Thread: Fuel pump change in D2a,,, with gas.

The first D2 I fitted with a rear corner tank had a very loud pump. I believe it's the noise of the relief valve operating in the pump housing. It's really bad when the pump is in a tin tank screwed to the floor. I ended up running an injector cut relay on the fuel pump relay actuating wire, easily accessible under the engine bay fuse box. The injector cut relay was wired up so whenever the gas was switched on and the injector signals were present the fuel pump was cut after 3 seconds. On overrun the injector signals cut off and the pump comes on for a short time. This way the pump runs occasionally keeping the pressure up for instant changeover.

I don't know exactly what your new pump was doing but a rail pressure test would be my first port of call. The relief valve setting might be too high? Also a piece of neoprene sponge rubber glued under the swirl pot helps to quiet down a pump.

BTW I believe the pump assembly is shared with the P38 with some different outlets according to model, replacements housings are probably mulitfit.

4 outlets = Td5 fuel pump ..... yes/no ?

Scared the crap out of me when I opened it Kev,,
but this unit is for both fuels,,,
according to Paddocks

hmm, looks like thew Great Database Crash of '11 took out a few posts,,

just to catch up---

Yes Fluids, it was the wrong pump, Paddocks sent the correct one that day and we fitted it on the weekend.
went like clockwork.

car still not starting properly.

so the pump and pressure relief valve can be ruled out. RAVE says the pump runs continuously while the ignition is switched to II, but if the starter is not engaged will switch off after 30 secs, I thought initially this might be the reason for the early failure, pump continually running (and just butting its head up against a very small metal wall,) even when the cars on Gas,, but the pump has a return to the swirl pot (actually in the pump housing) so its still pumps,, just in circles.

so it still appears to be draining fuel back into the tank over night, theres a lot of air/vapour control stuff in the V8 tank, but most of its designed to pressurize the tank,, so that sort of rules out suction,,
if the inline schrader valve was leaking air,, would'nt it leak fuel? any in-line fuel leak would make itself known with 50lb of pressure in the line.
I am running under the assumption if there was a leak I would have a fuel smell at some stage.

sigh,
Mrs Pedro is wanting another fire sale,,

on the remote hope someone is interested,,

I went to fill up the fuel tank today and upon undoing the fuel cap (and hearing the normal exhale of air pressure) a loud metal pop was heard--
just like a metal tank poping back into shape--
which reminds me of two occasions, both just after reinstallation of the unleaded tank, when driving along a thunk was heard and FELT through the car,, was sufficient for Mrs Pedro to comment on it.

obviously theres something blocked somewhere,,
but if the tank is under pressure, why does the fuel return?

Originally Posted by Pedro_The_Swift

on the remote hope someone is interested,,

I went to fill up the fuel tank today and upon undoing the fuel cap (and hearing the normal exhale of air pressure) a loud metal pop was heard--
just like a metal tank poping back into shape--
which reminds me of two occasions, both just after reinstallation of the unleaded tank, when driving along a thunk was heard and FELT through the car,, was sufficient for Mrs Pedro to comment on it.

obviously theres something blocked somewhere,,
but if the tank is under pressure, why does the fuel return?

The fuel tank breather cap holds a bit of pressure in the tank. If the tank has a flat side with a bit of welding distortion it will pop like that. Nothing much you can do other than to work out which panel it is and boof it from inside the tank one day.

I'm not sure what you mean, fuel return. Isn't this a single pipe-to-engine jobbie? Fuel is pumped to engine, engine uses some, pressure relief and return is entirely within the pump assembly. The pump just builds up a pressure above the vent pressure in the tank.

Originally Posted by Pedro_The_Swift

on the remote hope someone is interested,,

I went to fill up the fuel tank today and upon undoing the fuel cap (and hearing the normal exhale of air pressure) a loud metal pop was heard--
just like a metal tank poping back into shape--
which reminds me of two occasions, both just after reinstallation of the unleaded tank, when driving along a thunk was heard and FELT through the car,, was sufficient for Mrs Pedro to comment on it.

obviously theres something blocked somewhere,,
but if the tank is under pressure, why does the fuel return?

How about this ... when you stop the car and leave it overnight, that tank (with its "popped" side), is under pressure, but as the ambient temp drops, so too does the vapour temp of the gas pressurizing the tank ... and that causes the vapour to shrink, thus reducing the tanks pressure ... so when you let out the last bit of pressure opening the tank the wall pops back .... or, the vapour can cool sufficiently to cause a vacum in the tank. The fuel system is now trying to stop air getting in, not stop fuel getting out .... ????

I have 2x big 60L wheeled fuel transporters at work (they have a plastic hose and a trigger gun/hand pump + a stop cock on the hose outlet which is always closed), like giant outboard tanks. These can be puffed out like a puffer fish late afternoon, and when you come in early morning they are sucked in and anorexic.

... a schrader valve is meant to seal under pressure ... not vacum. I have no idea how much vacum a schrader valve will hold, if at all. The valve seat faces the wrong way.

Maybe the tank is under vacum when you go to start it and the fuel pump doesn't boost the pressure enough ... would be a pretty big vacum though. Vent the tank 1st thing in the morning before you start it ... under pressure or vacum ?

Just a thought.

Originally Posted by bee utey

I'm not sure what you mean, fuel return. Isn't this a single pipe-to-engine jobbie? Fuel is pumped to engine, engine uses some, pressure relief and return is entirely within the pump assembly. The pump just builds up a pressure above the vent pressure in the tank.

Yep single line, so fuel, if returning, has to come back through the pump line. I think the chances of BOTH pressure relif valves failing is remote.

Originally Posted by Fluids

How about this ... when you stop the car and leave it overnight, that tank (with its "popped" side), is under pressure, but as the ambient temp drops, so too does the vapour temp of the gas pressurizing the tank ... and that causes the vapour to shrink, thus reducing the tanks pressure ... so when you let out the last bit of pressure opening the tank the wall pops back .... or, the vapour can cool sufficiently to cause a vacum in the tank. The fuel system is now trying to stop air getting in, not stop fuel getting out .... ????

Originally Posted by Fluids

Maybe the tank is under vacum when you go to start it and the fuel pump doesn't boost the pressure enough ... would be a pretty big vacum though. Vent the tank 1st thing in the morning before you start it ... under pressure or vacum ?

Just a thought.

a good thought though,,
and the corresponding thought is to release it at switch off.

will try both,,

and try and figure out what the results mean


oh,, and all this popping and non-starting started on the very first zero degree morning---
the previous 12 months, no signs.