efi fuel pump

toughy V8 · Post by **toughy V8** » Wed Mar 28, 2007 6:43 pm

what pressure fuel pump do i need to run flapper efi, ive fitted an inline 3 bar bosch pump from a nova sri but it still wont start

Post by **Coops** » Wed Mar 28, 2007 7:41 pm

when you turn the ignition on and off does the pump buzz?? also when you turn ignition off (turn pump off) is there pressure in the fuel line still?
have you got the pump on the pressure line and not return? pipe that comes from the fuel rail via the pressure reg is the return just in case you were not sure.

toughy V8 · Post by **toughy V8** » Wed Mar 28, 2007 7:56 pm

the pump is working off the ecu, but shouldnt it stop once its up to pressure, then start again when you crank it over?

Post by **Coops** » Wed Mar 28, 2007 8:06 pm

no with the ignition in the on position it will run for a few seconds then stop,
BUT when the engine is running it will run constant and any excess fuel is returned to the tank via the fuel reg and return fuel line

toughy V8 · Post by **toughy V8** » Wed Mar 28, 2007 8:17 pm

when the ignition is on my pump is constantly running. does the flapper have this feature

Post by **Coops** » Wed Mar 28, 2007 8:26 pm

it should stop,
the flapper in the air flow meter aint stuck open a bit has it?

ramon alban · Post by **ramon alban** » Wed Mar 28, 2007 10:58 pm

toughy V8 wrote:what pressure fuel pump do i need to run flapper efi, ive fitted an inline 3 bar bosch pump from a nova sri but it still wont start

Toughy, The fuel pump in the feed line to the system only runs continuously when "cranking" or "engine running", and has to maintain a pressure of 36 psi minimum, generally it should be capable of going to 50 psi.

The pressure in the fuel rail will be in the range 26 to 36 psi depending upon the action of the fuel pressure regulator and how it reacts to manifold vacuum. The excess fuel is recirculated to the tank.

The reasons it wont start are probably due to wiring errors rather than component failure, and given the nature of your recent problems as posted on the forum, you probably need to check all the wiring of your Efi system according to the circuits previously mentioned but still available here:

http://www.vintagemodelairplane.com/pag ... uit01.html

The main components enabling the fuel pump to run are, ECU, Air flow meter internal FP switch, steering module (diodes), fuel pump relay and ignition switch, inline fuse and fuel pump itself.

Failure in any one of those may kill the pump.

In desperation you could bypass all these components and run a fused 12 volt feed to the pump and if it runs, try to start the engine. At least you will get to see an engine running result. The circuit diagram will help you follow my suggestions.

I am aware that you are not dealing with an SD1 sytem therfor my circuits will be of limited assistance, but the basics between RR and SD1 are pretty much the same.

hearbear · Post by **hearbear** » Thu Mar 29, 2007 2:53 pm

Might be stupid but is the pump in the right way and not trying to pump to tank

George

toughy V8 · Post by **toughy V8** » Thu Mar 29, 2007 6:55 pm

the pump is constantly running when wired to the ecu, i have a spark now, im getting 0.27-0.30v at the injectors,does that sound right?

hearbear · Post by **hearbear** » Thu Mar 29, 2007 7:37 pm

Looking at the wiring diagram posted you need to see if you have a feed on pin 20 on ecu this should be live for 2 secs when ignition turned on then drops of. if this happens the fuel relay may be stuck closed causing a feed all the time pull the relay and see if pump cuts out , if still running a short in fuel pump wiring. If it cuts out check the wire connections to the relay terminals 85 and 86 should both be dead one will only come live when ign turned on for the 2 secs.

Hope this helps George

toughy V8 · Post by **toughy V8** » Fri Mar 30, 2007 6:26 pm

it seems now that i have positive power to both terminals on the injectors but when i crank they both stay positive, ive tried another ecu to no avail

ramon alban · Post by **ramon alban** » Fri Mar 30, 2007 10:23 pm

toughy V8 wrote:it seems now that i have positive power to both terminals on the injectors but when i crank they both stay positive, ive tried another ecu to no avail

The ECU side of the injectors are only grounded for approx 10 milliseconds every other cycle so you will always see a positive voltage at both sides of the injectors with a regular voltmeter.

To observe what is happening one would need an oscilloscope on the injectors. Not normally within the ability of most of us.

GreenV8S · Post by **GreenV8S** » Sat Mar 31, 2007 12:23 pm

ramon alban wrote:To observe what is happening one would need an oscilloscope on the injectors. Not normally within the ability of most of us.

If you put a 12v LED in parallel with the injector, it responds quickly enough to be visible when the injector fires. At cranking speeds you can see the individual pulses, and when the engine is running you can still get a good indication of the injector duty cycle by the brightness.

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