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420A Fuel pump problem when hot

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dsm311

Probationary Member
12
1
Aug 15, 2013
Caguas, Puerto_Rico
im having this wierd problem with my aftermarket fuel pump. when it gets a bit hot outside and the fuel within the tank is in between half tank and quarter tank it fails to activate. Ive heard this is common because of where im at and how hot it can get here but im kinda looking for a more concrete answer.
 
have you tried a different fuel pump?
it never happened to me with the stock fuel pump but then I found out that apparently its common for this to happen when putting in an aftermarket fuel pump. Ive heard of people that cant go below quarter tank before this happens to them and others in different spots. the thing is that i made my car turbo so i need a higher flow of fuel that the stock one wont give me.
 
thats already been done. whats happening to me is called fuel injection vapor lock. this is a problem that from what ive seen on these pages doesnt happen in the US, im trying to find a fix so i can drive my car with less than half tank of gas.
 
When does the issue happen? Is it after driving or just when it's hot outside? A fuel pump that over heats can cause an issue if it cavitaes or if it doesn't have a strong enough ground circuit.
 
It only happens when its pretty hot outside. The car can be running and the pump just shuts off. To get the car to start again i have to wait for the car to cool down a bit and itll start again but for only a few minutes if that. But only when the fuel is at a certain point of the tank or when the pump seems to be exposed within the tank and its hot outside. Its not a power problem or wiring because its all been rewired already. Im not the only person this has happened too either, pretty much everybody that has changed out the stock fuelpump for an aftermarket one being aem or walbro it still happens.
 
Ive always heard with aftermarket fuel pumps to never let the car get too low on gas. Also, the fuel pump operates at its best when its above half a tank. When it gets low, all of that empty space just turns into hot air and is making your fuel pump work harder. Just keep more gas in the tank. I learned the hard way the day I bought my gs-t, it ran low on gas (below a quarter tank) and i had to struggle to get it cranked. Took it straight to the gas station and it hasnt given me a problem in the past 4 years
 
It's that the fuel pump is over heating then. The fuel that's in the tank is what helps keep the pump cool. Unless someone makes something to help keep the pump cool aftermarket it sounds like you will just have to keep more than a half tank in the car unless you want to change to a frame mount style pump.
 
so theres no real solution for this yet, besides keeping the fuel after a certain point which isnt a solution, its more of a compromise. Our next step was building a bracket so that the pump would sit lower within the tank which should give me some extra galons worth.
 
Have you actually checked with a volt meter if its getting the power all the way to the fuel pump when its hot? A rewire isnt going to help if the original relay behind the radio isnt engaging. Ive got a Walbro and it gets pretty hot here in SoCal, I dont have a problem getting my tank low to 1/8 remaining, and nor have any of my other previous DSMs
 
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but essentially it doesnt matter which one it is cuz its also happened to walbro fuel pumps too. it happens to anything but the stock fuel pump.
Why doesnt't it happen with the stock pump....that makes no sense to me. I know some aftermarket pumps sit alittle higher so you can't run them down as much. IMO just keep the tank above 1/2 its not that bad of a deal unless you do long commutes all the time
 
well to upadate the info on this thread, the AEM fuel pump that was mounted got burnt out and now i have a walbro. Some modifications were made to the fuel tank so it could breath better and wouldnt get too hot which is working fine while im driving within the city or for short periods of time. When driving for longer than 1hr+ is when the fuel pump is getting hot and shutting down. My question now is, could it be possible that the relay and cable may be resisting the current flow to the pump to such extent for it to transfer heat to the pump for it to overheat itself and shutoff?
 
That is the reason for rewiring the pumps, to take the load off of the existing skinny little wires and give the pump full battery voltage like the battery is sitting right there next to it. I agree you should double check the voltage at the pump or at least on the relay so you know it is getting the proper voltage.
 
My friend had a similar problem with a walbro pump in a corvette. He ignored it for a year. Then driving from Chicago to Texas he noticed it would consistently cut out around a 1/4 tank. Replaced the pump and problem solved. We believe it to to have been the pump overheating when it was above the fuel level in the tank. So it is possible you have a failing pump that cuts out as it warms up.

Also +1 to 1990TSIAWDTALON If there is to much draw on the stock wiring it may induce heat at a point with high resistance such as a relay or connector. A fuel pump rewire is a simple job and a good idea. Especially as you know your wiring is still healthy enough to support a stock pump. And if you are pushing your wiring with a higher amperage pump it may permanently fail if there is a problem with it.
 
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