fuel tank levels VERY different

[stevehotshot]

Hi everyone, i'm doing swap of intank components today, rain stopped play temporarily....i removed both units and there's plenty of fuel in offside (half full) but NONE in filter side (nearside)?? is this a problem or will it rectify it self in use? i have tried to keep it low as i knew i'd be dismantling it anytime. however i thought i'd try unplugging pump connector and attaching it to the "new" unit to see if it moved the gauge with ignition on....NO! nothing happening, all connected up...nothing. so i removed original pump and did the same...no movement on fuel gauge...pumps did run for 2 seconds but stopped even though they weren't in fuel.....thought they'd just keep running.
also in pump side i found an orange clip!! on the floor of tank. this surely must have been dropped in there by someone thinking it fitted that side. so i've fitted it to the ingoing unit, which already had a self tapper in it, for same purpose.
incidently i couldn't fit it to the original filter housing as filter wasn't tight enough for the correct clip alignment, and i couldn't tighten it ant more, so opted for fitting the replacement unit. is it this that has caused empty nearside tank. car has been running well.
P.S. in my attempt at running fuel level at minimum, pending dismantling, i did actually run out of petrol once, and put around 3 gallon in before starting. it started straight away and no probs running since. perhaps nearside tank level has not recovered since then, about 70 miles to and from work.
sorry for long post but i like to give as much info as i think may be relevant to aid any reply....thanks.

[Jules]

Have you checked the large O ring seal in the filter housing

The fuel gauge doesn't respond instantly when playing around with float sensors.
There's some processing goes on in the IPK which is a bit a black art

[stevehotshot]

Thanks Jules, thought i'd acquired duff units for a minute then.. i have not separated either filter unit... as i'm fitting one that is closed tight with orange clip now fitted AND a self tapping screw which was already there, so i'm assuming, (dangerous i know), that it is ok. if there was any fault with O ring on old unit then everything should now be hunky dory.. i DO have a White clip and seals ready to fit should i need them, but thought i'd try and see how it goes with just swapping for unit, "in perfect working order" as they said..cost me £40 so we'll see.
i think someone has had filter apart previously and attempted to fit clip, failed because filter wasn't screwed tight enough and seat for clip is not in line. so they've put screw in. somehow clip had found its way into other side below pump...strange because it don't float!!??

[Jules]

Have to be very careful with self tappers.

If diameter is too large it will bow the outer body causing even a new O ring to leak and hence suck air in.

I've seen rusty wood screws in there and all sorts.
Don't ask me the proper size as I don't have that info to hand

[T-Cut]

Originally Posted by stevehotshot

- - - there's plenty of fuel in offside (half full) but NONE in filter side (nearside)?? is this a problem or will it rectify it self in use?

That's the result of FFS, not a dicky pump directly. The pump transfers juice to the filter module and part of that flow drives the balancing venturi to send excess fuel back to the pump side. It's part of the level balancing system. However, when FFS strikes, there's a pressure leak from the filter module which prevents both the engine and the venturi from running. The fuel leak fills up the left side as the right side empties. This can only happen if the pump is operable and delivering fuel. If the delivery pressure is low and there's FFS, the result is the same.

Also in pump side I found an orange clip!! on the floor of tank. This surely must have been dropped in there by someone thinking it fitted that side.

Seems so.

- - couldn't fit it to the original filter housing as filter wasn't tight enough for the correct clip alignment and I couldn't tighten it any more, - - -

Sounds like the wrong o-ring may have been used (too thick)

TC

[RPWC]

TC , is FFS fuel filter separation? My ITP died,and I had it renewed yesterday at Colin's (2 diesels) . I noticed there were two parts to the pump,and watched Col dismantle the old and fit parts to the new one, not a job I would have tackled myself,as didn't know what to do. What is FFS then?

[Jules]

Again I hate to preach but any O rings must be fitted with an O ring lubricant or silicone grease.

A brilliant product I've used for donkeys years is the Mintex brake grease called Ceratec

[T-Cut]

Originally Posted by RPWC

TC , is FFS fuel filter separation?

As good as. When I first coined the term, it meant Fuel Filter Syndrome to describe the condition caused by filter separation.

TC

[stevehotshot]

Hi all repliers, and thanks...,i have swapped both units now and i'm happy that i've painstakingly assembled it correctly..although i've not separated the filter module... i understand your explanation of the level balancing venturi, but my PUMP side has fuel in and the filter side NONE, engine runs fine, so i'm off to put enough fuel in to hopefully flow over centre, to left side and maybe it will somehow prime itself...it will be interesting to see reading on gauge as at the moment it still says "empty" although pump side is at least half full. i'm thinking there needs to be fuel in both sides to show anything on gauge....will report.

[T-Cut]

Originally Posted by stevehotshot

- - - I understand your explanation of the level balancing venturi, but my PUMP side has fuel in and the filter side NONE

Oh, that is what you said, sorry. It is rather odd. If the line to the engine was blocked, that would probably happen. The bulk of the pumped fuel would find its way back to the pump side, including the fuel that was originally in the filter side.

I'm thinking there needs to be fuel in both sides to show anything on gauge....will report.

No, the gauge is the sum of both levels, with the float rheostats in series. It sounds to me like there's something wrong with the floats/rheostats. Maybe whoever adventured in there before you didn't know their way around the system and snarled it up? Can you check the individual rheostat readings with an ohm meter?



TC