nyrobbie77

So I've got my replacement fuel pump and new seals installed and am in process of trying to get the sending unit back in the tank. After a few twists and contortions I've got the sending unit in, almost. I can't get it to set all the way down. Its sitting up about 2" from going all the way down. I am not sure if the bottom is binding in that cup - how hard do you have to press it to seat? Or I'm thinking that pickup tube is missing the hole and binding on that.

Everything seems lined up top side just is up a couple inches up.

Any tips or tricks to get it in the last lil bit?

I've watched a few of the videos on YouTube but they all skip the part of getting it settled in the tank.

Thanks in advance.

BrianC72gt

First off, I assume when you referred to "sending unit" you mean the fuel pump housing itself. The sending units are the part that sends a signal to the fuel gauge indicating how much fuel is in the tank.

When you had the fuel pump housing out of the tank you noticed on the side there's a sort of pickup tube. it's been a while, but I recall the way to install the entire fuel pump housing assembly is to rotate it in clockwise.

Here's the trick: don't lower it down more than you have to at any point until it is perfectly aligned with the cup in the tank then seat it straight down. Problems arise if you push down before rotating it fully into position. The cup in the tank has a female receiver for the suction probe on the side of the fuel pump assembly. If you push the assembly down before rotating it into position, it will end up beside the female pickup port rather than over the top of it. A prom date flashback might be in order: you can stick your male probe in the vicinity, but miss the hole. Line it up first before thrusting.

Also, the plastic cup inside the tank is not securely fastened to the tank, it has a little bit of wiggle room. The only thing holding it in position are a series of corrugated hoses that plug into it think of it as the body of a spider and the corrugated suction hoses that are secured by clips to the bottom of the tank like a spiders legs. When you bolt the pump in you are securing the fuel pump assembly to the cup.

It is possible to have the male suction port mis-aligned and still be able to bolt the two together.

The fuel pump is not in the very bottom of the tank, it relies on that suction port and the series of hoses, "spider legs", to pick up fuel from the bottom of the tank, and fill the cup into which the fuel pump is always submerged. If the male spigot is misaligned, the fuel pump will work fine provided you have more than half a tank of gas. However once the fuel level falls lower than the rim of the cup, the system relies upon the suction hoses to constantly fill the cup in which the fuel pump should be submerged.

Bottom line: rotate the pump assembly into position using the alignment marks before lowering it fully down. As you rotate clockwise in, you will have to lower it down, but at any point along that path you still have a little vertical room. Keep the assembly up as high as you can at every point while rotating it until the marks are aligned, then push it straight down to fully seat the male spigot into the female port inside the tank.

I also lubricated the big rubber ring lightly with a little WD-40, which made seating and securing it that much easier.

Have fun,

Brian C.

nyrobbie77

Thanks Brian. Yes I meant fuel pump housing. Back in my GM days they called it the sending unit as in fuel tank sending unit - sends fuel from the tank to the engine.

I'm aware of the pick up tube and the cup, both mentioned in my post. Right now the whole assembly is up about 2" or so from being fully seated with the unit aligned properly. I should have shown a picture of the gasket seated to show the gap. The picture above has the gasket up against the fuel pump assembly and not seated in the tank opening.

It seems to be binding on something and won't seat or it takes much more force than I'm comfortable with to get that pickup tube to seat in. Rotating the unit either direction doesn't allow the fuel pump housing to seat in any farther. The assembly isn't "cocked" either direction, alignment marks are on, it seems that it should just simply drop straight down from it's current location.

I think I'm going to have to find a endoscope to go in and see what it is binding on.

A 8

Getting it seated properly is a bit tricky, you need to get in the other opening and if you have a camera you can stick in there which will help. Don't remember the details now but once one can see it was straight forward, obviously it helps if the tank is empty.

nyrobbie77

So this is a pic without the gasket to show u how much more the assembly needs to go down. Right now the fuel level is just at the top of the cup that the assembly nests into and the assembly is just wet with fuel on the very bottom. That's telling me that the assembly is down to at least the top of the cup, it just won't go farther. Not sure if it is binding on the cup or the pickup tube. It must just be one of those things where it has to be dead nuts on or won't seat.

I've ordered one of those USB endoscope cameras. I'll use it to take a look from the other tank opening to try to see what is it binding on.

I took the old pump apart and as seen before the commutator has excessive wear. Outside of the pump has a marking of 02/01 not sure if that's the date or not. If so, 14 years is pretty good service.

BrianC72gt

yes, you do have to get it dead nuts on for it to seat . Sometimes the answer is simply remove and try again. I've done two of them on two different D2s but it's well over five years ago. The cup inside the tank has a little bit of wiggle room, so you're trying to mate up with a moving target. Granted the amount of movement is very small, but it does make things interesting. If you get them jammed together but not quite right, drop the loooooong bolt in and tap down on it lightly to push the cup down when you remove the pump assembly. The idea being you don't want to pull the cup out of position when removing the assembly.

Also, I'm not certain if you need to remove the fuel level sender from the unit entirely while installing. The sender looks like the center of a roll of paper towels in white plastic. Can't hurt to slide it out completely so that's one less thing in the way while you are rotating the assembly in and down. Are you following the Bentley installation process? Basically you rotate it in clockwise until the arrows line up then push it down the last inch or so as the suction port lines up.

nyrobbie77

It's in, it's in, it's in!! I gave it another whirl yesterday while I'm still waiting for the inspection camera that I bought online. I got it to the same point where it felt like it was binding and started tilting it a couple degrees each way. As I tilted it a couple degrees, while the unit was the same 1.5"-2" up from seated position and clocked to my alignment marks, I felt it suddenly fall in place with no resistance. It is definitely a dead nuts on fitment. Now that I've felt it go in, I'm sure I could do it over and over again. There's probably a double entendre there but we'll just leave it at that.

What also helped was not having the large o-ring at the top of the fuel pump assembly in place. I had previously tried having it seated on the tank and not the assembly but having it totally out of the way gave those few mm of room I needed. Once the assembly is lined up, you can still lift the assembly up enough to get the o-ring in place. I chose to seat it to the tank first rather than on the pump and try to squish it in place.

So - did I get everything lined up right? Well I think so. Seems my 3.5 y/o likes to play in the car and leave lights on. Battery was so flat no lights would even come on the dash. I did manage to try to jump it and get a few cranks in to check for leaks. Right now the fuel level is just barely filling the "cup" the fuel assembly rests in and after a few cranks a slightly loose banjo bolt revealed a leak. So that should indicate that the pump is pulling from the low areas of the tank. I will double check with the inspection camera when/if it ever arrives.

Some reason the battery did not like being drained. Comes up with an error when trying to charge. I had replaced it January 2014 with a Napa unit. I took it back this morning and they verified it's failing under load and provided a free replacement. So tonight, with the new pump installed, new fuel filter in place, and a new battery I'm hoping to bring it back to life.

Thanks all for your help. Along with the Youtube videos via Bob D and some of the hints and tricks provided here and the archives helped a ton.

nyrobbie77

Got the battery in last night and now everything lights up and engine cranks over as it should. Once the fuel lines finally filled back up with fuel the engine started but is acting the same way it was before I replaced the fuel pump. Fuel level was approx. 1/3 tank, engine starts but stumbles and shakes terribly. Any throttle input causes the engine to stall. After a few tries I could add throttle input very gently but engine never smooths out. No engine light is on. Same exact characteristics as before I replaced the pump. Pump is a OEM VDO/Siemens with all new gasket set; also installed a new fuel filter.

I then added 5 gallons of fuel and it starts right up and runs good. There seems to be a slight shake at idle, but nothing like before I added fuel.

I can't confirm I have the pickup tube aligned properly but everything did seem to slide right into place w/no binding. Plus, if I understand correctly, if it is misaligned, the pump will starve and will not run at all. Before replacing the pump I had the same exact conditions. I previously tested fuel pressure before replacing the pump and it was only reading 15 psi - added fuel and read 50 psi. I've had the car for 3.5 years and no one has touched the fuel pump while I had it and it still had all the oem clamps in place. Fuel pump assembly had date of 5/10/97 so I don't believe anyone has been in there before.

While the assembly was out of the tank I did peak in and all the hoses seem to be attached and I didn't see any cracks in the "cup" housing either. Could there possibly be a restriction in one of those lines allowing some fuel but not enough flow? Any risk if I were to blow out those lines with an air hose?

BrianC72gt

Have you scanned the car for any error codes? I had a spate of coil failures about 2 years back...still carry a spare i the trunk. It would start OK, but as soon as it heated up, ran like crap.

If you can find a fuel barb with the same thread as the banjo bolt, you can rig up a long cheap fuel hose...just fuel rated, won't be under pressure...into a BIG empty gas can. Then you pop the cover off the fuel pump relay under passenger's footwell, wedge it closed with a matchbook cover or folded up plastic gas line and cycle the pump on using the ignition switch.

You should be able to pump out the entire tank. When you refill the tank, the filler neck directs gas directly into the cup. Pump it all out. Pour in a gallon, and get nearly all of it back out? Good to go. None of this drive it around and hope it doesn't stall shop manual jiggery pokerey.

Any lube on the big rubber wedge gasket makes that puppy slide in and snug up like butta.