N62, electric ignition, turns over, won's catch/start

[Clockwork]

Hi all,
has anyone here had the issue where their electronic (turn key and let go) ignition system will crank powerfully but just never catch the engine dn turn it over? It has been happenning more and more lately and when it does. I let it occur for about 3 seconds, then I turn off key, then on second attempt, every time, the N62 fires RIGHT up loud and proud.
I've replaced the fuel filter about 50k kms ago and use premium only gasoline and even seafoam in the fuel tank about every 5th fill just to keep the injectors adn fuel system as clean as possible.
No, I've never replaced the fuel injectors.

Since its not an every day occurance with the e53, I can't really bring it into a mech and ask for him to diagnose, becasue we all know if I did that, the problem would never occur whilst the X5 is in their shop.

If anyone has had this issue, did you resolve it, and if so, what was your remedy?

this is the only issue my beautiful 270k km N60B44 has currently and I'd love to resolve it.

[andrewwynn]

Symptom of fuel pressure problem.

I've seen this when the FPR fails which you've said replaced in a time frame that would not have failed but that is the most likely candidate.

Checking fuel pressure after engine off for example overnight it should still be 20-30#.

When wife's FPR failed, the psi would jiggle not stay steady.

The next most likely candidate is fuel pump. When they fail, it's a slow process that's masked by the FPR doing it's job.

On the v8s with "convenience start" that I've worked on, the fuel pump doesn't kick on at key on like the 3.0 models only once you turn to the start position so it's relying on some reserve pressure from the last drive.

If you have a scanner that can force the pump on you can prime the fuel rail before you crank to help diagnose.

You can use a cheap "throw away" tire pressure gauge for simple read of pressure overnight (in my testing this works for one session/day, it kills the guts and stops working) but for $1 dollar store gauge it works.

"Feels" like you'll be able to trace the problem within a few tests.

[Clockwork]

I replaced my OE fuel pump a few years back after the OE pump's fuel level sender was acting up. Not the pump per SE but just the level sender.
I still have the OE fuel pump...maybe I should swap it back in to see what happens

Thanks for your feedback.


Sent from my Pixel 6 using Tapatalk

[andrewwynn]

I'd measure first. Also: fuel pumps last an average of 5000 hours. How's old was the original?

[Clockwork]

Originally Posted by andrewwynn

I'd measure first. Also: fuel pumps last an average of 5000 hours. How's old was the original?

200k KMS I want to say...

Sent from my Pixel 6 using Tapatalk

[Clockwork]

Originally Posted by andrewwynn

Symptom of fuel pressure problem.

I've seen this when the FPR fails which you've said replaced in a time frame that would not have failed but that is the most likely candidate.

Checking fuel pressure after engine off for example overnight it should still be 20-30#.

When wife's FPR failed, the psi would jiggle not stay steady.

The next most likely candidate is fuel pump. When they fail, it's a slow process that's masked by the FPR doing it's job.

On the v8s with "convenience start" that I've worked on, the fuel pump doesn't kick on at key on like the 3.0 models only once you turn to the start position so it's relying on some reserve pressure from the last drive.

If you have a scanner that can force the pump on you can prime the fuel rail before you crank to help diagnose.

You can use a cheap "throw away" tire pressure gauge for simple read of pressure overnight (in my testing this works for one session/day, it kills the guts and stops working) but for $1 dollar store gauge it works.

"Feels" like you'll be able to trace the problem within a few tests.

SO, I finally got around to checking the fuel rail pressure on my N62. Vehicle was sitting forabout 36 hrs in my heated garage, after a nice 35 min drive. I hecked fuel pressure valve, nder engine cover, on right side, and nothing showed up on the old school tire pressure slide/tool. so i tried carefully pressing in the schrader valve with a tiny flat head screw driver and NOTHING. so I tried starting the v8 and it started instantly. so I let it run for a few mins and while running, i tried pressing the schrader valve to see if it worked and yes a volcano of fuel spit quickly. not an issue for pressure when running :p
so I turned off the engine and after 5 mins i checked fuel pressure a the rail and the tire gauge moved up afew psi. i pressed with flat head screwdriver and expected a small volcano and all i got was a tiny burp of fuel.
So, reading more about where in the fuel system is a one way valve and apparently it is built into the fuel filter? I guess even tho the filter has just about 60k kmson it, its worth trying a new one... but I'm bringing the x5 to my mech to fix. i just dont have time (nor want to do it again).
will keep this post updated.

[andrewwynn]

There's a check valve in the pump and also the FPR works as a check valve from my understanding. When wife's failed it was the tiny o-ring inside the FPR that drained pressure back to the siphon jet inlet.

[Clockwork]

So the fuel filter DOESNT have a the one way check valve in it? I can't see how the fuel pump would fit it in there. Seems tight. But I guess so is the fuel filter. I read your other post, Andrew, where you dug heavily into the design of the fuel tanks, fuel pump and other side pump and how it flows towards engine.... I thought the understanding was the fuel filter under the X5 had the one way check valve.


Sent from my Pixel 6 using Tapatalk

[Clockwork]

None the less, I don't have time to chase this so it's going to a mech as it is now occuring 3 to 4 times a week where the engine will crank but no fire.

Sent from my Pixel 6 using Tapatalk

[andrewwynn]

Have you ever replaced the fuel pump?

A good FPR will camouflage a failing fuel pump for a long time, often more than a year.

Divide your odometer by your average mph (will give you your estimated hours run). Example 132000/27.5=4800.

Fuel pump expected lifespan is 5000.

By pinching off the return and supply hoses to/from the fpr the mechanic can determine if the fuel pump (supply) or the FPR (return) are at fault.

That would be a very early failure on the filter = FPR but any part can fail any time.