Delay on make timer required
Discussion
So when I go to start my engine the ecu gets power at the same instant as the LP fuel pump. The ECU triggers the hp fuel pump for a brief period at the same instant. I would like to get the LP pump to run for say 5 secs before the ECU and HP pump is triggered in order to clear any vapour from the swirl pot and allow the LP circuit to prime. I am looking for a solid state fixed time delay encapsulated unit to install in my engine bay near to my LP pump. I have found a unit in the US made by Amperite but would like to source in UK if possible. Max 2 amp current prob less.
Im really missing something here with HP pumps being dry !!... what capacity is this header tank...and why does it not retain sufficient volume to both prime the HP pump and fuel rails up to the required, regulated pressure ? Are these issues due location/valving/design or air leaks/poss siphon??
Edited by 738 driver on Tuesday 6th September 09:36
738
To be honest all those things are possible except siphon although if non return valves in LP supplies are not sealing 100% simple drain back could be the culprit. My swirl pot is mounted high on bulkhead. Not clever with hindsight but seemed a great idea when retrofit of efi was being done.
To be honest all those things are possible except siphon although if non return valves in LP supplies are not sealing 100% simple drain back could be the culprit. My swirl pot is mounted high on bulkhead. Not clever with hindsight but seemed a great idea when retrofit of efi was being done.
MarkWebb said:
738
To be honest all those things are possible except siphon although if non return valves in LP supplies are not sealing 100% simple drain back could be the culprit. My swirl pot is mounted high on bulkhead. Not clever with hindsight but seemed a great idea when retrofit of efi was being done.
The height could be your problem.To be honest all those things are possible except siphon although if non return valves in LP supplies are not sealing 100% simple drain back could be the culprit. My swirl pot is mounted high on bulkhead. Not clever with hindsight but seemed a great idea when retrofit of efi was being done.
Any vapour will collect at the highest point in the system. That vapour, when it condenses, will suck in air from the vent pipe/overflow to the tank if the return does not go to the bottom of the tank.
The fuel system on my LS2 had the LP pump switched independantly and you energised it first then fired up the engine. This filled the swirl pot.
You could try fitting the pot lower down on a temp basis to see if this helps?
MarkWebb said:
Evidence of my fuel pressure gauge shows that especially when hot swirl pot empties completely. ie hp pump can be heard running but no pressure showing. causes the delay in hot start that you witnessed the other day I think.
As has been said I would start by putting a temporary supply to the pump which you can switch yourself from the cockpit to first prove your theory. Don't wire it direct to the ignition...going via the ECU is a safety feature so no pump is running if the engine is stopped.Put'12 volt timer module' into Google to bring up a number of UK options at around £20.
Steve
Movement of fluid through a system due to temp difference.... the warmest (especially if hot)fluid always makes it way to the highest point until it either cools at which point it sinks and is replaced by warmer stuff...or it evaporates/vapourizes, its a pretty constant cycle though rather than batched as described. Just the same as boiling water in a pan or kettle, the initial energy (heat) is at the bottom but the hottest water is always at the top.. The process of heating will not be stopped by simple valves....they conduct heat energy too as well as having some leakage. The process will pull fluids/ promote flow unassisted.
As in the other thread, the fuel cell (swirl, header or whatever you want it to be) which is supplying your HP pump needs to be as low in the Ultima engine bay as possible along with the HP pump. This gives benefits of always being in the loop for fuel flow (as opposed to vapour.. whether pressuruzed or thermo siphon condition) and always having lowest fuel temp in the particular loop when unpressurized.
You can do many things electronically and with complex systems but sorting the basics which will happen irrespective in an unpowered condition really should be the first considerations.
Its very hot under that clip, heat will always rise and build at the top, particularly in a stationary condition.
As in the other thread, the fuel cell (swirl, header or whatever you want it to be) which is supplying your HP pump needs to be as low in the Ultima engine bay as possible along with the HP pump. This gives benefits of always being in the loop for fuel flow (as opposed to vapour.. whether pressuruzed or thermo siphon condition) and always having lowest fuel temp in the particular loop when unpressurized.
You can do many things electronically and with complex systems but sorting the basics which will happen irrespective in an unpowered condition really should be the first considerations.
Its very hot under that clip, heat will always rise and build at the top, particularly in a stationary condition.
Edited by 738 driver on Tuesday 6th September 09:38
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