed at the truck a lot. The other day it fired once then wouldn't do anything but crank. Pulled a plug and looked for spark and had nothing. The not firing part has been an on going periodic issue that I thought was due to fuel draining out of the carb and it would always fire after some cranking. Ended up just biting the bullet and replacing the coil and ignition module, since then the truck has fired up first time every time usually quicker than the wifes EFI minivan and the stuttering problem is almost totally gone, I still get a periodic stutter at high RPM's but for the most part runs way better than it has in a long time, the idle even seems more stable without the low idle following the choke kicking off until it warms totally up issue. So, if anyone else is having a similar issue this may be something to try if you don't mind throwing down the $350 for the parts.

NBRanger

One way of looking at it,on these old trucks,you can't go wrong replacing a 30 yr old part so long as you use a good quality part.
Upgrading your fuel system was giving it some love....if you have nothing better to do.
But if you had fuel pressure and volume,established by pumping fuel in a can,then you could apply your attention to something else.

If you can lay hands on a little Mity-Vac pump you might check to see if your vacuum advance unit will hold a little vacuum.If not the diaphragm might have a hole in it.

Between your gas tank and the carb,are there any exhaust leaks or other heat sources to the fuel supply?You could be cooking up some vapor lock.


You might find a vacuum schematic,and trace the whole thing.Check every tube for cracks and location.

Look to make sure your heat riser is not stuck.

Check to see your pcv valve is working,the grommet seals,and that hose to the air cleaner is in place.

You might see how sloppy the distributor shaft is.

Terrys87

iTrader: (1)

Here is the intank filter. I have seen them get covered with a shell like material and can effect fuel flow.

Part number for a new intank filter is #77023-12050. On ebay it is called a TOYOTA FACTORY NIB FUEL FILTER SUCTION TUBE DIESEL. It was selling for $4.50 when I finally found it. I paid $15 at Toyota. (83 pg 8) This filter is for carburated trucks.

84YotaBuck

Have the filter already, just need to get it done. Just got back from driving the truck and runs great around town, but once again when I was coming up a hill in 2nd around 4000RPM had a steady stutter. Since the weather is getting better I just need to pull the bed off and open up that gas tank to replace the filter as well as the soft lines up by the engine compartment.

jimbyjimb

iTrader: (1)

You have two forms of advance, vacuum and mechanical. Without vacuum your total timing should be in the 30-34 BTDC range with an 8-10 degree idle. The vacuum advance is only functional at cruising RPM, partial throttle assuming your idle is correct. Not at WOT or idle. Total timing is easiest measured with a timing light that has a degree knob. You can check total without vacuum, then check again with vacuum and see the difference.

It's unlikely this is an ignition timing issue unless the diaphragm is sticking. From your prior posts that doesn't seem to be the case. You can try checking your float level, it seems to me like starvation.