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Trouble Starting Car with the issue still undiagnosed

Trouble Starting Car with the issue still undiagnosed

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Discussion

PatKing00

Original Poster:

22 posts

2 months

Monday 21st August
quotequote all
So, the battery was of course flat as a pancake, so has not been fully charged up.

The Fuel pump has arrived however it has a green pipe coming off the pump which I have not see in any other vehicles when researching videos of how to replace the fuel pump, they all seem to just be one unit without any external piping. Therefore is this pipe simply how this fuel pump takes in the fuel from the tank or does it have to be connected to something else. It may be another silly question but I'd just like to be sure and if someone else stumbles across this thread in future this will have all the bases covered for them as it seems there is not much info on this model of Audi A4 out there.

Kind Regards Patrick

PatKing00

Original Poster:

22 posts

2 months

Monday 21st August
quotequote all

PatKing00

Original Poster:

22 posts

2 months

Monday 21st August
quotequote all

E-bmw

2,841 posts

74 months

Monday 21st August
quotequote all
A few points that you haven't covered.

Did you try to start it with a charged battery? If so what happened?

I am sorry, but I would be returning that, I wouldn't fit something that dirty into my fuel tank!

Have you looked at yours to see if it is the same?

If it is, it should be obvious to replace like for like.

PatKing00

Original Poster:

22 posts

2 months

Monday 21st August
quotequote all
It started with a charged battery but just as it did before the battery was flattened so no change in circumstance.

I intend to give it a proper clean up before installing it (take apart and clean with carb cleaner)

It is defiantly the same fuel pump as it has the same OEM. I'd hope the green pipe will be an obvious part but was just hoping for clarification.

Kind Regards Patrick

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E-bmw

2,841 posts

74 months

Monday 21st August
quotequote all
Let me get this right.

You charged the battery & it started & you are still going ahead with the pump change why exactly?

PatKing00

Original Poster:

22 posts

2 months

Monday 21st August
quotequote all
So the original issue was that it cranks for a while then starts (the battery is new). It is this cranking which has caused the battery to drain. Now the battery has been charged it still cranks several times but needs easystart sometimes to get it going. This is the original issue. The battery is not the route of the problem.

Kind Regards Patrick

GreenV8S

24,726 posts

206 months

Monday 21st August
quotequote all
PatKing00 said:
So the original issue was that it cranks for a while then starts (the battery is new). It is this cranking which has caused the battery to drain.
That seems a little odd - normally, if the charging system is healthy it will recharge the battery fairly quickly once the engine is running. How long are you cranking it before it catches? And, are you doing lots of short journeys?

PatKing00

Original Poster:

22 posts

2 months

Tuesday 22nd August
quotequote all
Yes bump starting doesn't work.

I've just looked at the relays in the car but can't find a schematic of which one is the fuel pump relay, any ideas?


PatKing00

Original Poster:

22 posts

2 months

Tuesday 22nd August
quotequote all
The issue is random, it might crank once it might crank 30 times. It is totally intermittent. Most of my journeys are 5-10 minutes put I do take the car out for a few hours on the motorway a couple of times a month.

Kind Regards Patrick

PatKing00

Original Poster:

22 posts

2 months

Tuesday 22nd August
quotequote all
Just to add some more information, here you can see the car idling roughly. When revved it runs smoothly but as soon as it goes back to idle it shudders like it's being choked.

Check out these videos to illustrate:

https://youtu.be/f-Wh-1iKp6s

https://youtu.be/hdW0cmTOKbI

It shakes even more than my camera in my hand!


Kind Regards Patrick


PatKing00

Original Poster:

22 posts

2 months

Friday 25th August
quotequote all
The fuel pump has now been changed along with the fuel filter but this has made no difference. Anybody know a good scrap dealer?


E-bmw

2,841 posts

74 months

Friday 25th August
quotequote all
We already knew it wasn't likely to make a difference.

DuraAce

2,228 posts

82 months

Friday 25th August
quotequote all
Surely some proper fault diagnosis would be a good start? Rather than firing the random (used!) parts shotgun at the car?

Bit of live data monitoring fuel pressure, voltages to pump /injectors /sensors etc with a scope/VCDS should provide some direction

Defconluke

212 posts

76 months

Saturday 26th August
quotequote all
stevieturbo said:
Crank and cam triggers.....good chance when they put it back together after the head gasket, they did not align everything correctly
This, this and this again.

Cam sensor should be easier to get at but neither should be too arduous and cost should be £40 each tops.

I have a similar infrequent starting issue with my 1.9 TDI Ibiza (same engine but transverse instead of longitudinal). It will start perfectly for months at a time and then refuse to start no matter how much cranking. A quick wiggle of the crankshaft sensor wire and hey presto it fires right up first time. I'll replace it next time I'm doing an oil change but for the infrequent nature of the problem and the 10 seconds it takes to pop the bonnet and wiggle the wire, I'll make do for now.

bearman68

1,947 posts

54 months

Saturday 26th August
quotequote all
Just a few points. AFAIK the VCDS won't monitor fuel pressure. (It's not a common rail). Engine needs to turn over at 250 rpm or more to initiate the injectors. Scoping the cam and crank signal is where I would go, and check the compression when I'm at it.
Low output crank would be my guess.

Classy6

179 posts

99 months

Tuesday 5th September
quotequote all
If you carry on listening to users of this forum diagnosing willy nilly parts without actually carrying out physical tests you will carry on spending on thousands on this car. You need to start diagnosing, and secondly when you decide a part needs replacing, make sure they're new!

What is the mileage on the engine?

The video you last posted the battery is dead as other's have mentioned. 12v as an indicator to test a battery means absolutely nothing, other than if it's reading above 12v and it's not cranking it needs replacing/recharging.

If the engine is not running off easy start it's not going to be fuel related as this is the point of easy start as a diagnostic tool. Spraying that stuff into an inlet on any car with good compression/timing means it should run. There is the possibility that you are doing something wrong with it though, so I don't think it can be ruled out completely. What happens when you spray easy start down it when cranking it over?

To test the fuel lift pump, you need to multi meter capable of measuring amps. Find the relay or fuse and test amps passing through that circuit when cranking. So if you use the fuse, remove the fuse and run the multi meter wires into either side. If using the relay you want terminals 30 & 87. Should read around 3-5 amps when running. More amps means pump is seized/blocked, less means free spinning usually no fuel/not working all together.

Personally I would be looking at cam/crank sensors. Crank sensor will either be 2 pin inductive type or 3 pin like the cam sensor detailed below. If 2 pin you can connect a meter to each of the pins (backprobe) on AC function, crank the engine and you should begin to get an AC voltage reading that increases up to around 1.5-3v when cranking is up to full speed. Alternatively if you have an OBD/VCDS tool capable of reading actual values you can easily check for a reading on this.

Cam sensor should have 3 pins, measure 2 feeds either 5v or 12v or a mix of either. Other wire will be an earth. Set your meter to either Duty cycle/Hz/RPM/something that can measure switching and place common black meter wire to backprobe the earth, and whilst cranking again, backprobe one of the feed wires until you get a switching signal. The reading is irrelevant on there meter, as long as it's getting something.

Charge your battery up to full and have it checked with a proper BATTERY TESTER (halfords, local garage), recheck if the engine will start with easy start, make sure the engine is being cranked before you spray it in, spray in short burst intervals. If it isn't starting with easy start you need to have timing/compression checked. If it does run on easy start, do the above tests and report back.

PatKing00

Original Poster:

22 posts

2 months

Wednesday 20th September
quotequote all
The car is 120K

I have taken the battery to Halfords and they said it is fine. I have fully charged the battery.

Now that the weather is cooler the car will not start at all with or without easystart. It had previously started every time when spraying easystart whilst cranking.

I have tested the fuel lift pump, cam and crank sensors using the methods which you described and they all work as they should.

What would the next step be?

Kind Regards Patrick


E-bmw

2,841 posts

74 months

Wednesday 20th September
quotequote all
Well if it won't start on easy start the issue clearly isn't fuel for a start.

I assume you are spraying it in with the engine turning over, direct into the inlet/throttle?

PatKing00

Original Poster:

22 posts

2 months

Wednesday 20th September
quotequote all
It was starting with easystart but now it isn't. The only change I can think of is the cooler weather.

I am spraying it into the inlet whilst cranking.

What are the next things I should test?

Kind Regards Patrick