Author Topic: Lift pump opinions (Read 15017 times)

MikkiJayne · « **on:** November 09, 2007, 12:21:40 pm »

Hi all,

I'm putting a 1Z TDI in my Corrado this weekend and I'd like some opinions on my fuel tank options please

1, The Corrado tank has a low pressure gas lift pump
2, I have a mk3 Golf GTI tank, which has a high pressure gas pump
3, I also have a mk3 Golf TDI tank sender unit with no pump which will fit the GTI tank

Now I have to remove the tank whatever happens since the breather is blocked and it won't fill properly, so any of the above options is equally valid as the others.

Also I'm not leaving this at 90bhp :wink: I'm building a 200bhp AHU to go in the car eventually, so I'm looking for my best long term option. I've heard that the top end is better with a lift pump, hence my query.

All opinions welcome

Mikki x

RabbitGTDguy · « **Reply #1 on:** November 09, 2007, 03:55:33 pm »

The low pressure pump could act as a feed pump for now, pulling directly from the tank. It'd work nicely for this purpose as long as it is in good condition.

If needed...another low pressure pump could be installed at a later date inline somewhere in between the tank and pump to further "assist" the pulling of fuel.

So...I'd just use the in tank 'rado one for now.

Joe

jtanguay · « **Reply #2 on:** November 09, 2007, 07:30:54 pm »

low pressure gas pump? out of what car? the high pressure pumps are around 65 psi or more. using that will throw off your dynamic timing.

you would only want somewhere in the range of 5-9 psi.

RabbitGTDguy · « **Reply #3 on:** November 09, 2007, 08:29:10 pm »

On the gas VW's and depending on what fuel system you are using there are variations of pumps...

The pumps that exist in the tank themselves are merely low pressure "transfer" pumps... should cause no problems with our setups.
Its the similar to the "lift pump" provided in later TDI's tanks.
LATE MK1 cabbys (Digifant) have a lift pump in-tank, Digifant MKII's, most 16v cars and then you move into the MK3's and IV's as well if memory serves me correctly. MKIV PD's have there own "lift pump" that comes with the car and is now a popular upgrade for those with the MKIV ALH's that can simply add it to assist the VE pump cars.

Here is a pic of a cabby one..

The secondary pumps are usually the high pressure pumps that would provide TOOO much pressure for the injection pump. The highest pressure pumps are found on older CIS cars. The highest pressure one I can think of "stock" is the one found in the OLD MK1's with CIS, sits right under the passenger side just in front of the p side rear wheel (capable of 100psi just open flow)...

Here is what a b3 one looks like

Later CIS/ CIS-E Motronic systems and Digifant have a "secondary" pump located in a simlar location (p side, just in front of the rear p side wheel) but are much smaller, lower pressure and also have a accumlation box as well (Depending on what year, engine, fuel system VIN split, etc)

Here is a thread on TDIclub about it...
http://forums.tdiclub.com/showthread.php?t=143129

A fuel pressure regulator, etc. can be used to trim the pressure down as well.

Joe

MikkiJayne · « **Reply #4 on:** November 10, 2007, 02:00:16 am »

Ok thanks. So I could use the Corrado lift pump if needed, but not the Golf 3 pressure pump.

But is there any advantage to using the lift pump?

RabbitGTDguy · « **Reply #5 on:** November 10, 2007, 04:42:34 am »

The gasser transfer pump....the PD's lift pump (for MKIV PD people or ALH's wanting an upgrade) does have benefits in helping the injection pumps internal pump PULL fuel to the injection pump and keep enough fuel present to prevent starvation at the injection pump, air in the lines/bubbles forming, etc. It does have its benefits when the injection pump really needs to pull more fuel...especially in cars that are significantly fueled and even stock ones *several threads on here about it...even in the IDI forums*.

I can HEAR my fuel pump pick up, kick up...gear up...whatever you want to call it when the mTDI is demanding more fuel...
It does indeed have a benifit...mainly, to assist the injection pump in pulling fuel from the fuel supply.

Joe

jtanguay · « **Reply #6 on:** November 10, 2007, 09:15:30 am »

is the PD pump self regulated? i thought it delivers around 50 psi as the pump injectors cannot suck any fuel at all.

Tintin · « **Reply #7 on:** November 10, 2007, 08:41:37 pm »

The PD lift pump push only 10psi, there is another pump (tandem pump) on the side of the head which pushes 50-100psi at the injector unit.

Lift pump on a VE engine will not add power, but it will be useful to not lose some power and help the pump.

On other european car an truck with VE pump, lucas pump., zexel.....etc... the most of the time It have a lift pump, mechanic or electric.

7-10 psi is perfect.

jtanguay · « **Reply #8 on:** November 10, 2007, 10:23:10 pm »

Quote from: "Tintin"

The PD lift pump push only 10psi, there is another pump (tandem pump) on the side of the head which pushes 50-100psi at the injector unit.

ah this helps immensely! i might not need the in tank lift pump for my PD then...

RabbitGTDguy · « **Reply #9 on:** November 11, 2007, 07:27:43 am »

couldn't have answered it better myself

Joe

MikkiJayne · « **Reply #10 on:** November 13, 2007, 09:45:41 am »

Those of you that are running lift pumps - how are you powering them?

I think it would be too much strain on the pump and pipework to just run it on the ignition, and my ECU doesn't have any facility for an electric pump.

I'm thinking maybe a mk1 GTI fuel pump relay that switches on when it gets an rpm signal?

Thanks, Mikki x

RabbitGTDguy · « **Reply #11 on:** November 13, 2007, 04:00:22 pm »

Any switched circuit is going to require a connection at the ignition at somewhere/some point. This isn't a huge deal. If the pump draws quite a few amps, etc... it might be worthy to go ahead and "relay it" as there your only using the switch "ignition" circuit to acutate the relay and power for the pump is drawn directly from a power source connection (i.e. direct 12v power from the battery).

A pump though that draws the kind of power to need the relay really bad would be a primary pump on a gasser... thus the relay...

Pumps that are for our applications shouldn't draw that much power so I don't think a relay is required...but it never hurts.

Inline fuse....def.

Joe

MikkiJayne · « **Reply #12 on:** November 13, 2007, 04:47:23 pm »

Thanks, but current draw isn't a problem. It already has everything in place to power the pump (relay, fuse, etc) from the original engine. What I'm looking for is something that will only switch on the pump while the engine is running - this was done by the original gas ecu which is obviously now gone.

If it's simply switched on the ignition then the pump can run when the engine isn't, thus either stalling or overloading the pump, or over-pressurising the lines (unlikely).

If the inj pump has something like a carb float valve it will be fine and just return the excess fuel to the tank, but I don't know if it works like that?

vwmike · « **Reply #13 on:** November 13, 2007, 06:19:24 pm »

I put a PD150 in my MK3 and I kept the existing pump. Pressure would have been far too high so I ended up using a bypass regulator down under the car to drop pressure to ~2.5 bar. From there I have a non-return style Holley regulator under the hood with a gauge on it so I can fine tune the fuel pressure at around 10 psi. This has been working perfectly thus far. I would recommend you use the existing lift pump though as that should give you more volume than actual pressure which is what the pump needs. If you must use a higher pressure pump then you will want to regulate it down as I did.

RabbitGTDguy · « **Reply #14 on:** November 13, 2007, 06:48:16 pm »

The ECU has nothing to do with turning the pump on or off.

The fuel pump relay on the the corrado was switched "on" by the ignition circuit, off a switched current line. (Switched circuits have to somewhere operate on any car OFF the ignition circuit or a SEPERATE switch (therefore another "switched" circuit). Its the same on most every VW gasser I've worked on as well... as well as most any car with a factory electric fuel pump, etc.
The exception to this could be the "latest" cars that throw almost all control over to the ECU...but I'm skeptical that would be the case.

If you have it properly hooked up to the switched circuit, then it will "come on" when the relay is signaled at the "contact" position of the ignition switch...then turn off when the key is turned off.

If it runs with the ignition off...something is wrong with the wiring and/or the relay.

You can also run your own "switch" I suppose if you want independently...but with the lift pump operating with its simple job...I can't see why you'd want it off other than maybe just being able to kill it.

Most fuel/transfer/lift pumps... will not keep the lines "Pressurized" all the time...especially what you are talking about using...

The injection pump does not have anything like a carb float...but does have a return line circuit.

Hmm...make sense?

Joe