could not stop engine after taking out fuel pump fuse

Hi,

My car is Volvo 1988 240 GL sedan model.

I encountered an strange problem when trying to inspect an in-tank fuel
pump problem.

Basically according to the "Hayne's Manual" I need to start the engine,
pull out the fuel pump fuses, wait for the engine to stall and proceed
to the remaining procedures (disconnect the cable, take out the fuel
filler cap etc) to release the fuel pressure.

But after I took out the No 4 (in-tank pump fuse) and No 6 (main fuel
pump fuse) which listed in my car's manual, the engine can still be
started and continued to run without stall. I even took out all the
remaining 16 fuse in the fuse panel, the engine still could not stop.
And I checked other comonents such as horn, lights, they were
disconnected as normal.

I don't know how to proceed my checking of the faulty in-tank fuel
pump. Any suggestions will be greatly appreciated.

Thanks very much.

Regards

Martin

 

For my '82 Turbo, other numbers are designated, IIRC: #5 and 7.

Check again.

 

If he took them all out, and it still kept running, then someone has
modified the wiring, and nobody is going to be able to help without
having the car in front of them.

These things are fused for a reason, I'd get this issue fixed soon.

--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

Hi, All,

Thanks very much for the suggestions.

In order to check the in-tank fuel pump, the fuel system needs to be
de-pressured. Are there other ways to achieve this goal other than
taking out
the fuse and let the engine stall? What is the purpose of doing this
when
the negative cable that connects to the battery will be disconnected
anyway?

These are the steps to de-pressure the fuel system that mentioned in
the
Hayne's manual:
- take out the fuel pump fuse and let the engine to stall (the step
that I
failed to do and could not proceed)
- take out the fuel filler cap
- disconnect the negative cable connect to the battery.

Thanks

Regards

Martin

 

Depressurizing ends the possibility of gas bursting out into your face
at the point where you first crack open the fuel system.

All you need to do, really, is open a fuel line somewhere, let the
pressure escape, and you're good to go.

Oh yeah, disconnecting the battery cable ends the possibility of an
electrical spark causing your open fuel system to burst into flames.

 

Hi,

Thanks very much for the information. I will check it out.

By the way, I am still not 100% sure about the steps mentioned in the
Hayne's manual, just to wonder that:

The second step mentioned in the Hayne's Manual which is "take out the
fuel filler cap", will that do the job of depressurize the fuel
system?

And what is the purpose to let the engine to stall after taking out the
fuel pump fuse?

Thanks.

Regards

Martin

 

If the O2 sensor heater circuit is on when you pull the #4 fuse there is
an alternate feed path available via the control unit that will allow
the pumps to continue to run.

If you open a line in the engine compartment to relieve stored line
pressure do so gently and catch the outflow with a rag to reduce the
amount of spillage into the engine area. There are lots of things that
make sparks when you start an engine.

Since the fuel tank is part of a sealed vapor recovery system, returning
warmed overflow fuel from the engine compartment (fuel rail) will cause
a change in the vapor partial pressure on the fuel head in the tank. In
hot weather there will be a noticeable hiss when you open the fuel
filler cap as the vapor pressure is released. That one or two psi over
the surface of the remaining fuel will push fuel through any line that
is open. So to keep fuel from draining, particularly when changing a
fuel filter it is prudent and less messy to relieve any pressure on the
tank.

Bob

 

Another possibility is that the fuse panel is wrong. On the earlier
versions fuses 6-10 were bussed together and fed by the red wire supply.

Bob