well, it's taken me a while, but here's the "why does the stock one fail" (note, MS paint pictures ahead)
thanks to @MPS2NV for his explanation that he clearly doesnt remember giving me (also correct me if im wrong in any of this )
as some of you may/may not know, we have a cam driven fuel pump
this means, our pressure comes from a (somewhat) simple designed fuel pump...
at it's most basic, it's a piston going up and down off a camshaft lobe
so when it's working properly, it looks like this:
as you can see, the cam shaft lobe pushes the piston up and into the pump, thereby compressing the fuel
now, what happens when you see pressure drops is the following:
as you can see on the right, the piston has lost contact with the camshaft and this means the compression isnt as good on the fuel, and therefore results in less pressure being formed
as you get more power, the cam spins faster, making it more likely that the piston will not come back down with the camshaft lobe
i cant remember exactly what it is that the internals do, but from memory it increases the surface area and/or length of the piston, making it much more difficult to drop pressure
hopefully that helps people understand
Newbie FAQ My Build Thread
From stock, to GT3071, to substantially less modded, many lessons learned!
3" HTP | 100 Cel DP | Autotech HPFP | AP V3 - Self Tuned on E20 | JBR RSB | CPE S2 REM | JBR Shifter Bushings
That was one theory I heard of in early days, also by increasing the plunger/ element diameter the fuel volume with auto tech internals this must have an effect on this theary, on the other hand cpe do this and change the spring also to maintain correct plunger stroke and eliminate a "float" situation
By increasing the chamber volume the initial amount of fuel allowed in from lift pump is also increased to maintain snore stable fuel pressures
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Dam ifail lol
I don't think it's a normal cam shaped lobe on the pump, it's triangular (3 lobes) I.e shaped like a rotary.
Newbie FAQ My Build Thread
From stock, to GT3071, to substantially less modded, many lessons learned!
3" HTP | 100 Cel DP | Autotech HPFP | AP V3 - Self Tuned on E20 | JBR RSB | CPE S2 REM | JBR Shifter Bushings
Just installed HPFP internals for my Gen 1.
All seemed to go well except for some reason I decided to try & replaced the top section of the pump that has a wire connector with the one supplied. Which i now think is for the VW Golf....
I think I have installed the internals well enough, though it seems when I removed the wire connector a spring & a metal section that the spring sits in fell out. I found the pieces & placed the metal section in 1st then the spring.
I don't think this is right as when the car is below 2500 revs it stutters and when i get over 3000 it runs fine however there is a ringing sound coming from the motor. Dont want to hassle the peeps, but I tried to find a Parts Diagram for the Fuel Pump, but to no avail.
I'm driving the car very carefully so no chance of zoom boom.......
Any suggestions or directions to HPFP parts diagram would be appreciated.
Cheers
Sam
That doesn't sound right....
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Yeah it doesn't feel right either.
I'm going to reverse the installation of the spring & the metal sleeve this morning to see if it makes any difference.
If not I'm going to re-install the fuel pump.
Anyways if you think of anything let me know.
Cheers
Changed the spring & metal sleeve location.
All working well now!!!
Lesson learnt.........
Newbie FAQ My Build Thread
From stock, to GT3071, to substantially less modded, many lessons learned!
3" HTP | 100 Cel DP | Autotech HPFP | AP V3 - Self Tuned on E20 | JBR RSB | CPE S2 REM | JBR Shifter Bushings
Yeah, basically.
I installed the HPFP internal correctly.
What I did wrong was re-install the spring & metal sleeve of the sender (section that screws to the top of the pump with the electrical connection) back to front.
So I removed the sender with a large adjustable spanner, removed the spring & metal sleeve with a clean pair of long nosed pliers. Then placed the spring in 1st then the metal sleeve which sits over the spring & connects with the nipple at the bottom of the sender unit.
I hope that makes sense.
Moral of the story is don't remove SH** unless you have to
I don't know the correct terminology but I hope that makes sense......
Cheers
Wrong , moral to the story is (look carefully at how it comes apart ) place disassembly directly in sequence to removal.
Glad you got it fixed ,a simple operator error!!!!!.
Item was the spill valve ,or simply a by pass valve ..
Always a relief to find what went wrong, even better if you pick up on your own misstakes
Yeah, definitely & i would have done this if I noticed the parts in the 1st removal Oldhead, which I didn't cause they didn't pop out
Am very relieved it's sorted.
After a long think it sort of made sense though, if you know what I mean. The nipple on the spill valve needed a flat surface to operate.
Hey we all hopefully learn from our mistakes.
Quick question, have peeps been also cleaning the entire HPFP whilst changing over the internals, or just focusing on changing over the internals? It would seem an opportune time to give the entire HPFP a good clean...anyone got any thoughts?
perhaps, if you're very confident. I think by taking the whole assembly apart just creates more chances for things to go wrong
Yeah I just did the replacement internals. Cleaned down into the pump as much as I could but didn't take the whole thing apart
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The 3 I have done for others I chose to dissassemble the whole unit and clean the fine build up.
Ok problem. Car started fine and drove fine last night, as did it this morning, but when I started it tonight, it would start then die after about 2 seconds. Did this 3 times. Then I tried priming the pump 3 times, but the same thing happened again when I went to start. Next time I tried to start I gave it a bit of throttle and it started and from the on it ran and idled fine. Also started fine the next time. No idea what's going on!
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