Carb fire.. why? Options

[H2ohs]

Hi All, took the car out of storage, cleaned, took for a 20 min ride. Was running great. 3 min from home, it started to run really rough. Not sure if it was on fire at this point, but barely made it home. got out and flames were shooting from the grid. Fire extinguisher was close, so put out pretty quickly. Rain tray melted and made a mess. The carb filter totally burned and destroyed. All fuel lines in good shape, no leaks. So what would make the carb catch on fire like this? float? timing? this pic is after trying to clean the fire extinguisher mess off- it still runs fine actually. Ideas?

[Superhawk996]

Sorry this happened. At least you caught it before it became a total loss.

Repost from another fire thread about a week ago.

Is it the mid engine design?

First off I want to say I’m terribly sorry you lost your car.

No, fire potential isn’t related to mid engine. There are plenty of other mid engine cars that don’t burn as often as 914s.

In no way is this list meant to be specific to you, the other car in this link, or anyone in particular. Some of the things I’m going to list I’ve done myself in my younger days.

Top of the list. 914s are and have always been owned by cheap SOBs that are stretched thin financially just to own the car. As a result maintenance gets deferred or gets done by a shadetree DIY to a low standard. Sometimes this is due to money, other times due to ignorance and learning the hard way. This was me when I had my first 914 in my 20s.

Other contributors in no particular order:

Not properly routing fuel lines. Fuel line needs to be carefully routed away from exhaust and heat exchangers and needs to be properly secured to keep it where it belongs. You wouldn’t believe how quickly metal edge can saw through a vibrating rubber fuel line that touches it. Think vibrating multi-tool saw. Basically the same motion happening between two vibrating parts. Free plug for Tangerine Racing - great metal lines that properly route fuel line up though the engine shelf. I’ve seen rubber fuel lines routed up through that shelf without proper rubber grommets. Yeah - I did that too when I was young and dumb. (IMG:style_emoticons/default/screwy.gif)

Fuel hoses should never have another hose touching it or crossing it. Lines will wear though one another if left free to rub on each other.

Plastic fuel lines in tunnel - still a ton or cars out there with these

Using fuel hose that isn’t FI rated (noted by others)

Using old fuel hose - storage time matters. Both on the shelf before you bought it as well as time spent sitting in storage on your car. All OEMs moved away from rubber fuel lines eons ago. Rubber doesn’t age well.

Using worm drive hose clamps on fuel lines (I did this as a youngster (IMG:style_emoticons/default/headbang.gif) )

Regulators and fuel pressure gauges in the engine compartment. These just represent more potential leak paths and usually result in convoluted rubber fuel line routings to get to & from them . Do you really want the integrity of your fuel system to depend on a $10 gauge you bought off Amazon?

Plastic fuel filters in the engine compartment. Yes the OEM fuel filter is plastic and is also mounted down near the engine mount / heat exchangers. Not VWs finest engineering. It was the 70s and lots of drugs were the norm (IMG:style_emoticons/default/happy11.gif) Plastic fuel filters mounted down at the bottom of the floor pan & engine compartment edge can get damaged by road debris leaving fuel spraying right back to a hot exhaust. Believe it or not I’ve seen fuel filters hanging below the floor pan.

Leaky fuel injectors due to age. The rubber j-hoses right off the injectors, and general OEM fuel line routing for FI. Again not well conceived vs a modern car. All that rubber hose running a loop to/from the metal OEM FI tubes that connect to injectors. Would never fly in modern FI design, DFMEA analysis, or litigious environment.

3 port fuel pumps. Again OEM location is sub-optimal. The pump inlet outlet are plastic and can crack with age. At this point many have 50 year old rubber seals that can begin to leak at the electrical connector area and the main pump body.

Electrical connectors and wiring. Some of the wiring in 914s is abysmal by modern standards. Not fully fused. Not well routed or secured. Electrical wires crossing fuel lines. And this is all before 50 years of DAPO “fixes”. I’ve seen so much bad wiring on 914s over the years. Again - did some of it myself back in the day.

Not using grommets to protect electrical wires (including 4 ga battery +) at pass throughs.

Leaking CV joints - throwing grease onto hot exhaust and heat exchangers. Yes, really you can start a fire this way.

Rodent debris. Again, not kidding. Rodents love to build nests below the tin. Leaves get sucked in by the fan and build up. If any of this material gets hot enough it can combust.

Finally as previously stated, engine conversions bring all sorts of other potential issues into play (MFI, CIS hoses, even higher fuel pressures, cobbled wiring, etc.)

Bottom line: be very careful about the condition of the fuel system; this includes carbs. Leaking, weeping carbs may be lower fuel pressure but still can leak fuel onto hot exhaust and ignite. Carb backfires can catch Oil saturated K&N filters on fire which can spread to fuel lines.

Be careful out there!!