Sebastian
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| posted on 7/12/08 at 02:56 PM |
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Wrong Fuel Pressure??????
Well the problem with the blue injectors is solved, but now i think i have a problem with the fuel pressure, the thing is when i want to start the
engine it does everything accept run but when i help it with a bit of breakcleaner it runs perfect and steady on idle speed ( a bit to slow 800rpm )
but it runs and keeps running but when i push the throttle slightly it stalls and won't start on his own.
I have an electric fuelpump from an old BMW so are you guys with me on the conclusion that it doesn't produces enough pressure or is there
something else to check.
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Mark G
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| posted on 7/12/08 at 03:03 PM |
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depending on if you're using carbs or injectors you need to look at if the cylinder is getting enough fuel before you go for pressure.
Brake cleaner is as good as easy start so you can run an engine on that stuff without any fuel if you wanted to.
If injection, are the injectors wired in the right order? has the engine run before or is this the first start attempt?
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mark chandler
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| posted on 7/12/08 at 03:14 PM |
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Pressure is controlled by the regulator at the end of the fuel rail, not the pump.
So if you pull off the return pipe back to the tank if its squirting out fuel then the pump is able to overcome the regulator this so is okay (for
idle at least).
Lets assume that the pump is good but the regulator is just spilling fuel back to the tank so not holding pressure (it passes the test above), clamp
the fuel return the pressure will then leap to the pumps maximum capabilty ~ 4bar on the fuel rail and the car will run very rich but rev up okay.
If you have the fuel pipes on the wrong way, ie pump to regulator to fuel rail then it will probally just about idle but know more, so this is
possibly the suspect here if all was good when stripped so check and if unsure swap them over and try.
Regards Mark
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mark chandler
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| posted on 7/12/08 at 03:15 PM |
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Pressure is controlled by the regulator at the end of the fuel rail, not the pump.
So if you pull off the return pipe back to the tank if its squirting out fuel then the pump is able to overcome the regulator this so is okay (for
idle at least).
Lets assume that the pump is good but the regulator is just spilling fuel back to the tank so not holding pressure (it passes the test above), clamp
the fuel return the pressure will then leap to the pumps maximum capabilty ~ 4bar on the fuel rail and the car will run very rich but rev up okay.
If you have the fuel pipes on the wrong way, ie pump to regulator to fuel rail then it will probally just about idle but know more, so this is
possibly the suspect here if all was good when stripped so check and if unsure swap them over and try.
Regards Mark
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Sebastian
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| posted on 7/12/08 at 03:35 PM |
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This is the order i fitted it:
Fuelpump - Regulator - Pressuregauge - Fuelrail - Returnpipe.
This is the first attempt to start it, howeve this Dunnell injection system came of a 2.0 Zetec silvertop (as i have) and always worked perfect.
However the gauge is giving me a reading of 1 bar and when i clamp the resturnpipe it goes to at least 3 bar but this doesn't help.
Injectors are wired up a they should be, i have the pictures from a similar system, unless the cilinder at the front of the engine isn't number
1.
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matt_claydon
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| posted on 7/12/08 at 06:14 PM |
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quote:
Originally posted by Sebastian
This is the order i fitted it:
Fuelpump - Regulator - Pressuregauge - Fuelrail - Returnpipe.
This is the wrong way round. The regulator should be in the return line, after the fuel has been through the rail.
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Sebastian
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| posted on 7/12/08 at 08:00 PM |
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Oh no 
OK that is definitly wrong, so the fuel should always go through the fuelrail beginning at cilinder 1 then to the regulator and return to the tank.
I will make it right tomorrow and keep you posted.
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DIY Si
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| posted on 7/12/08 at 09:39 PM |
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Try and think of it like this:
The injectors sit in/on a common fuel rail, which has to be pressurised for them the injectors to work. The pump gives this pressure and as such needs
nothing between it and the rail, and then the regulator is there merely to bleed off the excess.
“Let your plans be dark and as impenetratable as night, and when you move, fall like a thunderbolt.”
Sun Tzu, The Art of War
My new blog: http://spritecave.blogspot.co.uk/
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