Low power with boost twist
01-13-2007, 04:34 PM
#33
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Today I plumbed in a 3/8" clear hose immediately before the lift pump. Air bubles were always present, predominately at part throttle when power is the lowest. Added 5 gal of fuel to tank and saw a reduction in air bubbles. Added 10 gal of fuel to the tank and saw more reduction in air bubbles. So it seems like I have a problem with the in-tank pick-up unit. Will replace and let you all know how it turns out.
Brian
Brian
01-27-2007, 09:38 PM
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Hey gang,
I pulled my old tank sending unit looking for problems. I did not see anything obivious. If I take it apart and stick my thumb on the bottom of the pickup and then suck on the suction fitting with my mouth it seems to hold vacuum. This was confusing me because it seemed that previously I concluded air was getting into the system from the in-tank sending unit (air bubbles in a clear fue line before the lift pump). Is my simple suction test of the old part flawed?
Brain
I pulled my old tank sending unit looking for problems. I did not see anything obivious. If I take it apart and stick my thumb on the bottom of the pickup and then suck on the suction fitting with my mouth it seems to hold vacuum. This was confusing me because it seemed that previously I concluded air was getting into the system from the in-tank sending unit (air bubbles in a clear fue line before the lift pump). Is my simple suction test of the old part flawed?
Brain
01-29-2007, 10:15 PM
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this was after i replaced the factory line with my own fuel line....
today i plumbed in the clear plastic line to check for bubbles. running the truck in the driveway with about 27.5 gallons in the tank and the new pick-up installed there was a very small bubble here and there (have to get <12" inches from the fuel line to see).
previously, with the original in-tank pick-up and about 8 gallons in the tank, air bubbles could be seen as a continuous stream of bubbles from 3-4 feet away. as i added 5 gallons the number of bubbles reduced. with another 5 gallons there were even fewer air bubbles.
i will leave the clear plastic line in for a few tanks and check for air bubbles as the tank empties.
something was definitely wrong and i hope this new in-tank pick-up unit fixes it.
today i plumbed in the clear plastic line to check for bubbles. running the truck in the driveway with about 27.5 gallons in the tank and the new pick-up installed there was a very small bubble here and there (have to get <12" inches from the fuel line to see).
previously, with the original in-tank pick-up and about 8 gallons in the tank, air bubbles could be seen as a continuous stream of bubbles from 3-4 feet away. as i added 5 gallons the number of bubbles reduced. with another 5 gallons there were even fewer air bubbles.
i will leave the clear plastic line in for a few tanks and check for air bubbles as the tank empties.
something was definitely wrong and i hope this new in-tank pick-up unit fixes it.
01-29-2007, 10:21 PM
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the symptoms of low power were obvious when it was cold outside. now that we have a cold front that's going to spend a few days i'm going to be watching that clear line for air bubbles as i let the tank level get lower.
i wonder if my simple test with my mouth and thumb was somehow flawed. maybe under the higher flow of the lift pump the system fails.
i wonder if my simple test with my mouth and thumb was somehow flawed. maybe under the higher flow of the lift pump the system fails.
01-31-2007, 07:02 PM
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well the temps were very low today for this area... between 12-25F all day. i drove the truck to and from work today about 21 miles each way. both my neighbor and i agree the truck sounds great at idle with no smoke, etc. however when i take it on the road it doesn't have a lot of power at higher rpms... this morning in the very cold weather it ran higher boost (maybe because the cold air is denser) but it didn't have gobs of power despite the block heater being plugged in for 7 hours.
when i got home i started checking more things. i noticed the little arm for the manual pump on the lift pump was not in the resting/locked position, but just below it so i put it where it should be. does this cause any problems?
i started the engine and it sounded the same at idle and the clear fuel line looked the same. i removed the bleeder banjo bolt and started the engine and fuel poured out of it so i cut the engine off. this told me the lift pump was pumping. next i put a cone shaped adpater into the bleeder to an old fuel psi gauge my dad had and at idle it makes 7 psi with fuel leaking out because the cone is not a great fit.
i checked throttle travel once again with my neighbor and we verified it works okay.
i guess i will test drive it again tomorrow to see if anything's changed. i don't think that arm on the lift pump being a little lower than the resting position had any effect?
i ordered a westech fuel psi gauage on geno's and will install it when it comes so i get some fuel psi readings at wot under load.
anybody thinking of what else may be wrong? i am thinking the injectors must be ok because otherwise it wouldn't idle so smooth.
brian
when i got home i started checking more things. i noticed the little arm for the manual pump on the lift pump was not in the resting/locked position, but just below it so i put it where it should be. does this cause any problems?
i started the engine and it sounded the same at idle and the clear fuel line looked the same. i removed the bleeder banjo bolt and started the engine and fuel poured out of it so i cut the engine off. this told me the lift pump was pumping. next i put a cone shaped adpater into the bleeder to an old fuel psi gauge my dad had and at idle it makes 7 psi with fuel leaking out because the cone is not a great fit.
i checked throttle travel once again with my neighbor and we verified it works okay.
i guess i will test drive it again tomorrow to see if anything's changed. i don't think that arm on the lift pump being a little lower than the resting position had any effect?
i ordered a westech fuel psi gauage on geno's and will install it when it comes so i get some fuel psi readings at wot under load.
anybody thinking of what else may be wrong? i am thinking the injectors must be ok because otherwise it wouldn't idle so smooth.
brian
01-31-2007, 07:43 PM
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i thought of 2 other questions.
first, the first time i cracked open then bleeder banjo bolt i heard a swoosh noise almost like it was sucking in air. i did not see any fuel leak out. i thought of this for a second but and dismissed it until after the second time when i opened the banjo and fuel came out. i wonder how this condition could have occurred? i am wondering if i could somehow have an air leak AFTER the lift pump??
also, so far i've left the RETURN line original. but there is a questionable 90 degree bend in the plastic return line a few inches from the tank where the line collapses some. i have wondered if this could be causing a restriction and causing fuel to back up inside the pump. keep in mind the supply line to the lift pump is brand new.
first, the first time i cracked open then bleeder banjo bolt i heard a swoosh noise almost like it was sucking in air. i did not see any fuel leak out. i thought of this for a second but and dismissed it until after the second time when i opened the banjo and fuel came out. i wonder how this condition could have occurred? i am wondering if i could somehow have an air leak AFTER the lift pump??
also, so far i've left the RETURN line original. but there is a questionable 90 degree bend in the plastic return line a few inches from the tank where the line collapses some. i have wondered if this could be causing a restriction and causing fuel to back up inside the pump. keep in mind the supply line to the lift pump is brand new.
01-31-2007, 08:14 PM
#44
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You know, that quick disconnect seems too easy (in my opinion) for failure.
Is this a suggested mod in the sticky? Because when I replaced the diaphragm lift pump to the piston lift pump I noticed this and it seemed a little shabby. After all these miles the O-rings must need replacing. I didnt have any extra boost before install but the truck runs MUCH better after upgrade.
Is this a suggested mod in the sticky? Because when I replaced the diaphragm lift pump to the piston lift pump I noticed this and it seemed a little shabby. After all these miles the O-rings must need replacing. I didnt have any extra boost before install but the truck runs MUCH better after upgrade.
02-03-2007, 09:30 AM
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still having problems!
Hey all,
I even changed the fuel heater o-ring and its still not running right all the time.
Right after I changed the o-ring we took it for a test drive and it worked great. Touch the accelerator pedal and the boost goes up and the truck moves faster... next morning it was ******* like usual. When it dogs the boost can stay around 5 psi and maybe get up to 10-12 psi on the freeway after a while.
I had a fuel pressure gauge that I used temporarily in the driveway and it says about 7-8 psi at idle and at WOT 7-8 psi. When I get the fuel psi gauge from Geno's I'll be able to find out what its doing on the freeway.
Could a problem with the return line cause any problems? I have not replaced it. I blew through it and did not find any major blockages.
I was not sure how to test for any leaks in the fuel system between the lift pump and the injection pump. I blew compressed air through the bleeder in the banjo bolt. Should the pump make a klunk noise when I do that? After a many times of shooting it with compressed air it seemed to stop doing that. It seems that the air goes out the return line in any case so the only way to test with air would be to pressure the entire system including the tank. I was using about 5-12 psi of dry nitrogen from a tank I use to test A/C. Now my throttle level leaks a drip of fuel every now and then.
Brian
I even changed the fuel heater o-ring and its still not running right all the time.
Right after I changed the o-ring we took it for a test drive and it worked great. Touch the accelerator pedal and the boost goes up and the truck moves faster... next morning it was ******* like usual. When it dogs the boost can stay around 5 psi and maybe get up to 10-12 psi on the freeway after a while.
I had a fuel pressure gauge that I used temporarily in the driveway and it says about 7-8 psi at idle and at WOT 7-8 psi. When I get the fuel psi gauge from Geno's I'll be able to find out what its doing on the freeway.
Could a problem with the return line cause any problems? I have not replaced it. I blew through it and did not find any major blockages.
I was not sure how to test for any leaks in the fuel system between the lift pump and the injection pump. I blew compressed air through the bleeder in the banjo bolt. Should the pump make a klunk noise when I do that? After a many times of shooting it with compressed air it seemed to stop doing that. It seems that the air goes out the return line in any case so the only way to test with air would be to pressure the entire system including the tank. I was using about 5-12 psi of dry nitrogen from a tank I use to test A/C. Now my throttle level leaks a drip of fuel every now and then.
Brian