85 GMC truck hesitates on hills occasionally

[gcoon]

Once in a while when going up a hill my truck acts like it is running out of gas.It will be getting gas then not causing a jerking. After getting to the top it will be fine and not give problems for weeks.

[geezer#99]

Surely you jest!!
There are no hills in Calgary!!
JK!!!
Welcome to the jungle!!

Could be your fuel pump give early signs of going kaput. Or a filter plugging off.

Pull the fuel line off the carb, check the filter inside the carb. Also put the end of the fuel line in a jar and crank it over. A good pump will pump a pint in 15 seconds.

[gcoon]

Thanks. I replaced filter and opened up the old one and it looked clean. I will try the flow with the jar. I've been told the fuel pump either fails or it works?

[cadillac_al]

Fuel pumps can dribble fuel too. It should be checked out. I'm not so sure that would cause a jerk, more of a gradual lack of power. EGR will make a vehicle jerk though.

[gcoon]

I will replace the fuel pump and see how it is. I have dual fuel tanks. Could a faulty selector valve cause this problem?

[Tucson38]

Originally Posted by gcoon

I will replace the fuel pump and see how it is. I have dual fuel tanks. Could a faulty selector valve cause this problem?

Yes it can reduce the flow to the point that you are experiencing. Three possibilities come to mind: Clogged fuel filter, low output from the fuel pump, or a problem with fuel delivery from the tank switching mechanism.

[gcoon]

Thanks everyone for the advice. I have replaced the fuel pump and will have to road test it.

[gcoon]

Did a test drive around the city going up lots of hills and seems all right. Will do a test drive out to the mountains this week. The dash switch was not always working when switching to the left tank you could not hear the motor or it would be for a short time. I pushed on the connector at the back and the switch broke apart. I replaced the switch but don't know if that was causing any problems.

[geezer#99]

Did you test it into a jar first?