odd starting problem o_O

[TiesTorN]

I'm confused as hell... anyone seen anything like this?


my car -most of the time- can not start without me interfering with the fuel delivery system. it just won't start unless I deliberately cut the fuel by pinching the fuel hose. I think the pistons are getting drown in fuel somehow, then starts when I cut the fuel.


sometimes it starts normally.


ps: injectors are brand new(bosch OE), there is absolutely no leak problem. fuel pump is brand new (OE pierburg), fuel filter is brand new(OE mahle)


recorded video of it;





only known problem in the car is the vanos. vanos' are not working for now (will be replaced soon with dr.vanos). but as far as I know, a faulty vanos won't do such a problem like this? am I right?


inpa shows only 2 error codes, which are;


33 - nockenwellensteuerung bank 1
34 - nockenwellensteuerung bank 2


and no, it's not the camshaft sensors that are faulty, they are only 10K kms old genuine bmw sensors. checked with a GT1 in a mechanic shop and it shows vanos error, not the sensors itself. can't remember the exact codes though.


anyway, anyone has any idea? what can cause this?

[JimLev]

What's your fuel pressure when you are cranking the engine and don't have the fuel line pinched off?

[TiesTorN]

dunno but what does this has to do with fuel pressure? do you mean there may be too much pressure ? because low pressure shouldn't do this.

[edjack]

Do what he and I say (in another post), and it will perhaps offer some clues.

[TiesTorN]

well I certainly can't do it myself but I'll try to have it done soon.

[StephenVA]

Pass the popcorn 🍿

[JimLev]

pass the popcorn 

lol.

[TiesTorN]

Pass the popcorn 

anything funny ?

[StephenVA]

It was the way you answered the question regarding fuel pressure if you need to know.

The poster was trying to help pin down what fuel pressure reading you have available in the fuel rails now (with key on and engine cranking) as the injectors only open and close, what the spray pattern looks like, volume of fuel that reaches the cylinders, etc is only based on pressure and volume available from the fuel line, pump, and fuel tank. A cheap fuel pressure gauge attached to the test port on the fuel rail or at the fuel filter (depending on the year and model in question) will show what pressure is available for the injectors to flow.
There are a TON of internet vids on this test procedure so you can see first hand what is required.

The Pinching the fuel line and the engine starts, is one of the most interesting postings I have seen in a while. Looking forward to the additional posting and final resolution of the problem.

Any competent BMW Indy can do this quickly if your DIY skills/tools/space is lacking.

[scyrusurcys]

OP, you can buy an OBDII plug-and-play scanner off eBay for close to $10. Some will sell it with phone software that you can download from the Google Play Store or Apple Store. I have something similar to this one but it allows you to check the fuel pressure, as well as a plethora of other real-time diagnostics information for your car:

Link to OBD2 Scanner

[JimLev]

That OBD scanner would be nice to have, but it won't tell you the fuel pressure. There is no fuel pressure sender on any E39.
You should have 50 PSI (or very close to it) at the test port on the fuel rail.
If your testing it before the engine it will be a few pounds higher.

Good answer StephenVA.

[StephenVA]

Thanks
Try to help those struggling with DIY skills, tools and a testing process of elimination....You know, test DON'T Guess to find out what is working correctly so you eliminate items that are working properly leaving items that could be going wrong. This approach requires that you actually know what good looks like (specs, visual inspection, measurement tool investment, and of course the skills to use them properly.) Real simple stuff like starting and charging systems, Ign systems, exhaust, etc. These things have been around for 100 years and all of the testing procedures have been well established. The only modern changes are in the areas of "How fuel gets delivered and what happens to the waste after combustion down stream".
I have come to the conclusion that a smart approach to problem solving will resolve even the most wacko Symptom Checklists.

I do however find lots of humor in the internet suggested part replacement diagnostics that is way too common on the forums. "Try this XX Part as it was the problem on mine." Gee, every car has the same part problem. Who knew? That will save $$.......
Common failures yes, we all know them. Symptom = part? Now that is a different conversation.

[TiesTorN]

still couldn't do pressure test. but I forgot to mention that when I switch the ignition to position 2 (just before cranking position) multimeter shows 8 volts on the injector connectors. is this how it should be? I thought injectors shouldn't be getting any voltage before actually cranking.

[vinyldude]

The injector control is generally done by grounding the other end of the injector, while the other end stays energized (constant DC voltage) at all times. Not sure what a good voltage value is, but the fact that you found voltage there does not sound surprising.

[sleuth255]

hmmm bad fuel pump? Pinching off the line allows pressure to build? Are you pinching off the pressure or return side (sorry, I'm an I6 owner)? Answering "the return side" would support this hypothesis...

[TiesTorN]

Pinching off the line allows pressure to build? Are you pinching off the pressure or return side (sorry, I'm an I6 owner)? Answering "the return side" would support this hypothesis...

I've actually thought about the same thing but when I checked realoem diagram it seems like it's the pressure side not the return side. I'm not sure though, there only seemed to be one hose anyway in the diagram;

http://www.realoem.com/bmw/enUS/show...diagId=13_2049

number 4 ?

and shouldn't there be any symptoms of it if the pressure was low when the engine is running? because once it starts, there is no other low pressure symptoms. and there is plenty power past 3500 rpm, because of vanos fault. never hesitates above that rpm.

[TiesTorN]

It was the way you answered the question regarding fuel pressure if you need to know.

I'd like to remind you guys that English is not my native language so I may not always be 100% accurate on what I want to express. Imagine yourself trying to express yourself in my language, could you?

anyway, back to the subject...

[StephenVA]

A pressure test at the fuel rail will determine if (engine off) there is pressure at the rail and it is not leaking down (leaking injectors, etc). The pinching the fuel supply is the same as turning off the fuel pump. When the engine does start, does it act as if it is "Flooded" (blows raw fuel out the tail pipes, engine firing stumbles until the plugs clean themselves off) and the engine warms up? Does the same problem occur on start HOT or Cold engine?

If the answer is "YES", look at why the injectors are open on cranking not cycling. Grounds, wiring harness, etc. As this is a classic example of at start runs rich issue. Injectors all fire and "click" the same?

Question: Does the car run normally after it starts and has not drive-ability issues? (Runs smooth, good power, no black smoke out of the exhaust pipes, etc?)

[TiesTorN]

A pressure test at the fuel rail will determine if (engine off) there is pressure at the rail and it is not leaking down (leaking injectors, etc).

I won't say it's impossible but it's highly unlikely that injectors are leaking. As I mentioned in the first post they are brand new OE bosch injectors.

The pinching the fuel supply is the same as turning off the fuel pump. When the engine does start, does it act as if it is "Flooded" (blows raw fuel out the tail pipes, engine firing stumbles until the plugs clean themselves off) and the engine warms up? Does the same problem occur on start HOT or Cold engine?

It's exactly like in the video. Did u watch it?

I haven't noticed any black smoke or raw fuel out the tail pipes. Happens mostly when the engine is cold but I have no hard evidence about it, could be just coincidence.

If the answer is "YES", look at why the injectors are open on cranking not cycling. Grounds, wiring harness, etc. As this is a classic example of at start runs rich issue. Injectors all fire and "click" the same?

yeah that was actually my concern. injectors staying open when cranking, not cycling. I guess we need to take out the injection tube and observe the injectors' behaviour while cranking.

Question: Does the car run normally after it starts and has not drive-ability issues? (Runs smooth, good power, no black smoke out of the exhaust pipes, etc?)

yeah it's running like how a vanosless car would run, no power below 3500 rpm but it runs smooth, no driveability issues.

I'm thinking of getting the vanoses fixed first (I just received dr.vanos units) and then continue from there. maybe this is happening because of wrong cam timing and faulty vanos.

[TiesTorN]

problem solved with new dr.vanos units and proper timing.