When I first bought the car this only happened when I had one gallon left, but now, almost a year later, it does it with a quarter tank. When I turn corners, it feels like i lose fuel pressure the car rpms dramatically drop and it stumbles until i am straight for about 2 seconds. Its not a huge deal but it is annoying and worries me slightly.

 

Perfectly normal.

2 fixes

1. Spend a ton of money rigging a baffled fuel tank.
2. Just fill up the gas tank and drive.

 

NOT "perfectly normal"

1. not the answer
2. still not the answer...

 

Normal. Put in a fuel cell with a sump

 

In that it is a commonly reported issue, it's normal. Fill up when you hit 1/4 tank isn't an unreasonable (and inexpensive) fix. Try it and see if it gets worse.

 

Good Post....

FYI, and this applies to ANY car running around with less than a 1/4 tank of fuel is a really good way to:

1. Burn up a fuel pump
2. Suck up any accumulated junk in the bottom of the tank.

Fuel pumps last a LOT longer when kept cool, this is done by surrounding them with fuel, keep it above 1/4 tank.

 

I've had my car since 1985 and I've only experienced the fuel starvation problem one time when I was going around a cloverleaf on a freeway transition. Based on that experience, I don't think it's "perfectly normal". I usually run my tank down pretty low, definitely less than 1/4 tank.

I don't understand the "accumulated junk in the bottom of the tank". The accumulated junk is going to be there whether the tank is empty or full. My own experience was when I took out the fuel pump about 10 years ago for the first time. The inside of the tank was spotless and I didn't see ANY "accumulated junk". The gas stations around here have inline fuel filters on all the pumps, so I don't see where this "junk" is going to come from. I've heard of people with rust in their tanks, but mine had none at all.

 

You guys can argue about it being "normal" or "not normal" all day if you want. The thing is its a well documented problem with our cars and like mentioned above only has a few fixes. Replace the tank or fill the tank..WW

 

What he said.

 

Like others have stated, the problem is common yet the fix CAN be costly for the avg street car.

Here is a way to fix this forever and save your fuel pump and add years to it as well.

This is the instruction on "HOW to build a fuel pump WELL"
A gas -sump in other words... cheap, easy and extremely effective.



From a PM that was sent to another member with the same problem. I have posted this several times and think its worthy of a 'sticky' for future reference.

**************************************** **************

No, but it was quite easy once the concept was thought out...

I realized that the return line was pouring fuel in the tank constantly and at the same time the pump was starving when going around corners and even under hard accelleration. When you loose the fuel pressure you also loose the return...so one problem created the other and so did solving one problem fix the other.
The factory windage "tray" (now used to hold pocket change on my dresser) broke away from the tank bottom as do most...I was having a horrible windage problem. I couldn't corner under power at all if the tank was below 1/2.

Not satisfied that the little 1" deep tray was much use AND a PITA to replace back in the tank, I wanted to stick something back in there that would hold enough fuel for at least several seconds running...enough for a long sweeping curve at high speed without slinging the fuel off the pump. 4 seconds is forever at 100+ mph in a decreasing radius turn...hitting the gas coming out of a turn like that and getting nothing....just sucks for lack of a better term.
I picked the LUCAS qt bottle (oil treatment) because it was the right diameter, round, deep (need 5-7"), and petroleum resistant. A common qt oil bottle also works well. (rectangular) Must be able to fit thru the tank opening in the tank top.

I cut the top off so the "well" portion was tall and equal. I cut a slot in a bottom rt edge for the pump strainer to fit thru since that is 3-4" long and will need to sit left-right in the tank. Then I marked approx where the bottle would rest against the return tube assy and stay clear of the float arm. I cut slits at 2 levels and used stainless steel safety wire to tie the side of the bottle onto the return tube and frame. Do not try to go around the whole bottle....just cut it so you're securing the left side to the tube .
This has to hold the bottle over against the tube so the float can never hook an edge or hang in its travel in any way. You might have to cut a slice off the top left edge of the well for float arm clearence if it swings too close. Once started, you'll see exactly what I'm trying to describe...

Then I took a small drill bit, 1/8 maybe, and drilled a couple holes in what would be the rear of the bottle at the bottom so fuel could flow in/out and seek its own level. Insert the whole pump/strainer/float mess in the bottle, making sure the strainer end fits thru the slot cut in the bottle bottom so the end of the strainer is sitting outside the bottle. Secure with the stainless wire thru the bottle and around the return line tube. Orient the bottle to clear the float. Get it tied tight so it does not float around or be moved by sloshing fuel.

I made NO holes in the left or right sides since the lateral forces of cornering might help drain it faster and that defeated the purpose of the design. The holes in the bottom rear allow for the level to equalize slowly. I did not want rapid equalizing anyway,....I would prefer that the 'well' always be deeper than the tank as long as the engine is running. This also serves to keep the bigger trash from getting to the whole strainer...since the strainers end (outside the well) can pull fuel in as well as the portion thats inside the well with the pump. Look at this and try to visualize the way it will be when mounted because the bottle with the strainer sticking out the right edge will be resting on the tank bottom, so you do not want to cause the strainer to be crushed or pinched off when its all bolted down. If done properly the 'well' will be right on the tank bottom and need just a little pressure to get the tank cover plate bolted down...

Oh yeah, the round LUCAS bottle is easier to get back in the tank than the rectangular qt oil bottle...thats why I went with the round well this time....

Drop the whole thing in the tank after double checking the float arm for clearence and secure the pump assembly plate with a new gasket.

I have run hard into a corner with the reserve lite ON and not had the engine stumble from fuel starvation...I installed a new sender assy a few months back, and have not run out of fuel yet, but I have pushed it to where it was reading down to 15 miles left and I put over 19 back in the tank...so I am CERTAIN that I am keeping a deeper fuel level in the "well" than the rest of the tank and that is uneffected by G-forces so far. This well design is part of the fuel pump assy instead of having to attach to the tank bottom where access is difficult and damage cannot be repaired easily.

I am not sure why I'm talking about this....I should be looking for the $5000 to file a patent....

Bottom line, it works.

If you want to build one and have any questions that this does not answer, ask me. Glad to help.

 

Sure, a lot of older C4s seem to suffer the same issues as they age, however, 55k 1984 C4s came off the line and "NONE" of them exhibited these "perfectly normal" symptoms at that time......

So, something occurred from the time it rolled off the line until now......

My suggestion is that one may address the issue "or" they can reinvent the wheel....

I find it fascinating to read that the only cure is the completely redesign the fuel tank and sump pump.....

 

My 87 doesn't starve for fuel on curves or turns even with only an 1/8th of a tank.

 

floggin' 'nother dead horse?

 

Thanks alot leesvet

 

Thats because your factory windage tray thats glued to the tank bottom is still glued to the tank bottom...

After pulling the pump/sender assy and bumping the tray a few times it breaks off the bottom and floats around....being rendered useless as far as an aid in fuel starvation. They work quite well when new...but as soon as the tray breaks away...its over. I've seen this on literally dozens of C4s.

 

YW.

Gather the needed stuff, including a NEW tank gasket, and a few spare 10mm bolts, a bottle of the proper dimension, also get some fuel injection hose and a double barbed fitting the same size to repair any fuel line damage on top of the sender assy, new hose clamops, safety wire and go for it. Should take about 2 hrs WITH problems.

The fuel lines on the sender nipples will be hell to get off. Cut them off using the minimal amount of waste hose. Pull the slack to re-install the remaining hose on the nipple when done. IF you should cut too much, thats where you install the double barb fitting and add as much fuel line as needed. Just be certain its fuel inj hose.
If done properly you can corner with a tablespoon of fuel and not loose power.

Have fun !

 

Exactly.

Throttle body injection with 2 injectors at 14 psi compared to TPI and 8 injectors at 45 psi and 10 times the GPM.

 

What happens in YOUR car is just that YOUR car.

You obviously have not pulled many fuel pumps, I've seen lots of BS sitting on the bottom of fuel tanks. Then again I've pulled my fair share of fuel pumps.

 

When I was running the stock tank, my car would suck air during a launch if the tank was not over 1/2 full (1984).

 

My 89 had the same problem. I took out the fuel pump and found the baffle tray floating in the tank. I drained the tank, let it dry for a couple days the glued the tray back in place. I also replaced the pump since I had it out. I put a new filter on the pickup also.

YES, I said glued the tray back in place. My partner on this car found a company that sells a two part epoxy that mixes as you pump it out. We did this in 2011 and the tray has stayed in place through several track days during One Lap of America events. JD