any advise on changing

I am going to try replacing my in tank pump on a 89 740. Any advise
and should I change the sock screen ? Do you access thru the trunk?

 

RUN! RUN! RUN! Run away man, are you mad?

I hope this is not a joke because I just spent a week taking mine
apart about 5 times.

What do you want to know?

1st question: Why are you doing this?
2nd question: what are you replacing it with?
3rd question: yes, replace the sock filter

Answer these questions and I'll tell you everything you need to know
to save you from a miserable experience.

Jamie

 

OK, couple things here:
Start with the main fuel pump. Check the wiring there, often times the
connections to the pump go bare. Make sure this pump is working. Just
'bump' the key each time, meaning, don't let the engine crank more
than one or two times. Just bumping the key will work the pump to
prime the line and you'll get a start. You'll hear the pump whine a
couple seconds after bumping the key.

If you can't hear the main pump, or think it doesn't work, you'll have
to drop the pump assembly to bench test. Here is what I did. I did
not know how to "jump" the fuses to fire the pump - so I pulled it
out.

1- Disconnect negative battery cable
2- Disconnect the fuel line to the pump. Phillips screw driver.
3- Disconnect the pump wiring.
4- Take a box or something and when you unbolt the 3 12mm screws
holding the rack, it can rest on the box while you undo the last line.
THIS LINE HAS PRESSURE AND SHOULD SPRAY GAS.
5- I use an impact wrench to CAREFULLY loosen the bolt. I only BUMP
the bolt about 1 SECOND and get the drill away in case of spark. I've
done this a dozen times - no problems.
6- After the spray stops, use your hand to unscrew the bolt. Remove
the assembly.

You can now bench test the pump or replace if necessary. I grabbed a
replacement pump for $35 at the junkyard. Look for the OEM style with
clip on connectors. The bolt on style might be another year or
aftermarket.

If you insist on removing the in-tank assembly, I'll tell you how.
first, I highly recommend you try jumping wires to see if the pump is
working.

Your car should start and idle well even with the in tank assembly
disconnected.

Jamie

 

http://brickboard.com/FAQ/700-900/FuelSystem.htm#FuelPumpandSenderReplacement

 

The car has 245,000 miles and don't think it has been changed. I am
having starting problems and stalling. Was thinking of changing both
pumps and the relay. I have an aftermarket pump that says it will fit
my car and some others like Audi etc.

 

Just be sure you replace the main pump (if it's failed/failing) and
the main filter. If you can get the car running, remove the gas cap
and put your ear beside the opening. if you can hear the in-tank pump
running - i'd leave the in-tank assembly alone.

It's just a job that becomes a pain in the butt the first time. It's
tight working space and the first time is VERY awkward.

If you get into it, remember 3 key tips, besides the obvious: FIRE.

Tip 1: Remove the large gas filler hose from the sending unit and
crawl under the car. Shove a short stick from the ground, up into this
hose. It will keep it face down and out of your way. You must get this
hose away to remove the assembly.

Tip 2: The rubber seal around the tank unit will come out around the
assembly. When you put the assembly back in the tank - put the large
rubber seal on the TANK opening and NOT the assembly. With the rubber
seal inside the tank opening, smear the assembly with vaseline
(petroleum jelly) to ease it back in.

Tip 3: mark how the assembly fits in the tank. The intake of the pump
needs to be all the way at the bottom of the tank to be accurate. This
puts the vent tube at 12 O'clock. But, I had to insert the assembly in
at an angle, then rotate the thing clockwise to position it right.

Like I said, I can give you step by step instructions - but when
you're crammed in a trunk, not much space for your hands, breathing
gas, fighting hoses in the way, one hand on the assembly and the other
trying to keep the tank seal straight -- it QUICKLY becomes a
nightmare.

Jamie