Long Crank Issue after Having Injectors Rebuilt - Leaky?

TXCarGeek

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So I did a bunch of work on my '08 BMW 550i with the N62tu engine recently including sending the injectors off to be rebuilt and cleaned being that they were original with about 235K miles on them. Everything went back together well, but now I'm having an intermittent long crank issue; when this happens, it'll briefly puff some black smoke and sniffing the intake manifold through the throttle body smells strongly of fuel. Checked fuel pressure: pressure drops from 50 psi to 20 psi over 1 hour with vehicle sitting. Fuel trims don't reveal anything super obvious while driving. Haven't pulled plugs or fuel rail yet, but figured pulling the rail from the manifold will show if an injector is leaking down slowly and flooding the cylinder.

My question is if anyone has ever experienced leaking injectors following a rebuild service?

Hindsight being 20/20, I should have just left them alone considering I was not having any injector related issues prior to the work :cautious:
 
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Your injector(s) is (are) dripping fuel. Fuel pressure should hold better after a one hour shutdown. Is 50 psi the proper spec for your engine? Did you renew the o-rings?

No injector related issues prior to the rebuild, then why did you decide to do it when they were working?
 
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but figured pulling the rail from the manifold will show if an injector is leaking down slowly and flooding the cylinder.

My question is if anyone has ever experienced leaking injectors following a rebuild service?
Any service that cleans injectors is going to test them for leaking and reject them if they are. Did you reset the ECM or relearn fuel trim adaptations after installing the injectors? I'm guessing the computer thinks the engine still had the old clogged injectors and is feeding it too much fuel than it needs.
 
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You could be losing fuel pressure if an injector isn't properly sealed to the fuel rail, but much better chance an injector is dripping. It's not going to be easy or quick to find the leak if you cleaned everything up before installing. Maybe fuel trims can point you to 1 bank at least.
 
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And what do you mean "rebuilt"? Unless it's a diesel injector, they are sealed units. They can't be opened up and parts replaced.

A2C53432878Z-Connector__ra_p.jpg
 
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Are you sure you received your original injectors back? Maybe you received somebody else's problem...
I wonder the same. Those injectors have to be coded to the vehicle based on flow data.

I still think servicing GDI injectors is a pointless exercise considering how problematic they are....and the HUGE issues that can occur if they fail.
 
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These are not GDI and do not need to be coded, they are a high ohm saturated injector with a projected pintel. This is one for a 2008 550i

2006 bmw 550.jpg

This is a special GDI one that is a real PITA, I don't do these at the moment. In general there are no issues servicing normal GDI units, most do not need coding. I do some that need coding but it is a process that is a bit much for posting.

bmw 650i.jpg

Edit: BTW I don't do the ones in the E350 V6 you have in you sig, those can be a problem.
 
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These are not GDI and do not need to be coded, they are a high ohm saturated injector with a projected pintel. This is one for a 2008 550i

View attachment 129576
This is a special GDI one that is a real PITA, I don't do these at the moment. In general there are no issues servicing normal GDI units, most do not need coding. I do some that need coding but it is a process that is a bit much for posting.

View attachment 129577
You're right - I was confusing the N62 with the N63. The N63 is GDI.
 

TXCarGeek

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Your injector(s) is (are) dripping fuel. Fuel pressure should hold better after a one hour shutdown. Is 50 psi the proper spec for your engine? Did you renew the o-rings?

No injector related issues prior to the rebuild, then why did you decide to do it when they were working?
Yes, 3.5bar or 50psi is spec for this engine. When I initially plugged the pressure gauge, the reading was 0psi which was after the vehicle had been sitting overnight. Fuel pump primes when you open the door. That put the pressure up to 50psi. Then over the ensuing hour, it dropped to 20psi.

Yes, All new o-rings.

Only sent the injectors off because of mileage. Should have followed the “ain’t broke don’t fix” mantra. Live and Learn.
 

TXCarGeek

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Any service that cleans injectors is going to test them for leaking and reject them if they are. Did you reset the ECM or relearn fuel trim adaptations after installing the injectors? I'm guessing the computer thinks the engine still had the old clogged injectors and is feeding it too much fuel than it needs.
Did not reset ECM or adaptations with a scan tool but the battery was disconnected for quite some time and should have allowed for the same relearn.
 

TXCarGeek

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You could be losing fuel pressure if an injector isn't properly sealed to the fuel rail, but much better chance an injector is dripping. It's not going to be easy or quick to find the leak if you cleaned everything up before installing. Maybe fuel trims can point you to 1 bank at least.
No obvious leaks from the fuel rail both visually nor by smell when I’ve inspected. Really does seem more like the injector itself. I’ve monitored fuel trims over the past few days and haven’t seen anything obvious.

I do plan to pull the rail which isn’t too hard to do on this car and allow it to sit pulled away from the manifold with the system pressured up. I lost 30 psi of pressure over 1 hr so if it’s a leaking injector, surely I’d see it.
 
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These are Siemens/Deka injectors and require a little different technique to properly clean them without damaging them, plugging them in and running them in an ultrasonic cleaner is not the right way. The nozzles on these can get damaged if allowed to get too hot at the nozzle (they are normally cooled with fuel) which can cause a leaker.
 

TXCarGeek

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These are Siemens/Deka injectors and require a little different technique to properly clean them without damaging them, plugging them in and running them in an ultrasonic cleaner is not the right way. The nozzles on these can get damaged if allowed to get too hot at the nozzle (they are normally cooled with fuel) which can cause a leaker.
Very cool info there!
 
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I fought a similar issue on our previous 2005 Ford 3.0L V6 at around 175K miles, sent off the factory injectors to a reputable shop that's always done good work for me and developed same symptoms you described...but only after a hot shutdown.

Extended troubleshooting found that it held fuel pressure fine when cold @ approx 70degF ambient and engine temp, but after a hot shutdown at operating temp it lost fuel pressure gradually over a 30min period. This was followed by a long crank and smoky exhaust, after which it ran fine.

I had sent the injectors off for servicing while troubleshooting a rough idle (turned out to be a collapsed hydraulic engine mount) and ~3% imbalanced LTFTs bank-to-bank at idle. Ended up replacing them with new Ford injectors and problem solved, same part # but with a different color stripe (purple vs. original brown?) which indicated ethanol flex-fuel compatibility according to the dealer parts guy. He said he'd seen the brown-stripe injectors fail at extended mileage running regular E10 gas, corrosion at the pintle seat.
 

TXCarGeek

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Update:

Life has been busy and the car has been sitting, but I finally had a chance to pull the injectors and there’s a few of them very obviously wet at the tip. You can see the yellow coloring of fuel vs the dry one in these pics.

I’ll send them off to Trav tomorrow to verify the issue and see what my options are.
 

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