Advice on low fuel pressure readings

[RhysM]

So following on from rebuilding the WUR as a first point of fuel pressures being way off, turns out it's made no difference at all.

System pressure is barely getting to 3 bar, as you can imagine the rest are also very far off.

Hoping for some advice, reading a lot of the topics on here the next culprit to probably replace is the fuel pumps? if not that injectors? the car was running fine off boost but run into troubles when you get past 3.5K RPM stumbling, fuel pressures way off.

For context, the car had sat for 30 years prior to my purachse, the fuel tank had been cleaned but there's been a myriad of small issues. Really hoping to bottom out the issues, get her running properly so I can focus on sorting the body work and paint out!

Thanks,

R

[gorskined]

sitting for 30 years? my 76 3.0l row sat for 17 it was a mess . i replaced the tank and pumps at first . still had constant issues kept clogging the inlet strainer on the fd as well as other things wur strainer . The car didn't run correct until i replaced everything that had fuel running through it. The tank accumulator, injectors ( two sets ) pumps, rebuilt fd ( twice) rebuilt 3 way adjustable wur twice. i replaced every fuel line including the tunnel lines with an5 lines. i also replaced the hard injector lines. They kept depositing crud into the injectors ruined a bran new set before i realized what was happening. with the an5 fuel lines i was able to make lines and buy components at a fraction of the cost of Porsche parts also with the an 5 lines my car only needed 1 new 200 series fuel pump. two pump sover pressurized and i was able to place gauges and sensors anyplace to trouble shoot and dial the car in. do yourself a favor replace everything one shot or you will risk mucking up new components and second guessing if they are good or bad.

Regards Ned

[RhysM]

Originally Posted by gorskined

sitting for 30 years? my 76 3.0l row sat for 17 it was a mess . i replaced the tank and pumps at first . still had constant issues kept clogging the inlet strainer on the fd as well as other things wur strainer . The car didn't run correct until i replaced everything that had fuel running through it. The tank accumulator, injectors ( two sets ) pumps, rebuilt fd ( twice) rebuilt 3 way adjustable wur twice. i replaced every fuel line including the tunnel lines with an5 lines. i also replaced the hard injector lines. They kept depositing crud into the injectors ruined a bran new set before i realized what was happening. with the an5 fuel lines i was able to make lines and buy components at a fraction of the cost of Porsche parts also with the an 5 lines my car only needed 1 new 200 series fuel pump. two pump sover pressurized and i was able to place gauges and sensors anyplace to trouble shoot and dial the car in. do yourself a favor replace everything one shot or you will risk mucking up new components and second guessing if they are good or bad.

Regards Ned

Thanks for the lengthy reply, Ned. That's good to know. It's had a new tank and some lines and filters, WUR is rebuilt but interesting to see what you to go to for it to work properly. Duly noted, I'm going to hopefully make a start on it in the coming weeks!

Thanks,

Rhys

[gsxrken]

I second Ned's "do it once, do it right" reply. 30 years of sitting is a non-recoverable event for fuel related items.
This is a photo of my well-maintained, never off the road 1986's fuel lines in 2020. The lining just breaks down over time and little bits jam up everything downstream. Pulling them through the tunnel is something of a baptism around here.
Talk to Len boxterGT on this forum for fuel lines, RarelyL8 here for rebuilt fuel head and go to TurboKraft to get non-counterfeited fuel pumps. You will be chasing your tail for ever otherwise and you'll end up hating the car.
CV joints and wheel bearings are probably on the short list too.

[Black_Hat]

did you check Fuel pump delivery = 1500cc /30 seconds ? Edit: older 930's deliver less fuel you should research
did you check for 12v at fuel pump when running or developing pressure ?

https://cis911primer.com/pages/test_pressures.html

[RhysM]

Originally Posted by gsxrken

I second Ned's "do it once, do it right" reply. 30 years of sitting is a non-recoverable event for fuel related items.
This is a photo of my well-maintained, never off the road 1986's fuel lines in 2020. The lining just breaks down over time and little bits jam up everything downstream. Pulling them through the tunnel is something of a baptism around here.
Talk to Len boxterGT on this forum for fuel lines, RarelyL8 here for rebuilt fuel head and go to TurboKraft to get non-counterfeited fuel pumps. You will be chasing your tail for ever otherwise and you'll end up hating the car.
CV joints and wheel bearings are probably on the short list too.

Thanks, Ken.

On those lines for what you've mentioned, the fuel hoses are top prio! I'm in the UK but we have sources for fuel pumps, I've been told to avoid anything but OEM fuel pumps! thanks for your input though really helpful. Yeah, when I had her running and driving even gently the wheel bearing has failed. Seeing the tools needed to replace I'll be giving a mechanic some cash for that one sadly I hate doing that but just can't justify the outlay for what the work is.

R

[gorskined]

Originally Posted by RhysM

Thanks, Ken.

On those lines for what you've mentioned, the fuel hoses are top prio! I'm in the UK but we have sources for fuel pumps, I've been told to avoid anything but OEM fuel pumps! thanks for your input though really helpful. Yeah, when I had her running and driving even gently the wheel bearing has failed. Seeing the tools needed to replace I'll be giving a mechanic some cash for that one sadly I hate doing that but just can't justify the outlay for what the work is.

R

You can save a bunch of money and run a single new 200 series Bosch pump . Each pump comes with a registration #, You need to register on line to prove its not counterfeit . Buy from a reputable place. The new pumps have a higher volume and pressure with less amperage than the oem . There is a thread on here some place with a bunch of members talking about running single 200 bosh pumps, with stock cars . im basically stock 3.0l with an ic sc cams and a k27 turbo. i have a fuel pressure gauge and a afr gauge in my center console . running 93 and 96 psi even under full boost with a single 200 Bosch. i did originally install two i was way over pressurized . i removed one pump and i was still over 100 psi. i eventually have to remove two pressure shim to drop my pressure to get to the mid 90s . i replace my rear pump with a jegs inline check valve. figured two checks are better than 1 plus it holds the spot if i ever went back to two pumps . the Oem stuff is pretty much all gone that's why its important when you have your wur rebuilt to make it fully adjustable . this way you can adjust to achieve the correct afr #s .. also a wideband afr gauge is a must if you really want to dial the car in.

[RhysM]

Originally Posted by gorskined

You can save a bunch of money and run a single new 200 series Bosch pump . Each pump comes with a registration #, You need to register on line to prove its not counterfeit . Buy from a reputable place. The new pumps have a higher volume and pressure with less amperage than the oem . There is a thread on here some place with a bunch of members talking about running single 200 bosh pumps, with stock cars . im basically stock 3.0l with an ic sc cams and a k27 turbo. i have a fuel pressure gauge and a afr gauge in my center console . running 93 and 96 psi even under full boost with a single 200 Bosch. i did originally install two i was way over pressurized . i removed one pump and i was still over 100 psi. i eventually have to remove two pressure shim to drop my pressure to get to the mid 90s . i replace my rear pump with a jegs inline check valve. figured two checks are better than 1 plus it holds the spot if i ever went back to two pumps . the Oem stuff is pretty much all gone that's why its important when you have your wur rebuilt to make it fully adjustable . this way you can adjust to achieve the correct afr #s .. also a wideband afr gauge is a must if you really want to dial the car in.

Ah that's super interesting re the pump. The hosing as mentioned here is the starting point, pumps may be fine, just may be upstream is fully clogged! until I get into it I can't possibly know! the WUR is ready to go. Wideband AFR is also on the shopping list!

thanks for the info!

R