Carbie drama (not strictly Toyota)

[Ben Wilson]

OK - It's a Datsun, but it's parked next to and stopping me from working on my mr2 )so there is some Toyota content here)..

I recently bought an '87 Navara ute (2.4 carb), the fuel system had some minor issues. Mainly uneven idle and occasional fuel starvation on hills.

It was fitted with the standard mid 80’s ‘orrible carbie with zero adjustments and more bizarre emission stuff than you can poke a stick at, so I dropped an Escort weber onto it.

It started nicely, idles beautifully and had much better throttle response - all good… Not so much, after about three seconds of anything more than about 10% throttle, it just dies. Sometimes it stalls completely - if I leave it for a while then start it again, it will run OK again….

Watching the mixtures with the wideband, it drops fully lean then slowly recovers like the float chamber isn’t refilling nicely.

In an attempt to fix it I’ve:

• Stripped and cleaned the carb (many times)
• Replaced the needle and seat
• Replaced the fuel filters
• Replaced the fuel pump
• Replaced the fuel lines
• Driven around with a multimeter hanging off the fuel pump (no voltage drop)
• Tried removing the fuel filler cap incase the tank vent was blocked
• I’ve even stuck a jerry full of fuel in the tray with a different feed line to the pump

None of this had made any real difference (changing the hose from the pump to the carb did richen the mixture a couple of points, so I assume there was some sort of blockage in there).

Running the fuel line straight into a bottle shows heaps of fuel flow - Carter electric pump.

I’m running out of ideas here - any suggestions?

[kingmick]

prob the air dampener! have a look on the net for webber trouble shooting, im sure there will be heaps on it!

[Ben Wilson]

OK - You've got me, I've just googled weber and "air dampener" and can't find any trace of it...

I've found some tuning guides which I'll try out, but I get the feeling there is something inherently wrong here.

[allencr]

The idle circuit is OK, but the primary isn't, and I'll assume that the accelerator pump circuit is OK, since you say it has "better throttle response", but I really don't know how it could be said to have any throttle response if it doesn't get more then 10% throttle.

It'll keep running if you keep pumping the throttle won't it?
That should allowing it to run, though crudely.

I'd first say that it's a blocked main jet or emulsion tube, but since you've taken it apart a number of times, its got to be something you've done to it repeatedly and it isn't going to change until you figure out what you've done wrong.
I'm guessing that you're missing a part, like an emulsion tube.

all of the fuel filter & lines & everything else was unnecessary from the getgo.

I don't have a clue what an "air dampener" is either!!

[Vios-GT_07]

please explain air dampener..

could be a fuel pressure thing i.e. it's starved of fuel at that point..? hm.. fuel pump big enough ? not worried about voltage , looking more at fuel pressure and volume here..

if it's a normal carb.. i'd say the float is a bit slow.. but if it's a webber... erm would it have 2 floats or something? sorry it's just me thinking aloud.. but yeh like you mentioned, the float chamber is a bit slow.. my guess is a mixture or valve acting retarded.. that or u've got too much timing ?

edit : if it is lean, and starved of fuel, and the pump gives off plenty of fuel, wouldn't it mean that the carbie would over-flow? i.e. flood?? can't u tell from the float (like a window or somehow, to see what state the webber is in) if it's flooding or starved when it stalls and dies? i could on a 4A-C...

[Ben Wilson]

allencr - It drives fine, but at more than 10% throttle it's for a very limited time (I can basically get to the top of second gear before it dies). Once it dies, no amount of pumping on the throttle helps - the wideband just reads 45:1 (as low as it goes) until the motor either stalls or just barely idles and the mixture slowly creeps back up again. All the emulsion tubes and jets are there. Under no load it free revs fine.

Vios-GT_07 - Unfortunately there is no window on the float chamber. After discussing it with some friends at lunch, I'm going to try driving it until it dies then shutting it down instantly and pulling the top off the carbie to see how much fuel is in the chamber.

Fuel pump should be fine, it's brand new and a friend ran one of these on his worked 351 Falcon and another one (using this exact carbie) on his Datsun without a problem.

[kingmick]

hahaha typo ment air diaphragm! lmao sorry was in a rush as i was on my way out the door! lol got everyone thinking
this link should help!
http://www.recarbco.com/technical/newtrouble.html

either the float is getting stuck or the diaphragm could be stuffed!

[Ben Wilson]

I think I've worked it out - If it's what I think it is I'm too embarrased to admit it so I'm not going to say anything more...

I don't think anyone else would think laterally (be stupid) enough to do this so not to worry.

Thanks for the suggestions, they go my brain working along the right path....

[kingmick]

hahahaahah i know what you did! these things happen!

[allencr]

Ben: you owe it!
kingmick: "air diaphragm" still doesn't do anything.

[kingmick]

i was using the discription of the site i was going to point to not mine! i know them as accelerator pump diaphrams{ i reckon i would have sold a few hundred of the last few years}, but thought if i said that and people read air diaphram there would be more questions! hahahaha looks like i was wrong, should have called it what i know not what somone else calls it!