Carb or Fuel delivery problem?

[Jdgrant96]

Truck was running almost perfectly until a couple days ago and I need some help figuring it out.

84 k10, Rochester Verajet, Inline 6

Tried to teach the girlfriend how to driver the day before, included lots of bucking and stalling. Drove home perfectly fine after. Started it up the next morning, got gas, trip to store, and back home, a 20 minute trip. About two minutes from the house, I lost all power. If I added any gas it would bog and stall.

Got it back home and cut it off. It started right up again, but anything more than slight throttle it would start to bog. Messed around with it for a bit and found that holding a rag over the intake would smoothen ought the idle significantly and throttle addition worked again. Ok, too much air/not enough fuel.

Took the carb off and opened it up, cleaned a lot of black sediment (rubber maybe) out of it, everything else inside looked good. Put it back on, fired right up and seemed to be good. Let it idle high for about 5 minutes, moved through the throttle and then went for a drive. After reaching operating temp it started limping again.

I don't know what to think. Fuel will squirt into the venturi with throttle addition. If I pump the throttle 10-15 times before starting it'll run fine for about 30 seconds. Rag over the intake smoothens it out.


My possibilities so far are that gas tank sediment got stirred up clogging something somewhere or the A/F mixture screw moved somehow or the fuel pump is going.

Sorry for the novel, what do y'all think?

 

[Poppy 87]

Next check I would do is fuel filter

 

[Dave M]

possibly a vacuum leak if, as you said, holding a rag over the carby and make it run better.

 

[Jdgrant96]

New filter is on order. All vacuum lines are sealed/connected properly. Any place else it may leak?

 

[Red Rex]

Leaks may occur baseplate to manifold, baseplate to carb body, top of carb to carb body. At idle spray carb cleaner around those areas to check for leaks.

 

[Big Chip]

Did you mean to say it smothers it out or smooths it out with the rag over the carb?

 

[Jdgrant96]

Smoothen out. Purchased a new filter, the old one doesn’t have the check valve. I haven’t replaced it yet because of work. I’ve got a new sender unit coming since I can’t get a replacement in tank strainer (fuel gauge also didn’t work).

 

[Big Chip]

Smoothen out. Purchased a new filter, the old one doesn’t have the check valve. I haven’t replaced it yet because of work. I’ve got a new sender unit coming since I can’t get a replacement in tank strainer (fuel gauge also didn’t work).

What @Red Rex said then, you’ve got a leaky gasket more than likely.

 

[Snoots]

Was the carb rebuilt with gaskets/seals that were ethanol compatible?

 

[Red Rex]

Forgot to add: spray the intake manifold where it meets the heads. Sometimes there are gasket leaks.

The presence of a leak will be revealed by an immediate and temporary change in engine rpm

 

[1987 GMC Jimmy]

I’ll throw the accelerator pump diaphragm into the ring. You mentioned that it’s squirting, but how responsive or instantaneous is said squirting? If there’s a lapse from when you start to move the throttle to when it actually does something, it might be bad. Of course this happens when you’re with your lady. Either that or vacuum leaks, particularly base gasket, manifold port open, throttle shaft, or brake booster, worn/corroded ignition components, or timing. I wouldn’t suspect ignition right away, but it’s something to play with if you get nowhere with the fuel/air side of possible problems.

 

[peats]

how about bad gas? we just had a hurricane come through.

 

[DoubleDingo]

how about bad gas? we just had a hurricane come through.

I can attest to bad gas. When we went to Texas for Christmas 2018, of course stopping at any old gas station is the norm because you need fuel and typically can't be choosy. Started getting misfire codes a few days in, but they went away once good fuel was introduced regularly. Of course this was a 2007 Forester, but bad gas doesn't care what it messes up. Bad gas, disintegrated gasket, vacuum leak, plugged fuel filter, carb needs a good cleaning internally....

 

[87scotty]

i would say bad gas as well havnt had it in a few years but.you know when you get it

 

[Bextreme04]

call the gas station you got the gas from... they might have had reports or know they got bad gas. They don't know all the people that might have gotten it so they aren't going to notify you as a customer, but they can certainly tell you when you call and ask