1998 v40 t4 phase 1 rising from the ashes

[moz T4]

Hi guys,
Right background:- ive owned the car for about 10 years and i love her...
6 years ago i suffered heart failure and took the car off the road where she sat sad and alone...good news heart's loads better and i want baby back on the road. So got the old bird mot'd she went through with £100 worth of brake pipes 2* droplinks and a suspention arm, and a new cambelt kit and water pump, but she was running badly stalling when hot very intermittantly and hesitating. So i got a bluetooth obd11 reader and got a p0141 trouble code, so the garage monkey said lambda sensor, we'll change the upstream and see if that fixes it but it may be the downstream also.....at this point i jumped on the brakes and did some reasearch on o2 sensors and fuel trims (thanks for all the information you lovley people have on this forum) it turned out upon advice from a thread the code related to the downstream sensor so i got it replaced and deleted the code great no codes...
However my fuel trims are very negative -20% + or - 10% so. ive cleaned the throttle body and ICV, replaced the air filter, cleaned the MAF , changed the plugs, epoxy resin repaired both coils with small crack's in.
The last thing i did was clean the MAF i used proper MAF cleaner before cleaning the fuel trims were negative but no more than 10% either way after cleaning they went berserk -30 and more. And now a p0172 fault code has appeared (powertrain system too rich bank 1)
Im by no means a mechanic which is good because i dont trust them they seem to want to play pass the parcel with parts.So i thought id learn to do this myself, im not stupid and im trying to learn as much about my car as i can hopefully with your expert help an advice.
so here goes would i be right in thinking the fuel pressure regulator on the fuel rail is leaking fuel back to the throttle body through a vac hose as the diaphram might be faulty....if you agree how would i test it to see...
any help would be greatly appreciated
Oh I have ordered a fuel pressure guage to test rail will be here in a few days , ill post results when i have them

[Ginga]

could be leaking injectors?
with the gauge you can some things.
If it makes the right pressure (~3bar); if it holds that pressure (without getting the engine to run)...

About fuel trims, read them at determined rpm.
Idle; 2000; 3000.

It could help you better diagnosing the source of your problem.

[ww1dm1]

Originally Posted by moz T4

the garage monkey said lambda sensor, we'll change the upstream and see if that fixes it but it may be the downstream also.....

I would backhand slap the ape as soon as he uttered this garbage. Don't give such bogus mechanics your money. Take it to a person who can diagnose at least a basic problem without throwing parts at it if you want someone else to do it.

You're on the right track. Starting with the FPR is good, it's a common failure point on the T4 and will cause rich mixture. First inspect the vacuum hose going to it. If it's intact and not leaking, remove it from the FPR side and watch for a few minutes if no fuel is escaping while the engine is working, that would indicate a ruptured diaphragm. If it seems fine, you can check the pressure it holds at the fuel rail. The base pressure for the T4 is exactly 3.09bar. It should be held when the engine is not working (fuel system primed) and should drop to ~2.4bar (not entirely sure) at idle.

[moz T4]

fuel pressure gauge finally arrived but no schrader fitting and i couldn't get 1 anywhere so
After much messing around i managed to attach a bike pump fitting. (i know what a pikey lol) Right pressure at the rail is 39 psi or 2.7 bar when primed, at idle 32 psi or 2.2 bar, the gauge looses approx 3 psi over 10 mins and 7 psi in 30 mins. with engine running if i remove the fpr vac hose at the throttle body pressure increases between 5-10 psi. if i increase rpm fuel pressure is stable...
my fuel trims are around -20% it appears both stft and ltft at -20% the short term dose not drop back to 0, I am using a blue tooth obd2 dongle and torque pro on my smart phone so im not sure how accurate the readings are, and at 2000, 3000 rpm fuel trims are -30%,
fuel pressure in my trusty haynes says 44 psi so seems a little off however i have a rich condition not a lean one so pressure should be ok?
is the few psi loss of fuel over 10 mins suggesting a injector is leaking or should there be a little loss in pressure over time?
a mechanic i know suggests replacing the throttle body entirely but couldn't explain why this would make the system run rich, so balls in your court oh wise forum members.

[ww1dm1]

Originally Posted by moz T4

fuel pressure gauge finally arrived but no schrader fitting and i couldn't get 1 anywhere so
After much messing around i managed to attach a bike pump fitting. (i know what a pikey lol) Right pressure at the rail is 39 psi or 2.7 bar when primed, at idle 32 psi or 2.2 bar, the gauge looses approx 3 psi over 10 mins and 7 psi in 30 mins. with engine running if i remove the fpr vac hose at the throttle body pressure increases between 5-10 psi. if i increase rpm fuel pressure is stable...
my fuel trims are around -20% it appears both stft and ltft at -20% the short term dose not drop back to 0, I am using a blue tooth obd2 dongle and torque pro on my smart phone so im not sure how accurate the readings are, and at 2000, 3000 rpm fuel trims are -30%,
fuel pressure in my trusty haynes says 44 psi so seems a little off however i have a rich condition not a lean one so pressure should be ok?
is the few psi loss of fuel over 10 mins suggesting a injector is leaking or should there be a little loss in pressure over time?
a mechanic i know suggests replacing the throttle body entirely but couldn't explain why this would make the system run rich, so balls in your court oh wise forum members.

2.7bar seems quite a bit low. Did you check if your diaphragm is leaking? Maybe it's low because it is leaking into the intake?

Pressure loss of 7psi in 30 minutes doesn't seem too bad. It's not necessarily the injectors leaking, the fuel pump has a check valve that leaks some pressure over time. Less when the pump is new, more when old, but it's nothing to worry about in general. If you have a serious suspicion it's the injectors leaking - here's something you can try: remove the whole fuel rail WITHOUT disconnecting the fuel feed or removing the injectors. Place in on a sheet of absorbent paper. Prime the system and keep an eye on the rail and paper for 10 minutes or so. You'll see if the injectors are leaking.

[Ginga]

That's a good test but make sure you have spare o-rings to replace on each injector!!

[moz T4]

OK update on the t4, i purchased an injector pulse tester and tested the injectors on a 50 pulse setting. No.1 injector drops 11 psi and the three others drop 9 psi, So im assuming that the No.1 injector is leaking more fuel which would cause my rich condition...
Can the injector be repaired or cleaned to solve this problem? Or do i just replace the faulty 1, also if replacing do i use new or second hand any advice would be greatly appreciated...