Fuel Problem with 96 12v

[merkurjared]

ok, the other day i was driving 20 miles perfectly in the morning. on the 20 miles home from work about 5 miles into the drive while getting on it, the truck lost all its balls and would barely go 35mph. so i limped home changed fuel filter idles fine, drives down the road 5 miles like a raped ape. next morn same trip to work runs great. way home runs like again. when running good i get nice amount of black smoke when i want it, while running ty i get tons of white smoke and it shutters real bad. any ideas? im stumpped.

[KickinGas]

Sounds like timing may have slipped.

[vitalwolf]

same exact thing happened to me the other day with my 96. must be the season. im replacing the overflow valve on the return line. ive heard the symptoms are pretty much whats happening to us, but could also be indicative of other stuff too. i figure its worth a try, given its a $40 part and they tend to wear out. ill let you know what happens if you do the same.

[Whistler]

Make sure your pre-filter screen is clean. Then run some good injector cleaner like lucas and drive 100 miles straight. You can pull the spring out of your overflow valve, measure it, stretch it to correct length, & re-install. Timing can also cause this. Just a few options for yall!

[merkurjared]

the weird thing is that the first 3 miles every day it runs great. the prefilter screen is fine. i will try some good injector cleaner and check the overflow valve. what is the correct length of the spring? i would think the timing would be an all the time thing, that it wouldnt run good at all even the first 3 miles. let me know if you come up with anything else.

[Whistler]

96-98 have a banjo fitting screwed into the overflow valve. Remove the banjo bolt and spring. Measure the spring. It should be about .550in. 94-95 don't have a removable banjo bolt. There is a way to adjust this spring on these but would probably be better to replace the whole valve.

[merkurjared]

i tried a new overflow valve, that didnt do anything. not that i want to go here but what are the warning signs of a bad lift pump or injection pump. i am going to try some good injector cleaner first but figured i ask

[Whistler]

You can check to see if your lift pump is good. You need to hook up a fuel pressure gauge. Watch the gauge and pinch the return line. If the pressure rises your lift pump is good. If it does not change it is bad. If your lift pump is good and you have low fuel pressure it is your overflow valve.

[vitalwolf]

i cant even get the truck started right now, so how do i check if the liftpump is bad? or diagnose anthing for that matter? my screen and gaskets are new and clean is are my fuel filter.

[Whistler]

Crack an injector line and spin the motor over to see if you get full. Also check that your shut off solenoid is pulling up as you hit the starter.

[merkurjared]

ok so assuming my lift pump is bad which i think it is, since i run veggie oil and it has 170k. would it be better to get a electric pump capable of 25psi or just replacing the mechanical lift pump?

[vitalwolf]

new overflow valve fixed mine. you could breath through the old valve and open it. fuel pressure went from barely reading at all to 24psi at idle.