hello diesel place,

i have a gmc g2500 1988 , yup the 6.2l v8

about a year and a half ago , i changed the side fuel pump since it was leaking more fuel on the ground than actually pumping to the motor.

so , i changed fuel filter , fuel filter gasket and THAT fuel pump on the side , not the db2 pump.

i never bleeded the fuel line right out through the injectors, i just bleeded the fuel filter , and everything worked.


i did a change thou, i cut the metal fuel line about 4 inch from the pump since it was rusted/jammed. i used a pipe cutter , did the same to a new bendable metal pipe , and just replace the old that was cut out. and link it with a rubber fuel line over with 4 metal clamps ( 2 per each side)

anyways it worked.


thou i got a lot of air accumulating always in the filter ( almost if the fuel was returning to the tank ) .


when i bleed from the fuel filter valve , the mix comes out 50/50 air/fuel

unless i pressed the pedal all the way , then the fuel comes out liquid with no bubbles.

last week i tossed my fuel cap , wich was causing an incredible vacuum / crushing my tank ( well i just diassembled the valve inside cause i dont want rain to drop in the tank)

so since iv been stallin when im too long at a light , or after too much stops , but i can got on highway no prob, im suspecting the fuel pump diaphragm may have openup cause of that defective cap.


anysuggestion ?!? this problem is escalating and giving me a rash , on top thats its pretty dangerous to stall when at a traffic light.


cheers to all you fellow mechanics.

neko



oh i forgot to mention , last week i retighten all links with no luck , the air is more present than ever. i have to drive with the internal hood off , so i can bleed when i run. nothing looks wet from under . nor drip marks on the pavement.

im about to try thread glue on my links ,

but what good trick could i use to find a leak (that doesnt drip) from gas tank to lift pump ? and lift pump to filter ?


im thinking soap and compressor ;) -joking

but seriously id love my first van ( car for the matter ) to run safely again.


thanks for any suggestion .

be careful with the mech pumps. Honestly i think they are junk after dealing with the one on my blazer. The diaphragm blew out on mine and it was pumping diesel into the engine oil.

Get an electric lift pump for a 93 6.5TD. you'll have to get the special o-ring screw on adapters as well. They can be found in the "help" section of any auto parts store usually.

I wired my electric lift pump to a relay that is turned on via key power at the fuel shutoff solenoid. It works great and the truck starts better than ever.

thanks dave , yea i know there's not a long way from that rod to the oil pan.

ill get it down again, see if i scrapped the new one as well. good tip for the electrical one,
i actually thought about adding an electric one before the mechanical one but your idea sounds better.



im afraid the the line could be spotted elsewhere too, and im out of idea about finding a vacuum leak (sucking air in fuel line) , thoses fluorecent products doent seems suited for inspecting this , any ideas on that too ?

dave on a side note, how you patched that hole the mechanical lift pump left ? you removed the rod as well or simply left the hole, cause that would drip to the floor wouldnt it ?

i bought a block off plate and removed the pushrod. the pushrod makes a nice chrome paperweight. :p:

you ahve to remove the pump then remove the pump backing plate. save the bolts as you'll need to reuse two of them(2 different sizes) but i can't remember which ones need to be reused.

i just bought the chrome blockoff plate from autozone. it's the only chrome thing on the motor but it does the job very well.

oh , that makes sense , getting smaller bolts (minus pump thinkness) , and you probably used the old pump (could be new) gasket ?

that sounds like a very good mod ; ill shure try it if that pump is the rash of all rash.

thou i said i suspected the pump to be messed up. it pumps all good, it just brings back air with the fuel, so i could be in the wrong and the problem could be before the lift pump going to the tank, or anything on the fuel filter assy since i see air-doped fuel coming from the bleed valve.

thanks , your response motivate me out of the grease blues.

more details i forgot :


hot start & cold start is on the quarter turn , start right on.

thou as soon as air saturate the filter , ill just go " GNNIIIGNIIIGNIIIIGNIIIII " till i turn the fuel valve.

patheric problem creating monstruous consequences in slow traffic ( actually i dont drive it daytime anymore since i find it dangerous to everybody else that would hide in my blindspot / plus i look like a retard with a van that has an aparent problem ppl usually get in the wintertime )

the block off plate i bought came with new bolts. the bolts you have to reuse are the ones for the fuel pump backing plate(not the ones that hold the fuel pump on), as the ones in the kit were not right.

the block off kit comes with a nice thick new gasket. i used Indian Head Sealant on the gasket and no leaks.

thou my last pump spilled all the fuel on the ground , the fuel filter never got saturated with air. (all the contrairy) still ran but cost me about 20$ for 1/8 of a mile.

now im thinking however that mod sounds nice, still, the truck ran awesome for the last year , with the new lift pump. i developped a suction in the tank in the lasts month, in 2009 actually . and ran a while thinking it was normal. then more and more air started cludding the filter

how can i test a gas tank mounted ? i suspect more the leaks coming from there than anything.
and when i say leak its not dripping , its more of an inward leak tube wise.
so you had air too in your fuel line ?

thou my last pump spilled all the fuel on the ground , the fuel filter never got saturated with air. (all the contrairy) still ran but cost me about 20$ for 1/8 of a mile.

now im thinking however that mod sounds nice, still, the truck ran awesome for the last year , with the new lift pump. i developped a suction in the tank in the lasts month, in 2009 actually . and ran a while thinking it was normal. then more and more air started cludding the filter

how can i test a gas tank mounted ? i suspect more the leaks coming from there than anything.
and when i say leak its not dripping , its more of an inward leak tube wise.
so you had air too in your fuel line ?

the big problem with the mechanical lift pumps is when the IP looses it prime. the mech pump only works when the engine is turning. by time you get fuel back up to the IP your batteries are probably dead, or you never get it started. The electric pump is immune to that. just turn it on and it primes the system for you.

I didn't have air in the lines on this truck but the ruptured diaphragm was causing the pump to leak out the weep hole and into the crankcase.

the big problem with the mechanical lift pumps is when the IP looses it prime. oh yea shure , thats would assure delivery the mech pump only works when the engine is turning. by time you get fuel back up to the IP your batteries are probably dead, or you never get it started. The electric pump is immune to that. just turn it on and it primes the system for you.
see, my 6.2 runs perfect , to the point where i get air coming from the fuel tank. and it accumulates in the fuel filter , i see what you means and it would be a more reliable system. but i have read about the close system here ( cap thread etc..) and since i have no documentation about my fuel tank internal as well as external linkage , return etc... i am wondering , how can i test my fuel tank.
I didn't have air in the lines on this truck but the ruptured diaphragm was causing the pump to leak out the weep hole and into the crankcase. oh im all aware of that , thanks , im wondering about the bubbles more than anything. in less than 12 hours the lift pump will be in my hand and have an accurate picture of the diaphragm. im just being proactive about how can i test my fuel tank ?

87180

see the four clamps on the fuel line that goes to the filter.

well its metal all the way to the fuel filter , about 2 inch from the filter the line becomes rubber tubing.

so what you see here is a choped in two metal line , with a very tight rubber tubing on top of the cutted section with about 2 inch in excess side to side and 4 clamps holding that scealed.

from the picture everything looks wet , that was taken not last winter but the other one before. replaced it outside at -20. i ran poerfect till the bubble camed in. about 4 months ago.

how can i inspect a fuel line for place where it would sucction air if no drip is appareant , since nothing is wet now.


cheers !

on mine, i bout the 6.5 1993 lift pump, and a piece of brake line that threaded into the pump, did a slight flare, cut the ends, got some rubber hose, wired it up on a switch, and i couldnt be happier, i started with a new mechanical pump, then got a mr. gasket pum (which failed after 6 months, not recomended) id say do it like i did, and you will be satisfied, one question, does it suck air when your tank is full?

on mine, i bout the 6.5 1993 lift pump, and a piece of brake line that threaded into the pump, did a slight flare, cut the ends, got some rubber hose, wired it up on a switch, and i couldnt be happier, i started with a new mechanical pump, then got a mr. gasket pum (which failed after 6 months, not recomended) id say do it like i did, and you will be satisfied, one question, does it suck air when your tank is full?

unfortunately yes, may be a -little- less , but barely noticeable.

i used to do stall after , say 30 miles, now its not even 800 meters and the thing starts to act popcorn before dieying on me, and thats with full / med / quarter tank. unless i bleed while driving with doghouse open or jerk the accelerator till it lug out. but if i dont turn that valve , its every second closer to the end.

i got to say your guys idea of the electric pump to keep the prime really makes sense , thou i fear the electrical pump would get the same air coming from the back.

that tank really started to act on me lately , even on hot days, when the truck just stayed there i would turn the fuel cap , and a HUGE vacuum was in there. its a little kinked inwards from under.

i might be thinning the oil with the fuel thou, since i used to have to add a little oil every now often , and at a certain level (of oil) the truck was less prone to stall, but i think this is just an illusion since now good oil bad oil , the filter just get saturated .

just a slight breif quarter turn of the air filter valve is enough to get me on a few dozen miles . till i drop the speed and break ofthen , and a slight breif quarter turn get met an other few. sometimes i have to do it about 15 times really quick to get it all out.

i m collecting the fuel that i bleed out , i could dump a complete oil pint full of fuel in about 2 to 9 starts.


cheers guy , i know im close to the problem's solution , and i apreciate you two sharing experiences. that helps me a lot .

> its a shame cause i did the whole direction , seering colum and universal joint to the gearbox, as well as changing all my glow plugs to double coil mil ones (that front truck driver side one was a dog at first) and a direct drive starter that doesnt need 2 top end batteries ( that are still in there , thou the one under is now moded at the back of my driver seat.

really first van , we go a long way , i wish it would like to travel again.

see i could buy an other one for 700 here (the whole van) , and beside redoing all the same work in an other or finding this fuel leak in mine i really prefer the later one. but its not leaving me a lot of hints.

i just read in an other thread :

i would qualify this a lug when it accumulates air in the fuel filter.

runs smooth ( for a big motor ) when i get the air out.

i rarely get any coloured smoke out the exhaust .



beside experience, is there any fuel tank diagrams that exist ? as per models ? that would get me a good idea what got cogged where or whats acting.

oooh , the flashback hits after a day of work doesnt it...


around feb i ran out of fuel , and simply bleeded from the valve while cranking, now i get why we have to bleed all the way through the injectors, i completely forgot to fill the filter after that mishaps.

man i feel like i missed the obvious when i pulled that filter and it was almost empty.

i filled all outs before filling the inlet, and then removed the filter mount so when i would plug it in it would keep most fuel than just trying to be quick.

when i cranked it , it sounded like last year.


ill be stress testing it all weekend see if how it goes , and try to bleed it throughout the injectors.


thanks guys , i had a lot happening at once and gess i missed the obvious. ( and forgot about that time :D )

cheers !!