350i FPR Failing or Leaky Injectors?

[mrzigazaga]

Hi Peeps....I have noticed that I'm getting the popping and banging again whilst accelerating, I checked the fuel pressure via the gauge on the FPR and twice now the pressure has dropped by around 10psi..Running!..I brought it back up to36-38psi at WOT and checked it again after a few days of driving..However the popping and banging came back and the pressure has fallen by 10psi..AGAIN!.

I was going to clamp the return from the fuel rail to see what the stall pressure was..I have also noticed that the pressure falls away as soon as i turn the engine off...Could this indicate weeping injectors?....Cheers
Ziga

[adam quantrill]

Possibly or the FPR itself is letting the pressure drop through the return pipe - it you clamp it off and then stop the engine that will tell you if it's that.

[mrzigazaga]

adam quantrill said:

Possibly or the FPR itself is letting the pressure drop through the return pipe - it you clamp it off and then stop the engine that will tell you if it's that.

Thanks Adam...Thats what i was thinking....Last time this happened the fuel pump failed...I was thinking it might of had something to do with the 3.5ltrs of diesel i put in by mistake a little while back..I did top up straight away with £30 of 97..I was wondering if it has turned to cheese and blocked the post filter or if there could be an issue with the FPR and this caused the pump to fail previously?....I have put a fair amount of petrol injector cleaner through since and it happens more once the engine is running up to temperature...I meant to whip a couple of plugs out earlier to see what they look like but totally forgot...Will do that in the morning....

[Wedg1e]

It could, hypothetically, be an injector sticking open - or worse still, an entire bank of 4 switching hard-on (hey, I said hard-on ) intermittently. Guess what might cause that

[mrzigazaga]

Wedg1e said:

It could, hypothetically, be an injector sticking open - or worse still, an entire bank of 4 switching hard-on (hey, I said hard-on ) intermittently. Guess what might cause that

ECU causing a "Hard-on"..Said the bishop to the actress....There was a mingey pin on the ECU connector but it was cleaned and checked...The unit was re-soldered...Or AFM????....So if i clamp the return and i still lose pressure that could be either the FPR or the Injector/s stuck open.....

[Wedg1e]

mrzigazaga said:

ECU causing a "Hard-on"..Said the bishop to the actress....There was a mingey pin on the ECU connector but it was cleaned and checked...The unit was re-soldered...Or AFM????....So if i clamp the return and i still lose pressure that could be either the FPR or the Injector/s stuck open.....

It wouldn't be totally unheard of, although it's rare, for the non-return valve in the fuel pump to be leaking back, so if you could nip off the high-pressure feed from the pump that would take it out of the equation too.
Is your cold-start injector still plumbed-in? Might even be an issue there...

[mrzigazaga]

Mmmm....I will unplug the cold start to see if that makes a difference...Clamping off the HP fuel side will need heavy duty clamps that i don't have...I bought some and then when i jacked the rear up i noticed armoured fuel hose has been used so trying to clamp it with normal clamps is just a waste of sweat...I will also check all the connections.....Cheers...Ziga

[Wedg1e]

Intermittent feed/ bad earth to the fuel pump? You could clamp off the inlet side to the pump, perhaps? That would prevent the pump draining back into the tanks so maintain the HP side.

[maston]

mrzigazaga said:

I have also noticed that the pressure falls away as soon as i turn the engine off...Could this indicate weeping injectors?....Cheers
Ziga

YES, that's exactly the problem I had and as you know I had weeping injectors.

[superwedge]

I think zig,that diesel you put in has done the seal on them,

[griffdude]

Hi Zig

I used these guys to sort out some troublesome injectors-

http://www.injectortune.co.uk/Injector_Cleaning.ht...

[mk1fan]

Nice link.

[mrzigazaga]

Mmm...I think the diesel may of done a tiny bit of oiling up of plugs although i won't know until i remove a couple of plugs which i was going to do this morning but had to go out and have only just got back...If she has cooled down enough before it gets dark then i will have a look at a couple, And i forgot to clamp the return fuel hose...Doh!..If it is weeping injectors wouldn't the fuel pressure be okay while its running?...This has happened before pre-diesel and changing the king lead sorted it out..However I'm not convinced that the pressure would drop down to the king lead starting to fail...

PS: Thanks for the link for the injector cleaning...I was recommended to them a few years ago and heard good things about them....For what its worth i found a receipt for eight injectors to be cleaned and one to be replaced with new...I think it was around 2008...I know nothing is guaranteed but its worth mentioning...I will dig the receipt out and have another look....Cheers

Edited by mrzigazaga on Wednesday 24th December 16:34

[TV8]

HiMark, I think I have a set of injectors somewhere if you need them. Give me a call after Christmas if you do.

[mrzigazaga]

TV8 said:

HiMark, I think I have a set of injectors somewhere if you need them. Give me a call after Christmas if you do.

Thanks mate....Thats worth knowing...I think i may well have a set also as i have a plenum...Fuel rail and trumpet base in the garage.....Cheers...Ziga

[mrzigazaga]

Well...After some further research it may be the case that the FPR is attached to the high pressure feed instead of it going to the fuel rail...(Copper pipe under bulkhead) ..The return is going straight to the tank from the fuel rail...Which means that the pressure I'm seeing is being dramatically decreased by use of the injectors and the tank return ...It would certainly explain why it was running lean and the pressure was fluctuating so much...And could also be the cause of the previous fuel pump failing!...Im going to swap it over tomorrow ..Energise the system and give it a blast...Maybe this is the reason why i get "Pinking" on anything above 3 degrees ignition timing...

I guess it could be an easy mistake to make but i should imagine that this was why the high pressure feed is visibly in copper in the engine bay..I mean why would you put it on the return which is of much lower pressure....Unfortunately i had no pictures of the engine before it went in to have work done...I just hope it hasn't caused any long term damage....

Copper feed....


Which goes to the FPR....

The tank return..Which should be the feed and NOT return.

[mrzigazaga]

Hi Peeps..Happy Christmas...Well i removed the fuel hose from the fuel rail..Blew down it and got resistance..Took the one off of the FPR..Blew down it..No resistance so it seems that the FPR is in the right place...I thought it strange that the return is the copper pipe coming from under the bulkhead...Oh well...Removed two plugs..
One from No.2...

And one from No.7


Look okay...Might be a bit of diesel remnants on them...Im going to try a new set of plugs...These are only about 6 months old...
Back to the drawing board...I might whack one of the solid state FPR that i have and a pressure gauge from a mate to see if its the reg....I just hope its not the injectors....I also have a new ignition amp that i will fit even though the old one looks new-ish...Cheers...Ziga

Edited by mrzigazaga on Thursday 25th December 10:02

[Jack Valiant]

Well did not want to comment having seen and worked on the car but....... your issue is not one of fluctuating pressure its just that you keep looking at the gauge and over thinking the issues IMPO. These gauges can give some sporadic readings due to engine bay temps and plenum vacuum. By all means try a standard fixed 2.5 bar FPR but as I recall you have done that previously and the lower pressure was causing pinking?? As I believe your motor has had some previous fettling (probably gas flowed etc) it needs a bit more than the stock FPR thus my recommendation to an adjustable FPR and tweaked up to 38 psi) The plugs selected show a reasonable burn so seem to compliment this diagnosis., just give them a good clean and replace.The issue of the burbing noise and intermittant pops / bangs under power are symptomatic of a weak flapper AFM spring as previosly mentioned fella. If you have a spare flapper then get in on and test to confirm this issue. Its a simple roadside job and would confirm / eliminate the problem. Once done then reassess to see if you need to go any deeper. I would then go for a Air Fuel Ratio test under load on the rollers. The diesel issue would have caused bigger problems if it was going to, so not relevent given the amount of time and mileage since the fuel incident. As mentioned previously replacement of the hi pressure fuel filter and fit a low pressure filter upstream of the pump at the same time for belt and braces. Get the spanners out matey

Chris

[mrzigazaga]

Thanks Chris...I do have a spare AFM ...Somewhere...Its funny i was thinking earlier the same thing about the FPR....A touch of the fiddles i think...It has started to sporadically cut out when pulling away or accelerating hard, Exactly the same as it was doing a while back and replacing the king lead cured it...Maybe its time to change the cheapo king lead that had been sat on a motor factors shelf for years that i got free...I will swap over the AFM and check the ECU plug as that was causing something similar..The second time was worst when it died when we were all on a run out...

I have monitored the FP and over the last two days it has held at 38-40psi which is a tad too high although stable..I will run her up to temp with the other AFM on tomorrow if it stays dry and adjust the FP if needed and then LEAVE ALONE, I may remove all the plugs for a clean before hand but again depends on the weather..
It would be advisable for me to change the fuel filter as you say, And fit a pre-filter...These symptoms are reminiscent of two things..

1. The king lead failing.
2. The fuel pump failing.

Or both!...Could be that the post filter if kaput-ten and is causing a pressure lock which is causing a reduced amount of fed fuel and causing the pump to overheat...Im just surmising of course...Well thanks for all the advice and help...Time now to open the bottle of scotch that my lovely new neighbours have bought me for Crimbo...Yum Yum....


Oh and if i come on here in about an hour ranting bullst...Actually id better rephrase that...Ranting total and utter bullst about either an Irish girl or alternate health practice....Or even the couple down the road who let their dog piss up my car cover every time they pass...Someone please call me and put me out my misery....Ta....Happy Christmas ya bastids....Ziga



Just unwrapped it...Oh dear...Im in trouble....
What kind lovely neighbours..

Edited by mrzigazaga on Thursday 25th December 19:33

[KKson]

mrzigazaga said:

Back to the drawing board...I might whack one of the solid state FPR that i have and a pressure gauge from a mate to see if its the reg....I just hope its not the injectors....I also have a new ignition amp that i will fit even though the old one looks new-ish...Cheers...Ziga

Mark, if you're still struggling then I've got a spare set of injectors and a standard fuel regulator if you want to give it a go, just to rule it out?