Hello All,
I am inexperienced when it comes to 914. I have a 1975 914, carb set up, engine rebuild by FAT. Car had been sitting a couple weeks. When i got in to start, starter cranked but seems no fuel delivery. suspecting fuel pump or clogged lines.
When I opened the Frunk, it looked like the expansion tank imploded. Severe damage like something dropped on it. Question, would the damaged Ex-Tank cause the fuel pump to suck air instead of fuel?Click to view attachment

Nope.

Your garage will smell like gas!

interesting damage. did it literally implode. something was not dropped on it?

on a stock car the tank vents (ie equalises air pressure through the carbon cannister via the fan bleed hose primarily) - at least to the best of my knowledge. could that damage have been caused by someone sealing off the fume vent line and disconnecting the charcoal can. the fume vent line in post 74 cars runs through the centre tunnel and into the engine bay. very small diameter black nylon hose.

i guess the fuel pump could cause enough suction with no way to pressure relieve to blow up 50 year old brittle plastic! !!! ????

as per other posters comments damage should not stop fuel delivery.
you just created a massive tank vent inlet.

What do I see in your avatar? Is that someone skateboarding in an empty swimming pool?

Call me. I left you a private message.

Thank you for the input. Nothing dropped on the tank and frunk lid has been closed in the garage, no damage to the hood. I only drove the car a few times since filling with gas. It literally looks like someone sucked the air out of a water bottle. I guess it could just be old plastic but the damage is severe and the plastic is not that thin (?!!).

Something is not right... I guess i look to the fuel pump next.

Might look closely at the hood for damage.

I'd look into the chamber as well.

Something laying on the top of that might do that type of damage if the hood was closed accidentally on it.

Small bottle of brake fluid might do that...

Pressure (or lack thereof) didn't do that.

That has been broken externally.

Try starting it with the gas cap removed.
Then while running, put your hand, or a round flat object on the gas tank and see if it gets sucked down tight over time.

Venting and possibly the fuel return line are blocked.

Looks crushed rather than exploded
In either case id have thought that would be tough to do.
Ive got spared if you want to replace it.

Someone left gas cap on top of the expansion tank and trunk got closed?

Bingo!
So simple an answer.

I'd bet East coaster is right...

If this is true then there should definitely be an obvious paint scar on the underside of the hood, right above the area of tank damage. Might also be body paint on the gas cap?

i'm with you.

while it could be a gas cap thats the villain i am sure that @914Y75 would have tended to notice that happening when he last closed the lid!


plastic looses its plasticizers over time. the plastic tanks are 50 years old.

if i am not mistaken these plastic expansion tanks are amongst the very first fuel tank components made with non metals on any cars. only the VW passat used plastic before the 914 and only by about a year. not sure if the USA got the passat and if it did not sure it was the one manufactured in germany with the plastic fuel tank.

fuel tank collapse and deformation is common when the tank vent system blocks.
even metal tanks. you can pressurize them to blow back out to original shape.
but its not going to deform if the plastic has become brittle, it will shatter. and impode rather than partially collapse and deform. by the way i have seen a deformed plastic fuel tank on a ford falcon here due to tank vent blockage. and i have also seen tanks shattered by impacts under the car. the original tanks in aussie falcons date from 1979 and any left in cars still running are suspect now. they have gone brittle.

also remember - no vented gas cap on 70s closed evap emissions system. all vent done through charcoal can.

what @914Y75 needs to look for is the vent hose. is it still connected to the ex tank?
or is the ex tank plugged where it goes? if the hose is still there where is the other end.
still in the engine bay? if it is there has it been crimped or sealed off?

its a carbed car and probably had its charcoal can system removed. it was probably set up to vent some other way. but maybe something was recently inadvertantly done to that vent or vent hose that has caused this.

Click to view attachment


might have burned the fuel pump out when it was trying to pull the gas through the line against the vacuum building in the tank.
sounds like the fuel pump is not running anymore.

as i said before the tank certainly does not appear to have a venting problem anymore.

the simple solution is to do an expansion tank removal.
vent the tank into the tank inlet spill hose.
as the european cars had.

not hard to find examples of imploding fuel tanks with a 5 minute search on the internet.
this one is interesting as it also describes fuel pump distress while the vacuum was building. and its a 928. legendary for plastic fuel tank failures.

https://rennlist.com/forums/928-forum/48815...tastrophic.html

as to exactly why it suddenly happened on this 914 not sure.
you have to determine how it was venting to look into it to see if if was due to lack of venting or whether it was an impact.
someone leaning on it with their hand while working that area might also cause it.
but if not its implosion.

the plastic ex tank on the 914 post late 74 would be the weak link in the system at this point half a century on. its not a big round shape like a fuel tank which might deform first. given its flat shape once it becones inflexible it would probably fail in the way the photo seems to show.

if it is a vent failure implosion just another thing to watch out for on the plastic tank 914s at this point in time half a century down the track.

Wow, you guys are great and gave me a lot to think about. I will check the vent line for clogs. No one has leaned on the ex-tank and trunk was not open for damage by external force. The hood has no damage, dent or scratch. Also, i filled the tank with gas a few weeks before. The gas cap was in-place as should be, it was not left on top prior to closing the hood. Thanks for those PM's i will respond separately.

Wow, you guys are great and gave me a lot to think about. I will check the vent line for clogs. No one has leaned on the ex-tank and trunk was not open for damage by external force. The hood has no damage, dent or scratch. Also, i filled the tank with gas a few weeks before. The gas cap was in-place as should be, it was not left on top prior to closing the hood. Thanks for those PM's i will respond separately.

Here's the wheels...

Winer, winner, chicken dinner!

the vent line works (and i think its the same in plastic too but not 100%) is there is a small hose on the filler neck just below filler cap. this is open to main fuel tank.
that feeds to expansion tank where there is a nipple on right hand side. at least with metal tank. at the other end of expansion tank, left hand side is the fume (vent) line that runs off to the can. which in a mid74 and onwards is located in engine compartment. that little line runs through the centre tunnel and is small diameter nylon (or some kind of black plastic line). there is no valve in the original 914 (VW) charcoal can system. it all just runs into the charcoal can which has access to atmospheric pressure via both the fan bleed air hose and also the aircleaner. when the car is not running all that is at atmospheric pressure and equalized. tank can release any expanded pressure down both those routes. hydrocarbons get absorbed on the way through the charcoal. when the car is running the fan bleed hose is supplying plenty of air in the opposite direction for the fume line to relieve the vacuum in the tank.

without that fume line open or the nipples open on the tank you can get the old vacuum problem causing issues.

the european cars also used the expansion tank. but instead of running the fume line off to a charcoal can they looped it back around and fed it into a T junction on the filler neck drain hose which is the big diameter hose comes off the outer filler spill tray and heads off down to the underside of the car.

you got two ways to go. get a replacement expansion tank and run the vent off to a T on the overflow hose as per europe. or do an expansion tank delete and run the fume line directly from the neck either to a T with the overflow or route in down and out the bottom of the car somehow. you will smell fumes when the car is sitting still in the garage with either of those solutions. and you will smell fumes somewhere anyway if it no longer has its charcoal can set up.

well -----the avatar character was not wind surfing (with optional air bag wipe out protection) in a full one.