Starting Problems: Causes vs. Symptoms

Hi,

Having also experienced starting problems myself, I came up with the idea of summarizing the suggestions from the technical article and older posts. Furthermore, I would like to focus on the following in particular:
- Demonstrate the various causes with testing methods that anyone can use (even someone without diagnostic equipment or familiarity with the engine compartment).
- The causes should be categorized in a way that allows a non-expert who commissions a troubleshooting process to provide the workshop with a meaningful sequence of steps, which, on average, leads to the solution at the lowest cost. For this, two factors are essential: How expensive is the relevant test or part replacement? And: How likely is a defect in this area?

First, the (unsorted) list:
1. Spark plugs defective, fuse blown.
2. Fuel tank ventilation malfunction.
3. Oil lines are leaking/porous.
4. Incorrect static injection timing.
5. Loose crankshaft bolt.
6. The ESP needs to be purged.
7. Defective engine or coolant temperature sensor.
8. Cylinder head gasket.
9. Poor spray pattern, fuel injectors.

Here are some tips for easily checking or ruling out this error:
1: Only relevant at temperatures below 5 degrees Celsius.
2: Leave the fuel cap open, then start the engine.
3: Start the vehicle with the necessary organ components engaged. Then, turn it off and restart it. If prolonged engagement of the organ components is again required, the issue is likely not related to the oil leak lines.
Furthermore, if the problem is more dependent on temperature than on dwell time, this also argues against leaking oil lines.
Regarding points 4, 5, 6, 8, and 9: These are likely temperature-independent. Furthermore, they should also cause problems during operation.
8: Are the oil and coolant levels correct?

Unfortunately, I'm not a professional either, and (almost) everything I wrote was taken from articles.
Therefore, I would appreciate a review and expansion of the two lists, as well as suggestions for how to sort them.

Hi.

Quote:

A layperson who commissions troubleshooting

can suggest a meaningful sequence of steps to the workshop.
Based on experience, that usually results in nonsense.

Either you have enough knowledge to identify the error and conduct meaningful troubleshooting, in which case you should do it yourself, or you don't have any knowledge, in which case you can learn by asking questions and researching here.

Or, if you have absolutely no idea what you're talking about and just want to act like a know-it-all in the workshop, then you're in the wrong forum.

No one can avoid the personal learning process. Providing a guide for complete beginners who, after a quick overview, might feel qualified to give advice to professionals is bound to go wrong.

Best regards, Rainer.

Hi,

You're absolutely right to point out that I've dramatized things. The purpose of this thread is not to help know-it-alls, but rather to help reasonable people issue a repair request and avoid being completely ripped off.

'Den persönlichen Lernprozess kann sich NIEMAND ersparen, [...]'Please provide the text you would like me to translate from German to English.'

I think you can sometimes do without it. An instruction manual can not only be wrong, but a good manual can actually help in eliminating potential sources of error. For example: If a vehicle doesn't start at temperatures around 30 degrees Celsius, it can't be due to the glow plugs. Result: You've eliminated a potential source of error without having any real knowledge.

Therefore, I also believe it's useful to be able to rule out certain potential causes of problems, even for someone with very little knowledge. For example, most people, even those with no technical expertise, can probably tell whether a starting problem is related to temperature or how long the engine has been idle.

Example: If a vehicle doesn't start when the temperature is around 30 degrees, it cannot be due to the glow plugs.

I want to see how your car, with almost 100% ethanol in the fuel, starts at an outside temperature of 30°C without any preheating. In other words, you shouldn't generalize things like that, which you unfortunately are doing. Well-intentioned, but not well-thought-out .

You're right. The statements should naturally also apply to vehicles powered by kerosene. That was a really silly idea of mine.

I'd be happy to explain in more detail: This is not a comprehensive diagnosis, but rather guidance for laypersons in typical situations.

That's right. The statements should naturally also apply to vehicles with kerosene engines. It was really a silly idea of mine.



Perhaps that was a poorly chosen example, but what if someone with a 1Z engine with 320,000 km, worn-out injectors with an opening pressure of 160 bar, and a weakening battery, suddenly decides to fill up with biodiesel, assuming their vehicle is explicitly approved for it.

In a cold start in freezing temperatures, the glow plugs might be working correctly, but the engine might require several attempts to start because too little of the poorly atomized fuel is vaporizing and igniting.

I know some people who tend to go in that direction - but if they are that dumb, then at least I occasionally earn a little pocket money when I have to get their cars running again after their cheap fuel experiments .

I would be happy to explain in more detail: This is not a comprehensive diagnosis, but rather assistance for laypersons under typical circumstances.

That's what technical articles are for, or are you trying to reinvent the wheel?

Do you really think a complete beginner would be able to understand your points (other than point 2), let alone find the parts in the engine compartment? And suggesting what the workshop should do borders on being a know-it-all, as Rainer already mentioned.

Quote:

That's what technical articles are for, or do you want to reinvent the wheel?

I completely agree. The issue is too complex to be generalized into simple, easy-to-understand instructions. There are many other potential causes that can lead to similar symptoms.

I don't see any real benefit for anyone, but rather I suspect that many users might be misled by it.

That's what technical articles are for, or are you trying to reinvent the wheel?

Do you really think a complete beginner would be able to understand your points (other than point 2), let alone find the parts in the engine compartment? And suggesting things to the workshop borders on being a know-it-all, as Rainer already mentioned.

Um, I wrote that I want to summarize expert articles and knowledge from contributions. The result should be improvement suggestions for the FA (presumably, 'Fachartikel' or 'feature article').

But whatever. Since most people will probably prefer to discuss the pros and cons of this idea, it probably won't happen. Someone who couldn't make sense of it wouldn't have had to. I think there are a lot of semi-experts around, and something like this would actually help them and me. But no problem, we can just keep answering the question of why the engine isn't starting properly every week.
I wanted to save people about 4 hours of work using a rudimentary search function, as I had to do.

Um, I wrote that I want to summarize expert articles and know-how from contributions. The result should be improvement suggestions for the FA.


It's all explained there, and it's quite comprehensive. I wouldn't recommend that people who have absolutely no technical knowledge start tinkering with their cars. It can end up being more expensive than going to an incompetent workshop (which at least can replace parts).

Immobilizer active (engine turns off approximately 1 second after starting):
-> Try other authorized keys; if necessary, have the key repaired or properly programmed.

Defects in the area of the engine temperature sensor:
-> Check with VAG-COM, and if necessary, replace it or repair any damaged cables or connectors.

The valve that shuts off the distribution pump is not opening properly.
-> Measure the supply voltage and resistance (approximately 8 ohms). If these are okay, check for internal connection problems and, if necessary, remove any burrs.

Difficulty in operation or electrical faults in the dosing unit of the VP 37 (often in conjunction with error memory entries):
-> Make it common or replace the pump, or repair the cable.

Other electrical or electronic defects in the area of the Electronic Control Unit (ECU) or wiring harness, relay 109, etc.:
-> inspect and replace / repair.

Starting quantity specified is too low.
-> It is calculated based on temperature and may, depending on the software and the tolerances of the temperature sensor, be slightly low for cold or warm starts. It can be increased using VAG-COM.

Low starter motor speed despite a fully charged battery:
-> If the engine starts immediately when jump-starting or rolling, first clean all the corroded contacts between the battery and the starter.
-> If crimp connections, cable kinks, etc., become hot quickly while playing the organ, replace these cables.
-> If all the cables are in good condition, replacing the starter motor might improve the situation.
However, when reeling in the cable quickly, a (slightly) higher compaction is achieved, which can mask poor compression values. In such cases, replacing the reeling mechanism will not yield any significant improvement.

Weak battery (noticeable by a tired starter motor and, for example, a very dim interior lighting).
-> If a measurement of approximately 0.1 A is taken with an ammeter between a disconnected battery terminal and the battery terminal of a parked vehicle, starting problems may occur after only a few days, and even sooner with higher fault currents. -> Investigate and eliminate faults in the vehicle's electrical system.
-> If the charging voltage at the battery is correct (around 14 volts) while the engine is running, check the acid density, etc., and if necessary, replace the battery.
-> If the voltage is below 13.5 volts, check the cables between the alternator (LiMa) and the battery for kinks, breaks, corrosion, etc., and repair them if necessary.
-> If the cables are okay, check/repair/replace the alternator, including the regulator and charging control.

Incorrect setting of the VP 37 pump (start of injection).
-> see the relevant article.


Flow meter adjusted too lean (VP 37 only).
-> Use VAG-COM to measure the idle fuel quantity. If it is above approximately 6 mg with a warm engine and no electrical consumers or air conditioning turned on, and/or if the engine exhibits noticeably weak performance with slight acceleration at low RPM and load, you can try adjusting the fuel mixture slightly richer (up to just before the point where it starts to stumble), see the 'technical article on the fuel mixture control / RWG' and the error database 'DIY solution for stumbling issues with VP 37 engines'.

Engine control malfunction (e.g., crankshaft timing belt pulley loosened, camshaft timing incorrectly adjusted, errors during timing belt replacement), sometimes in conjunction with incorrect pump adjustment.
-> Have it corrected or repaired.

Compression loss / Wear on the clamping jaws.
-> For a preliminary check, see 'Used Car Tips'. A more thorough compression test may be necessary, and repairs should be carried out based on the results.

Other defects or excessive wear in the area of the pump and injectors; heavy deposits in the injection system due to poor fuel / biodiesel, etc.:
-> Replace or have the affected parts cleaned.

Fuel with a cetane number that is too low, and sulfuration caused by excessively low outside temperatures.
-> Drain/siphon (including pump) and fill with the correct diesel fuel.




I think that in this forum, there are many people who are not fully knowledgeable, and something like this would be helpful to them and to me.

They are invited to read along and study the technical articles. And it's best to do that before they send the car's fax.


But no problem, we'd rather answer the question about why the engine is hard to start individually every week.


As you (perhaps by chance?) correctly identified, the forum is the place for individual questions. Standard topics are covered in the articles and in older threads (use the search function – it's a powerful tool).

I wanted to save people about 4 hours of work using a rudimentary search function, as I had to do.

For a layperson who wants to save a few hundred, I think it's perfectly fine if they educate themselves about the search function and feature articles. That way, they at least understand the purpose of what they're doing.
And the time it takes is also reasonable, considering that we are answering the questions in this forum for free and in our free time, . To avoid wasting any more of this valuable time, I'm here to help!

Um, I wrote that I want to summarize expert articles and know-how from contributions. The result should be improvement suggestions for the FA.


'Everything is included, and it's also explained at the same time.'


Not right now! As mentioned before, in many cases, it's possible to narrow down the cause of the problem, for example, by simply determining whether the issue (e.g., the car starts poorly) is exacerbated by prolonged inactivity or by low (or high) outside temperatures. Unfortunately, these questions, which can be answered immediately by anyone, are only associated with errors in rare cases.

A case study:
If a car fails to start, especially in extremely low temperatures, regardless of how long it has been idle, the problem is likely...
1. frequently on the oil feed lines.
or
2. Never touch the oil lines.

I would say 2, but if these are leaking, then it's a problem that's independent of temperature.
As you can see, not everything is included in the article. In fact, by definition, absolutely everything can never be contained in any single document. However, people can be interested in ongoing updates and expansions. And these updates would be helpful to some (not all), whether you believe it or not.