Difficulty starting up in the morning or after sitting for a few hours

[fabric8]

My 2002 A4 recently started having difficulty starting up in the mornings, or if I've gone somewhere and let the car sit for a few hours. It cranks no problem so it's not the battery. But it takes 2-4 cranks to get it started. Once it's running, it runs perfectly fine. And if I turn it off and start it back up again, it starts right up perfectly.

This morning, I tried priming the fuel by turning on the ignition and back off then pulling out the key a total of 3 times. It took two cranks to start, but when it started, it stumbled a little, then cleared after a couple of seconds and idled perfectly. I think that process of priming it perhaps one too many times flooded it.

I scanned it and there are zero codes.

I replaced my fuel filter on June 6, 2015 at 121k miles
In 2016 at 136k miles, I replaced the crankshaft position sensor due to hard starting and an associated code for it. I'm now at 184k miles.

Since therea are no codes, it's probably not the camshaft or crankshaft position sensors, correct?

Could it be the fuel pump not delivering enough pressure during startup? What else can I do to rule things out?

[Puddin Tane]

Could it be the fuel pump not delivering enough pressure during startup? What else can I do to rule things out?

Sluggish fuel pressure does seem likely. I would invest in a fuel pressure test gauge and watch the thing while someone else cranks.

Is the fuel pump still original? If so, at 184K it's long overdue for problems. Replacing it wouldn't even count as "throwing parts," more like routine maintenance. Mine started acting screwy at 160K.

How old are the spark plugs? Pull one and have a look, or just replace.

[Puddin Tane]

If you do replace the pump, do the filter again too. Standard procedure.

[fabric8]

Yup, it's the orignal fuel pump. Spark plugs were replaced at 174k and they are bkr7e's. I know I'm 5k overdue LOL. I'll go ahead and replace those today.

I'll see if autozone rents out a fuel pressure test guage. What psi should I see while it's cranking? I'm curious what PSI I'll get out of this existing fuel pump vs what I get out of a new one.

Also, I've read that the coolant temp sensor could also possibly a culprit? I have replaced both of those over the years. I'll wait overnight for things to cool down and and will check it's reading tomorrow morning before cranking. Since there are two CTS's (one on the rear coolant flange and the other is the one where you drain the coolant), which meauring blocks measure each?

Edit: I found another post that lists the measuring blocks for each of those coolant temp sensors:

Group 135:
Radiator Outlet Temp:

Group 001:
Engine Coolant Temp:

I'll probably just replace the fuel pump (and filter) like you suggest. What brand did you go with? I see Amazon lists a URO for $123.

[Turbo510]

Radiator temp won't be important concerning the cold-start problem. If your engine coolant temp seem reasonably close to overnight air temp, then perhaps a leaky injector. I just replace all six of mine, and fuel smell at startup seems gone. I'd not be leaning towards the fuel pump or filter, since those would cause the most problems when fuel usage is maximized; hard acceleration.

[fabric8]

Are you referring to the o-rings for the fuel injectors that leak?

I've got no leaks on my fuel injectors from the orings. I installed the billet injector cups about 2 yrs ago and have no fuel smell. I've got 550cc injectors which I installed at 128k miles on 1/12/2016.

[Turbo510]

If you've got new injectors, then probably a fuel drip from one or more is not likely. But not mentioned is the possibility of an air leak, which could make the starting mixture just lean enough to have trouble lighting.

[Puddin Tane]

I'll see if autozone rents out a fuel pressure test guage. What psi should I see while it's cranking?

I believe it should be 4 bar / 60 PSI

I'll probably just replace the fuel pump (and filter) like you suggest. What brand did you go with? I see Amazon lists a URO for $123.

Don't do it! "Cheap" Audi parts are often false bargains. The real bargain is knowing the OEM for the part, in this case VDO (now owned by Continental, so may be branded as such). That's what I used and recommend. Here it is. If you can find a better price for the VDO pump go for it. From the looks of your injector discussion you seem interested in more power, so you may want to upgrade the pump too in which case I don't know what's what. Not into all that. The stock car is plenty peppy enough for my sucky driving.

[Puddin Tane]

And when doing the fuel pump first watch YouTube videos of burn victims, have the car out in the open but shaded, and have a fire extinguisher close at hand. Scary shit!

[fabric8]

I believe it should be 4 bar / 60 PSI

Don't do it! "Cheap" Audi parts are often false bargains. The real bargain is knowing the OEM for the part, in this case VDO (now owned by Continental, so may be branded as such). That's what I used and recommend. Here it is. If you can find a better price for the VDO pump go for it. From the looks of your injector discussion you seem interested in more power, so you may want to upgrade the pump too in which case I don't know what's what. Not into all that. The stock car is plenty peppy enough for my sucky driving.

Thanks! I may have not have been clear with my posts about my injectors. I've had a motoza stg 1.5 tune paired with with the 550cc injectors. I've had this setup now for over 5 years without any issue and fueling has never been a problem. Dave (from Motoza) had said the stock fuel pump is more than adequate for my fueling needs. If I had a BAT and needed more fuel, then yes, I'd go for an aftermarket fuel pump.

[Turbo510]

Don't do it! "Cheap" Audi parts are often false bargains. The real bargain is knowing the OEM for the part, in this case VDO (now owned by Continental, so may be branded as such). That's what I used and recommend.

I learned about that the hard way, in my B5. I put in an inexpensive knock-off, thinking 'what's the difference'? Well, one day I was doing 80 on the freeway, when all of the sudden I felt my foot instinctively pressing the gas pedal, as the car slowed down. Then the tach dropped to zero, and the oil/alt lights came on. What made the situation worse was that due to recent construction on the freeway, there was no emergency lane; my right lane was it and cars were coming up behind me. In addition, there was no place to park as far as I could see. With the emergency flashers on, I continued to coast, slowing as I crested a rise in the freeway. Up ahead I could see that the concrete K-rails ended at a small dirt area. Down to maybe 20 mph, I swerved into the gravel and skidded to a stop with pulse rate way up there. That experience made the VDO pump seem not so expensive after all.

[EuroxS4]

Certain parts you can get by with aftermarket or oem equivalent from a good vendor not china shit. Also a fuel pump is not nothing I would buy in the aftermarket to avoid issues.

[fabric8]

Sounds good thanks for the recommendation. Ill order the oem fuel pump from europaparts. Should i I also order a new seal part number 1J0919133B?

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[europeein]

Good read. My initial guess would be leaky fuel injector once the car shuts off but seems everyone is favoring the fuel pump. Can't wait to see the results.

[Puddin Tane]

Should i I also order a new seal part number 1J0919133B?

YES. Also standard procedure. Forgot.

@europein: Turbo's knowledge is way beyond mine. He (and you) may turn out to be right. Thing is, at such high mileage I think doing the pump is necessary preventive maintenance anyway.

[fabric8]

Thanks for all the suggestions so far guys! I went ahead and ordered the fuel pump, seal and fuel filter. I'll chalk this all up as preventative maintenance if it doesn't fix the starting problem.

Regarding a possible leaking injector. I've been doing more reading and it sounds like the leak mentioned is not from an oring, but rather the injector failing to 'shut itself' after the engine has been turned off, causing fuel from the presurized rail to leak through the injector and into the piston, correct?

It looks like autozone rents out fuel pressure test kits. I'm planning on renting one today while I wait for the parts to arrive. It sounds like I would:
1. with the vehicle off, connect the fuel pressure guage to the schrader valve on the pressure rail
2. start the vehicle
3. record the fuel pressure reading while the engine is running
4. shut off the vehicle
5. monitor the fuel pressure reading. It may go down possibly up to ~2psi after it's shut off, but over a period of time, ie 5min, it should not continue to go down, is that correct?

On another note, before starting the car this morning, I read the measuring blocks and they appeared OK:
Ambient temp = 26.5C
Coolant temp = 34C
Engine outlet temp = 33C
Intake Air temp = 34C
Radiator outlet temp = 30C

One final note, yesterday afternoon upon starting the car, I heard a brief hum/squeal sound from under the rear seat. I'm 99% sure it's the sound of the fuel pump that others have described. Does anyone know how the fuel pump work? Does it have an impeller, somewhat like the water pump? What part of the fuel pump would make that sound?

[Puddin Tane]

yesterday afternoon upon starting the car, I heard a brief hum/squeal sound from under the rear seat.

Geez, dunno. When mine started crapping it made ticking/grinding noises. All I can say is hearing weird noises loud enough to be audible through the seat is a sure sign the pump is about to try to kill you in traffic. Have a back-up car to drive? I wouldn't so much as run that one til the new pump is in.

Speaking of which, here's some great tips for doing the pump job
procedure by A4mods
cheap-o DIY pump wrench. 1/2" OD aluminum tube from the sheet metal rack at Lowe's works great.
A detail that's soooo easy to miss: see the little funnel-shaped notch in the edge of the pump basket, at "top" in this view? There's a corresponding little black tube coming off the top of the pump with two ell bends formed into it. The pump needs to be oriented so that tube wants to go into that funnel, and the tube needs to be guided into the funnel when the pump is lowered into the basket. The tube is the fuel return, and it can cause trouble if not routed into the little funnel.

[Turbo510]

On another note, before starting the car this morning, I read the measuring blocks and they appeared OK:
Ambient temp = 26.5C
Coolant temp = 34C
Engine outlet temp = 33C
Intake Air temp = 34C
Radiator outlet temp = 30C

One final note, yesterday afternoon upon starting the car, I heard a brief hum/squeal sound from under the rear seat. I'm 99% sure it's the sound of the fuel pump that others have described. Does anyone know how the fuel pump work? Does it have an impeller, somewhat like the water pump? What part of the fuel pump would make that sound?

That coolant temp is over 93 F. Did the car sit long enough for the coolant and ambient air to match? If the starting mixture was too lean, that coolant temp sensor could be the reason.

These fuel pumps are turbine-types, not a positive-displacement arrangement. I have very occasionally heard a momentary squeal on startup. I don't like it but so-far it's rare.

[fabric8]

Geez, dunno. When mine started crapping it made ticking/grinding noises. All I can say is hearing weird noises loud enough to be audible through the seat is a sure sign the pump is about to try to kill you in traffic. Have a back-up car to drive? I wouldn't so much as run that one til the new pump is in.

Yup, the A4 is my daily and I have another car to drive.

Speaking of which, here's some great tips for doing the pump job
procedure by A4mods
cheap-o DIY pump wrench. 1/2" OD aluminum tube from the sheet metal rack at Lowe's works great.
A detail that's soooo easy to miss: see the little funnel-shaped notch in the edge of the pump basket, at "top" in this view? There's a corresponding little black tube coming off the top of the pump with two ell bends formed into it. The pump needs to be oriented so that tube wants to go into that funnel, and the tube needs to be guided into the funnel when the pump is lowered into the basket. The tube is the fuel return, and it can cause trouble if not routed into the little funnel.

Thanks for sharing those links and tips - especially the one about the fuel return line. I've replaced the fuel level sender before (the part on the right side of the rear passenger seat) so at least I'm familiar with removing the locking ring. I"ll pickup some 1/2 OD aluminum tubing to make those 'hockey stick's'

That coolant temp is over 93 F. Did the car sit long enough for the coolant and ambient air to match? If the starting mixture was too lean, that coolant temp sensor could be the reason.
These fuel pumps are turbine-types, not a positive-displacement arrangement. I have very occasionally heard a momentary squeal on startup. I don't like it but so-far it's rare.

I was surprised as well with those readings, but yes, the coolant was actually warm to the touch. The car sat overnight in my garage, but we had a 102F day yesterday here in Las Vegas, so the garage was definitely warm, and so was the coolant. I couldn't believe that the coolant would be that warm after sitting overnight, so I removed the expansion tank cover, stuck my finger into the coolant and it felt warm. I'd say it was an accurate 93F. It's interesting that this starting issue developed as soon as it started to get warm here in Vegas this year, about a week or so ago. But through every previous very hot summer we've had, it's never had an issue starting on the 1st try.

So perhaps not enough fuel upon startup due to a weak fuel pump combined with warm coolant, leading to a lean'ish condition like you suggest? Sounds plausible?

[europeein]

One final note, yesterday afternoon upon starting the car, I heard a brief hum/squeal sound from under the rear seat.

I've heard this before and agree, can't say the cause is a faulty pump but like others have said, pump should be looked at as routine maintenance anyway. Will be interesting to see your pressure numbers at the rail when you test for a possible leaking injector.

[BumblebVR6]

Replace the pump/seal/fuel filter. My original died and left me stranded at around 160K miles as stated above. If not planning on modding the car with any additional fueling demands, pick up a good quality oem pump and you'll be fine.

[A4Maine-iac]

Back when i had my 02 A4 i went through the same issue and turned out to be crankshaft position sensors.

As for the fuel pump it will hum when priming. But if it hums when running then it maybe on its way out. This happened as well.

Hope this helps

[Turbo510]

So perhaps not enough fuel upon startup due to a weak fuel pump combined with warm coolant, leading to a lean'ish condition like you suggest? Sounds plausible?

You've got a 1.8T so it would be easy to add a little fuel, by disconnecting the big intercooler hose at the TB, easing the throttle plate open, and giving it a shot of carb cleaner for instance. If it lights off right away, that would imply the starting fuel is barely sufficient, due to fuel pressure or the coolant sensor.

[fabric8]

How old are the spark plugs? Pull one and have a look, or just replace.

good update to report:

So as I had previously replied, the plugs are a little over 10k miles. They are the copper bkr6e plugs which I know should be changed out every 5k miles. I was being lazy and putting it off tending to other things since they 'seemed' to still be OK.

Well I just changed them a few minutes ago and drove the car to rent the fuel pressure tester from Autozone. And guess what? The car starts immediateley and strong now on the first crank - each time. It's literally a night and day difference.

While the plugs were out, I took a flashlight and looked into each cylinder and saw that each of the four piston heads were bone dry. A possible/good sign the injectors aren't leaking?

I'm waiting for the engine to cool down to connect the fuel pressure tester, then will check the fuel pressure while its running then will monitor it after I turn off the engine.

If tomorrow morning it starts right up again, then it was the spark plugs for sure and I'm a complete bonehead for being lazy about changing them religiously like I used to.

I'll still install the new VDO fuel pump and filter arriving this Friday over the weekend for peace of mind for an upcoming road trip. I also really want to compare the difference in fuel pressure between a 21yr old 184k mile fuel pump and a brand new one

Oh, and all 4 worn plugs were at a gap of .031. The new ones are properly gapped to .028. The old plugs dont look all that bad. I'm wondering if the enlarged gap was the real issue?



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[fabric8]

Ok, scratch that last update. The car sat for 2 hours and upon starting, had the hard starting again and the pump made more noises during priming

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[fabric8]

Update: I performed the fuel pressure test with a loaner tool from Autozone and it was brand new.

Here's a video:


So as you can see, the pressue is at 0 when the car is off. When the igintion is turned on, pressure shoots to 60psi for a couple of seconds (which means the fuel pump primed it), then starts falling quickly.
Once the engine is started, pressure is back to 60.
Once I shut the engine off, pressure drops back to 0 within a couple of seconds

Is this normal behavior for the 1.8t? Or should the fuel rail hold ~60psi of pressure even after the engine is shut off?

[EuroxS4]

Rail should be holding pressure from what I know. But how is it plumbed? Depending on how its plumbed it wount tell you whether the drop is at the rail or as t filter or or pump. This is why it needs to have 2 valves to determined the cause.

[Turbo510]

In my opinion, two things that don't involve external leakage could cause the pressure to drop: A leaky fuel regulator in the filter, or a leaky check-valve at the pump. But if you get normal fuel pressure when the pump is running, that rules out the issue of fuel pressure being the problem. Still, since you have that pump on the way, install it.

If you have never changed the pump before, a few suggestions: make sure that you do this when the fuel level is pretty low, and especially not when the tank is anywhere near full. The fuel level would be higher than the tank access.

Second, unlocking the pump basket from the base-holder in the tank is easy when using a "crossed bar" approach. Use non-spark material such as Aluminum, and with the bar ends into opposite notches of the pump basket, cross them and grab the upper ends, which allows you to twist the basket without trying to get your hand on the basket. You should note that the basket has a molded-in groove or ridge, and the base inside the tank has two marks, which is your alignment guide to install the new one. So initially line up the basket and base marks, such that with a slight clockwise rotation the basket and second base mark line up.

The fuel line couplings are most easily removed with special pliers, probably available for borrowing from your auto parts store.

One last thing; there is an overflow tube from the white plastic tank cover which must be fitted through a funnel-shaped receptacle in the base. If not in place, this can interfere with the level sender float arm, as I found out.

If you've done this once, you can probably change the thing in 15 minutes.

[fabric8]

Rail should be holding pressure from what I know. But how is it plumbed? Depending on how its plumbed it wount tell you whether the drop is at the rail or as t filter or or pump. This is why it needs to have 2 valves to determined the cause.

In my opinion, two things that don't involve external leakage could cause the pressure to drop: A leaky fuel regulator in the filter, or a leaky check-valve at the pump. But if you get normal fuel pressure when the pump is running, that rules out the issue of fuel pressure being the problem. Still, since you have that pump on the way, install it.

If you have never changed the pump before, a few suggestions: make sure that you do this when the fuel level is pretty low, and especially not when the tank is anywhere near full. The fuel level would be higher than the tank access.

Second, unlocking the pump basket from the base-holder in the tank is easy when using a "crossed bar" approach. Use non-spark material such as Aluminum, and with the bar ends into opposite notches of the pump basket, cross them and grab the upper ends, which allows you to twist the basket without trying to get your hand on the basket. You should note that the basket has a molded-in groove or ridge, and the base inside the tank has two marks, which is your alignment guide to install the new one. So initially line up the basket and base marks, such that with a slight clockwise rotation the basket and second base mark line up.

The fuel line couplings are most easily removed with special pliers, probably available for borrowing from your auto parts store.

One last thing; there is an overflow tube from the white plastic tank cover which must be fitted through a funnel-shaped receptacle in the base. If not in place, this can interfere with the level sender float arm, as I found out.

If you've done this once, you can probably change the thing in 15 minutes.

Thanks guys!! Ok got it. Since fuel pressure while running has not been an issue, is it plausible to say that either a leaky pressure regulator inside the fuel filter or a bad check valve on the fuel pump is causing the hard starting becuase of not enough constant fuel pressure during startup? And that it's unlikely that it's one or all 4 injectors leaking since I'm not seeing any wetness on the surfaces of the pistons when I removed the spark plugs?

Also, is there any other fuel check valve ie. between the fuel filter and the fuel rail?

Thanks for the tips on replacing the fuel filter. Going to tackle it this Saturday.

To rule out the injectors leaking, would this make sense: unbolt the fuel rail from the intake manifold with the injectors still attached to it, then set it on top of a large aluminum baking pan. Then turn the ignition on to have the fuel pump prime, and inspect the injectors. They should NOT leak any fuel, is that correct?

[Turbo510]

...the hard starting becuase of not enough constant fuel pressure during startup?

If your pressure gauge shows 60 PSI upon cranking, and while running, then it can't be a fuel pressure issue. Have you tried the spray-of-fuel past the throttle-plate test? That should take only a few minutes to show whether a bit more fuel fires the engine.

[fabric8]

If your pressure gauge shows 60 PSI upon cranking, and while running, then it can't be a fuel pressure issue. Have you tried the spray-of-fuel past the throttle-plate test? That should take only a few minutes to show whether a bit more fuel fires the engine.

I have yet to try that. I'll need to get someone to help me crank the engine while I spray the starting fuel. I'd rather not bother my wife for this :D

I'm at the point now of just buying a new crankshaft position sensor as well since this symptom is similar to when it failed before. Although there are no codes for it this time. I've read a crank position sensor could be bad and not throw a code. I replaced it in 2016 with 136k on the clock, so gone through 7yrs/ 48k miles.

[Puddin Tane]

About those pliers...

They're a must for this job. Seeing as you did the fuel filter in 2015 you may know all about that and have a pair. If not, and you can't find them locally, this one's a good value IMO. The perfect size and the return spring is an important touch.

In my experience those hose quick connects are a snap to assemble, literally, but a royal PITA to open. Dust packs into them over the years and jams them so the little buttons don't release as intended. That's why compressed air is important for this job. You can clean them out with a needle tip blowgun and QD electronic cleaner. When you lift the access hatch under the back seat you'll also discover a ridiculous amount of dust covering the entire surgical field. Blow gun to the rescue again.

[fabric8]

About those pliers...

They're a must for this job. Seeing as you did the fuel filter in 2015 you may know all about that and have a pair. If not, and you can't find them locally, this one's a good value IMO. The perfect size and the return spring is an important touch.

In my experience those hose quick connects are a snap to assemble, literally, but a royal PITA to open. Dust packs into them over the years and jams them so the little buttons don't release as intended. That's why compressed air is important for this job. You can clean them out with a needle tip blowgun and QD electronic cleaner. When you lift the access hatch under the back seat you'll also discover a ridiculous amount of dust covering the entire surgical field. Blow gun to the rescue again.

You know, its funny but I dont have those special pliers and never had any trouble removing the clips the last time. Watch me struggle this time

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[Puddin Tane]

Maybe it's an effect of my location (rural Georgia, dirt roads, year-round high humidity, 60 inches of rain)

[Turbo510]

I have yet to try that. I'll need to get someone to help me crank the engine while I spray the starting fuel. I'd rather not bother my wife for this.

I wasn't clear about this, sorry. I meant that you pull the hose from the TB, tip the butterfly open enough to shoot a bit of carb cleaner in, then put the hose back. Then crank and see what happens. No need to involve the wife, which I know from experience actually makes the job take longer.

[old guy]

Pull the fuel rail. Pre-weigh four containers. Put the injectors into the containers. Turn the key to the on position and look for any injector leaks. Next, have someone crank the engine while you observe the spray patterns to see if they are uniform. Then weigh the containers to see if the the injectors are reasonably balanced.

[fabric8]

I wasn't clear about this, sorry. I meant that you pull the hose from the TB, tip the butterfly open enough to shoot a bit of carb cleaner in, then put the hose back. Then crank and see what happens. No need to involve the wife, which I know from experience actually makes the job take longer.

Ohhh, ok got it. I don't have any carb cleaner on hand at the moment, but may swing to the auto store and pickup a can. It's always useful to have around.
By "shoot a bit", would a 3 second burst sprayed through the straw be sufficient?

[fabric8]

Pull the fuel rail. Pre-weigh four containers. Put the injectors into the containers. Turn the key to the on position and look for any injector leaks. Next, have someone crank the engine while you observe the spray patterns to see if they are uniform. Then weigh the containers to see if the the injectors are reasonably balanced.

Excellent idea! If when I turn the key to the on position and see any or all of the injectors leak, that should be a clear sign that's my real problem correct? And at that point, is there any sense in proceeding to start the engine?

If one or more injectors leak during priming, can the injectors be fixed? Or should I just buy new 550cc injectors? They only have about 56k on them. My stock injectors were at ~120k on them when I pulled them.

[old guy]

There should not be any leakage when you prime the fuel line. Even if you do have leakage, it would still be worth checking the spray pattern to see if one is partially clogged. If so, some injector cleaner may help.

[BumblebVR6]

I had a similar problem w/ a Bosch 040 pump I had. Always took two tries to start. Put an oem one back in and it fired up right away. Most likely the regulator in the pump.