Fault code 23 low fuel pressure

[chris52]

Following on from my last post. I am still getting fault code 23 low fuel pressure. This does not bring on the MIL light. I have have checked the fuel pressure and all seems good, fuel pump fairly new from Power and the regulator is not old. The car runs fine with no issues most of the time. Then all of a sudden it will start pinking really badly at full throttle over 4K rpm. Whenever I have checked Rovergauge after this I find the low fuel pressure fault stored in the ECU.
So can a pump work ok most of the time (ran fine for 100 miles today lots of WOT before messing about)and then suddenly for no reason start running weak, I have checked the wireing and this seems good. I've replaced the fuel filter so that shouldn't be the issue. Fuel pressure at idle no vac 40psi with vac 30psi.
Low fuel pressure could cause the pinking especially at WOT. There is no fuel pressure sensor within the ECU so think it's determining it this because of the lean running. But could this be anything else causing this. Car is fully RR set up by Mark Adams so the map will be ok.
Any experience or ideas would be appreciated.
Chris

[chris52]

Thanks Mark will check the wiring first to see if there is a problem further up the loom to the pump as the connections to the pump itself are all good.
Chris

[chris52]

Mark I have sent you a PM.
Chris

[chris52]

Thanks Mark it is a possibility and well worth checking.
Using Rovergauge I can run the pump continuously. My plan is to run the pump with no Vac so max load on the pump having to keep the pressure at around 40psi and see if I can see if the fuel pressure drops at all with various tests on wiring relays etc. The only thing here is I may need to run it for quite some time but I cant see why that would matter.
Chris

[chris52]

Yes I see what you mean the only issue here is that I did 100 miles in the car on Sunday and the first 98 the car performed perfectly with no issues then all of a sudden went really lean and started pinking like mad. What sort of fuel pressure drop would cause this as there must still have been reasonable pressure as the car accelerated very well and didn't feel down on power the only difference really was the pinking and the low fuel pressure fault code.
My thoughts were that if it's a bad joint or bad earth then simply watching the gauge while someone rattles the wires around might show a drop in pressure of say 10psi which would then point to a wiring issue. If there was no difference then chances are that the issue could be somthing else
Ideally a rolling road session would be best but I had the car on a rolling road with Mark Adams for over 4 hours while he set up the fuelling and no low fuel pressure issues or running lean happened. I then drove 170miles home and still no problems. The next time out 10 miles and its pinking it's nuts off again. I cant see that the regulator could stick so it's reducing the pressure as if it had vacuum in the plenum especially as this is supercharged and it will have a positive pressure in the plenum pushing the diaphram which should in theory give more fuel pressure unless the regulator has a stop point.
Just thinking about what you said earlier about a fuel tank this happened when I got down to 1/4 tank I know there is still at least 2 gallons of fuel in it then as I drained the tank when I replaced the pump and filled 2 one gallon cans up to the brim with less than a 1/4 tank showing but it may be relevant and is definatley worth checking.
Chris

[chris52]

Th tank is alloy on mine so I suppose less likely to be a blockage unless somthing was dropped in it. Will do some more investigation work this weekend.
Cheers for all the help and advice
Chris

[chris52]

s p a c e m a n said:

Took me ages to find the cause of random stutterings on mine, crappy connections on the fuel pump. Every couple of weeks at completely random moments in time I'd lose all power for a second or two and then it would carry on like normal, eventually plugged it into roverguage and got a low pressure fault. Spade connectors were pushed all the way on but after checking them I never got the fault again so I can only assume that one of them had a poor contact.

I bought a new fuel pump as I thought it was the pump and did find a poor spade connection, the big one same as yours but the new pump has bolt on connections so they should be fine. But it could well be a bad connection further down the loom. I remember having an issue with a Griff I had about 10 years ago and that was a bad connection in the wiring behind the passenger door but that stopped the pump altogether but hoping to find something there which will be an easy repair.
Chris

[chris52]

Struggling with this one. Found the wiring fault only giving 10v to the pump replaced the wiring and the pump sped up dramatically so thought I had found the fault. But a blast out yesterday and starts pinking again plugged back into RG and fault 23 low fuel pressure lit. No idea what to look at next. Could check the regiulator as I have a spare just to rule it out completely but it check out ok with a pressure gauge.
Any ideas what else can cause this fault code?
Chris

[chris52]

Trevor450 said:

A mate of mine had this on his P38 and it turned out to be the throttle potentiometer.

Thanks for the info but it was changed a few weeks ago by Mark Adams when it was on the rollers being set up. 6 hours on the rollers and the car never faulted once no pinking no fault codes behaved as good as gold massive power maxed out the rollers as it had to be run in 5th gear because it was spinning up in 4th even with the boot full of steel weights Mark said it was spinning up in 5th but he managed to set the Map ok. he couldn't give me a definite BHP but he says it will be over 400. Just wish I could sort out this problem.
Chris

[chris52]

Agree I need to monitor the pressure when driving. It may be that the pump just can't supply the amount of fuel needed it also might be the fuel pressure regulator is pulling the fuel pressure too low when on vacuum and that is bringing the light on. When I got the car it had the vacuum pipe was disconnected from the regulator which makes me think this has been an ongoing problem so it may be worth seeing how it goes with that disconnected again. I have a boost gauge fitted and it goes off the scale in the vacuum side over 20hg so could in theory be bringing the pressure to low when running in closed loop and putting the light on.
The pinking though points to lean running at WOT but this could also be a timing issue or intake temps or too much boost etc etc.
Will check the pressure when I can and report back.

[chris52]

Ok not had chance to check the pressure yet but have now spoken to the company that manufactured the fuel pump supplied to me by *** ***** who advised me that this was the pump I needed for a supercharged 5.0l the manufacturer has advised me that this pump is not powerful enough as they max out at 350 bhp which if this is the case is extremely disappointing from a company with their expertise and knowledge of these cars.
Ive been recommended to get a Bosch 044 which should hopefully resolve the problem. fingers crossed
Chris