Basically something really odd happened this evening. It was probably the first time I've driven it quite this hard since I had the Dellorto's fitted and it just kind of died after idling outside my friend's place for about 5 minutes and I couldn't get it moving again for about 15 minutes. It would catch and usually start but only for a couple of seconds and every time I tried to give it fuel the revs would just drop and it would die. If I didn't give it fuel it would still die. Does that sound like what happens when the carbs get too hot and the fuel starts boiling? This is an 8v setup, by the way, so the carbs sit above the exhaust manifold. I was stuck at quite a number of traffic lights before I got to the friend's place so that would've added to the heat build-up I imagine.
Oh snap. That would make sense as the engine bay was reallly warm after it died. But the second time it happened it actually died while I was driving. It surged a little bit and then lost all power, kind of like icing. But it was really hot down there. Still vapor lock? Actually both times it stalled. First time while I was waiting, and the second while I was driving.
Bit of a guess this, as I've never AFAIK experienced vapour lock while rolling, but I think the driveability (or lack thereof) might feel similar to icing. I say that, because last time I experienced icing, the lambda showed radical overfuelling during the symptoms.
But it sounds like when you get a vapour lock you're suddenly starved of fuel? Wrapping your fuel hoses with alumin(i)um foil... Will that actually help keep your fuel hoses cooler? Meant to be a performance mod if you can keep your fuel as cool as possible.
It depends which bit is getting hottest. If it's the carb(s) themselves and the contents of the float bowl(s), then you'll get lots of vapour coming off the top and being vented into the airstream entering the venturi. That will add to the normal fuelling. If you're rolling and the fuel pump is working normally, the float bowls will still be getting topped up to the normal level, so you won't 'run out'. The hotter the carbs get, the more easily the fuel will flow through the various passages of the carb's internals too, adding even more fuelling, I'd think. Much too much fuel for the available oxygen, and it starts to run badly or even stop. Tin foil wrapping sounds like a good plan, IFF it's the fuel lines that are getting overhot. Would reflect most of the radiant heat incident on them, but I suspect that isn't a great deal.
OK I had a vapour/air lock today starting from cold. So it's not actually a vapour lock that's stopping fuel getting to the carbs. Then what is it?
Got a pic of your pump and inline filter installation? I keep coming across the phrase "For best results, mount the pump close to the fuel tank and below the fuel level" when I google facet pumps. It may be that there isn't an air leak, but that after you shut the engine down, heatsoak is vapourising fuel in the lines/pump and pushing liquid fuel back into the tank. Then when you go to start next time, the pump is failing to self-prime? Or you have a dodgy connection somewhere, have you checked/re-made any?
Remade all the connections and removed old inline paper filter. It worked again after that, but I don't know if that's because I "fixed" it, or just because it decided to kick in again because it's an annoying, intermittent little "sharp scratch". I did notice that the small section of hose that I removed, which went from the inline filter to the pump (about 2" long) disintegrated when I pulled it off the pump not sure how much that has to do with anything though. As in a part of the inner lining/hose ripped and stayed on the pump barb. I think "close to fuel tank" only applies to the Solid State facet pumps and not the Red/Silver Tops. Below fuel level, is that below the tank, or below the carbs? It's lower than the carbs yeah.
I would think that they are referring to 'lower than the minimum tank level', but hey, phone up your supplier and ask. Simple test, if the problem happens more when the tank is nearly empty, than when it's nearly full...
i'm begining to think, reading this thread and the symptoms that is the cause of my issues to. The caddy only runs rough/poorly in slow/stationary traffic when the engine gets above its normal happy working temps, then is a bugger for a while till it cools back down completely. yes the fan works in these situations. All of those symptoms it lists are true of my journey this evening. was fine till i hit traffic. Now how to solve this? I plan to clean out the cooling system of the car but how do i keep the inlet manifold and carb cool from the roasting exhaust manifold it sits above? also the fuel pump is on the front bottom part of the engine, i can't mount or make it any cooler?
Again, Jon, have you noticed any reduction in symptoms/problems when the tank is brimmed? I'd guess that the fuel pump has a much lighter load when there's a 'head' of fuel at the far end of the car.
last journey and last nights journey were completed on half a tank of fuel. tbh my caddy only gets used for to and from work trips which are 20mins and no traffic what so ever. i love living in the countryside only on the longer, having to go through towns, sit in traffic does it become an issue. I will see what happens on the return journey tomorrow as i'll be adding some more fuel. I know if i manage to keep the engine cool/within its normal operating temps its fine, go above that and it starts playing silly buggers great find on the link but it doesn't say how to solve it
yeah it does... wrap your fuel lines in tin foil! and drop some water on your pump and maybe the carbs when it starts playing up.
If you are using the facet red or silver top pumps that are a round cylinder (not the little square ones) they need to be mounted so the end that comes off with the filter inside is in the down position. The way they work is with a solenoid driving the internal piston one way and it relies on gravity to drop the piston back ready for the next stroke. If it is horizontal it does not "reset" the piston properly. They say they can be mounted anywhere in the fuel sytem but ommit to state the orientation. I put mine to the back of the car after having problems and mounted it this way and it was much happier. The pump even sounded completely different. The 8v design with the carbs over the exhaust is far from ideal and heat soak and fuel vapourising can be an issue. I had webers on my 8v rally car and hated the end of a stage when you had been going flat out and then had to stop and get the time card marked. Just waiting for the fire to happen!! I had a plate between the exhaust and carbs aswell as wrap on the exhaust to try to keep them cool. Carry a fire extinguisher with this setup just in case. The real fix is 16v
yeah I can't believe how long it took me to realize it "preferred" being a certain way up... and I took someone else's (Mike_H) advice and put an extinguisher in the passenger footwell. certainly attracted quizzical looks from my polo team.
