plastic gas tank

[mutley]

does anyone know if there is a plastic fuel tank available for the c4 ?

 

[Hib Halverson]

No.
But the stock C4 tanks are lined with a rubber/plastic material.

 

[mutley]

Thanks Hib. so then the rust that is getting in my filter must be coming from the fuel pipes ? would that be correct ? and if so would i need to change them or is there a way around it. i havent actualy looked in the tank the rust in the tank is just an assumption i made. im way too busy at work fixing other cars to be fixing mine unfortunately just trying to gather info so as im led in the right direction of repair.

 

[John Robinson]

It only takes 10 min to get the fuel pump out. The Corvette is one of the easiest cars you will ever work on when it comes to the fuel pump removal. Take the fuel filler door off and pull the rubber shield off and then remove the 10mm bolts holding it in place. No dropping the tank just standing there looking into it. Suck the fuel out remove the fuel pick up screen and the filter under the door. Now put some gas in the tank and set the fuel pump back in the tank and use an air hose to pressure the tank. That should force the fuel and crud out of the open fuel line at the filter you took off under the door. When it flushes clean put the new fuel pump and filter in tank and put a new filter under the door. You might have to replace the inline filter again in a couple of weeks just to be on the safe side. If as you said the car sat for a long time before you bought it most of what is clogging your pick up filter is the sediment from the evaporated gas. As for a plastic tank I have no idea if one is available but I do think that the tank you have can be cleaned.

 

[boomdriver]

Thanks Hib. so then the rust that is getting in my filter must be coming from the fuel pipes ? would that be correct ? and if so would i need to change them or is there a way around it. i havent actualy looked in the tank the rust in the tank is just an assumption i made. im way too busy at work fixing other cars to be fixing mine unfortunately just trying to gather info so as im led in the right direction of repair.

you're going to have to actually look in the tank before making any assumptions....
the steel lines in the pump/sender assy can rust if neglected for long periods. They can be cleaned as well.

Takes 10 min to get the assy out and your face IN the tank.

Siphon the fuel out and use the suction to "vacuum" the tank bottom and any loose stuff floating around. Then reach in with a clean rag and wipe out the remaining specs of dirt. Not a big deal. Just work in a ventilated area, with fans. Not IN the garage. IF there is a lot of crud in the tank...plan on replacing the inline filter/ pump and strainer at the same time. If trash made it to the filter, it had to go thru the pump to get there. Impending failure, so be pro-active and fix it before it leaves you stranded. If you do any "spirited" driving now is the time to construct a "pump well" to keep the pump submerged in fuel at all times under all conditions. Works very well, and can be made with common materials found in the garage. If interested send me a PM and I will send you the details of the project. Solves many problems with C4 fuel starvation and pump wear from sucking air.

 

[mutley]

thanks boys foe your advice... I took the pump out today ... i think i found the problem. The earth lead that is connected to the pump is tacked on to the body of the pump but the body of the pump right by the earth lead is so badly rusted that the body of the pump has expanded and flaking away. It is only a small spot but it is right where the earth sits so when the exhaust gets hot , the rusted connection is causing the earth supply to tricle to the pump because rust is not a good conductor so its a bad earth so until my new pump arrives i will re-supply a better earth to the pump via a good point of the chassis from underneath and test it to see if it cures the problem. I had a word with an auto electrician and he said that would definately cause a problem wether or not it is the cause remains to be seen but its definately is a problem so we see how we go .

will let you know how we get on.... does what i found make sense to you guys too ? by the way there is no rust in the tank.

 

[John Robinson]

There is one thing for sure on a Corvette and that is the grounds are the lifeblood of the electrical system. The ecm reads the ground voltage to determine what fuel spark timing is needed to make it run. I am not electrically knowlegeable but I do no that an intermittent ground would cause the fuel pump to stop pumping. It makes sense to me that when the fuel gets hot the metal expands and the bad ground breaks contact causing a shut down of the pump. Looking forward to finding out what happens with the external ground from the pump.

 

[boomdriver]

thanks boys foe your advice... I took the pump out today ... i think i found the problem. The earth lead that is connected to the pump is tacked on to the body of the pump but the body of the pump right by the earth lead is so badly rusted that the body of the pump has expanded and flaking away. It is only a small spot but it is right where the earth sits so when the exhaust gets hot , the rusted connection is causing the earth supply to tricle to the pump because rust is not a good conductor so its a bad earth so until my new pump arrives i will re-supply a better earth to the pump via a good point of the chassis from underneath and test it to see if it cures the problem. I had a word with an auto electrician and he said that would definately cause a problem wether or not it is the cause remains to be seen but its definately is a problem so we see how we go .

will let you know how we get on.... does what i found make sense to you guys too ? by the way there is no rust in the tank.

you mean the top plate?

I would look closely at the FSM drawing to be damn certain that is a ground path that is to chassis. The car has more "control grounds" than it does simple earth-grounds. The wires often lead to other things or the ECM for control purposes. Just make sure of what it is and where it goes before "modifying" the harness.

I do not believe that to be the source of the problems...but go for it.
If it did not need to be repaired today, it would tomorrow...
When you disassemble the pump from the pump/sender assembly, clean the steel gently with as little scratching as possible on parts inside the tank. More scars mean more places for rust to grow inside the tank on the tubes. Be gentle with the float arm and sensor.

The outside is just appearance. I bead blast the outside of mine and paint it to protect against rusting.

Ground for the sender assy goes thru the tubes, the wire, bolts, thru most of the assy. Its gets a ground somewhere.

When you reassemble, use a NEW sender assy tank gasket and do not over-tighten the 11 bolts. clean the gasket mating surfaces and lay the new gasket in place. It will leak gas if you try to use the old rubber gasket. Careful with the fuel hoses on the sender nipples, they rip and there is only a short section of rubber...then its coupled to steel tubing. Once that rubber has been cut off from tearing, its gone. You have to do a more extensive repair to get more high pressure hose in place. Its NOT plain ol fuel hose....Its high pressure fuel injection hose.

 

[John Robinson]

I just remembered something from my motorcycle restoration days. There was a product that I used to reseal the inside of the tanks that were coated in rust. You might think about checking a bike shop for that and using it to re coat the fuel pump tube after you clean them up.

 

[mutley]

I hear what your saying boomdriver. its good advice rather than kill the car first check then check again , it could be costly.. the top plate is what im talking about and this particular wire is attached to the top plate and under the top plate is the rubber gasket to stop leaks but that gasket does not isolate the top plate because the bolts go through the top plate and bolt on to the tank and the tank must be connected to ground so that being the case im guessing the wire must be ground too. so then using your advice what i shall do then rather than add a new ground wire what ill do is ill clean all connections and make sure what ever it is designed to get ,ie ground or what ever, should then be working ok. like i said earlier it may not be the cause but is a problem i dicovered and though it may not cure the problem there is a chance it may so im going to proceed with caution and care.

 

[mutley]

you're going to have to actually look in the tank before making any assumptions....
the steel lines in the pump/sender assy can rust if neglected for long periods. They can be cleaned as well.

Takes 10 min to get the assy out and your face IN the tank.

Siphon the fuel out and use the suction to "vacuum" the tank bottom and any loose stuff floating around. Then reach in with a clean rag and wipe out the remaining specs of dirt. Not a big deal. Just work in a ventilated area, with fans. Not IN the garage. IF there is a lot of crud in the tank...plan on replacing the inline filter/ pump and strainer at the same time. If trash made it to the filter, it had to go thru the pump to get there. Impending failure, so be pro-active and fix it before it leaves you stranded. If you do any "spirited" driving now is the time to construct a "pump well" to keep the pump submerged in fuel at all times under all conditions. Works very well, and can be made with common materials found in the garage. If interested send me a PM and I will send you the details of the project. Solves many problems with C4 fuel starvation and pump wear from sucking air.

There is acually a white plastic well in the tank that the pump sits in so its always imersed in fuel.

 

[boomdriver]

There is acually a white plastic well in the tank that the pump sits in so its always imersed in fuel.

yeah....

about that little tray.

Chances are they it'll get broken off when you re-insert the pump with the screen down there. The pump sits right in or on that thing and as you position the top plate the pump beats against that tray and pops it off the tank floor. Its just glued on...and completely inadequate anyway. You'll discover this the first time that you exit a corner and apply gas when you are down to 1/4 tank of fuel.
This is where some of your problems may have originated...

Whenever this happens the pump sucks air for a few seconds. As the pump runs dry the rubber impeller starts to chew itself up fr om no lubrication (gasoline) and bits of the impeller plastic get pushed into the system to be captured by the fuel filter and mistaken for rust. Its often hard plastic or rubber bits. Pump wears out, cars starts performing poorly and the cause is not discovered until the pump fails completely and has to be replaced.

Thats why I designed a "well" thats 6-7" deep, completely DIY project thats a 30 min job, and allows you to keep the pump fully submerged in fuel no matter what the tank level is.
I'll find the basic instruction and post them. If you have some tie-straps or stainless steel safety wire, some other typical automotive maint items in the garage or house, you can build this is minutes, drop the whole mess in and forget it. It solves a lot of problems.
The pump is cooled and lubed by fuel, so whenever the tank gets low the pump gets hot and tries to run dry. That can cause them to stop or seize. Once they have worn to a point they may still pump fuel but its not the volume thats required and the pressures are going to be reduced. Poor engine performance. I think that most intank fuel pumps wear out from running dry or running in low tanks where they do not get enough cooling and lube.

 

[K & B Special Products]

The new sender assemblies sold by all the catalog folks are stainless & won't rust + they're ethanol compliant.. If the pump picks up any debris, then it's a short termer at best.

 

[mutley]

yeah....

about that little tray.

Chances are they it'll get broken off when you re-insert the pump with the screen down there. The pump sits right in or on that thing and as you position the top plate the pump beats against that tray and pops it off the tank floor. Its just glued on...and completely inadequate anyway. You'll discover this the first time that you exit a corner and apply gas when you are down to 1/4 tank of fuel.
This is where some of your problems may have originated...

Whenever this happens the pump sucks air for a few seconds. As the pump runs dry the rubber impeller starts to chew itself up fr om no lubrication (gasoline) and bits of the impeller plastic get pushed into the system to be captured by the fuel filter and mistaken for rust. Its often hard plastic or rubber bits. Pump wears out, cars starts performing poorly and the cause is not discovered until the pump fails completely and has to be replaced.

Thats why I designed a "well" thats 6-7" deep, completely DIY project thats a 30 min job, and allows you to keep the pump fully submerged in fuel no matter what the tank level is.
I'll find the basic instruction and post them. If you have some tie-straps or stainless steel safety wire, some other typical automotive maint items in the garage or house, you can build this is minutes, drop the whole mess in and forget it. It solves a lot of problems.
The pump is cooled and lubed by fuel, so whenever the tank gets low the pump gets hot and tries to run dry. That can cause them to stop or seize. Once they have worn to a point they may still pump fuel but its not the volume thats required and the pressures are going to be reduced. Poor engine performance. I think that most intank fuel pumps wear out from running dry or running in low tanks where they do not get enough cooling and lube.

Thanks boomdriver i would like the plans if possible.