What does an ALH with low/no compression sound like when it turns over?

csb · Oct 16, 2013

I'm an import mechanic, however, my experience with diesel motors is a work-in-progress. I recently purchased an ALH Jetta that will crank normally but will not start. I was told by the dealer who took it in on trade (a VW dealer) that is had "no compression in the cylinders". The timing belt looked good upon visual inspection which I realize doesn't mean much. No immobilizer/key issues, no stored codes (checked with RossTech), fuel is at the injectors, etc. I am used to gas engines having a very "unique" sound when they have low/no compression and turn over. This ALH sounds just like my other ALH diesels, though. I have NOT performed a compression test yet but that is my next plan.

jettawreck · Oct 17, 2013

Quit cranking it (not that it probably matters anymore) and inspect the TB system carefully. Only a couple reasons for no compression, if in fact there is little/none, and they aren't good. If the TB is intact, properly tensioned, and rotates when cranking then check the compression.
Not compression related, but is the anti-shutter valve open when cranking?
Low compression that is not TB related is often due to hydrolocking which bends the rods.

Powder Hound · Oct 17, 2013

If you are in doubt about whether there is compression, just put a wrench on the crank bolt and turn it over by hand. That will tell the tale in 1 revolution.

oilhammer · Oct 17, 2013

If the anti-shudder valve sticks shut, the engine won't have compression. I've had a LOT of cars towed here from dealers like that.

csb · Oct 17, 2013

OK guys...thanks so much for the replies. Here is a play-by-play on the car. The prior owner had it towed to a local VW dealership due to a no-start condition. The dealership replaced that "valve" or "sensor" (sorry, I can't recall the name of it) that threads into the top of the injection pump at the end nearest the driver's side. Can someone name this part for me? It is brass and roughly the diameter of a 1/2 dollar. The car started and was road-tested after this part was installed. Fast forward to the very next day. The car was towed in again due to a no-start condition. According to the service advisor, the tech performed a compression test and the advisor told me he found that the car "had no compression in any cylinders". The car shows no trouble codes and the key is definitely programmed correctly (the light on the cluster with the key through it is solid for a couple seconds, then turns off). The car turns over normally (based on how my other ALH TDI's sound) but that is all it will do. I did move the "lever" on the anti-shudder valve back and forth. It returns to it's original position (up, I believe) on its own and moves smoothly. Is this normal? Anyway, I have ordered a proper compression test gauge and adaptor but won't have that for a few days. The TB "looks fine" and yes, I know looks can be deceiving. It is not noticeably loose, cracked, etc. So that's where I'm at with the car presently! Anyone have any input or ideas aside from "check the timing" and/or "perform a compression test"? Thanks a lot

.

gquenstedt · Oct 17, 2013

Does the glow plug light come on when you turn the key on?

When the 109 relay is not working, the car sounds weird while cranking.

csb · Oct 17, 2013

gquenstedt said:
Does the glow plug light come on when you turn the key on?
When the 109 relay is not working, the car sounds weird while cranking.

The light comes on and turns off after roughly 1-2 seconds. The car doesn't sound weird when cranking, that's the thing.

drewkeen · Oct 17, 2013

Thats most likely the magnetic shut off valve you are talking about.

I know you said there is fuel at the injectors and this may sound silly, but drain the fuel filter using the valve at the bottom. If there is water the filter has swollen up and blocked fuel from passing. Got some bad diesel in the truck one time and this was the fix. Also, is there plenty of fuel in the tank? Also, there could be a small leak in the fuel system causing it to lose prime.

oilhammer · Oct 18, 2013

Just take a 17mm wrench and crack a couple delivery pipes loose at the injectors and crank it, see if fuel dribbles out.

csb · Oct 18, 2013

oilhammer said:
Just take a 17mm wrench and crack a couple delivery pipes loose at the injectors and crank it, see if fuel dribbles out.

I did that a couple days ago. When I loosened the nuts and lifted them up, I could see fuel pooled at the tops of the nozzles. I then reattached the nuts but left them loose and cranked the engine. Fuel ran out of each of the unions while cranking. Haven't checked the fuel filter yet.

csb · Oct 18, 2013

Oh, and the fuel tank is about 90% full atm.

jettawreck · Oct 18, 2013

I think the "valve" on the IP you refer to may be the fuel shut off soleniod.
You can remove the intake tube just before the EGR where the anti-shutter valve is at and have someone watch and verify that its open when cranking.
I have no idea what a no compression TDI sounds like really. When I first got the '01 in wrecked condition the engine was damaged from the accident (engine mounts broken and derailed the TB so almost all the lifters/etc were destroyed) and it cranked over "normal" sounding, but made horrendous backfiring noise up thru the intake when it was trying to fire. Instant clue that there was BIG problems.
If the TB is intact and very tight so that you are confident you are not incurring more damage, follow oilhammers advice and verify you are getting fuel to the injectors. Not just a dribble, but a healthy squirt from every revolution.

nexus665 · Oct 18, 2013

Hi,

it's very simple to test - take an ALH, physically block the ASV in the closed position.

This will create a near-vacuum inside the cylinder bores, and you will hear the starter speed up a lot and the engine crank much faster once the air pressure is gone.

Sounds strange, really.

Regards

csb · Oct 18, 2013

nexus665 said:
Hi,

it's very simple to test - take an ALH, physically block the ASV in the closed position.

This will create a near-vacuum inside the cylinder bores, and you will hear the starter speed up a lot and the engine crank much faster once the air pressure is gone.

Sounds strange, really.

Regards[/QUOTE

I believe I did that. I have read that the ASV can get stuck or sticky in its range of movement. On my car, it moved very smoothly by hand when I actuated the "lever" between it and the EGR. I did have a friend hold it in a position which is directly opposite of when it is at rest, then I turned the key. The engine immediately turned over much more quickly during that time and returned to "normal" as soon as he let go of the lever. What should this tell me?

nexus665 · Oct 18, 2013

Hi,

at rest/without engine running, the ASV is in the "closed" position.

This is so the engine shuts off more quickly and without shuddering.

If it started up way more easily when your friend held it open - either the ASV is not moving as it should or the vacuum hose isn't airtight/losing vacuum somewhere, maybe.

Regards

jettawreck · Oct 18, 2013

nexus665 said:
Hi,

at rest/without engine running, the ASV is in the "closed" position.

This is so the engine shuts off more quickly and without shuddering.

If it started up way more easily when your friend held it open - either the ASV is not moving as it should or the vacuum hose isn't airtight/losing vacuum somewhere, maybe.

Regards

I believe the ASV "at rest" is actually open. It closes briefly at shut down and then the vacuum goes away and it reopens.
Please correct me if this is wrong.

csb · Oct 18, 2013

nexus665 said:
Hi,

at rest/without engine running, the ASV is in the "closed" position.

This is so the engine shuts off more quickly and without shuddering.

If it started up way more easily when your friend held it open - either the ASV is not moving as it should or the vacuum hose isn't airtight/losing vacuum somewhere, maybe.

Regards

That's the point of my thread, though...the engine doesn't start! It just
cranks normally UNLESS the ASV is held, then it turns over as though
it has little compression (which is apparently normal).

jettawreck · Oct 18, 2013

csb said:
That's the point of my thread, though...the engine doesn't start! It just
cranks normally UNLESS the ASV is held, then it turns over as though
it has little compression (which is apparently normal).

Remove the intake hose just before the EGR/ASV and verify the valve is open when cranking. It won't affect the starting/running at idle.
Sounds as if you ASV is working correctly, at least to me.
Need to do the compression test to really know.
Lots of fuel at injector(s) with the fitting off??
ASV open, fuel getting injected and still no start I would be setting the crank at TDC, cam lock in place and see where the IP line up hole is at.
Something catistrophic would have happened in the TB/valvetrain system to not have any compression in all cylinders. I think the dealership/tech are probably dolts.

csb · Oct 18, 2013

jettawreck said:
Remove the intake hose just before the EGR/ASV and verify the valve is open when cranking. It won't affect the starting/running at idle.
Sounds as if you ASV is working correctly, at least to me.
Need to do the compression test to really know.
Lots of fuel at injector(s) with the fitting off??
ASV open, fuel getting injected and still no start I would be setting the crank at TDC, cam lock in place and see where the IP line up hole is at.
Something catistrophic would have happened in the TB/valvetrain system to not have any compression in all cylinders. I think the dealership/tech are probably dolts.

That's what I thought. Engine sounds normal while cranking. I would think
this would not be the case if it had no compression in any cylinder. Plus...
as mentioned, the TB seems tight and spins well. As for fuel at the injectors, how
much should come out if the fittings are loose? I mean...should it spray or dribble?
I will remove the intake hose and do a visual inspection tomorrow.
What should compression numbers be when the engine is cold in a 40
deg F environment?

jettawreck · Oct 18, 2013

It won't really "spray" out of the hard line, but it should be a pretty good squirt, much more than a dribble. Lay out some rags to absorb the fuel. Perhaps one line at instead of all four?
You should get 400-450+ psi, I would guess. Test with all GPs out, battery fully charged.More important is variation between cylinders (or lack of variation). Some (cheap) gauges will read a lot different than others. My cheap small engine compression gauge reads 20% less than a good shop quality gauge on snowmobiles, etc I work on but it lets me know if a cylinder is low compared to the others.
Be careful removing GPs. They can be sooted up inside and be tough to remove sometimes. Head is aluminum threads.

Franko6 · Oct 19, 2013

Disable IQ or fuel shutoff when compression testing...

csb · Oct 25, 2013

I'm not sure how to close this thread...sorry. I've begun a new one to address other issues.

Clev · Jan 18, 2018

Compression problems?

Hi, I think I have the same issue here. Engine cut out on the highway at 4000rpm(180km/h) with thick greyish black smoke emitting as well as the battery light going on. Next thing was the glow plug light flashing. Pulled over and started the car up again and there was a violent shudder on the engine. Just the glow plug light flashing, temp guage was at 90deg Celsius. Car seems to have very little compression never carried over 60km/h. Mechanic suspected glow plugs issue but later says compression rings. Didn't do a compression test yet. He says the engine shudder is due to a miss or low compression. The glow plugs were wet according to him but the car starts with a second swing of the key.

KCTDI · Jan 19, 2018

csb said:
That's what I thought. Engine sounds normal while cranking. I would think
this would not be the case if it had no compression in any cylinder. Plus...
as mentioned, the TB seems tight and spins well. As for fuel at the injectors, how
much should come out if the fittings are loose? I mean...should it spray or dribble?
I will remove the intake hose and do a visual inspection tomorrow.
What should compression numbers be when the engine is cold in a 40
deg F environment?

Have you tried starting with the intake hose unhooked at the ASV?
Perhaps some one worked on it and left a rag/plug in the hoses/intercooler?

flee · Jan 19, 2018

Clev, seriously, stop re-animating old threads and start your own!

The MkIV forum would be a good choice.

What does an ALH with low/no compression sound like when it turns over?

Veteran Member

Top Post Dawg

Top Post Dawg

Certified Volkswagen Nut & Vendor

Veteran Member

Veteran Member

Veteran Member

Veteran Member

Certified Volkswagen Nut & Vendor

Veteran Member

Veteran Member

Top Post Dawg

Veteran Member

Veteran Member

Veteran Member

Top Post Dawg

Veteran Member

Top Post Dawg

Veteran Member

Top Post Dawg

Vendor , w/Business number

Veteran Member

Member

Veteran Member

Veteran Member