First, I'm newly registered (been lurking for a little while).

I have an 85 truck that I purchased last winter and been slowly bringing it back from the dead (it's has 240,000 very hard miles on it). The truck barely ran when I bought it, carb had been extensively messed with in all the wrong ways yet in true toyota fashion kept soldering on. I limped it home, new plugs, wires, proper timing, fluids, flush(es) and a bit of tinkering with the carb later and it was running much better. Still not ideal... but better.

After some time of messing with the carb in an attempt to get it running better I started down the rebuild path and discovered that several of the internal springs in the carb were broken and linkages mixed up so I abandoned that carb and bought one out of a junk yard. Got it home, full idle adjustment (speed, mix, speed, mix, speed... you get the point). After this the truck was running quite well, no more bucking at constant speed, smooth take offs from lights, good enough power to crawl up steep grades without having to dump the clutch at all... life was good.

So, in the sprirt of the truck running good I towed the boat to the river (which it did quite well) and this is when the new trouble started, after backing the boat in the river twice (first of the season trips... ya know) the truck started acting up. If I let the clutch out with very little throttle it just falls on it's face completely. The only way to get it going is to be very aggressive with the throttle and slipping to get into the secondary's a tad otherwise it just completely falls on its face. I have double, and triple checked timing, vacuum lines (including with starter fluid) tried putting the mixture screw back to factory rather than peak rpm... etc. Nothing works.

So, right now the truck still falls on its face if you try to properly leave from a stop, has a very large dead spot before you crack the secondary open at speed. And if you crack the throttle at the carb and hold it in a stationary position the engine revs initially then slowly dies down accompanied by a sucking noise (originating from the carb not a vacuum source). During this time if you manually depress the accelerator pump it revs back up, so it is starving of fuel at constant throttle position without anything having changed from before the boat ramp incident. Pump puts out good amount of fuel and it idles pretty well.

Sorry for the novel but I'm fairly stumped and I've done everything from forged internal engine builds to custom swaps so I'm coming to the toyota experts here. Can anyone help?

Thanks,

 

have you checked your clutch fluid? it may need to be bleed

 

No offense, I appreciate the suggestion but it is not the clutch.

 

hahaha i dunno where that came from.. but have you taken the truck on steep grades before the boat ramp? might have knocked somthing loose through the overflow venturi possibly? http://pirate4x4.com/forum/showthread.php?t=775780 thats a link to ALOT of toyota knowledge in one organized place..check out the carb section...u might have to rebuild...

 

so it will idle fine, but if you rev the engine it will die if you don't manually hit the AP right?

 

Truck had spent several hours each day the two days prior to this going up, down and on pretty heavy side angle trails. That thought had crossed my mind as well but like I said, had spent hours on much more extreme angles than the ramp the previous two days.

It will rev up initially, then rpms will fall off and either it will stumble and rev back up and repeat or just die. Unless manually depressing the AP, correct.

 

Also I should add that I drained and filled up the fuel bowl with chem carb thinking that perhaps an internal passage on the primary loop had become clogged. Didn't make much difference.

 

This might seem like a stupid question but there is a reason why I am asking. How much fuel is left in the tank?

 

3/4 tank or more.

 

ok then that all but eliminates the chance you mixed up some of the 3 fuel pump lines. Vent/Supply/Return. But not 100% on that as I am not completely sure where that return line dumps into the tank.

Could be a bad fuel pump which isn't supplying enough pressure as well. Even though you said it's supplying plenty of fuel, a little fuel goes a long way and you cannot be certain on that unless you do a pressure and volume check as well.

 

^ I thought about the fuel pump not keeping up as well but if the fuel bowl were emptying faster than it was being replenished then the AP wouldn't be able to pull fuel from it either, unless the pickups for the primary loops and AP are at substantially different heights in the bowl, which I suppose they could be.

 

Have you checked the exhaust? My brothers chevy acted similarly after backing his boat into the lake. What they found out was part of the inside of the exhaust pipe had collapsed and restricked the the flow.

 

Have you changed the fuel filter perhaps when you backed down the boat ramp you knocked some crud in the tank loose.

Something to think about!!

 

If I read this right, you're saying it picks up if you hit the AP or open the throttle enough to get into the secondaries?

If that's the case then something in the primary side is plugged up. I haven't been into my carb yet but I'd guess there are jets in these things, right? If a bit of debris gets into the primary jet it will behave exactly as you're describing and depending on what the debris is, carb cleaner won't do anything to it.

I once had a pine needle get stuck in the primary jet on my old Nissan and it did exactly what you're describing. Enough fuel for idle was able to get through but not enough to run off-idle until the secondaries opened.