Plugged Fueltank cap

[bison]

Tank vaccuum will become exessive if the cap is plugged(my cap happens to be solid plugged) which can in worse case scenario cause a collapsed tank.
It is also equally hard on the LP and IP cause less fuel to the IP means less IP cooling and less fuel for the engine.
I prefer no tank vacuum at all and to circumvent any vac problem i always left the cap loose but i found that while driving the cap seated itself back on the neck over time and as the tanks level got lower the fuel pressure got lower also till in the end it was 0.
There was 3-4 PSI fuel pressure diff in having vacuum or not.

Yesterday after the umtied episode with vacuum forming again i decided to take the cap apart and have a looky see wat's ailing.
The white insert is held in place by 4 tabs in the black lid and can be taken out by careful prying with a thinbladed screwdriver between the insert and the tab and lifting the insert up to clear one tab and stick a piece of wire trough the slot under it to keep it from snapping back before prying the next tab.
Once you got the insert out you''ll find there is a screen on the backside of the insert,..in my case it was solid plugged with dirt.
After cleaning the screen and pressing the insert back in the lid the cap should be back to new.
If you like me don't want any vac in the tank,you can take the little valve(tankside) out of the insert by breaking out the slotted circle in the centre and removing the spring and valve.
Now i can crank the cap down and never have to worry about vacuum again.

Some pics before and after.

 

[Burning oil]

Reminds me of a gas mask valve.

 

[3500GMC]

So the micro screen plugs up eh? Now we know...

Gonna check the 93 tmrow..

My fuel cap is gonna get some lip action from me in public, you watch! (should be able to force air thru by mouth, correct?)

 

[bison]

Nope,unless you remove the valve

 

[3500GMC]

I can do that.. yep.

 

[JMJNet]

So picture no 3 is the after?

 

[bison]

yep

 

[flyinvega75]

Sounds awesome bison I do the same thing with leaving cap loose and damn things always reseats itself I'm going to do this tomorrow thanks for the heads up.

 

[nealpellecchia]

very good info thanks! It makes me wonder what about all those years my brother had the truck with a locking cap when I got it. Dealer says they don't have locking caps so what was his? I lost that one about 8-9 yrs ago and still have the next one that I lost the key to and will perform your surgery on it tonight. But!, Back to the return hose on top that I replaced with new fuel line as per the local Diesel and Gas guys recommend. I can't keep tight clamps on it! when cranked down the small clamps get off center and loosen up/ pop out of the grooves. The bad starting started again...not the still headache electrical bad starting but the sucking in air one. So rather than pulling the tank out duty I was finally gonna perform I said to myself that every time I remove that top little return hose and stick on the clear hose it starts. And it did! Runs great again but the clear hose softens up soon and is even worse to clamp but it sticks on good for a day. I used that fuel line and clamps elsewhere by the fuel cannister to inj. pump and drain hose but they are straight and less stressful connectors. NAPA sold me 2 different style "Injector hose clamps" finally got some , I heard there was another style. I'm worried about all the high rpm, keep it running, starting up that I had to do "cold" to clear out the air in lines. Well I hope at 340,000 miles the engine has been properly run in so it can take it. Also I was gonna take a 3/8 clear hose and shove it down into the bottom of the tank and try and siphon out the bottom of the tank " fish tank" style to see what I get just for fun through the filler opening but I just checked the filter for any more black grunge that I saw on the bottom, water portion of the filter the last time I changed it. It was clear. I thought I finally got a water in fuel light and a service engine code. but they don't stay on like other cars do. Maybe that black grunge was from using ATF to lubricate the pump and clean out the injectors like i did a lot of. It seemed to work great and ATF can be gotten from the recycle yards for free instead of 32.00 for a big Lucas.

 

[nealpellecchia]

I'm not getting notifications of messages anymore?

 

[bison]

very good info thanks! It makes me wonder what about all those years my brother had the truck with a locking cap when I got it. Dealer says they don't have locking caps so what was his? I lost that one about 8-9 yrs ago and still have the next one that I lost the key to and will perform your surgery on it tonight. But!, Back to the return hose on top that I replaced with new fuel line as per the local Diesel and Gas guys recommend. I can't keep tight clamps on it! when cranked down the small clamps get off center and loosen up/ pop out of the grooves. The bad starting started again...not the still headache electrical bad starting but the sucking in air one. So rather than pulling the tank out duty I was finally gonna perform I said to myself that every time I remove that top little return hose and stick on the clear hose it starts. And it did! Runs great again but the clear hose softens up soon and is even worse to clamp but it sticks on good for a day. I used that fuel line and clamps elsewhere by the fuel cannister to inj. pump and drain hose but they are straight and less stressful connectors. NAPA sold me 2 different style "Injector hose clamps" finally got some , I heard there was another style. I'm worried about all the high rpm, keep it running, starting up that I had to do "cold" to clear out the air in lines. Well I hope at 340,000 miles the engine has been properly run in so it can take it. Also I was gonna take a 3/8 clear hose and shove it down into the bottom of the tank and try and siphon out the bottom of the tank " fish tank" style to see what I get just for fun through the filler opening but I just checked the filter for any more black grunge that I saw on the bottom, water portion of the filter the last time I changed it. It was clear. I thought I finally got a water in fuel light and a service engine code. but they don't stay on like other cars do. Maybe that black grunge was from using ATF to lubricate the pump and clean out the injectors like i did a lot of. It seemed to work great and ATF can be gotten from the recycle yards for free instead of 32.00 for a big Lucas.

Wonder what kind of tubing you use,mine tends to harden up instead. I Just push the 1/4" clear tubing on the fitting and leave it at that.
I have'nt had a problem yet.

No need for inj return hose clamps either, i just cut a small piece of the end of the stock hose and push the hose on the nipple,never had one leak or pop off either.

 

[tanman_2006]

Took an old gasser cap and knocked the middle out of it today, drove bout 100 miles and no vacuum, no more collapsed tank. My cap was different than yours but same principle, I had to break the middle out because there were no clips and there was no filter inside.

 

[JMJNet]

Can we just drill that middle section with a small hole? like 1/8".

Seems a lot easier to do and faster.

 

[bison]

There's a rubber poppet in the center, drilling wiil just spin it and if you do get trough it won't result in a clean hole anyway.
Breaking the center piece out off the plastic part is done fast with the tip of a knife.
The reason for plugging is mainly because of dirt between the cap and insert so one needs to take the cap apart anyway

 

[DieselSlug]

I drilled a hole in the center of my cap, and it still had vacuum. So i always just don't tighten it completely. Guess i didnt drill through deep enough. I will have to dis-assemble mine..

 

[nealpellecchia]

Wonder what kind of tubing you use,mine tends to harden up instead. I Just push the 1/4" clear tubing on the fitting and leave it at that.
I have'nt had a problem yet.

No need for inj return hose clamps either, i just cut a small piece of the end of the stock hose and push the hose on the nipple,never had one leak or pop off either.

I want to know where you get your tubing? years ago my dad who fixed printing presses had some thick clear hose that I just stuck on my tri-power 389 65 GTO gas lines. no clamps. But my clear tubing comes from a Home Depot kind of store. How long is the diesel gonna take to eat that plastic? Man , I had that new fuel line hose clamped tight. It's a mystery why that hose had to come off again and that was the problem. The return hose on top. 6 in. long. You know the one I mean? I cant believe that's still the problem. And for the starter?...my old timer radiator shop guy says that well, "you have low voltage." nobody knows why. He finally added a remote starter switch to his old truck. Thick wiring to both the solenoid and battery terminal by pushing a button. He gave up on the stock wiring. My bulkhead connector scares me as a potential can of worms where the problem may lie. The new cheap solenoids on the rebuilds need higher voltage I think.

 

[bison]

I get the clear tubing by the local auto and farmsupply store,it is thicker wall than that homehardware crap.It is not fuel rated perse but it works fine.
Chainsaw fuel hose would be a good choice too but i don't know if they make that stuff in 1/4".

 

[nealpellecchia]

I get the clear tubing by the local auto and farmsupply store,it is thicker wall than that homehardware crap.It is not fuel rated perse but it works fine.
Chainsaw fuel hose would be a good choice too but i don't know if they make that stuff in 1/4".

ok, i took off for the weekend without checking for your info. 26 miles later I got stuck. my garbage hose was soft and leaky. Put on the fuel like with different hose clamps tight. But, the starter wouldn't work after cranking like mad at first when stuck.

Rebuilt starter, box says new, man said new, 1 yr warranty. failed in the first 3 mos. hot won't start. he replaced the solenoid ok for about 4 mos... I start feeling guilty about asking this little man to do it again...no starter problem ever before!.. so I commit myself to finding low voltage. click sometimes no click others. voltage meter to s terminal while my son turns key to start numerous times getting all kinds of different readings. But starts with a screwdriver through the fender well. except when battery terminal loose. then all gets worse after several mos. of using screwdriver etc. replace both grounds, cut rubber off of positive lead wire good but corrosion about 1/2 through where wire attaches to factory side mount screw on terminal. saw off with a hacksaw blade, thick!! Put on cheap clamp the wire terminal, can barely get the wire in their. I think, Oh finally I found the deeply hidden problem but cranks the same with intermittent no crank.

I took the starter out recently and man took it apart and checked the brushes ok , opened up the solenoid; washer too thin he says put in new thicker, I saw, Copper washer. originals are not copper, silver in color. Works for a few days like all of my recent repairs. I thought i had it back to always starting with a screwdriver until today. Man held the switch on start for me "click". I lay on the ground and hit it with a hammer a lot, finally it cranks! but I'm only priming the fuel line...then it won't crank again with hammer. I wait about an hour and then finely it starts with key only. What do you think?

 

[bison]

Did you check/clean all the batt connections/cables and groundlugs?
Are the batts load tested?.
If above is ok and you get 12v at the small starter solenoid wire then i say the starter has serious issues either with the solenoid contacts or with poor brush contact to the armature slip ring.
Stiff starterfork/bendex(dryed or no grease,cold weather) movement can prevent the solenoid washer to bottom out against the contact bolts.

 

[JMJNet]

x2 with bison.

Also, if you still have the nice rubber/plastic cap on the battery cable terminal connector, peel it off so the metal part can have better connection.

Do us a favor by having a signature that signifies the model year of the truck, etc. so we know what we are talking about without going to the 1st page.