04-07-2022, 11:01 AM
Courtesy of Schmoberger (Kieran):
A nasty stigma that has been attached to aircooled VW's since the beginning of time is that they are a firebomb which are capable of combusting at the drop of a hat... and the common uneducated view is that "Oh, yeh... VW's catch fire because they are aircooled so they overheat!" :?
Puuuh-leazze!... A tiny bit of common sense and a basic understanding of the principles behind combustion should be enought to prove that this is codswallop... if the engine got hot enough to ignite even a magnesium crankcase on a type 1-2 engine, then.... well... you wouldnt expect the rear of the bus to still exist!
In reaality, I'd guess that 99% of vintage Volkswagen fires can be attributed to a compromised or poorly maintained fuel system.... for instance degraded or incorrect fuel hose, leaking carburetters, a leaking fuel pump, or "popped" hoses. The other 1% are electrical in nature or caused by oil contacting hot surfaces, and are unlikely to occur.
In this article, you will learn all the tricks to prevent you ever being in the situation that a Melbourne kombi-pilot was in in mid-2005... standing on the footpath watching helplessly as your kombi burns furiously on the road... :?
Read on....
Firstly, you should replace all of your fuel lines anually... as the high temperatures generated by an aircooled engine, combined with constant contact with petrol can cause the rubber hose to degrade fairly rapidly... it begins to split, crack, and eventually burst over time. you may easily get over a year from a set of fuel lines... up to a few years if you are lucky... however it is not a risk worth taking. The job is simple, as all fuel lines are flexible rubber hose, and on a Kombi, the fuel tank is behind the firewall, so the distance the hose has to travel is minimal.
When replacing fuel lines, always buy the highest quality German cotton-sheathed rubber fuel hose, in the correct thickness and diameter for your bus. Some American sizes can be made to fit, however this is dangerous water, so avoid it. Correct diameter is important, as using to narrow a diameter will put excessive strain onto the hose ends, leading to splitting... too wide a diameter will slip off. As an imprecise measure, the fuel hose should fit firmly on the brass fitting, and require some effort to push, but not require shoving or pliers to push all the way home. it also should not stretch more than about 1mm in diameter when on the fitting.
Also avoid using cheap and nasty hoses that happen to be the right diameter.... they may fit, but many arent designed to stand up to high pressures, temperatures, and exposure to fuel, and will hence break down very quickly indeed.
Observing these precautions is doubly important on fuel-injected buses... as much higher pressures exist in such systems.
When cutting lengths of fuel line, ensure that you have a clean, square cut, and make sure you cut enough hose off to allow for some slack... tight or stretched hoses can cause problems.
After replacing fuel lines, EVERY end should be clamped to it's fitting, preferably with screw-type clamps, to reduce the chances of the hose working loose and slipping off the fitting. Saying that though, it is important that you do not overtighten the clamps, as this puts excess stress on the rubber... simply tighten until it bites and holds.
Once your fuel lines have been clamped... get lockwire or similar and wind it around the hose tightly then follw through and wind tightly around the clamp, then wind tightly around the fuel pump or carburetter body. This ensures that the hoses can never come completely off under any circumstance, however there is also a far more importnt reason for this extra precaution... the brass fittings themselves in the carbies and fuel pumps of aircooled VW's have a nasty nasty habit of coming unstuck from inside the unit and falling out, causing fuel to be sprayed over the hot engine. In fact this is one of the most common causes of fuel related kombi fires. By securing the hoses with wire, you relieve some of the strain from the fitting itself, making it slightly less likely to come loose... however in the event that it does come unstuck, it will remain in place, and at worst only dribble a little fuel, rather than falling right out and turning the entire engine bay into a bomb. In the case ot the T-section in between the carbies on a type 4 engine, wire it in the same manner as the carbs, but follow through in a triangle pattern onto the next hose, then the next one then back to the one you started with... this will keep everything together in that area if done tightly.
Another idea which I believe to be helpful is to insulate the T-section with good quality heat resistant electrical tape. The idea of this is to ensure that if the T cracks, as many of them are plastic, the fuel will be more or less contained if the tape is applied tightly and without gaps. I actually use this to secure the T rather than using clamps, as it seems just as effective.... however it will count for nothing if you use cheap tape.
With regards to fuel filters, ensure that you have it installed in the line between the fuel tank and the pump, not between the pump and carbs... the pressure from the fuel pump can easily blow the filter off or even crack or explode some cheap plastic ones if they are on the pressurised side of the pump, resulting in a fireball... so dont do it, even if it seems easier...on that note, a filter after the pump serves no purpose, the pump has its own strainer, meaning contaminants dont enter the engine anyway... if you have a filter, it is to prolong the life of the pump by removing gunge before it enters it. If your bus already has a filter after the pump... remove it before you drive the bus any further, or you are endangering it's life!
Another common cause of fuel plumbing failure is due to abrasion or laceration. Every VW with an aircooled engine has a hole in the rear engine tinware through which the fuel inlet hose from the tank passes into the engin bay to feed the carburetter/s. This tinware is only a few millimeters thinck and has sharpish edges, so a rubber grommet is installed from the factory in the fuel hose hole to prevent chaffing or cutting of the hose. EXCELLENT!... however there is a problem... like rubber fuel hose, this rubber grommet deteriorates with age and heat and can evntually fall out or disintegrate... leaving the delicate fuel hose resting and rubbing on the sharp tinware. If left unchecked, the tinware will cut or rub through the fuel hose, and eventually it will rupture and potentially cause a fire. For this reason it is a good idea to change this grommet anually with the fuel lines.
Another abbrasion hazard is found in late bays... in the form of a small metal tab at the top of the rear tinware. This tab is a guide for the fuel line into the left hand carburetter... i am not entirely sure of how many peole actually use it as such, however if you do, it is advisable to wrap heat resistant 'leccy tape around the section of fuel hose that sits in this guide, this should prevent any abbrasive action against the actual hose.
The final fire risk is from leaking hardware such as pumps carbies and inlet manifolds. Inlet manifolds can occasionally crack, however this is not terribly common, so I am just mentioning it for posterity.
Carbies can be prone to leaking or weeping from seals that are old.... slight weeping is usually not cause for concern... however profuse leakage should be rectified ASAP.
Same deal with fuel pumps, over time they can develop leaks around the gasket. on a type 4 engined kombi, this is not too much of an issue unless it is profusely dripping fuel, as the fuel pump is located under the engine away from most hot bits. On a kombi with a type 2 engine though, any fuel pump leakage should be rectified, as the pump is in the engine bay.
By now, your fuel system should be fireproof, however you should inspect all hoses and fittings for condition and fit at least fortnightly to ensure they stay that way... I check mine at least weekly. When inspecting the fuel system, you should inspect hoses for cracks, splits, bulges, or other damage that will inevitably lead to failure and fire if left unchecked. Press each fuel hose between a finger and thunmb along it's length... it should be firm but supple. If any hose is hard, it has degraded and requires immediate replacement with the correct replacement hose as described earlier in this article. The same applies if any splits are found along the length of the hose, or if cracks are found at either end, or if bulges or blisters are found in any hose... replace the offending hose/s right away. Check fittings by ently but firmly wiggling them ever so slightly... when you are satisfied the fittings are in correctly, give the hose ends a gental push home. After the plumbing has been taken care of, check the fuel pump gasket and carburetter gaskets and seals for leakage, and rectify if needed... be your own judge... as mentioned before, a thin coating of residue around the gasket or pump body of carby seals is ok... but if there is a consistent dampness or worse... its a good idea to rectify it.
Now that you are aware of all the VW fire-safety precautions, there should never be any reason for your bus to ignite... however, just to be safe... ALWAYS, ALWAYS, carry a charged extinguisher on board... it's even better if you have two or three. If you have the room to put it, I would recommend a CO2 (black) extinguisher of around 7kg, and a smaller dry powder type of aroung 1kg.
Now that you have an insight into what causes fires in VWs, you can go and take preventative meausures, plan an inspection and maintenance regime for your fuel system, and drive your bus with confidence and peace-of-mind!
Cheers!
Kieran
A nasty stigma that has been attached to aircooled VW's since the beginning of time is that they are a firebomb which are capable of combusting at the drop of a hat... and the common uneducated view is that "Oh, yeh... VW's catch fire because they are aircooled so they overheat!" :?
Puuuh-leazze!... A tiny bit of common sense and a basic understanding of the principles behind combustion should be enought to prove that this is codswallop... if the engine got hot enough to ignite even a magnesium crankcase on a type 1-2 engine, then.... well... you wouldnt expect the rear of the bus to still exist!
In reaality, I'd guess that 99% of vintage Volkswagen fires can be attributed to a compromised or poorly maintained fuel system.... for instance degraded or incorrect fuel hose, leaking carburetters, a leaking fuel pump, or "popped" hoses. The other 1% are electrical in nature or caused by oil contacting hot surfaces, and are unlikely to occur.
In this article, you will learn all the tricks to prevent you ever being in the situation that a Melbourne kombi-pilot was in in mid-2005... standing on the footpath watching helplessly as your kombi burns furiously on the road... :?
Read on....
Firstly, you should replace all of your fuel lines anually... as the high temperatures generated by an aircooled engine, combined with constant contact with petrol can cause the rubber hose to degrade fairly rapidly... it begins to split, crack, and eventually burst over time. you may easily get over a year from a set of fuel lines... up to a few years if you are lucky... however it is not a risk worth taking. The job is simple, as all fuel lines are flexible rubber hose, and on a Kombi, the fuel tank is behind the firewall, so the distance the hose has to travel is minimal.
When replacing fuel lines, always buy the highest quality German cotton-sheathed rubber fuel hose, in the correct thickness and diameter for your bus. Some American sizes can be made to fit, however this is dangerous water, so avoid it. Correct diameter is important, as using to narrow a diameter will put excessive strain onto the hose ends, leading to splitting... too wide a diameter will slip off. As an imprecise measure, the fuel hose should fit firmly on the brass fitting, and require some effort to push, but not require shoving or pliers to push all the way home. it also should not stretch more than about 1mm in diameter when on the fitting.
Also avoid using cheap and nasty hoses that happen to be the right diameter.... they may fit, but many arent designed to stand up to high pressures, temperatures, and exposure to fuel, and will hence break down very quickly indeed.
Observing these precautions is doubly important on fuel-injected buses... as much higher pressures exist in such systems.
When cutting lengths of fuel line, ensure that you have a clean, square cut, and make sure you cut enough hose off to allow for some slack... tight or stretched hoses can cause problems.
After replacing fuel lines, EVERY end should be clamped to it's fitting, preferably with screw-type clamps, to reduce the chances of the hose working loose and slipping off the fitting. Saying that though, it is important that you do not overtighten the clamps, as this puts excess stress on the rubber... simply tighten until it bites and holds.
Once your fuel lines have been clamped... get lockwire or similar and wind it around the hose tightly then follw through and wind tightly around the clamp, then wind tightly around the fuel pump or carburetter body. This ensures that the hoses can never come completely off under any circumstance, however there is also a far more importnt reason for this extra precaution... the brass fittings themselves in the carbies and fuel pumps of aircooled VW's have a nasty nasty habit of coming unstuck from inside the unit and falling out, causing fuel to be sprayed over the hot engine. In fact this is one of the most common causes of fuel related kombi fires. By securing the hoses with wire, you relieve some of the strain from the fitting itself, making it slightly less likely to come loose... however in the event that it does come unstuck, it will remain in place, and at worst only dribble a little fuel, rather than falling right out and turning the entire engine bay into a bomb. In the case ot the T-section in between the carbies on a type 4 engine, wire it in the same manner as the carbs, but follow through in a triangle pattern onto the next hose, then the next one then back to the one you started with... this will keep everything together in that area if done tightly.
Another idea which I believe to be helpful is to insulate the T-section with good quality heat resistant electrical tape. The idea of this is to ensure that if the T cracks, as many of them are plastic, the fuel will be more or less contained if the tape is applied tightly and without gaps. I actually use this to secure the T rather than using clamps, as it seems just as effective.... however it will count for nothing if you use cheap tape.
With regards to fuel filters, ensure that you have it installed in the line between the fuel tank and the pump, not between the pump and carbs... the pressure from the fuel pump can easily blow the filter off or even crack or explode some cheap plastic ones if they are on the pressurised side of the pump, resulting in a fireball... so dont do it, even if it seems easier...on that note, a filter after the pump serves no purpose, the pump has its own strainer, meaning contaminants dont enter the engine anyway... if you have a filter, it is to prolong the life of the pump by removing gunge before it enters it. If your bus already has a filter after the pump... remove it before you drive the bus any further, or you are endangering it's life!
Another common cause of fuel plumbing failure is due to abrasion or laceration. Every VW with an aircooled engine has a hole in the rear engine tinware through which the fuel inlet hose from the tank passes into the engin bay to feed the carburetter/s. This tinware is only a few millimeters thinck and has sharpish edges, so a rubber grommet is installed from the factory in the fuel hose hole to prevent chaffing or cutting of the hose. EXCELLENT!... however there is a problem... like rubber fuel hose, this rubber grommet deteriorates with age and heat and can evntually fall out or disintegrate... leaving the delicate fuel hose resting and rubbing on the sharp tinware. If left unchecked, the tinware will cut or rub through the fuel hose, and eventually it will rupture and potentially cause a fire. For this reason it is a good idea to change this grommet anually with the fuel lines.
Another abbrasion hazard is found in late bays... in the form of a small metal tab at the top of the rear tinware. This tab is a guide for the fuel line into the left hand carburetter... i am not entirely sure of how many peole actually use it as such, however if you do, it is advisable to wrap heat resistant 'leccy tape around the section of fuel hose that sits in this guide, this should prevent any abbrasive action against the actual hose.
The final fire risk is from leaking hardware such as pumps carbies and inlet manifolds. Inlet manifolds can occasionally crack, however this is not terribly common, so I am just mentioning it for posterity.
Carbies can be prone to leaking or weeping from seals that are old.... slight weeping is usually not cause for concern... however profuse leakage should be rectified ASAP.
Same deal with fuel pumps, over time they can develop leaks around the gasket. on a type 4 engined kombi, this is not too much of an issue unless it is profusely dripping fuel, as the fuel pump is located under the engine away from most hot bits. On a kombi with a type 2 engine though, any fuel pump leakage should be rectified, as the pump is in the engine bay.
By now, your fuel system should be fireproof, however you should inspect all hoses and fittings for condition and fit at least fortnightly to ensure they stay that way... I check mine at least weekly. When inspecting the fuel system, you should inspect hoses for cracks, splits, bulges, or other damage that will inevitably lead to failure and fire if left unchecked. Press each fuel hose between a finger and thunmb along it's length... it should be firm but supple. If any hose is hard, it has degraded and requires immediate replacement with the correct replacement hose as described earlier in this article. The same applies if any splits are found along the length of the hose, or if cracks are found at either end, or if bulges or blisters are found in any hose... replace the offending hose/s right away. Check fittings by ently but firmly wiggling them ever so slightly... when you are satisfied the fittings are in correctly, give the hose ends a gental push home. After the plumbing has been taken care of, check the fuel pump gasket and carburetter gaskets and seals for leakage, and rectify if needed... be your own judge... as mentioned before, a thin coating of residue around the gasket or pump body of carby seals is ok... but if there is a consistent dampness or worse... its a good idea to rectify it.
Now that you are aware of all the VW fire-safety precautions, there should never be any reason for your bus to ignite... however, just to be safe... ALWAYS, ALWAYS, carry a charged extinguisher on board... it's even better if you have two or three. If you have the room to put it, I would recommend a CO2 (black) extinguisher of around 7kg, and a smaller dry powder type of aroung 1kg.
Now that you have an insight into what causes fires in VWs, you can go and take preventative meausures, plan an inspection and maintenance regime for your fuel system, and drive your bus with confidence and peace-of-mind!
Cheers!
Kieran