HELP! Fuel pump differences - pics!

This site contains affiliate links for which LandyZone may be compensated if you make a purchase.
MikeV8SE

MikeV8SE

New Member
Posts
1,771
Location
Bucks
OK, I'm currently replacing the fuel pump and sender unit (one piece) on my 1991 3.9 V8. The pump worked fine, but the sender didn't appear to be (fuel gauge doesnt work).

Whilst removing the original unit the metal pipes on top have twisted, so that's buggered. However, having removed the original pump from the tank, it looks a bit different from the replacement unit! The replacement is on the left, the original on the right.

photo-1.jpg

photo2.jpg


On the original pump (on the right) there's a black box with brass cap on the pipe, which itself is thicker. The other, thinner pipe (I assume the return) also twists rather than being straight. So, 2 questions:

1. What is the extra block on the fuel pipe for?
2. Will the new unit, which is idential in every other respect, work?

Cheers!
 
OK, managed to fit the nrew pump and sender unit, BUT the fuel gauge only moves a bit - just off empty, red light still on. So, I went and put another £20 of unleaded in it...same thing! Still the same reading!

So, the fuel gauge is now moving off empty, but still not giving a true reading. Any ideas?
 
MikeV8SE said:
OK, managed to fit the nrew pump and sender unit, BUT the fuel gauge only moves a bit - just off empty, red light still on. So, I went and put another £20 of unleaded in it...same thing! Still the same reading!

So, the fuel gauge is now moving off empty, but still not giving a true reading. Any ideas?
Click to expand...

You did not bend the float arm when you fitted the pump by any chance did you.
 
MikeV8SE said:
Nope, was very careful not to bend it!
Click to expand...

Don't know then really. You should have connected fuel gauge wires and moved it through it's range when pump was out to see what you got. It does not have one of those volt regulating devices on the back of the clocks does it. It's like a little oblong box with a tag on one end to screw it down and a couple of lucar connectors. Regulates voltage for gauges. Don't know much about classic but just a thought.
 
I'll be honest, the battery was disconnected until I had it all plumbed back in, so didn't test it out! However, moving the float arm up and down before fitting, you could here the connectors making contact, something you couldn't with the original. Also, I checked it moved freely up and down the scale, which it did.

No idea what a voltage regulating device is (can take a guess!) or looks like, but will go poke around behind the dash clocks tomorrow, see if it helps!

Cheers for your help.
 
OK, havent had a chance to do any more investigative work to the gauge and why it only reads a little bit off empty, but anyone know what the difference between the two pump & sender units pictured above is?
 
Hi Kev,

I think the earlier models had a steel tank and later (post-1990?) models had a larger plastic tank - I believe the replacement pump came from a 1991 vehicle also, but can't be sure! Also no idea if mine was original, although looking at the corrosion on the top of it, I would guess it was.

Seems to work OK - drives fine so that's good. But fuel gauge still isn't reading correctly, although it does not at least move! Looks like I'll have to have it out AGAIN this weekend, although am going to try wammers' suggestion of checking behind the clocks first - but I'm guessing this will be OK as the gauge does now move, just not a lot!!
 
MikeV8SE said:
Hi Kev,

I think the earlier models had a steel tank and later (post-1990?) models had a larger plastic tank - I believe the replacement pump came from a 1991 vehicle also, but can't be sure! Also no idea if mine was original, although looking at the corrosion on the top of it, I would guess it was.

Seems to work OK - drives fine so that's good. But fuel gauge still isn't reading correctly, although it does not at least move! Looks like I'll have to have it out AGAIN this weekend, although am going to try wammers' suggestion of checking behind the clocks first - but I'm guessing this will be OK as the gauge does now move, just not a lot!!
Click to expand...

You most likely have the wrong pump and sender. The little volt regulator was used to reduce voltage to 9 volts for various gauges. If it failed you got silly readings. It was just a thought. Think the steel tank was replaced in late 90 early 91.
 
Aaah I see, thanks for clarifying! So some pumps ran on 12V and others 9V? Or are they all 12V but the guage takes a reading from either 12V or 9V depending on year?

My car is a 1991 with a plastic tank - I thought prior to that the sender unit was seperate and on the side of the tank, and when they changed to plastic tanks they made the pump and sender all one unit, and introduced the "inspection hatch" in the boot floor? Could be wrong...!
 
MikeV8SE said:
Aaah I see, thanks for clarifying! So some pumps ran on 12V and others 9V? Or are they all 12V but the guage takes a reading from either 12V or 9V depending on year?

My car is a 1991 with a plastic tank - I thought prior to that the sender unit was seperate and on the side of the tank, and when they changed to plastic tanks they made the pump and sender all one unit, and introduced the "inspection hatch" in the boot floor? Could be wrong...!
Click to expand...

No not the pumps the gauges. The pumps all use 12 volts the gauges on some vehicle used a lower voltage. Don't know about the classic but just maybe. You are correct about tank change.
 
OK, cheers! So how do I find out if my gauge is 9V or 12V? Sorry, car electrics are really not my strong point - I'm better with nuts and bolts, hammers!

So the pump I've fitted must have come out of a post-1990/1 car then, but I still don't know what the extra parts on the (original?) pump that I took out are for?!
 
MikeV8SE said:
OK, cheers! So how do I find out if my gauge is 9V or 12V? Sorry, car electrics are really not my strong point - I'm better with nuts and bolts, hammers!

So the pump I've fitted must have come out of a post-1990/1 car then, but I still don't know what the extra parts on the (original?) pump that I took out are for?!
Click to expand...

You will have to look at back of clocks for little regulator. It is a little alloy oblong box about 25mm long 15mm high and 15mm wide. With a couple of Lucar connectors on it. Held down by a screw through a tab on one end. Don't even know if it will have one. But many makes of vehicle from seventies to early nineties had them. It regulated voltage for the instruments to eliminate fluctuations which gave wrong readings. Can you not get a copy of RAVE for the Classic?
 
Oh, will have to get a copy of that then I guess! Got a Haynes manual? But then that said the sender unit was on the side of the tank!!
 
You need to check your VIN then look for the right pump. Check out fuel pumps at Rimmer Bros or FamousFour, I'll bet yours is the more expensive unit for vin pre-KA642684 I know mine is because like you mine is a '91 Classic, VIN starts HA and about this time there were a number of changes for example, mine has ABS but the front axle is definately the same as a 1990 model - go figure!!
 
You must log in or register to reply here.

Similar threads

doodle bug
Fuel pump woes
Replies
17
Views
1K
doodle bug
doodle bug
jimmacD
P38 Diesel intank sender...... pump only?
Replies
7
Views
733
Alexander V
Alexander V
A
1984 109 FFR 24v oil temp gauge issues
Replies
1
Views
469
layfin
L
G
Diesel fuel pipes ?
Replies
16
Views
889
grewth
G
Montyjohn
P38A Adding a valve to manually fill EAS tank and why did my pump fail again?
Replies
14
Views
1K
Datatek
Datatek
Back
Top