2002 Jetta cranks but no start

Hi! I'm very new at this so sorry for what must be a frequent topic around here.

My 2002 Jetta (165k miles) cranks but will not start. It cranks somewhat slowly, around 125 RPMs but I'm not sure if this is slow enough to indicate a problem. I've tried going through several guides but I'm struggling on how to narrow it down from all of the possible issues.

Possibly related symptoms: mild electrical sound with key turned before ignition (possibly normal for glow plugs). During cranking overhead dome lights dim and flicker. This has always been the case and I thought it was normal but perhaps it is related. After the engine stops turning, there is an electrical sounding BZZZZZZZT for a few seconds. I think this is the starter motor, not sure if that's a normal noise or not. Car has always had trouble starting in cold, and failed to start in extreme cold weather once though this was possibly a result of fuel gelling.

Of note also, the last time the car ran it was refueled. Could indicate a bad batch of fuel???

Here are the hypotheses I've come up with:

Bad battery: unlikely, battery is less than 1 month old. Checked by O'reilly, rated as good. Voltage normally reads about 12.75v, drops to 10.9v while the engine is turning over. Seems normal to me, but I could be wrong.

Bad starter motor: possible, matches symptoms as described by people who had this problem before of low crank RPMs, trouble starting in the cold, and flickering dome light. I tested the voltage between the two electrodes on the solenoid and it seems to be getting good voltage so I don't think it's a connection issue. How do I determine if the motor itself is the problem (aside from replacing it)?

Lack of fuel supply to the engine: lots of possible problems here. How do I know if it's a fuel problem, and if it is how do I narrow it down? Timing suggests it could be a fuel problem. It's about time to change the fuel filter so I ordered the materials and I'll see if that helps but I have no idea if that's the problem. Also, several people have mentioned checking the clear plastic tube between the filter and the fuel intake pump for bubbles, but in my car this tube is black for some reason—perhaps it was replaced at some point? Not sure how to check if there's air in the line without the clear tube.

Lack of air supply to the engine: same issue as with fuel. How do I know if the problem is one of air supply and if so how do I narrow it down from there? Anti-shutter valve tested and seems to be working fine. Similarly the engine air filter is due for a change, so I'm gonna do this but the filter doesn't look super dirty so I doubt that's the problem.

I also checked the fuel shut off wire voltage. It was around 11.5v which seems a little low but not low enough to cause a problem???
Timing belt looks to be in good shape, not sure how to tell if it has slipped but it's pretty tight so that doesn't seem real likely.

Any hunches or tests to run would be really helpful. My dad is sending me a PELA pump I accidentally left at his house, which hopefully I will be able to use to diagnose fuel blockages but it won't be here for a few days. So until that gets here I'm sort of out of ideas of things to check.

Thanks for reading this wall of text!

Diags

You battery is ok, no trouble there.
The electrical noise when you turn the key is the fuel pump, priming. Also normal. Air bubbles in you fuel line is also acceptable.

I had a similar issue twice and it was 1: relay 109 and 2: the immobilizer. I would try to start the car for minutes at a time and it would not start.

1st time it started as soon as I switched the relay to a new one.
2nd time, i disconnected the battery and removed the keys from ignition for about 15 min and it seemed to have reset the immobilizer issue.

Also, check the fuses along the way...

If all this doesn't help, try to hook up VCDS to it and do a diagnostic on it. Maybe it will shed some light on the matter.

Best of luck!

tretch, this is an ALH engine and it doesn't have an in-tank fuel pump.

125 cranking RPM is too slow.

You can check for blocked air supply by pulling off the rubber elbow right at the EGR valve.

You can check for fuel being injected by cracking open the fuel line fitting at the injectors and watching for fuel spurting out when cranking. I would hold off on the fuel filter for now. If you change the fuel filter, you are introducing air into system, therefore you are introducing another variable. Crack the fuel lines and if you are getting any fuel out, skip the filter for now. What you ultimately want from the injector fittings is fuel spurting way up, not just dribbling out.

Thanks for the help guys. Unfortunately I had already changed the fuel filter when I saw this post, but it should be OK. As per whitedog's advice, I loosened a nut at the fuel injectors and cranked the engine but nothing came out, not even a drip. So I believe it is a fuel restriction somewhere in the system. However I did not crank the engine for very long since I have no way to easily charge the battery should it die, so it could be just some air in the line.

I used my oil vacuum pump as a crude way to bleed air and I was able to get a good flow of fuel from the fuel filter where it supplies the pump. However, when I hooked it up to where the pump sends fuel back to the filter I got nothing which leads me to believe there is a blockage between these two points. I tried to remove the line that takes fuel from the filter to the pump so I could test that hose, but the hose seems to have swollen in such a way that I could not get the clamp off. I'll try again tomorrow. Any tips for this? It's one of those spring clamps you remove with pliers but it doesn't get big enough to fully remove.

And if it's not in that hose I guess the next step is to remove the pump and look inside it?

Give that hose another shot. Squeeze with the pliers and pull. If the clamp won't pull off, just leave it, but squeeze it and pull. I am assuming that this is proper formed fuel line?

Boy those clamps are a pain in the butt. I managed to get it off, but I couldn't get it back on again completely... however I think it is snug enough for now. The line was clean, so I re-checked the one from yesterday (the one that goes pump -> filter) and I still couldn't get anything to flow. So I'm going to do a bit of reading about the fuel pump and see if I can't take it apart to see what might be blocking it.

Just to confirm, that line leading from the pump to the filter should be open to flow under normal conditions, correct? It doesn't get closed off when the engine is not turning or anything like that like that?

SummerSmoke said:

It cranks somewhat slowly, around 125 RPMs but I'm not sure if this is slow enough to indicate a problem.

Click to expand...

SummerSmoke said:

I loosened a nut at the fuel injectors and cranked the engine but nothing came out, not even a drip.

Click to expand...

I remember reading here the ECU won't inject fuel unless the crank speed is at least 300rpm.

I think you'll need to sort out the cranking problem first, probably worn out starter or bad connections. Dimming lights with a good battery suggests the latter, check to see if the heavy cables from the battery are getting warm after a cranking session.

Simon

Simon, it sounds like he isn't getting any fuel TO the injection pump.

Smoke, please be patient with me here: I want to make sure you don't pull the pump apart for nothing...

The line from the filter that feeds to the pump is number 2 in this picture:



So, if that's the right line, did you try pulling a vacuum where that hose connects to the pump and did you get fuel there?

whitedog said:

So, if that's the right line, did you try pulling a vacuum where that hose connects to the pump and did you get fuel there?

Click to expand...

Yes that is the one I was having trouble getting off. I checked it and it seems to get a pretty good flow of fuel. In contrast, I tried applying a vacuum to where line 3 connects to to the fuel pump (ie sucking from the pump itself) and got nothing. I don't quite understand how all of the fuel is routed around inside of the pump/injection system but my understanding is based on those two tests that there is some obstruction or air leak in either the pump or perhaps where it connects to the injectors.

Unless I am misunderstanding something here...

Try a pressure bleed on the pump before pulling it apart. You can do this with a jug and a hose routed to the inlet of the pump. Suspend the jug of fuel from the hood.

It can be as elaborate as this:

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...or as simple as an upside down soda bottle with a hose in the cap and the bottom cut off.

My answer to these problems is always found in my toolbox in the form of a little green pump that has alligator clips on it and goes inline at point #1 in the above diagram. It puts ~5psi positive pressure on the fuel feed.

This also quite-reliably finds fuel leaks on the inlet side of the pump (which are AIR LEAKS when you're shut down and are a common cause of "no starts" or "hard starts" after the car has been sitting for a few days.)