12/31/2023 0 Comments Engine vapor lock![]() ![]() your only sure bet is to bleed the vapor out of the rail, usually through the schraeder valve on the end of the rail. If you have a dead head rail system no amount of fuel pumps/booster pumps will solve the issue, once the fuel has vaporized you can't put enough pressure to it to re-condense it. Most custom builders will run a flow through rail, where fuel is continually being circulated through the fuel rail and back to either a vapor seperation tank, or to the main fuel tank. OEM builders make their engines this way 1) cheaper than having a flow through and less complicated to install because there is no return line to the main fuel tank, and 2) warming of the fuel by flowing it through the rail adds slightly to it's evap rate, and this is a huge EPA hurdle in the name of emmisions testing. This is one reason I switched to the new 340 Cat-EX with the in tank pump, I have heard, however, that you shouldn't run your tank less than 1/3 on a hot day with this pump as the pump can overheat if it is not covered in fuel.Vapor lock today is a symptom of a dead headed fuel rail combined with low boiling point shitty ethanol fuel. Works like a charm, just don't forget to take them off before you go. The secret is to keep a couple of old towels and when you want to shut down for a short period of time while the engine is hot soak the towels and lay them directly on the rails. When you shut down the hot engine and let it sit for a while the radiant heat off the manifolds simply vapourizes the fuel in the rails and your stuck until it totally cools off. Finally got the straight goods from our local dealer. I totally drained my tank last year,changed all the fuel filters and the fuel water separator and still had the same problem with good fresh gas from a different supplier. There are a lot of thoughts on fuel type/water etc.but the problem is the on-motor fuel pump and the rails sitting next to all that hot steel. After I got home, about 1 hour, I hooked hose to flush pro and she fired right up and purred like a kitten. After 15 minutes of towing, tried starting again and it fired but ran very rough. Finaly would not fire at all, would crank fine but no fire at all. Shut it off and tried again but even worse. When restarting, ran rough and barely idled. After the last long run, we shut down for about 30 minutes. Started and stoped several times in that 4 hours. Ran for about 4 hours today and all was well. If you had vapour lock, I don't think it would start.įilter replaced less than 10 hours prior to problem.Ġ6 VLX Monsoon. This could be due to low fuel level, fuel pump or just a plugged fuel filter. ![]() ![]() It sound like you are have fuel delivery problems. Have you changed the fuel filters lately. The Throttle Body Injection may or may not be a "real EFI" unit, but Chevy, MC & Indmar all said they did not know of any vapor lock problems with it. I never had the problem again.ĮFI may or may not ever have the problem, but I had every symptom to indicate I had vapor lock. There was about 12" - 18" of metal fuel line on either side of the filter & up to the EFI. It came with instructions to depressurize the fuel rail, remove the inline filter & put this insulation on the metal fuel line. It was nothing but several feet of fuel line insulation, or what looked to me like black rubber hose. I suspect vapor lock for 2 years but was told by every mechanic online & in person that EFI does not get vapor lock.Īfter 2 yrs of trying different things, and taking it to 2 dealers who couldn't solve the problem, I bought the "anti-vapor lock kit" for the carb motors in MC from the early 90s & late 80s from SkiDIM for the problem. I verified time & time again that I had good spark, and while there was fuel in the EFI (the TBI looks like a carb that you can look down the throat), it wasn't a nice fine mist but larger drops. Let it cool down for 30 minutes with the spark arrestor off & the motor cover up, and it would start right up. Over the course of 2 summers I had an issue where if I cruised around at low speed on a hot day, then shut the motor down & tried to restart it shortly after, it would turn over, but wouldn't start. I know it's not even close to the same EFI on the Malibu, but it might give you some ideas. I had a 1994 Mastercraft 205 with the TBI EFI 350 Chevy. ![]()
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