Cab tank fuel filter

[motzingg]

Last night the ol' girl let me down again... our second excursion out on the road and i forgot the supplemental 'underhood' gas can that i was using for when the fuel supply cut out... ended up taking a longish walk.

So the fuel pump seems to be working o.k. Not the best suction perhaps, but with a steady flow or hooked up to a gas can under the hood she runs great, but the flow coming out of the tank is weak.

I started the truck up and she idled like a champ for about a half hour, but out on the road she cut out on me with no fuel in the line from the pump to the carb.

So the question is this: Is there an in-tank fuel filter that is full of varnish gunk, or is my line plugged? If so, how do you get at the thing? Is there any good way of getting the tank cleaned out without having to remove it?

I know that diesel trucks have their tanks flushed sometimes, northern tool sells a rig to do it in their catalog. Do you think this is something i could get a diesel shop to do for me?

I was about empty when i bought the truck and i put in 5 or so gallons with some fuel system cleaner. The fuel is coming out of the pump looking like root beer.

Also, is there a fuel filter underneath the aluminum screw on can-looking thing on the fuel pump? I've tried everything to get it off without smashing it and no dice. I might have to make a 3-point spanner wrench if it needs to come off.

[amycyclenut]

If your fuel pump looks similar to this:


Then the bottom canister unscrews and accepts a filter. This could very well be your problem. I had a similar situation, my truck had sit so long that the tank had rusted and the fuel filter was filled to the brim with this rust.... experienced the same issues as you. Changed the filter (and the in-cab fuel tank in my case) and good as new.

[motzingg]

hmm, well, its similar, this is on a 240 six so the canister sticks up and has a weird 3 point spanner wrench pattern on it.

the fuel line coming in from the cab barely has a trickle and when i blow hard into the gas cap, it pisses a little more but not as much flow as i think should be there.

i guess i'll have to make that spanner wrench and get it off, or maybe try to rig up some kind of strap wrench. I don't think that filter is the main problem but it could be adding up.

Did you notice when you were working with your tank if there is an in-tank filter?

[68 Ford Stepside]

Some of them have a sock type strainer attached to the suction pipe in the tank. When you pull out the fuel level sending unit, the strainer will come out with it if it has one.

[68RGR]

The only filters I am aware of are the canister type on the fuel pump and the inline filters near the carb. Tanks aren't cheap but they are available. There's nothing worse than a corroded fuel tank. Not much way of getting around one either. You can have them cleaned/repaired, replace them with a new tank or even relocate the tank using one of a different design.

I had a canister filter spring a leak once from corrosion My guess is you are going to find a load of gunk in that canister when you take it off.

[1967 f-bomb]

with the gas cap off take a blow gun and blow the line out backwards from normal flow

[mrtleavitt]

I went through similar problems when I rebuilt my truck. It would act fine sometimes and then randomly leave me stranded. There was no rhyme or reason on when or where it was going to cut out. So I bypassed the mechanical pump with electric pump and it still did it. So I bit the bullet and took out the tank, drained the gas, put a chain in it and sloshed it around to break all the gunk up- rinse and repeat a few times. (or buy a new tank). Then I replaced all the rubber lines and clamps. But my main problem was the metal hard line from my tank to the engine bay. With the tank off and the line disconnected from the fuel pump, I ran compressed air through the metal line and I just watched the sludge come out! After putting everything back in I've never had another problem-going on 6 years now.

[motzingg]

yeah i'm thinking its something in the line. I made a homemade strap wrench out of a ratchet strap and got the canister on the fuel pump off. Not only was it mostly dry ( i assume that thing is supposed to be full of fuel) it was corroded on the insde and had a fair bit of rust and crap in it.

The other possibility (because fuel will come out the line when i blow in the filler cap) is that the check valves in the fuel pump are corroded or full of rust and gunk. I'll probably try to get that off sometime later this week, i've got a full plate today trying to sort out my other projects.

If the fuel pump is shot i might just go to the SBC carter recommended in the tech articles.

I know where a pretty clean junkyard tank is, but i'm really thinking it might just be easier to fab a fuel cell for the area under the front of the bed where it is wide open. Looks like it would be about $100 worth of aluminum or $40 worth of steel....

Damn i was hoping this would be a 'just replace the mesh strainer in the tank' kinda easy fix... oh well.

[max_alberta]

Also if it is the fuel pump don't be afraid of replacing the original fuel pump with another mechanical one... on the 300 it's easy to get to, and replacing it isn't really a hard job, just make sure to scrape the old gasket off completely. On my 390, the fuel pump got weak, leading to stalling under heavy acceleration, but perfectly fine performance at idle and for low speed driving. A new pump fixed things right up, and I didn't need to mess around with wiring in an electric one, and worrying about giving the carburetor too much pressure.

[motzingg]

had a minute or two to work on it last night, blew out the lines, checked in the tank... couldn't see much but there didn't appear to be a strainer in there. Blew out all the lines and fuel seemed to be flowing well.

took the filter housing off the top of the fuel pump and gave it a crank (i know dangerous as hell.. i had a fire extinguisher nearby) and there was a pretty good geyser just from a little crank.

buttoned it all up and let it run for awhile, all's good, took it around the block and it died again- same thing, no fuel at the carb inlet.

now i'm thinking the fuel pump is shot after all, probably gunk in the check valves. Its obviously a crimped-together unit but i might try cutting it apart just to see what i can see. The aftermarket carter retrofit that they talk about on classic inlines looks like the ticket, but the 'super strip' pump is out of my price range. They have a SBC 'muscle car' pump on summit for 20 bucks so i think i'll try that out if i cant figure out how to get in and fix the ford hardware.

[motzingg]

ok, got the pump off and tried messing with it a bit last night... more questions than answers really.

First of all, the 'foot' is shaped differently than the one in the classic inlines writeup:
this is mine: from the summit website

this is the picture from classic inlines with the 'small six' stock fuel pump and carter


there is a little 'shoe' on the lever, not sure if that matters or not... otherwise everything looks the same. anyone try doing this mod with the fuel pump shown or another one? probably a long shot but i thought i'd ask. Summit lists like 20 different styles of pumps for the '300' six cylinder, some of them say they go on everything from the 223 (i think that's the 50's style 6 right?) to the 4.9, some list only for the 4.9, some list for the small 6's and the 300 but no 240?... probably doesn't matter, right?

The next question is about the mechanical fuel pump itself. I've never had to mess with one in the past, but i'm noticing that when i put my finger over the inlet nipple and pump the lever, it doesn't suck very hard on my finger, if at all. Should it be developing a strong suction force or is that limited by the integral fuel pressure regulator? I guess i dont really understand how these work, apparently the pumping diaphragm is limited, probably by a spring, at how much pressure it can deliver to the outlet so the pump automatically stops pumping when a certain pressure builds?

Either way, i guess its not a huge expense to buy the carter and try it, but I hate throwing parts at a problem until I'm 90% sure thats what it is. I don't want to cut my old one up until i know its shot, but i don't know its shot until i cut it up... catch 22.

[max_alberta]

Has the engine received other performance modifications which require a larger fuel pump? Why not just go to NAPA (or your preferred parts supplier), tell them the year, model, and engine, and use what they have on the shelf? The stock pump is completely adequate for a stock engine, and that way you don't need to mess around with modifications etc. Should be on the shelf in any reasonably major city too, and if it goes bad you've got a store to bring it back to.

[motzingg]

well, i'm planning on a turbo build with it once i sort out all the basics, so i need something i can boost reference and get up to 7 or 8 psi. Plus if i can get something that is better and cheaper, why not?

whenever i run into problems like this that frustrate me and leave me stranded, i like to fix them with a 10lb sledgehammer worth of overkill so i don't have to deal with it again.

I'm looking at the summit brand 'street strip' knockoff one now, it has screws holding it together which would be nice if i need to modify it.


this is the link fron classic inlines with the pump mod: http://www.classicinlines.com/FuelPump.asp

[motzingg]

Took the plunge and bought the cheap carter 'muscle car' pump for SBC. I'll post an update when i get it and perform the conversion.
http://www.summitracing.com/parts/crt-m6624

Couldn't sleep last night with a million crazy thoughts, came up with an idea to cut apart the old pump and make a band clamp out of the crimped on clamp ring. Cut the ring in two places and weld nuts on either side so i can put a bolt through them and pull it together... It would let me open it up and see how it ticks, maybe possible to fix it or add a stiffer spring. Something to try either way. I'll probably give it a shot tonight while i wait on the new pump to come.

I cant help coming back to the idea of somehow flushing the tank without having to remove it and dump out five + gallons of nasty gas. That sounds like the kind of job that would end up involving my wife and me or both of us covered in awful varnish smell... leading to certain repercussions...

Maybe when the new pump comes i can run it backwards using a long fuel line sucking from the gas filler hole, back through the engine pump (while the engine runs off gravity feed from a gas can) and pushing the accumulated gunk back into the tank through the stock fuel line. Sounds like a great way to smoke a brand new fuel pump... i'd rather avoid using some kind of sketchy harbor freight drill pump or something like that.

[motzingg]

So by now this has become the most boring thread on the planet, one guy talking to himself about stupid fuel issues that aren't even interesting... bah!

Just in case someone ends up referencing this later, I found the main source of my problem: There is a little short section of fuel line under the cab of my truck where the hard line coming out of the tank joins the hard line going into the engine bay. 10 years ago it had a nice little loop in it but thanks to ethanol gas now it has a hard kink in it.

When the engine runs at low RPM the kink flows just fine, but when it runs hard the kink gets sucked down on itself and cuts off fuel flow!

Talk about a crazy problem... Probably should just go ahead and get started replacing all the hoses and lines from here on out.


I also cut apart my old fuel pump. The check valves in it are rubber diaphragm type and they were in really bad shape. Not regretting tearing it apart. Tha' Carter should be here today or tomorrow from summit, I'll post that up when i get the levers swapped.