Calling carb. and fuel Gurus! (1 Viewer)

[ClemsonCruiser]

My problem is my carb. is cutting out at highway speeds and also underloads(up hills). It seems as if the 40 has a rev. limiter........ I believe it isn't getting enough fuel.

The background is; I have a 1977 fj40, it has a freshly rebuilt engine, stock intake and exhaust, and I am running a non-usa distributor., and I have an electric fuel pump that I purchased for the weber carb. from TPI4x4. that I was running up until now.

I was until recently running a weber carb. and with this set-up I had no such similiar problems. Then I decided to go back stock on the carb. as well. So I had a 76 2bbl. asain rebuilt for me. I have the carb. dialed in and running smooth at idle, it runs great until the afore mentioned cutting out at high end. The only thing I can think that might be the problem is the eletric fuel pump might not be flowing enough gas at high rpms and wide open throttle. I still have my stock fuel pump and am considering reinstalling it to see if that will solve the issue, but before I yank the eletric pump out I wanted to hear from you guys.

 

[cabron]

i just got home to post the same exact question, trippy....

 

[ClemsonCruiser]

mmmmmmm hope it isn't bad cruiser karma.........

well I just went out and I was watching the sight glass in the float bowl, and when I got on wide open throttle the carb. would suck the gas down to where it basically wasn't visible. I am guessing this is more evidence that the electric fuel pump isn't flowing enough, but I am going to wait for some input from someone who knows much more about this than me........

 

[jjhancock]

Sounds like your fuel pump isn't working right to me... Or, you could have some bad fuel line between your fuel pump and carb. Some on this board have had the experience of the hoses seeming to be in ok shape, when in reality the inner structure of the hose has cracked and there are loose pieces inside that will move with fuel flow, causing fuel to not flow as fast as your carb would need it, thus the fuel level thru the sight glass going down under heavy accelleration.

I would probably check the hoses and see what you come up with. They aren't super easy to reach, but it would be worth while I think to check them first because it could be a very cheap fix if that were the culprit.

 

[ClemsonCruiser]

sounds like a plan, I will look at that here shortly.

Keep the ideas coming guys

Thanks
JP

 

[jjhancock]

I had carb problems and considered going to an electric fuel pump but didn't. I convinced myself that my carb needed rebuilding, which is where I'm at now... getting it rebuilt. The guys around here say that when they use an electric fuel pump, they use it between the gas tank and the fuel filter, but STILL use the mechanical fuel pump and it works great. I *think* they just run a switch of some sorts to fire up the electric fuel pump to get fuel to the mechanical fuel pump. You might want to try searching the site for more information on that. Could be your electric fuel pump just isn't delivering the amount of fuel you need when the motor is really sucking gas, or quite possibly be the fuel lines are deteriorated inside as well. If you have your old mechanical fuel pump around you could also try bolting that back on and seeing if it makes a difference. Could there possibly be a bad ground from the fuel pump?

 

[Cat Scan]

Well, when I had my 2F and had the symtoms described on an uphill climb or highway speeds, the fuel filter was the problem. Maybe you changed it and I missed it in the write up. I would go that route first, if not. You made some changes that might be requiring a little more fuel flow.

Disregard this post if you have already changed the filter.

 

[ClemsonCruiser]

my mistake for not specifing I changed the fuel filter when I installed the new carb.

 

[NJFJ40]

my mistake for not specifing I changed the fuel filter when I installed the new carb.

Replace it again. Take out the one you recently put in and cut it open to see if its clogged. If your gas tank is rusty or lots of scale in there it will just clog up the filter regardless of it is new or not.

Best to rule out the obvious and easiset fix first before you start digging deeper. Fuel filter is like $5 so no big deal if you waste one.

AndrewT

 

[ClemsonCruiser]

just ordered one it will be here in the morn. Thanks for the help

 

[ClemsonCruiser]

Update, I re-installed the stock fuel pump, but the it did not fix the problem.........

Tomorrow I am going to replace the fuel lines and fuel filter, then if that doesn't work I don't know where to go next.

On aside note is this something that could be cause by my valves not being tuned in just right???

 

[surfpig]

Had this same problem when I got my '77(Calif.) Fj55 a few years ago. PO had a long repair history of same problem. I got the carb "professionally" rebuilt locally, still gutless. Finally figured out the "secondary throttle diaphragm" thingie, while I was rebuilding the carb myself. Also, make sure ALL your vacuum lines are in good shape, and your smog components (if you have 'em) are working. That diaphragm, through engine vacuum (i think) makes the secondary open up under load, so you can get up the hills, accelerate, etc. Once I got that figured out, I soon realized I needed a new fuel pump, filter, and fuel lines (to move all that gas)!!!

Have fun...

Nial

 

[ms3820]

X2 for fuel filter. I bought a CCOT plastic and had shavings build up in the fuel filter. I have a cheap napa see through now. When I hit 50 it would buck.
-------"The guys around here say that when they use an electric fuel pump, they use it between the gas tank and the fuel filter, but STILL use the mechanical fuel pump and it works great.

Why would not just let the stock pump get the gas? unless you had an aux. tank?

 

[ken_79-fj40]

I ran 2 pumps on mine for a while when I was having fuel delivery problems. Turned out to be crap in the tank clogging the pickup tube, which running a second pump did nothing to help. I continued to run 2 pumps until someone told me if the mechanical pump goes, the electric pump would fill the crankcase with gas. So now I carry the electric as an emergency backup.

 

[jcj_78FJ40]

mmmmmmm hope it isn't bad cruiser karma.........

well I just went out and I was watching the sight glass in the float bowl, and when I got on wide open throttle the carb. would suck the gas down to where it basically wasn't visible. ........

This may be OK. A sinking float opens up a needle valve to allow more gas in the carb. But you might get the same symptoms if the float is stuck.

Check to make sure that the gas level is centered in the sight glass at idle. If not, the float is not properly adjusted. Open the throttle plates again. When the gas level goes down, tap the top of the float bowl with a hammer and see if things improve. If you see an improvement, then the float might be binding.

Good Luck

 

[ClemsonCruiser]

well good news, after replacing all the fuel lines and also he fuel filter, the problem has almost vanished, there is still a tiny brief hesitation at wide open throttle up around 2700rpms, but I don't really go that high when driving. I took it for a spin and was able to hit 60 without any problems and that is as fast as I want to go anyways. Should be fine for getting me to Tellico this weekend.

I opened up the old fuel filter as recommended and it wasn't full of debris, I believe part of my problem lied in the patch work of fuel lines installed by the PO, that might not have been allowing smooth flow of fuel. Because the new continous single fuel line seems to just about solved it. I intend to have the tank inspected and cleaned after this weekends trip to see if that won't clear everything up for good.

Thanks for all the help guys!!!!

 

[mhdsummers]

I had the same problem a while back. Replacing the fuel line from the pump to the carb fixed my problem. I had also replace the pump, filter, return lines, and rebuilt the carb with no luck. I have not had the problem since.
Hopefully this is the end of your problems as well.