Bew runs grate but wont start up on its own unless wd-40 is used.

I'm a single dad working a full time job and dont have have alot of time to fiddle with stuff, so any help is hugely appreciated

04 jetta BEW tdi manual

Short list.
Fuel pump went out and replaced it and the car would run but cranks for a while if it sits over night, drove it for a week like this then it stopped running but will start if I use wd-40 and runs grate but need to use wd-40 if it sits overnight.

Long version
So one morning I go out to leave for work and the jetta wont start.

I test the fuel pump and it's getting power but not running and I removed the feed line and yupp, nothing.
So order a new pump from IDparts and install it in the assembly and put it back in the tank and cranked it for awhile till the air passes through and it ran grate and the next morning it cranked for a little bit until it fired up but would fire right up unless it sat for more then 8 hours. (Like the fuel line drains)

But when I got home I noticed the fans were running even after I turned the key off and it's never done that before.
And they run for 5mins if the engine is cold or hot.
They operate normally when the key is on and the engine is running but will turn on every time when the engine is off and key is off.

So drove it for a few week like this then tried to start it one cold morning and it ran rough ( bleeding out air ) then it died and wouldn't start.
Would try and start it a few days through the week and confirmed it was pumping fuel but nothing.

So yesterday I sprayed wd-40 in the intake and it started and stays running and runs grate, let it sit overnight and it wouldn't start untill I used the wd-40 and runs grate and drove it to work (108 mile round trip) with no issues.

It's like the injectors are not firing while its cranking.

Before all this happened, I was having cruise control issues, the speed would bleed off until I tapped the throttle and it would go back up but then it just stopped working.

The tandem/vacume pump on the motor does weap diesel but has for years without showing any mechanical problems.

Any ideas or anything I can test?

Here is a video of the car starting and running after wd-40
Will post one before wd-40 later.

I never noticed the intake making that thumping sound, normal?

https://youtu.be/YsW59qpfBKM

Have you tried letting the fuel pump run for 20-30 seconds before cranking it?
May be getting air in the line and needs a purge before It'll run, WD gives it a few to start.
That leak you mentioned seems like it could be the culprit.

Sent from my Armor_2 using Tapatalk

eddieleephd said:

Have you tried letting the fuel pump run for 20-30 seconds before cranking it?
May be getting air in the line and needs a purge before It'll run, WD gives it a few to start.
That leak you mentioned seems like it could be the culprit.

Sent from my Armor_2 using Tapatalk

Click to expand...

Yes I always let the pump run.
I normally wait till the chime stops before starting.

It's a possibility, but it's my understanding they dont bo bad.
They just leak and a gasket kit is not available so the only way for it to stop leaking is replace the whole thing.

Vacuum test, looks good to me.

From -57 to 0 took about 10mins when I killed it.

https://youtu.be/jmQUFfxscSQ

Thumping Sound?

Not an expert but have you checked your camshaft? Not sure if it would impact starting though?

The other thought I had was when you replaced the pump you knocked the return hose off, or maybe broke it slightly and this is letting air into the line and the rest drain out off the pickup line/pump.
I would pull the pump back out and inspect it before banging my head anymore.

Sent from my Armor_2 using Tapatalk

It might be getting air in the lines when it sits for a while.

If there’s no obvious leak that you can see, my next guess would be the tandem pump leaking. They can leak internally and allow fuel to enter the crankcase, so check your oil level occasionally to make sure it’s not increasing. When the engine isn’t running, it might let air into the fuel system.

Here’s a test you can do. Next time it has been sitting for a while, and won’t start, instead of using WD40, remove the glowplugs and try starting it until you see puffs of fuel mist coming out of the glowplug holes. If it takes a while to see fuel, you’ll know there was air. Normally you’d see fuel mist immediately.

Once you do get puffs of fuel mist, put the glowplugs back in and try to start it. I bet it fires right up.

When there’s air in the fuel system, it would take a lot of cranking to get it out. The battery would die first. The injectors aren’t meant to pump air, and they’re pumping against a lot of pressure in the cylinder. With the glowplugs removed, the injectors are pumping against nothing (atmospheric pressure) so they are able to push the air out in a reasonable amount of time, like 20 seconds in my experience, if there’s a lot of air in the lines.

I have not checked the camshaft, it's been well maintained and has not displayed any sign of a bad cam. (smoke, knock, shaving in the filter)
But wont hurt to pull the valve cover.

There is just a supply line and the return is a opening in the body, there isn't a actual hose.

Mike_04GolfTDI said:

It might be getting air in the lines when it sits for a while.

If there’s no obvious leak that you can see, my next guess would be the tandem pump leaking. They can leak internally and allow fuel to enter the crankcase, so check your oil level occasionally to make sure it’s not increasing. When the engine isn’t running, it might let air into the fuel system.

Here’s a test you can do. Next time it has been sitting for a while, and won’t start, instead of using WD40, remove the glowplugs and try starting it until you see puffs of fuel mist coming out of the glowplug holes. If it takes a while to see fuel, you’ll know there was air. Normally you’d see fuel mist immediately.

Once you do get puffs of fuel mist, put the glowplugs back in and try to start it. I bet it fires right up.

When there’s air in the fuel system, it would take a lot of cranking to get it out. The battery would die first. The injectors aren’t meant to pump air, and they’re pumping against a lot of pressure in the cylinder. With the glowplugs removed, the injectors are pumping against nothing (atmospheric pressure) so they are able to push the air out in a reasonable amount of time, like 20 seconds in my experience, if there’s a lot of air in the lines.

Click to expand...

Will do, I'll check it tomorrow morning.

The tandem pump is wet at the bottom and sides but no visible drips.

My oil level stays the same.

I checked my fuel pressure, the tee is between the hard supply line and the tandem pump.

Video.
https://youtu.be/Xxzqtu_N2so

I will leave it hooked up and also check the pressure when it wont start.

Morning start fuel pressure.
https://youtu.be/TYyPbSPtmhE

Glow plugs out, no fuel no start short vid.
https://youtu.be/k9SzkyXlm3s

Loading another vid.

No fuel, no start, add wd-40 and will continue to start and run.
https://youtu.be/8e3lHPBYa-k

I did notice that while it was not running the cooling fans did not turn on when I turned the key off.

Then added the wd-40 and the car runs and i turned it off the fans came on (engine still cold) and would run for the 10mins and turn off.

Could my fan control module be back feeding current to the ecm and allowing it not to start until the cam or crank signal see's it's running and turns the fuel on?

That make sense??

Witch does not make sense why this only happens after sitting for 10+hours or overnight.

Tandem pump leaking on bottom means at minimum gasket needs replaced, if it were mine, I would replace the entire tandem pump (I did). It takes 20 minutes. Change your fuel filter and o rings on the thermo-T. You have a small air leak SOMEWHERE, you need to find it.

Looking at the video with glowplugs removed, there’s no fuel being injected, for whatever reason. Has to be either air in the lines, or like you said the ECU is not allowing the injectors to fire.

So to rule out an ECU problem, you could try disconnecting the large plug on the end of the head, which is the wires to the injectors. I’m not sure what each pin in the plug does, but it should be a ground, plus a wire for each of the four injectors. So five wires if I remember correctly. I’m not sure if you’d need a test light, or an oscilloscope or what to see if electrical pulses are being sent to the injectors. I assume a light should do the trick, as long as the pulses are long enough to make it flash. I’ve never delved into that myself. Should be 12 volts.

You could take the valve cover off and have a look at the wires to the injectors to figure out which ones you need to put the test light on. Or maybe google image search for Pumpe Duse injector wire loom and see if you can figure it out.

Anyway, when the engine is in a no start condition, if you can prove that the ECU is trying to fire the injectors, then air in the fuel is the more likely problem.

My guess is your tandem pump is bad, and it works just well enough that if you can get it spinning fast enough with WD 40, then it’ll keep running. Cranking with the starter motor isn’t fast enough, once air gets in the lines, combined with a marginally working tandem pump.

By the way, the fuel pressure you’re checking I assume is just from the in tank electric pump? You must have connected that somewhere in the fuel lines between the fuel filter and the tandem pump?

That is not the pressure that the injectors see. They get fuel through passages in the head, and I believe it is closer to 150 PSI.

The pump in the fuel tank just sends fuel to the tandem pump. The tandem pump does the real work of feeding the injectors.

This video shows someone checking both pressures. The low pressure side, which you have checked, and the high pressure injector galley pressure in the head.

https://youtu.be/cebaaW1Lj6A

Very nice, I will check that out.

Thanks for your help!
I disconnected the fan module just to rule that out sense both issues happened at the same time.
So will find out in the morning if its messing with the ecm.

I will need to get a higher gauge to test the output psi on the tandem pump.
Might just replace it sense it's been leaking anyway.

I was just doing some reading on the fuel injectors and read that the tandem pump puts out the 150 ish psi as you mentioned and the injectors bump that up to almost 3000 psi when they fire.
Pretty complex setup, no wonder why they are so expensive. Haha

Add another zero. 30,000 PSI. Incredible.

Yupp,


So, car still didn't start this morning with the fan module unplugged but it did try at one point.

But again, shot of lube in the intake and it fired right up and continued to fire up after that and drove it into work.

Going to order a new tandem pump and valve cover gasket today, should have them by the weekend.

I will try and get to testing the injector pulse this week.

I've had my valve cover off about twenty times using the same gasket. No leaks.

Wouldn't worry about the gasket.

Good call getting a new tandem pump. That's likely the problem.

broncomitch said:

Yes I always let the pump run.
I normally wait till the chime stops before starting.
It's a possibility, but it's my understanding they dont bo bad.
They just leak and a gasket kit is not available so the only way for it to stop leaking is replace the whole thing.

Click to expand...

My dealership sells just the gaskets. I also have taken the gaskets of, cleaned them and put a light coating of rtv on it and they seal very well

broncomitch said:

Yupp,
So, car still didn't start this morning with the fan module unplugged but it did try at one point.
But again, shot of lube in the intake and it fired right up and continued to fire up after that and drove it into work.
Going to order a new tandem pump and valve cover gasket today, should have them by the weekend.
I will try and get to testing the injector pulse this week.

Click to expand...

Try dissembling your tandem pump, I have had luck taking them apart, either replacing the springs or shimming them on the fuel side. They are very simple

Mike_04GolfTDI said:

I've had my valve cover off about twenty times using the same gasket. No leaks.

Wouldn't worry about the gasket.

Good call getting a new tandem pump. That's likely the problem.

Click to expand...

Well, already ordered the gasket. Lol
Oh well.

Feel like this thing is falling apart, lift pump, tandem pump, fan module, throttle body blade, glow plugs and harness, vacuum actuator, all this month and yesterday my ECT sensor crapped out and was reading the coolant @ 300 degrees at all times so replaced that last night after I put my daughter to bed,and it was snowing. ?

Also, I think the tandem pump will definitely fix my issue because yesterday I was searching around the web for answers (like every day sense this started) and found someone mentioned clamping the supply and return line on the motor and that should isolate the tandem pump, so tried it last night and it fired right up this morning!

It's still so confusing, it's getting so much air trapped in the pump it wont start on it's own but will start and run if wd is used to fire it off?
I would think if it was getting that much air into the system it wouldn't keep running on its own.
?

ktmkris said:

My dealership sells just the gaskets. I also have taken the gaskets of, cleaned them and put a light coating of rtv on it and they seal very well

Click to expand...

Seriously?

I can only find the back metal gasket here in the states.

I suspect that driving the car for a period of time with a failed in-tank pump weakened the tandem pump and now it's not delivering enough pressurized fuel to the injectors to fire on start up. You probably need a new one.

broncomitch said:

Well, already ordered the gasket. Lol
Oh well.
Feel like this thing is falling apart, lift pump, tandem pump, fan module, throttle body blade, glow plugs and harness, vacuum actuator, all this month and yesterday my ECT sensor crapped out and was reading the coolant @ 300 degrees at all times so replaced that last night after I put my daughter to bed,and it was snowing. ?
Also, I think the tandem pump will definitely fix my issue because yesterday I was searching around the web for answers (like every day sense this started) and found someone mentioned clamping the supply and return line on the motor and that should isolate the tandem pump, so tried it last night and it fired right up this morning!
It's still so confusing, it's getting so much air trapped in the pump it wont start on it's own but will start and run if wd is used to fire it off?
I would think if it was getting that much air into the system it wouldn't keep running on its own.
?

Click to expand...

This is all normal for a car of that age. I bought mine new and in the 15 years I've owned it, I've had to replace a tandem pump, in-tank pump, coolant temperature sensor, all the suspension components, wheel bearings, ECU, window switches, and even rebuilt the engine after a timing belt failure. This included pistons, rings, connecting rods and bearings, main bearings, cam, cam bearings, valves, valve stem seals, and lifters. Probably other stuff I've forgotten.

They basically have a trouble-free life of 10 years. After that, anything could happen. Once you replace everything, it should be good for another 10 years.

IndigoBlueWagon said:

I suspect that driving the car for a period of time with a failed in-tank pump weakened the tandem pump and now it's not delivering enough pressurized fuel to the injectors to fire on start up. You probably need a new one.

Click to expand...

That is exactly what happened to me. I noticed a little more power and easier cold starts after tandem pump replacement

So replaced the tandem pump and all of the rubber fuel lines,
Didn't take alot of cranking for it to start running and it was obviously running rough until it blead out the air and was running good so took it for a drive and made it 5 houses down and lost power and it died.

Cranked it for a little bit and it started again so turned around and made it home but died 3 more times along the way,
So let it sit running with the gas cap removed and would keep the revs up and it never died but the rpm would dip a few times then it had no issues sitting there.

Let it idel for 10 mins and took it for another drive and it never died but I have no power past 2500rpm and when I hit 2400-2800 rpm it feels like it misses or surges but I can floor it and it wont go past 3000rpm.

I just realized, I didn't remove the two black plugs from the new tandem pump.

*palm face*