Replacing the Fuel lines
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Fuel problems are potentially extremely dangerous as the consequences can mean loss of your car or even worse loss of life so if in any doubt entrust work on fuel systems to a competent person.
Fuel problems are potentially extremely dangerous as the consequences can mean loss of your car or even worse loss of life so if in any doubt entrust work on fuel systems to a competent person.
Several owners have lost cars due to fuel fires and I have had several leaks from the original Griffith fuel system so after the last incident I decided to look at the system in more detail and attempt some improvements. Early cars vented the fuel tank to the air through the filler cap, later cars with Catalytic converters have a sealed fuel system to prevent petrol fumes reaching the atmosphere
Description: Fuel is fed initially through a simple plastic filter within the tank base, this prevents any muck in the tank reaching the fuel pump. The tank outlet is via a short rubber hose that feeds a semi circular brass tube to clear the rear suspension (both inside diameter 12.0mm). The brass tube connects to the fuel pump inlet (diameter 12mm) with another short hose. The 8mm outlet from the fuel pump then feeds the full flow fuel filter eventually reaching the injector rail at the engine. A pressure regulator on the injector rail ensures that fuel is kept at a constant pressure, around 35 psi at idle. Any surplus fuel is returned via the regulator at a low pressure (3-4 psi) to the fuel tank at the rear. Later cars have a sealed filler cap and a breather hose running from just below the cap via a roll over valve all the way to the offside inner wing where it vents petrol fumes into a plastic canister containing carbon. The carbon traps the petrol fumes when the car is at rest. Another hose connects the canister to the plenum chamber via a purge valve. When the engine is up to speed the purge valve opens and the depression in the plenum sucks in the accumulated petrol fumes to be burnt. A third hose on the canister is open to the air to flush out the fumes. The roll over valve in the boot cuts off the vent to prevent fuel loss in an accident. All fuel lines except the tank to fuel pump are 8mm inside diameter tubing, a mixture of rubber hose and copper tube. On the surplus fuel return run there are no less than six connections, all potential sources of leaks. The high pressure side has eight connections. Another complication is that two connections are very inaccessible, one behind the engine on the bulkhead the other by the side of the gearbox on a chassis rail. It is these two inaccessible junctions where most owners experience fuel leaks. As the volume of fuel leaving the tank far exceeds the surplus returning, the tank would soon implode unless a vent was in place. The feed to the carbon cannister also provides this vent indicated by arrows in the diagram, i.e, fumes out or vent air in to the tank.
The complete fuel feed and return lines are illustrated below, the original TVR rubber hoses to the engine had previously been replaced with short lengths of SS braided hose:
Pictures may be enlarged by clicking
Description: Fuel is fed initially through a simple plastic filter within the tank base, this prevents any muck in the tank reaching the fuel pump. The tank outlet is via a short rubber hose that feeds a semi circular brass tube to clear the rear suspension (both inside diameter 12.0mm). The brass tube connects to the fuel pump inlet (diameter 12mm) with another short hose. The 8mm outlet from the fuel pump then feeds the full flow fuel filter eventually reaching the injector rail at the engine. A pressure regulator on the injector rail ensures that fuel is kept at a constant pressure, around 35 psi at idle. Any surplus fuel is returned via the regulator at a low pressure (3-4 psi) to the fuel tank at the rear. Later cars have a sealed filler cap and a breather hose running from just below the cap via a roll over valve all the way to the offside inner wing where it vents petrol fumes into a plastic canister containing carbon. The carbon traps the petrol fumes when the car is at rest. Another hose connects the canister to the plenum chamber via a purge valve. When the engine is up to speed the purge valve opens and the depression in the plenum sucks in the accumulated petrol fumes to be burnt. A third hose on the canister is open to the air to flush out the fumes. The roll over valve in the boot cuts off the vent to prevent fuel loss in an accident. All fuel lines except the tank to fuel pump are 8mm inside diameter tubing, a mixture of rubber hose and copper tube. On the surplus fuel return run there are no less than six connections, all potential sources of leaks. The high pressure side has eight connections. Another complication is that two connections are very inaccessible, one behind the engine on the bulkhead the other by the side of the gearbox on a chassis rail. It is these two inaccessible junctions where most owners experience fuel leaks. As the volume of fuel leaving the tank far exceeds the surplus returning, the tank would soon implode unless a vent was in place. The feed to the carbon cannister also provides this vent indicated by arrows in the diagram, i.e, fumes out or vent air in to the tank.
The complete fuel feed and return lines are illustrated below, the original TVR rubber hoses to the engine had previously been replaced with short lengths of SS braided hose:
Pictures may be enlarged by clicking
The surplus fuel return line from the regulator initially connects to a short 8mm rubber hose and then to a short 8mm steel pipe to get around the rear of the plenum then to rubber hose that connects to a copper pipe under the car by the gearbox side finishing with rubber hose to the tank. This 8mm steel pipe appears completely redundant, perhaps a legacy from the original Range Rover engine layout. Anyway it serves no useful purpose so can be omitted. The original return line of six connections can be replaced with a single SS braided hose, i.e. just two connections, one on the pressure regulator and the other directly on the tank. I used Cohline** stainless braided fuel hose of 7.5mm inside diameter suitable for ethanol petrol. For the short 12mm id hose I used Car Builders Solutions, Ethanol proof 12mm id hose, Reference FUHO12ET.
As my leaks had always occurred at joints between copper and rubber I suspect that the copper/rubber/ethanol combination could possibly react adversely in some way to cause the problem, especially when laid up over the winter, bearing this in mind I thought it prudent to get rid of the copper pipes in the main fuel lines.
The high pressure fuel supply can be simplified by running another SS braided hose from the filter outlet to the injector rail. this does away with the original copper pipe and thus two connections. ** Cohline are OEM suppliers of fuel hose to Mercedes
Close up views of the Brass tube to clear the rear suspension bottom wishbone, the redundant steel tube around the plenum and the in tank filter:
As my leaks had always occurred at joints between copper and rubber I suspect that the copper/rubber/ethanol combination could possibly react adversely in some way to cause the problem, especially when laid up over the winter, bearing this in mind I thought it prudent to get rid of the copper pipes in the main fuel lines.
The high pressure fuel supply can be simplified by running another SS braided hose from the filter outlet to the injector rail. this does away with the original copper pipe and thus two connections. ** Cohline are OEM suppliers of fuel hose to Mercedes
Close up views of the Brass tube to clear the rear suspension bottom wishbone, the redundant steel tube around the plenum and the in tank filter:
The fuel tank removed and showing the outlet connection, blanked off here to test for leaks after refitting the filter.
Breather hose changes to copper The main fuel feed and copper breather running together The breather changes back to rubber
The tank needs to be drained before removal. It is secured by four bolts two to the bulkhead and two to the floor but the various hoses must be disconnected before it can be removed from the boot. The breather connects to the filler neck via the plastic roll over valve but be careful as it is easily damaged. The returned fuel line connects to an inlet on the off side of the tank (seen above). The filler cap assembly is just silicon sealed to the body. The fuel sender cable has to be unplugged from the tank top. Access under the car is needed to disconnect the short main fuel supply hose, mine was sealed to the body with a substantial amount of silicon sealer that has to be removed. I removed the internal tank filter attached to the outlet and was surprised to see hardly any contamination, after 19 years and 55,000 miles I expected it to be clogged with debris.. Be careful also removing the outlet as I managed to break the fibre sealing washer, its a strange size. HHC my local TVR dealer kindly supplied another.
The new SS braided hose return fuel feed from the pressure regulator to the tank follows the original path without any problems there being adequate room to run the wider 13mm outside diameter hose. Running the SS braided high pressure (HP) feed from the external fuel filter to the injector rail however was not so simple. This hose and the rubber breather from the tank to the carbon cannister both run along the near side chassis rail. Originally the HP feed changed from rubber to 8mm copper tube to allow both pipes to pass through the narrow space between the chassis and the body, but with the new 13mm SS hose and the original rubber breather hose there is not enough room. To solve this I replaced the original rubber breather hose in this area with 8mm copper tube salvaged from the original installation and rejoined it back to rubber above the front suspension. A tight squeeze but OK. The original breather hose had an in line joint above the rear suspension but as a considerable length of rubber breather hose has now been removed this connector and the rubber hose back to the tank can now be discarded and the longer length of breather connected straight to the tank filler neck. The new breather thus starts as rubber from the filler neck, joins to copper just forward of the nearside rear suspension and joins back to rubber above the front suspension as seen in the pics above . This arrangement has introduced an additional connection but as the breather is not under significant pressure, and only carries fuel vapour or venting air there is little chance of a leak. Correct fuel clips are used throughout, these grip the fuel hose far more effectively than jubilee clips. I prefer ABA Stainless clips to others available on the high street. I managed to break the original plastic roll over valve but replaced it with a much neater aluminium device.
The bent brass tube that is supposed to clear the rear suspension could cause problems. The curve is unfortunately in the wrong place being too far forward and not directly over the suspension so it is possible for the suspension arm to hit the brass tube under certain circumstances. See pics below:
I smeared some grease on the suspension arm went for a run and sure enough the grease transferred to the brass tube, a sorry state of affairs. Both rear springs and shock-absorbers have done few miles so the situation could be much worse for high mileage components. I decided to position the tube higher by using some tie wraps to shift it up as far as possible without straining the rubber hose. This created about 13mm clearance. After a 300 mile run to Oulton Park and rechecking, the grease had not transferred so for the time being it seems OK. When the car is off the road for the winter.a better solution to create a larger clearance will need to be sorted .
The basic problem is caused by the fuel outlet being too low down in the tank so that the fuel feed hose has to clear the lower rear suspension arm. At least one owner has completely altered the arrangement by modifying the tank with the outlet higher up, but this was considered too drastic at this time so a simpler solution was executed. The bend in the brass tube does not occur soon enough to clear the arm as seen in the fourth picture below, so the brass tube has been moved closer to the tank and now gives adequate clearance. The final picture below shows that the kink in the tube now sits directly over the arm giving significantly more leeway. My car is a 1996 500 and as seen below the tank fuel outlet protudes outside of the fibre glass body. An interesting post on Pistonheads by Peter Wiggins describes improvements he has made to the fuel runs on his early car. From his pictures it would seem that the fuel outlet on his car is set much further back into the boot, and higher up than mine which is confirmed by him not perceiving a problem with his new braided hose clearing the suspension arm.
Where the fuel tank outlet joins the short 12mm fuel hose a large hole has been cut by TVR in the fibre glass boot . The original arrangement is seen below second left. To seal the hole TVR in their wisdom squirted in about half a tube of silicon sealant, not the best solution. I decided to cobble a thin stainless steel blanking plate to cover the hole leaving room for the main fuel hose and the breather hose at the top. The plate was sealed by silicon sealant around the edges. The 12mm id hose I used had an outside diameter of 18mm but this increases to around 20mm when connected to the fuel tank and brass tube. This diameter proved impossible to clamp using conventional fuse hose clips as the maximum I could find were 16-18mm (17mm). Eventually I settled for some neat stainless standard clips sold by Glencoe.
The 12mm ID Ethanol proof hose is avaiable from Car Builders Solutions
Where the fuel tank outlet joins the short 12mm fuel hose a large hole has been cut by TVR in the fibre glass boot . The original arrangement is seen below second left. To seal the hole TVR in their wisdom squirted in about half a tube of silicon sealant, not the best solution. I decided to cobble a thin stainless steel blanking plate to cover the hole leaving room for the main fuel hose and the breather hose at the top. The plate was sealed by silicon sealant around the edges. The 12mm id hose I used had an outside diameter of 18mm but this increases to around 20mm when connected to the fuel tank and brass tube. This diameter proved impossible to clamp using conventional fuse hose clips as the maximum I could find were 16-18mm (17mm). Eventually I settled for some neat stainless standard clips sold by Glencoe.
The 12mm ID Ethanol proof hose is avaiable from Car Builders Solutions