reb78 Posted February 1, 2016 Share Posted February 1, 2016 I suppose this is a question for those running Tdi's. A while back at a service, I noticed my lift pump wasn't filling the fuel filter properly. Checked a few times and it appeared the pump had failed. I had not experienced any decrease in performance associated with this. Fed up with lift pumps going, i replaced with a facet pump that has a flow rate that should be fine for the max requirements of the FIP. This is controlled by a switch. I occasionally forget to turn it on and it makes absolutely no difference to the performance at all. The 110 will do 80 with or without the lift pump turned on and will get there just as fast either way too. Why do we have them? Is it simply to decrease strain on the FIP so that it doesnt have to work too hard drawing its own fuel? Quote Link to comment Share on other sites More sharing options...
mmgemini Posted February 1, 2016 Share Posted February 1, 2016 You don't if you have a gravity feed system LOL Quote Link to comment Share on other sites More sharing options...
landroversforever Posted February 1, 2016 Share Posted February 1, 2016 I suspect it will make more of a difference offroad when the fuel will need to be going uphill. Quote Link to comment Share on other sites More sharing options...
Soren Frimodt Posted February 1, 2016 Share Posted February 1, 2016 i would suspect its there to make sure that no air gets into the system. Trying to bleed the fuel system without the lift pump would probably be neigh on impossible. And air bubbles could easily show up when driving with a low fuel level or offroad. But on another note, I'd actually rather have an electric fuel pump than a mechanical lift pump. In my experience there are less problems with electric pumps and bleeding the system, or draining it is a whole lot easier. Also finding a replacement electric pump on your travels would be a lot easier, as most types would do the job. Whereas a mechanical pump has to fit exactly your application. Though of course you could fit the electric pump should the problem occur Quote Link to comment Share on other sites More sharing options...
western Posted February 1, 2016 Share Posted February 1, 2016 injection pump needs the fuel pressure created by the lift pump ---------------- http://fuelab.com/diesel-lift-pumps-what-is-more-importantpressure-or-flow/ Quote Link to comment Share on other sites More sharing options...
miketomcat Posted February 1, 2016 Share Posted February 1, 2016 Have had several fail on different cars and I can say it depends on the injection pump and your use. One of mine I didn't realize it had failed till I towed with it, another wouldn't go above 60mph without it and another failed to the point it wouldn't run so I bypassed it then it would do 80 and towed no problem before I had chance to replace it. So yes you do need it but it doesn't have to be mechanical. Mike Quote Link to comment Share on other sites More sharing options...
reb78 Posted February 1, 2016 Author Share Posted February 1, 2016 Have had several fail on different cars and I can say it depends on the injection pump and your use. One of mine I didn't realize it had failed till I towed with it, another wouldn't go above 60mph without it and another failed to the point it wouldn't run so I bypassed it then it would do 80 and towed no problem before I had chance to replace it. So yes you do need it but it doesn't have to be mechanical. Mike Its interesting though that i can tow, travel at speed on the motorway etc and simply dont notice any difference if the pump is turned on or off. The only time i have noticed a performance failure is when one of the mechanical pumps was leaking. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted February 1, 2016 Share Posted February 1, 2016 Why not wire it up to an ignition controlled relay and not worry about it anymore Quote Link to comment Share on other sites More sharing options...
reb78 Posted February 1, 2016 Author Share Posted February 1, 2016 injection pump needs the fuel pressure created by the lift pump ---------------- http://fuelab.com/diesel-lift-pumps-what-is-more-importantpressure-or-flow/ Now that poses an interesting question. At some point, someone has put what i presume are larger than standard output banjos (?) on the fuel filter outlet and FIP inlet together with a fuel hose with a larger internal diameter. I say presume as its larger than the rest of the fuel lines and i bought a replacement filter head a while back and it had a smaller outlet on it than the old one. So, my facet lift pump has good flow, but could the pressure be wrong? Quote Link to comment Share on other sites More sharing options...
reb78 Posted February 1, 2016 Author Share Posted February 1, 2016 Why not wire it up to an ignition controlled relay and not worry about it anymore I left it on a switch so i could leave it off if i was sat in the car listening to the radio. I dont mind using the switch, i was just curious as to why the pump seemed to have no effect whether on or off! Quote Link to comment Share on other sites More sharing options...
western Posted February 1, 2016 Share Posted February 1, 2016 same engine as your 110, my fuel pipes from tank to lift pump to fuel filter to injection pump are all the same diameter. 1st pic fuel filter head to injection pump 2nd lift pump to fuel filter head Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted February 1, 2016 Share Posted February 1, 2016 I left it on a switch so i could leave it off if i was sat in the car listening to the radio. I dont mind using the switch, i was just curious as to why the pump seemed to have no effect whether on or off! Do defenders have an 'ACC' position on the ignition switch? If so wire your radio ignition live to that Quote Link to comment Share on other sites More sharing options...
Ex Member Posted February 1, 2016 Share Posted February 1, 2016 If the system is completely tight with no air leaks, it will run fine without the pump. The injection pump can suck. Lot of other vehicles that use this pump do not have a lift pump. The lift pump will keep it running with a small leak and allow the system to self bleed. If you get any air in there and don't have a functioning lift pump, you are screwed. Quote Link to comment Share on other sites More sharing options...
qwakers Posted February 1, 2016 Share Posted February 1, 2016 my trayback wont go above 1800 rpm without my facet plugged in, my mech lift pump is buggered and my fuel tank is sat on top of the tubular crossmember so not that far off standard. there are defiantly no leaks, so im thinking my injection pump is a bit worn. Quote Link to comment Share on other sites More sharing options...
reb78 Posted February 1, 2016 Author Share Posted February 1, 2016 same engine as your 110, my fuel pipes from tank to lift pump to fuel filter to injection pump are all the same diameter. 1st pic fuel filter head to injection pump 2nd lift pump to fuel filter head Thats interesting Ralph. My pipe from filter to FIP is definitely larger internal bore. I wonder if this is causing pressure drop and maybe contributing to the noise i reported here?http://forums.lr4x4.com/index.php?showtopic=95946 It was this paragraph in your link above that made me wonder: 'Pressure exists due to a resistance in flow. When it is put that way, it sounds like a bad thing. However, pressure is necessary for a fuel system. Many fuel injection pumps rely on fuel pressure to operate the timing circuit. All fuel systems benefit from pressure during high demand situations. A diesel engine running at 3000 RPM has very little time to fill a pumping element before the next cyclemilliseconds, literally. Pressure helps to fill the pumping element. If pressure drops too far, the pumping element will pull a vacuum. It will live with some vacuum, but too much will cause cavitation and vaporization. This condition can cause more damage than dirty fuel. In laymans terms, cavitation causes the fuel to vaporize. The vapor fills the pump cavity; then the pump pressurizes the vapor. When the vapor is compressed, it implodes. The implosion erodes the metal away and leaves craters in the surface.' But then again, if these pumps run fine without a lift pump as Red90 says, then maybe the two things are unrelated? Quote Link to comment Share on other sites More sharing options...
reb78 Posted February 1, 2016 Author Share Posted February 1, 2016 Do defenders have an 'ACC' position on the ignition switch? If so wire your radio ignition live to that Not the diesels. I don't know about the petrol variants. Quote Link to comment Share on other sites More sharing options...
vulcan bomber Posted February 1, 2016 Share Posted February 1, 2016 But then again, if these pumps run fine without a lift pump as Red90 says, then maybe the two things are unrelated? They only run without a lift pump on smaller engines, around the 1.6 litre mark where the delivery head on the pump is only 9mm as opposed to the 11mm used on our TDi engines. The fuel demand is much less so the rotary pump (low pressure) in the front half of the injector pump can keep up with demand in all conditions... That said the only time my 110 seems to suffer is when it's full of Veg oil and a tad cold. The Disco suffered notably with a bust lift pump, but that's a 300... Quote Link to comment Share on other sites More sharing options...
Ex Member Posted February 2, 2016 Share Posted February 2, 2016 They run fine without a lift pump..... I had a dead lift pump for years on my 200TDI (without knowing it). There was absolutely no reduction in performance. Anyone that has trouble, has a leak in their system. All the early 2000 VWs used the same injection pump with no lift pump. People run 200 hp all day out of those. Quote Link to comment Share on other sites More sharing options...
d-9 Posted February 2, 2016 Share Posted February 2, 2016 i was just curious as to why the pump seemed to have no effect whether on or off! Blocked tank breathers? I dropped a tank off a trooper on sunday which wasnt running over 1500rpm, because a breather had snapped off the top of the tank and it couldnt pressurise the tank with the fuel return, seemed like an odd setup, but blocking the hole made it run properly again. Quote Link to comment Share on other sites More sharing options...
Aragorn Posted February 2, 2016 Share Posted February 2, 2016 I know on VAG TDI's with rotary pumps, people retrofit the lift pump from the later PD engines when really turning the wick up, and find it makes a big difference at higher RPM. But thats on engines with modified pump heads, huge injector nozzles, turbo upgrades etc etc. The VE pump has a pump built in to lift fuel from the tank but clearly it struggles in those high demand situations. I would imagine that on a standard 300tdi its plenty good enough on its own, so long as the broken lift pump doesnt act to block the pipe. Quote Link to comment Share on other sites More sharing options...
Defender Posted February 2, 2016 Share Posted February 2, 2016 My 300tdi 90 ran fine with a failed lift pump the only time I realised there was an issue was when climbing a hill it started to surge like you were pumping the accelerator, it wasn't until I thought it seems like a fuel problem so I'll start by changing the filter I realised that there was no fuel coming out of the bleed screw. It must have been like it for a while because the performance increase when towing was quite noticeable . I guess the IP could suck fuel until it got to a point that the engine was under too much load climbing the hill. Quote Link to comment Share on other sites More sharing options...
nickwilliams Posted February 2, 2016 Share Posted February 2, 2016 I run a 300tdi. My lift pump failed on Friday evening last week and the vehicle certainly wasn't usable until I'd fixed it - it would run at idle but would not rev. and I had to use low range to crawl up a slight hill to get it home. Luckily I was less than 250m from home when the pump failed. Quote Link to comment Share on other sites More sharing options...
reb78 Posted February 2, 2016 Author Share Posted February 2, 2016 I run a 300tdi. My lift pump failed on Friday evening last week and the vehicle certainly wasn't usable until I'd fixed it - it would run at idle but would not rev. and I had to use low range to crawl up a slight hill to get it home. Luckily I was less than 250m from home when the pump failed. Was yours leaking Nick? Mine ran very poorly with a leaking mechanical one, but absolutely fine if it simply wasnt pumping. Quote Link to comment Share on other sites More sharing options...
reb78 Posted February 2, 2016 Author Share Posted February 2, 2016 Blocked tank breathers? I dropped a tank off a trooper on sunday which wasnt running over 1500rpm, because a breather had snapped off the top of the tank and it couldnt pressurise the tank with the fuel return, seemed like an odd setup, but blocking the hole made it run properly again. Thats the thing - i dont have a problem. It runs perfectly whether the pump is turned on or off! Quote Link to comment Share on other sites More sharing options...
nickwilliams Posted February 3, 2016 Share Posted February 3, 2016 Was yours leaking Nick? Mine ran very poorly with a leaking mechanical one, but absolutely fine if it simply wasnt pumping. No, no leaks. The end had sheared off the pin which drives the diaphragm up and down. Quote Link to comment Share on other sites More sharing options...
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