CHERRY70SS Posted April 27, 2011 Posted April 27, 2011 My 70 MCSS 454 is very hard to start when temps are above 80 and engine is at operating temps.It cranks fine,seems as it is not getting gas or a vapor lock? The engine is original and recently rebuilt, carb is original quadrajet and it has also been rebuilt. Starts fine in cooler weather. Quote
7tonemonte Posted April 27, 2011 Posted April 27, 2011 I had a similar issue with my small block, but it was cured by re routing the fuel line. I had it coming up the front of the engine like the factory, but then had a rubber line across the intake manifold with a fuel filter in there, it was kind of boiling the fuel up into the carb and flooding it after I shut it down. It never liked to fire back up until I changed the routing of the line. Heres a link to an old thread Quote
Mike 57 Posted April 27, 2011 Posted April 27, 2011 I agree with Tony, sounds like a percolation issue. Quote
CrazyDavey Posted April 27, 2011 Posted April 27, 2011 could be the fuel pump is just tried and not providing good pressure when hot.... Quote
RDLBOX1970 Posted April 27, 2011 Posted April 27, 2011 Hey Cherry, Here might be an answer about vaporlock. I posted this last week and did some research. Doe's Anyone Have This? Here is a post on another site that talks about them for 68-69 Chevy's. Why this is not mentioned in any GM publication for 70 Monte Carlo's is beyond me. Vapor Retun Line on 69 Hope it helps! Quote
Andy's Auto Posted April 27, 2011 Posted April 27, 2011 Put some Windex on it. By "Very Hard To Start" are you incinuating it hard cranks or cranks beautifully but don't catch? Not wanting to lead you down the wrong path, but which is it? Left or right? Up or down. Here or there? Quote
CHERRY70SS Posted April 28, 2011 Author Posted April 28, 2011 The fuel line is routed away as much as possible from heat sources. The engine cranks fine but I have to pump the gas pedal quite a few times to get it to finally restart. Quote
LIL' Mac Posted April 28, 2011 Posted April 28, 2011 I wonder if your bowl plugs are leaking off. I always JB them when I do a rebuild whether they show seepage or not. It would most likely be hard to start cold too though, if that were the case. Most likely perculating, as has already been mentioned. Quote
wallaby Posted April 28, 2011 Posted April 28, 2011 Now I thought percolation was when the gas in the carb slowly begins to boil over when the underhood temps get high (like right aftet you shut off the engine), and vapor lock is when the suction side of the fuel pump lines get hot and prevent the pump from drawing fuel. It might seem like nit-picking because both conditions are heat related, but the end results are opposite. With pecolation, the carb overflows into the engine and although the carb itself may go dry, the intake manifold is full of fuel and the engine is flooded. With vapor lock the engine can't get enough fuel because the fuel pump stops working, and the engine is hard to start because it acts like its out of gas. I always thought vapor lock was more of a situation of high load and high heat..like pulling a grade in the desert and having the engine surging and cutting out, and prcolation was a condition seen after you shut off the engine and underhood temps spike. I'm just talking out loud here, but does this sound right? If so, both conditions would make the engine hard to restart but the method for restart would be different: percolation would want the throttle held wide open to overcome the flooding, and vaporlock would want the pedal pumped to overcome fuel starvation. Once you figure out which condition you actually have it will be much easier to start when it happens again. Quote
CrazyDavey Posted April 28, 2011 Posted April 28, 2011 clothes pins!!! clothes pins are the answer!!! Quote
abigfoot Posted April 30, 2011 Posted April 30, 2011 Elec.pump = no more problems with vaporlock. Quote
wallaby Posted April 30, 2011 Posted April 30, 2011 clothes pins!!! clothes pins are the answer!!! Wow...that's pretty old-school! I had a similar setup: here's a shot of my fuel line with pins all neatly organized, stretched out in the sun ready for painting. But then when I went in to get the rattle can, my neighbor lady ruined it forever. Quote
astrochimp Posted May 6, 2011 Posted May 6, 2011 after reading this, i think i have a percolation issue. engine turns when hot but doesn't fire up. Fuel line is far away from engine. So I was thinking of spending a couple bucks on an INSULATING carb spacer.. would this fix it? any way else to fix? Quote
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