'74 1.8 - fuel tank interior plumbing / layout

[h16]

Vaporlock has struck me too many times - I am in midst of my own version of pump relocation to the front (will leave those details out for this post).

I bought this car many years ago - it's been modified in many ways by someone else. The center fuel lines have been replaced with some sort of metal line - also not directly relevant to this post.

Fuel tank was just pulled, and I'm in midst of trying to identify Supply and Return tank fittings. It's my current understanding that the fitting at the rear of the tank (closer to the passenger compartment) is the Supply line, and the forward line (closer to the front bumper) is the Return line. In my vehicle the rearward line is coupled to an older-style fabric-covered hose (possible original equipment). The rearward line is a rubber fuel line. The hose clamps at both ends appear to be aftermarket and non-original. The rearward hose looks to be larger diameter than the rubber line - also possible supporting evidence that rearward is the Supply line.

Now comes the question for this post - what is the layout inside of the tank - does this look right?



It looks like a cylinder exists to maybe help mitigate sloshing and fuel starvation? Is the line inside the cylinder the supply line? Does this even look right?




Sorry if this has been covered elsewhere - I did try to search several ways. Point me to other articles if covered elsewhere.

Here is shot of fittings/lines exiting tank




thanks for the help

[Dave at Pelican Parts]

Looks right. The cylinder is indeed there to help prevent sloshing, there should be holes in it somewhere to let fuel into and out of it. The tall thing on the one fitting is a metal screen "sock" filter that is supposed to keep the larger chunks of any debris out of the pickup. And it should start out up above the tank floor by a little bit.

So I think you've got it all figured out correctly.

BTW, the factory lines are metal at the front, and then go to plastic inside the center tunnel.

Do yourself a favor and replace all the rubber and rubber/cloth hoses. Fuel leaks are just plain bad news.

--DD

[Tobra]

The inside of that tank looks pretty darn good.

Replace ALL the rubber hoses with the appropriate high pressure hose for fuel injection. If you leave the ones under the tank a little long, it makes it easier to take out the tank in the future. You can use this thread to get an idea of how old the hoses are down the road.

Don't forget to replace the ones that go to the expansion tank, they are smaller and low pressure, but will give you fuel smell. Gasket and fuel filler cap are the same as like a '69 standard beetle if I remember right, probably ought to replace that gasket too.

The FI on the 1.8 is sensitive to air leaks, new o rings on the injectors is not a bad idea, and you can flow test them while you have them out, or at least make sure they are flowing equal amounts.

I trust you have a fire extinguisher handy while you are doing all this stuff.

[h16]

thanks for the info -

lines inside tunnel appear to be all metal now - based on visual inspection and magnetism test.

I just determined that supply and return lines had been crossed, so fuel pump was drawing from the return port. That likely explains why car lurched/cut out during hard cornering, etc, particularly with low fuel level in tank. Hopefully the strainer in the tank is not full of junk - will maybe try and flush or swap downstream filter soon after it's back in working order.

In in midst of plumbing in the aftermarket fuel pump up front, will update later.

My thinking has been to leave the old fuel pump in place, and just let fuel pass through as it's pushed from the new pump in the nose. I may rethink that - am open to suggestions/comments on that notion.

[Dave at Pelican Parts]

The old pump will be a pretty effective plug in the supply line. Just remove it, and plumb around where it used to be.

--DD

[h16]

question about fuel pressure readings - I've relocated fuel pump up into nose, it's an aftermarket high-pressure pump from summit racing - old pump and plumbing removed - now it's just one supply line and a single return passing from front to back of car. I also put a fuel pressure gauge on the passenger-side fuel rail - using the connection that is capped with a bolt which sticks upward, between the two injectors on the rail. I did not yet touch the pressure regulator, left it adjusted as it was prior to relocation of pump. When pump is running but engine is not, gauge reads ~39 lbs. When engine is running, gauge reads ~34 lbs. Does this sound about right for a 74 1.8 (L Jetronic?)?

thanks