This one is for 70-72 vintage El Caminos...

Can someone who has dropped their tank give me a rough idea of the dimensions of the evaporative emission control fuel/vapor separator tank that sits over the top of the tank?

I have a copy of the fuel system section of the assembly manual for '72 so I already have a pretty good idea of how the system is setup. But some dimensions would be a good confirmation that I am on the right track with what I am fabricating up.

Thanks.

I removed the tank from the 72 parts car. Is the separator attached to the underside of the body? If it is I can take some photos for you and post the dimensions. I do remember it had 2 vent pipes, one in each of the forward upper corners with hoses attached. There were a few colonys of black widow spiders living under the car so I didn't spend much time looking around after the tank was out.

That is the one I am talking about. Should have 4 hoses: one to each front corner of the tank, one to the front middle of the tank, and one to the hardline to the charcoal cannister up front.

Someone pointed me to a picture of one for sale in the classifieds. Looks like it really was not very big at all. If my estimates and math are correct this setup should be good for about 12-15* of tilt on a full tank before the vapor/vent line sees liquid.

It is interesting that the center tank vent uses a larger tubing size than the outside vents.

If I get home before dark I'll take some photos for you and post them.

Got home at dark-thirty today. I'll try again tomorrow.

Steve I have some photos to post, it will take me a minute or two to do it.

Here they are
http://i80.photobucket.com/albums/j199/64elcamino/72vaporseperator2.jpg

http://i80.photobucket.com/albums/j199/64elcamino/72vaporseperator1.jpg

http://i80.photobucket.com/albums/j199/64elcamino/72vaporseperator.jpg

Thanks for getting and posting those.

The first picture showing the mounting and hose routing through/under the front bed channel was very interesting. My '68 does not have that same type of center form so I am going to have to figure an alternative. The actual mount is very compatible with the '68 sheet metal though.

That separator tank is a lot smaller than I might have thought.

FWIW on later G-body El Caminos the fuel tank has a pyramid formed into the top of the tank to fit up into much the same space and likely for exactly the same purpose.

Thanks for getting and posting those.

The first picture showing the mounting and hose routing through/under the front bed channel was very interesting. My '68 does not have that same type of center form so I am going to have to figure an alternative. The actual mount is very compatible with the '68 sheet metal though.



This car is going to the crusher, if you want that piece for your 68 let me know.

Thanks for the offer but I have one of the vapor separator tanks on the way (and it has all the nipples on it) and swapping the sheet metal cross member is beyond what I want to take on to do this. My current thought is to drill/cut holes through the cross member and install the hoses with grommets.

Got the seperator tank... and noted something unexpected: it clunks when you shake it. I am guessing this is a float valve intended to shutoff the vent when the seperator tank fills with fuel? That would be very cool.

Also sounds like something useful to prevent fuel pouring out of tank vents in general as many have experienced on their Chevelles. I know the Chevelle allowed for a higher seperator tank height than the El Camino, I wonder if they also had a float-based shutoff?

Could this part malfunctioning be the cause of my El Camino puking gas all over the 1/4 panel everytime I fill it no matter how slow the fill rate is?

I would tend to attribute it to the design of the filler pipe. The size of the hole provided for the vent is rather small and I suspect insufficient to provide the vent air escape needed during filling. The real point of this separator tank is to combine the 3 vent tubes into one heading off to the charcoal cannister. The 3 tubes arise from the arrangement of the vents inside the tank where there is one at each front corner and one at the back middle thus forming a triangle. At any time one of these vent tubes should be above fuel level. My theory on the float is that if the vehicle angle exceeds the critical angle, to where the fuel level in the tank is above the separator tank level, the float will shut off the vent when the seperator tank fills with fuel.

I have not looked at the innards of the non-vented tank I pulled out of my '68 but the filler pipe had a second pipe inside with holes. I think the idea behind this is to provide an air vent path while filling.

The '70+ reproduction tank I bought has nothing in the filler pipe at all. If yours is similiar it could be that air venting back up the filler pipe exagerates the splash when full affect. I have not had a chance to study modern filler design too much at the local Pick-n-Pull but intend to at some point, if for no other reason than to find a way to improve upon the "El Camino lean" at the gas station. One area I am going to focus on is the back venting on the filler. I think many fillers have a large (like 1/2") secondary vent hose running back up to the filler pipe above where gas is filling in. It may also be the case that by arranging the dump of the main filler versus this vent that a softer full indication can be provided.

Steve thanks for the explanation. Currently I am trying to find a gas tank from a 92-96 Caprice or Roadmaster wagon. I beleive it will fit in the frame of the El Camino and may solve both problems I am having, the fuel fill issue and the need for an intank pump to feed the TPI injectors. I was able to get measurements from a Caprice sedan tank and it is very close to being a drop in. The wagon set up gives me the side fuel fill the El Camino.

I am putting an in-tank fuel pump module into mine for multi-port EFI. I may be biased :D but I think I have come up with a pretty darn good solution.

I am all ears (and eyes if you can post a picture). Right now the system I have is two external pumps, one to pull fuel to the tank and the other to build pressure for the system. It does work well, but when the tank gets low it tends to suck air when cornering or accelerating.

I am on my third generation of fuel system design before moving any bolts. The external surge tank with two fuel pumps was my first generation concept. I went so far as to aquire all the pumps/parts before I changed course to simplify with fewer components and less mounting hassles.

I have taken some pictures and will put together a page with the pictures and writeup at some point.

The basic magic is an AC Delco fuel pump module MU2021 for a 1999 Ford F250/350/450 pickup. These trucks had a plastic tank so the sender mounts to the top of the tank using screws rather than a special twist lock. Inside the tank is an internal surge tank/cup and the fuel pump. These are common to many late EFI setups and the difference between GMs approach and Fords is how the surge cup mounts. GM likes to use spring loaded rods and thus is specific to the height of the fuel tank. Ford builds a locator cage into the bottom of the tank so the cup can be move around a bit and the flex lines can accomodate different tank heights. Part of the magic in this module is they use high pressure fuel to pump more fuel into the surge cup much like a paint sprayer or sandblaster work. So they get the function of two fuel pumps out of one pump. Of course the return also goes back into the surge cup.

I took a brand new tank and cut a 4.5" hole around the fuel sender and then drilled 6 holes for mounting bolts. These holes work out to be in the recess bevel around the sender so the bolt mount is a bit tricky. I used 1/4-20 bolts and silver soldered them in as mounting studs. I plan to cut a 1/4" thick piece of nylon plastic to serve as a mounting shim and use fuel resistant silicone to glue it to the tank top. The sender lid will seal against the top of this plastic using it's normal rubber seal.

I made up a mounting cage using thin galvanized sheet from the hardware store and silver soldered it to the bottom of the tank in the flattened area in the middle. I offset this cage to the DS to improve clearances a bit and provide room for the longer in-tank hoses to bend around without kinking. This soldering was probably the hardest part of the process because you apply heat from the outside while working the solder through the hole and inside. So you cannot see exactly where you are heating/soldering at the same time. It helped a lot when I drew a half-circle on the bottom of the tank where the cage was inside.

I also shortened the fuel gauge float rod by about 2" to give an effective radius of 5". This is needed so that the float moves through almost 90* within the 7" fuel tank height from empty to full. I will add a 5k ohm resister in parallel with the fuel sender to correct the 150 ohm Ford sender to interface with the 90 ohm Chevy gauge.

Ford runs this type of surge cup fuel pump module without any baffling in wide flat modern tanks.

Interesting approach and sounds workable. Is the Ford module very expensive? Some of the new GM units run over $300 when the pump goes out because the pump is not servicable by itself.

since my seperator did not survive the tank removal I am going to open it up to see what is actually in it. I will post a photo for you.

Well... not cheap. I picked mine up on Ebay for $50 :D

I do think the fuel pump is serviceable in these and upgradeable to higher flow versions. The pump itself is basically a Walbro. I have had it out and compared with the 255 lph Walbro I was going to use. Slight differences in bottom but overall same size and configuration.

PS Rockauto.com lists the MU2021 for about $250.

Could this part malfunctioning be the cause of my El Camino puking gas all over the 1/4 panel everytime I fill it no matter how slow the fill rate is?
To come back to this thought...

It occurred to me that this is probably the only/last time that I will be able to use open flame around my fuel tank without a lot of extra precautions or maybe at all. So I decided to fix another problem that any owner of at least a 3rd gen El Camino is familiar with: the gas station fill up lean. You know the pose: you go to fill up but the new small unleaded pump nozzles will not stay in that big old regular gas fill pipe so you have to stand there and hold it in for the whole time.

I went to the wrecking yard and pulled a gas filler out of a '90 Chevy pickup (hey at least I used Chevy parts for a change, I often come home with Ford parts). This is a 2" pipe with a rubber connection hose and side 1/2" vent line. I whacked off a few inches from the end of the 2" regular gas filler pipe. Took an exhaust pipe expander to the tank filler so the 2" unleaded filler would fit inside the 2" tank filler pipe. Got about a 3/4" overlap and soldered the unleaded filler neck into the tank filler pipe.

Part of the late model setup was a 12" hard line for the vent with rubber connections on both ends. I picked that up along with the special bent rubber hose. I still need to solder that hardline into the tank and connect it all up.

So now the darn unleaded pump nozzles should latch into my filler pipe and I should have sufficient venting to handle whatever. It will be interesting to see if it eliminates the fuel gush when the tank is full.

Note that this works because I am updating the venting system to the '71 and later setup, otherwise the late model sealed cap could cause problems.

This car is going to the crusher, if you want that piece for your 68 let me know.Do you still have it?

Keith yes I do. I am sure it is not usable in its present condition, but your welcome to it. PM your address and I'll send it to you. It may be about a week though before I can get to it.