Is it possible to feel a worn out HPFP? (SOLVED)

[TheObjectivist]

My hpfp has ~80k miles and im concerned its getting weak. (especially with E30-40 fuel)

Would a weak pump cause a lack of power or rough idle? Anything a familiar driver could actually feel?

Ive had codes for a faulty pump trigger twice now and especially with an E30 tune the car feels doggy.

Note: I replaced the LPFP with a walbro 535 last year due to sub 50psi readings. Everything reads OK now though

 

[bakerdou]

run a WOT 3rd/4th gear log, if the hpfp is on its way out, you may find the high fuel pressure drops below 2000psi or even less when the car is still trying to build up boost, and the AFR may increase above 13 or 14

 

[martymil]

If your getting the pump codes its usually the electric valve on the pump and its not long for this world.

Sometimes they make a rattling noise under load but not always.

80k was a good run for a HPFP, I had 2 fail with under 25k running e85 not over driven on our single turbo setup with pi.

 

[TheObjectivist]

Hi all - quick follow-up in case others experience the same thing:

Yes. It seems you can feel a worn out HPFP even if the flow rates appear well within spec



I swapped a new pump and both new sensors (w/updated lpfp line), and the car is a different animal. Far more power, much smoother, and (don't know how its possible), seems to be getting better MPG.

I'm uncertain how the pump would be so bad yet show me proper flow numbers. I data logged constantly, and the only anomaly was that low pressures were ~90+psi. The high LP rate started immediately after replacing my failing LPFP with a walbro 535.

Does this speak to what martymil above said regarding the electrics failing?

 

[martymil]

The problem with stock fuel lines especially if the rail is not drilled out is the lack of flow or volume of fuel, you can still be hitting hpfp targets but thats where you have to watch the afr's, look at your's before and after.

Also a failing LPFP will starve your hpfp limiting its life span and the lpfp sensor hardline is a huge bottle neck.

 

[proboner]

The problem with stock fuel lines especially if the rail is not drilled out is the lack of flow or volume of fuel, you can still be hitting hpfp targets but thats where you have to watch the afr's, look at your's before and after.

Also a failing LPFP will starve your hpfp limiting its life span and the lpfp sensor hardline is a huge bottle neck.

I haven't looked into this at all, but is there any reason this can't be replaced with a -6AN flexible line?

 

[martymil]

We cut off all the bends and weld on a 6an just before the lpfp sensor so you can connect your line and get rid of the bottleneck, it works as seen on a number off cars where on the limit and it raised the fuel pressure on the hpfp rail by 200 to 300 psi which stopped hitting the safety.

It's not much but enough to help run on full e85 at 20psi with no overdrive or pi, that's enough for most people and budget concious builds.