450 fuel pump issues

[torana68]

Hi All,
My 450 is happily puring along but it does not like starting sometimes, seems sometimes the fuel pump comes on with ignition sometimes not, when its a not the start up isn't good. Is this a relay issue or do I need to look at the thingy in the inlet? (you know, the thingy that turns the pump off  if the engine isn't running)
Roger

[koan]

My 450 is happily puring along but it does not like starting sometimes, seems sometimes the fuel pump comes on with ignition sometimes not, when its a not the start up isn't good. Is this a relay issue or do I need to look at the thingy in the inlet? (you know, the thingy that turns the pump off  if the engine isn't running)

The fuel pump should run only when the engine is running (doh!) or when cranking. When the ignition is first turned on.the pump shouldn't run.

Unplugging the safety switch connector from the inlet thingy will allow the pump to run when the ignition is on.

You could try priming the fuel system before starting by turning the key to start with transmission in R or D for a few seconds before a "proper" start. If the engine now starts reliably you may have a faulty fuel accumulator or one way flow valve.

koan

[OldMercs3]

The fuel pump should run only when the engine is running (doh!) or when cranking. When the ignition is first turned on.the pump shouldn't run.

Does this only apply to K-Jet cars?  The pump on my D-Jet car comes on for a short time when the ignition is turned on to pressurize the system (like any other EFI car).  Also, I thought I was having a cold start issue but (get this), I then tried pumping the pedal (as in a carbureted car) once while the ignition was on; this must've activated the cold start injector because I heard the pump hum a second time after which the engine started easily.  Pumping the pedal does not otherwise cause anything to happen unless the temps are cold.

[koan]

I was assuming K-Jet, sorry no idea about D-Jet.

koan

[john skene]

Believe it or not, but starting is sometimes related to the charge in the battery. Try slow charging your battery overnight and see what happens, it may surprise you.

[oscar]

The fuel pump should run only when the engine is running (doh!) or when cranking. When the ignition is first turned on.the pump shouldn't run.

Does this only apply to K-Jet cars?  The pump on my D-Jet car comes on for a short time when the ignition is turned on to pressurize the system (like any other EFI car).  Also, I thought I was having a cold start issue but (get this), I then tried pumping the pedal (as in a carbureted car) once while the ignition was on; this must've activated the cold start injector because I heard the pump hum a second time after which the engine started easily.  Pumping the pedal does not otherwise cause anything to happen unless the temps are cold.

OldMercs,

I just tried the same thing on my d-jet 350 - didn't do the same thing.  The pump should come on as you say as far as pressurizing the system.  The cold start injector only comes on when you turn the key to activate the starter.  Once the key returns to the II position, ie the engine running, the cold start injector is shut off.

As to how you got the pump to work twice without starting the engine, no idea.  If I speculate, maybe the fuel dampener or regulator needs adjustment or replacement but I wouldn't touch em without the ability to properly measure the pressure.

Sorry torana, no ideas from me.

[torana68]

Thanks all, Yep its K jet, went out just now, took the aircleaner off, depressed the air flap, no fuel pressure at all, ignition on pump started and continued for 10 seconds maybe then shut off, depressed the air flap, pump relay clicked but I couldn't hear the pump but I had fuel flow. Relay seems to click on and off ok with the movement of the air flap, not sure why it sometimes comes on with the ignition only? and should I have fuel pressure from cold? if not where is the bit I need to look at? thanks
Roger
(been cold here -5 in the mornings snow on the mountaims around us)

[koan]

should I have fuel pressure from cold? if not where is the bit I need to look at?

Yes, the idea is that the fuel accumulator maintains fuel pressure when the engine is off, but if any of the up front components are leaking internally (or externally!) fuel pressure will drop off while not running.

koan

[torana68]

Ok, latest is , changed the pump relay, pump no longer come on when it shouldnt,  so where is the accumulator located?
Roger

[koan]

so where is the accumulator located?

Down the back with the fuel pump and filter.

koan

[torana68]

thanks, I have spares so Ill do a swap when I can for a known good one and see how things go.
Roger