VR6 hot start problem - fixed at last?!

[harryc 0]

My hot start problem is getting worse and worse. It's taking longer and longer to start now after it's been driven. I ve replaced the engine earth and fuel pump relay but it's made no difference. The issue I have is the fuel pump not priming and hence it not starting and just turning over and over.

I have a new ignition switch which I'm waiting to fit but I'm trying to think of what else it would be. Would a flat key battery stop the fuel pump priming due to immobiliser issues?

I know exactly when the cars going to start and when it's not because I can hear the pump prime. Whenever the car is driven and left for a couple of minutes it will not prime/start for about half an hour, it's getting ridiculous!

Car is a 95 vr6 (coilpack) with original scorpion alarm.

Edited March 28, 2011 by harryc

[volksworld13 0]

sounds like a coolant temp sensor problem, get vagcom on it,

[harryc 0]

Ive had it plugged in to my vag com and it didn't throw anything up, not sure if I trust it though. It would show up on the general scan right?

[RW1 0]

If there is no fault codes in the 01 - Engine fault code screen, then next is to look at the groups of Measuring Blocks. Ignore groups 000 & 006. Look at the groups 001 thro' 005 and see if anything differs drastically from this warmed-up engine operating normally.

 

download/file.php?id=24708&mode=view

 

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[harryc 0]

Will this let me know which of the 3 temp sensors is faulty? I've booked it into a garage up here in Ox as i dont have access to my tools, workspace or VAG.com and they said they need more time to figure out which sensor is faulty. They also said VW gave 14 options for the sensor so they would need slighlt longer to identify which one is needed?

[poll250 0]

Which garage did you take it to? Graham at GK Autos on Abingdon Road is the man I'd take it to...

[harryc 0]

French and italian cars on cowley, only as thats where i live so picking up the car is easy. Been quoted 44 quid for diagnosis to determine which sensor then about 65 for parts and labour.

[harryc 0]

Just as a reference for anyone else it ended up costing me £91 for diagnostic, sensor and labour.

I could have saved a third if id managed to identify which sensor was playing up using vagcom but left my cable in kent :brickwall:

The new sensor has greatly improved the problem although it still sometimes needs the second turn of the key to fire when hot. Hoping a new ignition switch should solve this!

[poll250 0]

Nice one! Which sensor did they replace?

[harryc 0]

Right i am about to go outside and burn the car. The hot start problem hasnt happened like this since i've had the sensor placed. I stopped outside the bakery in town got a sandwhich and the car wouldnt start. Been on a 1hr drive before so it was fully up to temp. The problem is the fuel pump is not priming and it wont start. What is the process between turning the key and the car starting. By this i mean exactly what signals are sent and recieved in order for every process to occur and the car actually starts.

I've replaced;

-Fuel filter

-Engine eath

-Blue collant sensor

-Leads

-Plugs

-Coil pack isnt that old

 

What exactly is the process of the fuel pump priming? What prevents it from priming?

[Kevin Bacon 5]

I do hope the sandwich was ham?

 

1) Ignition Key stage 2 - Fuel pump runs for approx 1 - 2 seconds to build up rail pressure, then stops. *

2) Ignition key stage 3 - Engine cranks, ECU looks for crank signal. **

3) Crank signal found, coils and injectors turned on.

4) Engine fires and runs.

5) You drive to the bakery to get a sandwich.

 

* - Is your's a 95 CP ECU with immobiliser? If so, priming still takes place. If an immobiliser fault (key or key reader), engine starts, engine stops again almost immediately. Not starting at all is not symptomatic of a duff factory immobiliser.

 

If you're using an aftermarket immobiliser (which I don't recommend), that's where I'd start my investigation as you said you've replaced Relay 167 already. Another possibility is the fuel pump itself. They're known to get tired with age and cause these symptoms. As well as general tiredness, they have a non-return valve in them to maintain rail pressure for quick restarts. Dirt and grit can easily bind the valve open with age.

 

** - The classic cause for lengthy and non starting issues. No crank signal, no fuel or spark. Have you checked for fuel and spark?

If it is the crank sensor (£150), then eventually it will get so bad it won't start at all. Unfortunately Bosch's diagnostics leaves a lot to be desired. You cannot monitor the crank signal for missed signals and resync counts.

[harryc 0]

Kev your a hero, it has a horrible plain chicken breast on brown bread with no mayo because im cutting weight. It was dry, very dry.

I'll have to check on the ecu number. It has the factory alarm, not sure of the state of the immobiliser or if it works as the factory remote central locking doesnt work.

I've checked for spark but not fuel pressure. I know when the car is going to start because i hear the priming noise coming from the rear near side by the fuel pump and it fires as soon as i crank it. Sometimes when hot you wont hear the pump prime and i know it won't start before i have even cranked it.

The car doesnt begin to fire its like its not fuelling at all unless you hear the pump prime.

[Kevin Bacon 5]

Oh dear, Friday is "tasty sandwich" day! Cardboard sarnies are for Mon-Thurs only! :D

 

Yeah if you slide the ECU out from under it's rock, you'll see a sticker on top of it with a bosch 0 280 xxx xxx number on it, and a VAG p/n. At the end of one of the numbers will be AG if it's a non-immobilised car, or CP if it's immobilised. Another way to tell is if you can see a black plastic sleeve around your ignition barrel with a wire attached to it. You'll spot that when you go in there to attack the ignition switch.

 

So no spluttering or anything whilst cranking? Just pure nothingness? I really doubt it's the ECU wiring to fuel pump relay. The only question mark there is your alarm type and whether it's cut into the fuel circuit or not. Aftermarket immobs cut the starter and fuel pump relay wires. Now I come to think of it, I did once have a fecked Clifford Concept 50 that did what your's is doing. The AA guy bypassed it and off I went again.

 

So yeah, I reckon it's either that, the pump relay, or the pump itself mate.

[harryc 0]

Thanks Kev, just got the car back. Effing typical, car broke down at 11, came back to it a few hours later when cool, still nothing. Called the AA, 30 mins later i try to restart, nothing. AA man arrives (6.5 hrs after the car broke down), i sit in the car, describe the problem with the pump not priming and turn the key to illustrate. Car fires in to life first turn. I apologise profusely and drive the car home. Try to restart it and nothing, quickly checked for spark and its sparking fine. As far as im aware there is nothing aftermarket, the entire car was totally standard, it has the vag siren, vag fob and no paperwork or evidence otherwise. It still has the factory scorpian alarm box in the passenger footwell which i attacked when i first had the problem.

Forgot to mention i also tested and replaced the fuel pump relay. Whats the best way to test the pump, complete removal jobbie?

[poll250 0]

Harry I have this exact problem too. Most annoying/likely to happen at petrol stations as that seems the optimum amount of time!

 

If you leave the key turned for a couple of minutes sometimes you will hear the pump prime and away you go.

 

I've replaced fuel pump, sender, filter, ecu and fuel pump relays and ignition switch in the last couple of years.

 

How's your battery/ earths/ starter motor?

[harryc 0]

Harry I have this exact problem too. Most annoying/likely to happen at petrol stations as that seems the optimum amount of time!

 

If you leave the key turned for a couple of minutes sometimes you will hear the pump prime and away you go.

 

I've replaced fuel pump, sender, filter, ecu and fuel pump relays and ignition switch in the last couple of years.

 

How's your battery/ earths/ starter motor?

 

Have you managed to sort the problem? Earths are new, battery seems to hold charge, starter cranks the engine quickly.

[harryc 0]

Finally the problem may be fixed!!!111! Threw in the towel after the car failed to start at the clacket lane services. Lft the car at Wheelbase in Hersham while i went to Germany for the week. Got back to a bill of £370 only £70 of which was on parts. Aaaaaanyway, the bill reads;

Carry out extensive electrical tests

Renew faulty ignition switch

Renew crankshaft positioning sensor, engine still not running

trace fault to fuel pump relay not receiving earth activation signal from ecu,

repair wiring to rear of fuse box

remove broken intake manifold back fire box

 

Anyway my gf paid for the work and when i got back from Germany i drove the car up to Ox, stopped to fill up outside Oxford and couldnt restart the car........

Left it til today so the car would be cold, went to restart it and still nothing! Called the AA out again and the bloke got the car started by fiddling with the no4 relay for the ignition. Drove the car back to wheelbase told them the problem had not been fixed at all and that the AA man recommended a new relay. Anyway, new relay is in place and the garage say the problem is now fixed but we will have to wait and see.

Not sure how to feel about the bill, they spent a lot off time and money replacing parts that were not the cause of the problem and the AA man was able to locate the fault in 5 mins and fix it......

Anyway hoping the problem is now sorted so will confirm by tomorrow!

[dukest 0]

mine is getting worse and worse for this, it still always starts when cold, but if left for less than about 10mins its very unreliable. havent changed anything yet but it can only be something that would get worse with heat/running as its always spot on from cold..

 

how much was the new no.4 relay?

[harryc 0]

Got it for free as the £400 worth of work they had done before had made no difference to the problem. The problem is much better, it cranks a little longer when hot but its starting!! The only thing I havnt replaced that i believe could be causing a problem is the pump but I have a feeling its more to do with an immobiliser some where. The garage replaced a lot of the hacked up wire I had behind the fusebox. I just cant understand why its been so hard to find the source of this problem!!

[poll250 0]

How is yours running now Harry? Mine is seemingly getting worse!

[VW_OwneR_85 1]

wow reading through this makes me feel greatful for the one i have,even though its got/had its fair share of problems,

my vr sometimes takes awhile to start roughly 4 seconds is that normal for a vr?, i never hear my fuel pump prime though,

should it be priming on the first turn of the key when the dash lights light up? it allways starts hot or cold.realy hope you guys find what the cause of this is......

[poll250 0]

Ok, this problem is getting a bit ridiculous now!

 

I wasted 30 minutes on Friday night when I stopped at a Tesco express near my mates house, car still wouldn’t start and we needed to leave so I took the Fuel pump relay out and left the car at Tesco for the night (so no one could steal it!).

 

Returned at 1pm yesterday to a very hot cabin, stuck the relay back in and it still wouldn’t start. Just cranked, no fuel pump priming. It did this for about half an hour then it kicked into life and I drove off.

 

I Stopped off for some lunch, leaving the windows and sunroof open, and about an hour later when I came back it wouldn’t start again! 30 mins of trying and the fuel pump primed, and off I went!

 

That’s 1h30 minutes of my weekend!

 

A lot of the time, if I leave the key in position 2, the fuel pump will prime after a few minutes.

 

I’ve replaced ecu relay, fuel pump relay, fuel pump x2, crank sensor, leads, coilpack, ignition switch etc

 

I read something about no4 Load Reduction relay possibly being at fault? Does anyone have experience of this? Harryc did that fix yours?

 

Does anyone have the part number?

 

Thanks

Edited June 27, 2011 by poll250

[harryc 0]

Have you managed to sort the problem? My turned out to be a relay after spending hundreds on re-wiring (not fuel pump, will dig out the paper work next time i get access to the car)

[vwpower71 0]

have you tried the ignition cap behind your ignition key they are known for given problems on starting