Cold Start Problems

And fer gosh sakes, STAY AWAY from your stealer! The fuel lines under the hood amount to about $10 of tubing, NO MORE. You can overpay for the "shaped" lines if you want, but any good "Hose and Hydraulic" retailer will be more than happy to bury you in 5/16" interior diameter fuel-grade hose for $400. You only need a few feet of it, and even grossly overpriced it doesn't cross $20.

BTW: I've replaced the under-hood lines from the filter to the pump (both) and the inter-injector lines and it only cost me $4.

Yea, your dealer is trying to "help you" as much as they can. They don't like seeing you lift such a heavy wallet.

I had a 7 to 15 second starting problem when I got my Golf TDI used (98k miles). Cleaning the intake manifold and erg valve got me down to 5 to 8 seconds to get started. Replacing the stock engine stretch bolts with head studs got it below 2 seconds. New battery took off another second...started right up after sitting for 12 days.

Well, as I'm up for just about any idea at this point, I just ordered the ARP bolts. I'm down to about 3-5 seconds right now with all the stuff I've changed and 148k on the engine. It runs like a screaming devil when it's running... It's just starting thats the problem.

Sorry for lack of updates. I spent the weekend college hopping.

The starting problem is getting worse. It's taking longer to start. I will take a video of it starting and post it later tonight.

Also, I heard some people having problems with injections pumps. It it worth buying new o-rings and replacing them?

http://www.dieselgeek.com/Detail.bok?no=443

Ive got the same issue you got in my 2000jetta tdi. So far ive replaced the fuel filter, t fitting, return lines from injectors to pump, and replaced the ****ty spring clamps on top of the filter with hose clamps. However mine picks and chooses when it wants to be stubborn. Some days it starts within 5 seconds of cranking, other days its over 30. When it finally does fire, theres whiteish/grey smoke everywhere!. I find if the car sits for under 4 hours it will start O.K but not great, anything after that, might as well say goodbye to the ozone layer now lol

fpruter said:

It it worth buying new o-rings and replacing them?

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Before you get into the IP, please say whether or not the fuel filter has been changed recently.

I changed it about 3 months ago. I had problems with it before I change; however, it is continiously getting worse. Changing the fuel filter had no noticeable effect neither positive or negative initially. I also replaced the tee connector.

My friend and I are going to clean out the intake manifold and egr. I know this will not fix air in the fuel lines.

Can you tell form which side the air is coming? Right after turning it off, I assume there is very little air in the line, right? If the bubble gets bigger, you should be able to see which side it's coming from. If from the pump, make sure all connections are perfect, and if so, perhaps digging into it is needed.

I really haven't noticed many people having problems with the IP's leaking air - generally there the pressure is such that you see fuel coming out where air would go in.

The o-rings with the T are set to go in one way, I believe the larger (black?) one is towards the top of the "t" while the smaller one is the first one that goes into the filter when you plug it in.

Good luck. I'd spend some time just looking in the engine bay.

While the engine is running a lot of air bubbles flow through the fuel lines. From how it looks, it is flowing from the fuel filter to the IP. I'm not sure if it's me being paranoid, but I noticed the engine seems to shudder every now and then. Like I said, it might just be me being paranoid.

"Another thing to add is that when it finally does start it pours a lot of smoke out of the exhaust."

I just replaced a fuel filter and got a lot of air in the lines. When it did finally restart it smoked for about 30 seconds. Ithink the air in the high pressure lines prevented the correct timing, hence fuel arrived late and was unburned.

If it only smokes when ahrd starting, thats the problem.

I recently saw anoth erposter who tracked a fuel line air leak to his fuel sender in the tank.
He used a section of plastic pen cartridge to try to seal it. Try searching on 'pen'.

How long has it been running ULSD?
Try bypassing the fuel system with a short new line to an inline filter then a jug of fuel.
If it cold starts ok, you have a fuel system leak. The problem still can be in the f.i.p. though.

Try watching the clear fuel line very carefully to discern the direction of the bubbles.
fiter -> ip indicates leak before the i.p.
i.p. -> filter indicates leak at the i.p.

With a friends old leaking air in fuel Jetta, we noticed
1. Couldn't really see any bubbles leaving fuel filter.
2. a big bubble appeared one second after the engine was turned off. It came up out of the ip.
Air wa leaking into the i.p. and 'held' in place by the pump vacumn.
When the pump stopped the vacumn stopped and released the bubles upward.
A mechanic diagnosed it as a leaky main shaft seal.

When the fuel is moving, it has to go to the IP from the FF - that's the flow.

The fact that you're getting quite a few of them indicates to me that there is an issue with the system - either at the filter or perhaps the pickup in the tank. I'd try to take further steps to isolate the problem. If you've exhausted all possibilities at the filter - that leaves the pickup in the tank.

I had this same problem for about a year before I finally solved it. You may have a leaking o-ring in the fuel pickup inside the tank and it may not be a bad o-ring either. There is a spring inside the pickup that was probably never really strong enough. Once removed, the whole pickup assembly is easily dis/re-assembled. It's like a snap together model. Anyway... If you seem to have this problem more often when the car has less than about a half tank of fuel, then just take that spring out and stretch the crap out of it. I stretched mine out about twice its original length. After reassembly, I've never had the problem again. An easy test to see if this is your problem, try to keep the tank all the way filled for several days. If you don't experience the problem anymore the o-ring is the culprit.

i have had a cold starting problem for over a year now and ive changed a lot of parts. my engine is a pd 115 AJM

1: Fuel filter & o rings
2: Fuel filter T piece
3: non return valve (in hose beside fuel filter)
4: Lift pump in the tank
5: tandem pump
6: thermatat
7: map sensor
8: removed and reseated injectors
9: all 4 heater plugs
10: 4 new injectors
11: n75 valve
12: maf

the car takes 5-6 seconds to fire up on first start. if i run for just 10 seconds and re start it starts on the key. it will start on the key for the rest of the day and will only start taking time to start if i leave it for a couple of hours.
No matter what the outside temp is the car takes exactly the same time to start. it was -3 degrees c the other morning and it started the same (if not slightly faster than other mornings)

there are no faults on vagcom either. the glow plug relay is fine also. i even tried running a live to the heater plugs and heating for 10-15 seconds, this had no effect in starting either.

the egr and inlet manifold where only fitted 10 months ago so no gunk yet.
the anti shudder flap works fine also.

the car had several mods in the course of all this and apart from starting the car goes the very best with very little smoke on WOT.

Have i missed anything ? any other temp sensors i can try ?

My car starting problem still exist. I took it to my friend's dad shop who replaced the timing belt. I also got a new starter and battery.

The mechanic was able to show me how to start it on the dime everytime. He told me to unplug the temperature sensor, put the key in the ignition and turn it to let the glow plugs warm up for the 20 full seconds. Then you take the key out and do it again. This time when the glow plug light turns off you start the car.

This tricks the car into thinking it's freezing.

Any idea what can be causing this? I am happy the I can drive it again with this hack, but I would like to fix it porperly.

The problems with mine turned out to be an internal part in the injection pump, potentially damaged by the switchover to ULSD. Look at my previos threads or search on hard starting Jetta for the whole sad tale... But the lack of obvious symptoms sounds familiar.

My mechanic (who turned out to not be that great) told me about the whole glow plug thing too, while Todd (Pitboy) and I both were of the opinion that in Florida's 80+ degree weather, the glow plugs were NOT needed for anything else than plugging those holes in the engine.

YMMV, but I would talk to a diesel Bosch shop. Ask them if they have the ability to bench-test the starting ability of the pump. Mine was fine once it was turning at 800rpm or more, but that little low-pressure supply pump was not doing enough when turning at the 275-325rpm of starting.

I will call the shop Monday and see if they tested that when they were trying to troubleshooting it.

When I try to cold start it without the trick, it just cranks and might start. But the second I do it, it starts.


Do you have any other suggestions?

I think a few things have been overlooked, several are particularly considering it's a bio-diesel car...

Let's start with timing. If the timing is right, it should start within just a few compression strokes. If a timing belt job has been done and no VAG-COM was used, chances are the timing is not right. Git'er done... since you don't have the equipment, check here... http://anglo-hexon.net:88//beowulf9/tdi/vagcom/vagcom.asp

A compression test wouldn't be untoward.

When first using bio in high concentrations, it 'cleans out' the tank. All that stuff has to go somewhere, so any bottleneck in the system will accumulate that gunk.

There are two one-way valves in the fuel guage cannister in the tank. The cannister is under a access plate in beneath the rear seat. The "in" valve is supposed to only let fuel back into the tank. The "out" valve only lets it toward the filter. You can test each line, without removing the cannister to see that they are working properly. Probably the easiest place to test from is at the lines from the tank at the fuel filter. It would not be unlikely that your "out" line is requiring too much suction and the quick-release seals are letting air into the system. There are two sets on the quick release couplings; one right next to the in-tank cannister and the others are at the firewall.

Another problem can be in the injector pump. The bio-D does make the seals leak. If you see any leakage on the pump, a seal kit will repair that. The pump seal installation is a bit tricky. Get help.

Also, there is a special plug bolt on the front and top of the pump. It is the cover screw for the orfice that maintains the pressure in the pump. That can cause hard starting.

To fix that issue, first clean the bolt head and blow all the crud off. Remove the plug and washer. Inside is a steel pin. It should be flat in the housing that holds it. If it isn't, push it back down. That's all there is to it. Reinstall the plug.

That covers a few likely options for your issue.

My car is not bio diesel.

Your Coolant Temperature Sensor, which is what they unplug to fool the Glow Plugs, could be bad. The old black coloured ones were crap and now they have a green coloured version. You can use VAG Com to adjust the Glow Plug duration IIRC, not sure how to do it though.... the glow plugs don't really cut in until it is below 45F though.
I would really check the timing with a VAG COM, retarded timing can cause a lot of the issues you are reporting. Use the TDI Graph plugin so you can see it visually and set it in the upper area of the graph.
Franko6 is talking about the fuel sender issues in the tank which can plug up when it gets cold or can easily get plugged if small contaminants get into the fuel. People have reported blades of grass plugging there fuel sender.

Which Vag-Com should I buy? I plan on buying a brand new TDI in a few years.

VAG Com is a program that you can download and run on your Laptop, the program is free - BUT - the cable to plug into your diagnostic port costs you. If you go to Ross Tech - http://www.ross-tech.com/ then you can figure out which interface you need. If you want to work with your current VW and something more modern later then you might need one of the more expensive interface cables - $349.00. I think there are off shore knock offs but not sure how well they work.....
This program gives you a similar capability to adjust your cars ECU and other components as the dealership has. If you are going to do your own timing then it is worth it since the dealer charges $80 to read a code..... Four visits and its paid for itself....

On another forum someone suggested my pump timing might be off, how do I test that?

You need a VAG Com to check your timing since you have to read the ECU to find out what it is. There is a plugin for the program that will graph it for you called TDI Graph. Get someone who had done it before to check it for you and move it up to the top of the graph to improve cold weather starting. IIRC you need a 21mm wrench and a 13mm socket to adjust the timing once you find out which way it needs to go.

This is assuming that the engine will start right?

I am having a similar problem, my issue is a big bubble turned to a complete loss of prime.

Its either leaky gasket in fuel pump or bad injection timing. Since my dad found some liquid diesel under the pump and I just had the timing belt done by metalman (cant imagine he did it wrong) I am assuming for now that the pump needs to be relsealed.

NorthernMage said:

You need a VAG Com to check your timing since you have to read the ECU to find out what it is. There is a plugin for the program that will graph it for you called TDI Graph....

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Alex, the liquid diesel could have just as easily leaked from a faulty fuel filter water seperation drain, which would also cause air to get into the system from an empty filter.... when did you last replace your filter or drain it for water? There could also be a leak at the T on your fuel filter or one of the lines not being connected properly. Remember that the IP "sucks" fuel through the filter from the tank and any air leaks means it will suck air instead..... sounds like you might have a major air leak somewhere.... see what was disturbed during the TB change and recheck it....