Fuel pump revisited

Fri Jan 21, 2011 6:01 pm

After a Christmas lay-off I'm resuming trying to resolve the various issues on my '87 cab!

First up is trying to work out what's going on with my fuel pumps. The car starts and runs fine, but with a buzzing from the external pump. I am now trying to ascertain if this is because THIS pump is on the way out, or the in-tank one is. When I unplug the two-pin connector from the in-tank pump the car starts and runs normally, and there's no sign of any vibration or noise from the in-tank pump with the engine running, back seat squab out and inspection cover off so I suspect this is the culprit (assuming there should be noticeable vibration or noise). However, to eliminate all possibilities does the relay next to the fusebox cover both pumps in a two-pump set up (i.e if it was dead would both pumps fail)? I guess the other possibility is that there's no electrical supply to the pump (need to borrow a multimeter!) or that the in-tank pump has been bypassed in some way, but I'm not sure how to tell that this is the case.

All help and advice gratefully received...!

Cheers,

Tim

Fri Jan 21, 2011 7:12 pm

The two pumps share the same supply and earth connection.
Disconnect a wire from the high pressure pump and short 30 to 87 on the pump relay.
If fuel is still pumped from the fuel supply line at the engine (at much reduced pressure), then the in tank pump is running.

Fri Jan 21, 2011 11:03 pm

So, to confirm for a novice:

Disconnect either wire from the external pump to disable it
Remove fuel pump relay
Link holes corresponding to pins 30 and 87 together (via bent paper clip for example?)

Stupid questions perhaps, and I know I'm going to feel very daft very soon, but should ignition be on, and how will I know fuel is being pumped at the engine?

Cheers,

Tim

Fri Jan 21, 2011 11:50 pm

Ignition not on.
Remove the fuel pipe that goes directly to the fuel rail, not the one that goes to the pressure regulator, and hold it over a pot to catch the fuel.
Smoking not recommended.

Sat Jan 22, 2011 12:20 am

Thanks for more great advice Brian. Just got to pluck up the courage to start messing with fuel now!

Sun Jan 23, 2011 12:57 am

Presumably before doing all this I should run the engine then remove the relay with engine running to de-pressurise the system?

Sun Jan 23, 2011 9:46 am

twindad65 wrote:Presumably before doing all this I should run the engine then remove the relay with engine running to de-pressurise the system?

Always a good idea!

Wed Mar 23, 2011 9:41 pm

Finally got round to doing the above today: no fuel whatsoever emerged from the disconnected fuel pipe at the windscreen end of the fuel rail. There is power to the pump at the two pin plug, so presumably (and predictably) the in-tank pump is knackered.

Thanks as ever for the great advice: now need to find a replacement pump!

Tim