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Engine Specific Info and Questions => IDI Engine => Topic started by: darrenjlobb on December 30, 2009, 02:04:41 pm
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Hey guys...
I seem to be having problems keeping the fuel up high, well was before...ive read about people using lift pumps to try and help?
Has anyone seen prooven gains with this?
Can you supply the pump direct with a pressurized line, or do you need a swirl pot or something, and if feeding direct will it do the pump any good being understand load holding pressure?
Cheers
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my car ran much better after i added a small electric pump before the filter. never loses prime, and if you run out of fuel, no worries, just fill it back up and take off. definitely not a bad thing to add in my opinion. why would they put them on like every other diesel ever produced? cummins, fords, chevys, all of them have lift pumps.
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It wont do the pump any harm having a pressurized input then? Or do i need a mini pot in the bay so its still suction feed to the pump? My lift pump is one ive put in the tank..not sure of pressure, but seems a little bit, if you hold finger over end you get a fair air build up behind it...
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I don't think you want any more than maybe 3-5 psi. If you feed it too much pressure you will start to mess with the timing curve.
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You also need to make sure that the lift pump will not restrict fuel flow under high fuel demands. I don't know what the required GPH is though.
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do you think the stock in tank lift pump from a mk2 CIS gasser would flow enough?
supposedly they put out 5PSI
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I thought they were in the 15 psi range?
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I heard that the cis lift pump was 5psi and the Digi pump was higher as it only has one fuel pump not two like the CIS system.
but I have been wrong before, so...
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lots of folk do this for running veg oil.
use a 4psi faclet? pump
just in line is the usual. fine at top end can flow plenty.
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my lift pump will flow just fine, even when its completely off with just the IP to suck fuel through it. the injection pump uses way less fuel at WOT than what the pump puts out. my lift pump puts out atleast twice the fuel my IP could ever return back to the tank.
and as for the in tank pumps, mk1's dont even have a lift pump in the tank do they? all my gasser rabbits have an external pump right after the tank, and it puts out like 90 psi. but no in tank pump. my jetta has an in tank pump that puts out about 5 psi.
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So im fine pressurizing the input line to the pump?... or do i need a regulator / pot in the engine bay...
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I heard that the cis lift pump was 5psi and the Digi pump was higher as it only has one fuel pump not two like the CIS system.
but I have been wrong before, so...
Digi cars still have two pumps. The main pump doesn't make as much pressure as a CIS pump but I'm not sure about the transfer pump.
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I heard that the cis lift pump was 5psi and the Digi pump was higher as it only has one fuel pump not two like the CIS system.
but I have been wrong before, so...
Digi cars still have two pumps. The main pump doesn't make as much pressure as a CIS pump but I'm not sure about the transfer pump.
Basic CIS has one pump (usually earlier A1 cars), Electronic CIS has 2 pumps (later A1 cars and early A2), Digifant 1&2 also have 2 pumps (later A2 cars and early A3 cars) and all transfer pumps that ive read about put out around 5 psi or so. the in tank pump just pumps fuel to a smaller tank that the fuel pump sits in. the smaller tank is so that the pump is always surrounded by fuel, and fuel is what cools the fuel pumps. so you can be a cheapskate and run around with no more than 5 bucks worth of gas in your tank and not be overheating your fuel pump and killing it early. clear as mud?
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I have an mkII gasser in tank pump in my jetta. I used a gauge at the fitler once and couldn't get more than a few psi. The gauge i used may have been to blame. But it seems to have plenty of fuel flow across the RPM range. At any rate the pump is nice for filter changes.
I'm gonna play with diff psi going in to the pump. Have heard around 15 helps up top with timing curve for added power. I have thought about using a GM TBI fuel pump as i have access to them and the TBI system pressure is 15-20 on 2.5l-5.7l engines, so with a regulator i have no doubt it will flow enough at 10-15psi for my 1.6l.
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So having a smaller tank in the engine bay, which the lift pump just sends / returns to, and the injector pump sends / returns to would be a better idea?
Or doing the inlet / oulet pipe...i guess that would work...altho would the fuel not find ti easier to go this way than to the pump / starve the pump just the same,...
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why not route a return pipe into the car through the window etc into a big clear bottle to see if you are still returning fule under high load, then you know if you are geting enough fule to the pump or not, so you know if you need to bother about a lift pump or not.
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Because the pump will still return fuel, even if its not getting enough... its just the internal pressures drops....
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So having a smaller tank in the engine bay, which the lift pump just sends / returns to, and the injector pump sends / returns to would be a better idea?
Or doing the inlet / oulet pipe...i guess that would work...altho would the fuel not find ti easier to go this way than to the pump / starve the pump just the same,...
its not necessary to have 2 tanks, you are overthinking, and overcomplicating things. i would just hook up a few psi feed directly to the pump inlet. its worked fine for those of us that have done it.
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Or doing the inlet / oulet pipe...i guess that would work...altho would the fuel not find ti easier to go this way than to the pump / starve the pump just the same,...
I assume this is in regard to what I last posted. If a higher than 5-psi pump is used, then the whole point is to alleviate the higher pressure so that it doesn't mess up the dynamic advance. The point is to eliminate both pressure or vacuum at the pump inlet and let the injection pump will draw it's own fuel which it has no trouble doing unless there is a fuel restriction or the pump is severely worn. There is no way that alleviating excessive inlet pressure in the described manner would starve the pump unless the vane pump didn't function at all. In which case, your dynamic timing advance would not function at all, your power would be off and your fuel economy would be terrible. Under that condition you'd want to replace the pump anyway.
that was clear as mud.
so are you saying that its fine to run a lift pump, or are you saying not to run one?
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Right this was my plan...basically im just trying to allow the pump to have fuel right there ready for it, so it dosnt have to drag it so far, i am thiniking to just t across the lines with a one way valve, because the pump can easily suck what it needs then...
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The only issue that I can see with teeing across the pump is that there may end up being too much pressure on the return side and the injector return lines may start leaking.
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I can see your point here yes....would have to try it i suppose...if i had to i suppose i could run the t;ed pipe back a dedicated return...
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There is a seller on ebay who sells solid state fuel pumps that are diesel safe.
just search "solid state fuel pump"
and there are a few with different pressure ranges. I've wanted to get one for a while i just need to justify spending more money on the car first.
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CIS pumps run hot. When I had my Mercedes with a cis system, pump pressures would reach beyond 90PSI. I would be careful with that.
I have a walbro FPR-15 lift pump made for this application, It ran me about $90 and is biodiesel ready. It's outlined elsewhere on this forum.
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You guys need to listen to what Andrew said. Use a by-pass and check valve. I tried a Facet pump for a while, Its about 4 psi, Hooked it up with the pump return pressure gauge installed. It will change the timing curve. I didn't like it.
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you guys are sure that 3 psi is going to affect timing that much? dont our pumps have almost 100psi in them at 3k rpms? how is 3 psi going to negatively affect timing that much? dont we all try and advance our timing anyway? im just not getting it so good. my car ran WAY BETTER when i added a lift pump.
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Question,
I'm using a Facet lift pump inline to a Giles pump. My engine makes a noise such as if the timming is wrong at idle, and smokes, but when loaded, the noise seems to deminish. At least that what it sounds like.
Is this due to the lift pump. I guess the only way to tell is to remove it and check.
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how many psi are you running at the pump inlet? the way andrew described it, that would sound about right, building some excessive pressure on the inlet side of the pump, and then its retarding the timing.
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What ever the psi rating of the pump plus the location.
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I've had a small Facet pump mounted between the filter + Ip for the last 60k miles. When I 1st put it on, I ended up blowing the small return lines off the injectors. I then put a CR press. regulator and gauge on-set it around 3 psi-haven't had a problem since.
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I just went out and started the truck. It fires right up and then but not even 4sec. after running, it strts to make the noise. Is that because the pressure dif. between the inlet and the pump?
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tee a pressure gauge into the inlet of the pump, if the noise comes and goes as pressure increases and decreases on the gauge, then that very well might be your problem.
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Spearco,
Just unplug the pump it will still draw fuel through it. You can check to see if your problem goes away. 8)
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Spearco,
Just unplug the pump it will still draw fuel through it. You can check to see if your problem goes away. 8)
that would be alot easier..
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Nope no different. But got some 1.9 AAZ injectors to install. Then we'll see.
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I just went out and started the truck. It fires right up and then but not even 4sec. after running, it strts to make the noise. Is that because the pressure dif. between the inlet and the pump?
I believe that's due to the internal pressure taking a bit of time to build up.
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Andrew,
when I experimented with adding the Facet pump to lift for the Giles pump, I felt like it advanced the timing. I got a 4 psi increase in pump pressure on the gauge. Driving it, it knocked more on acceleration than without it. So I quit using it.
What would happen to the timing if I were to enlarge the tiny hole on the return side a few thousands? Anybody played with this?
Cheers,
Jeff
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andrew says it retards the timing tho. and i believe him. (not saying i dont believe you) but he gave an explanation as to why it retards it, and it very well might.
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Today we had a VE pump on the bench. It was for an AAZ making 20 PSI. We hadn`t really set anything up yet, just made sure that the max fueling was "close". I forget what RPM we were running, maybe 2000-3000 engine? With the pump being feed with 0 PSI the internal pump pressure was 75 PSI. We turned the feed pump pressure up to 20 PSI and the internal pump pressure rose to 95 psi. Therefore, positive pressure at the inlet of the pump will advance the timing.
I was expecting to see no change since pressure is being applied to both sides of the regulator but I was wrong.
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So it looks like all that matters is the pressure difference on each side of the advance piston 8)
Hey Burn, did you happen to see what the dynamic timing did?
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You know, I thought about looking at the piston before we started the experiment but once it was in action I totally forgot. Odds are the pump will still be on the bench when I get in in the morning. Maybe there will be time to check it out first thing.
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Just finished testing, there was no change in the advance.
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We cranked it up to around 45 psi when we were looking at the advance. I did see the gauge jump once though. I don't think it changed the actual advance, just jumped. I could be wrong though it was very quick
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We share the same thoughts Andrew. Not necessarily needing to have a regulator makes things a lot easier.
Next I want to hook a VE pump up to a flow gauge and see just how much fuel flow (GPH) is required under the most demanding situations. I don't know if I'll be able to do that though because I think it would require modifying one of the test benches
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GPH sounds like something one could test on the (work) bench pretty easily, messily, but easily.
Run it for ten minutes, do the match, etc. I think.
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I talked to Giles about it, we'll see what we can do.
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My question is I have a extremely hard time keeping the return line (to pump) from leaking with a 5 psi pump. Is it possible for the pump pressure to have increased?
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Internal pump pressure does increase when you add a lift pump. It sounds like you have a restricted return though.
Something to note, if you add a lift pump you will want to be careful not to blow up your filter. The stock filter is built for vacuum, I'm not sure how much pressure it can handle.
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Internal pump pressure does increase when you add a lift pump. It sounds like you have a restricted return though.
Something to note, if you add a lift pump you will want to be careful not to blow up your filter. The stock filter is built for vacuum, I'm not sure how much pressure it can handle.
Come to think of it, I saw an old diagram once of the vw diesel fuel system and it showed a mechanical fuel pump like the carbureted gassers have, running off the IM shaft lobe.
The diesel IM shaft gear is cut opposite of the gasser ones, hence it's a different piece so it shouldn't have the lobe either, yet it does.....my guess is vw decided the lift pump wasn't needed and ditched it. ;D
I'll see if I can find the pic again.
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if i had a carb'd rabbit fuel pump, i would try and use it as a lift pump. it cant make much pressure, maybe a couple psi max..
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That's a great idea (if it'd work). I have one I could pull off of a '73 audi 1.5 gasser, 827 block like ours. New ones are still available and cheap though-
(http://shop.oreillyauto.com/product_images/img/bos/68802.jpg)
http://frugalmechanic.com/auto-part/1144380-bosch-fuel-pump-mech-68802 (http://frugalmechanic.com/auto-part/1144380-bosch-fuel-pump-mech-68802)
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Is that one pictured to proper one?
One disadvantage of a mechanical lift pump is it won't help prime a system like an electric one will
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Carter makes the lift pump for the cummins in the dodges. Here's a one that is set to 6psi with 72gph that should be more than enough.
http://www.summitracing.com/parts/CRT-P4070/ (http://www.summitracing.com/parts/CRT-P4070/)
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the gas and diesel camshafts are the same casting, they just have a different gear pressed on the end.
I doubt the carburetor mechanical pump would flow enough for our engines, as it is designed for a non-return fuel system(which flows very little)
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whoops, you are right.
silly me, I did indeed mean IM shafts.
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thanks for catching it for me.
school just started, and my brain is all over the place.
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I found that diagram of the lift pump, I tried blowing it up a bit but alas, I failed :P:
(http://i249.photobucket.com/albums/gg218/rabbitdude82/Liftpumpdiagram.jpg)
Appears to me that there's a pressure regulator built into the fuel filter mount, probably not as handy for filling the IP as an electric pump is.
I found that here: http://www.vwdiesel.net/forum/index.php?topic=12943.0 (http://www.vwdiesel.net/forum/index.php?topic=12943.0)
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Where can that filter assembly be got from...could make it much easier just running that filter...would sort the pressure problem..
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Where can that filter assembly be got from...could make it much easier just running that filter...would sort the pressure problem..
No idea, that looks like something vw changed there mind on really early.
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I saw it mentioned that the Digifant pump sits in fuel to keep it cool. Could I use it without the in-tank lift pump to prime my fuel lines, or will it overheat? Is it otherwise a good idea? I'm tired of breaking out the vacuum pump every time I want to drive the car...
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use the in tank pump. the primary pump puts out like 40 psi. the in tank pump puts out around 5 psi. get rid of the primary EFI pump.
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The pumps are regulated via voltage or current aren't they? usually on a relay maybe that is the answer? You could run a toggle/pot to turn the pump up or down for demand, or if you could wire a pressure sensor on the return line you could make a small circuit to do it automatically for high boos/high fuel situations. 8)
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The pumps are regulated via voltage or current aren't they? usually on a relay maybe that is the answer? You could run a toggle/pot to turn the pump up or down for demand, or if you could wire a pressure sensor on the return line you could make a small circuit to do it automatically for high boos/high fuel situations. 8)
the pumps run or dont run, theres no half way, its either on or off. the regulator on the fuel rail dictates how much fuel pressure the pump makes. and for boosted apps, usually a RRFPR is used to increase fuel pressure with boost pressure.