1995 Audi 90 12V lost power at 65MPH, stalled. Now cranks, does not start

[cgharibo]

On a 350 mile drive, 30 miles left to go at about 65 MPH, my 90q over about a mile lost power and stalled.

The fuel pump primes, all the right lights come on, the car cranks beautifully, but does not start. I pulled the codes and they relate to oxygen sensor, EGR temp sensor and EGR system and I think these are just old and unrelated.

Any ideas on why the 90q cranks but does not start?

[K Simmonds]

Have you pulled a plug out and checked you've got a spark? When you say 12V are you referring to a V6 engine We didn't get them in 90Q's in Europe, if it's the US then it'll be an AAH engine I believe.

Failing that check the cambelt hasn't snapped, will take no time at all and sometimes the car will still crank fine depending on where the valves are, unlikely but you need to rule it out.

Then if still no joy check the fuel pressure. The engine need's three things to run, fuel at the correct pressure, spark and compression so it should be something fairly obvious.

[david1980]

The uk did get a 12v 90 quattro v6

[K Simmonds]

The uk did get a 12v 90 quattro v6

That's interesting, I'm sure you right... I thought they'd pretty much phased out the 90 by 1992 when the first V6 cars launched and have only ever seen B4 80's or Coupes or Cabby's with the V6 engine in a small chassis car, it must have only been for a very brief period and they've got to very rare! Do know if it was the lovely 2.8 AAH motor or the somewhat more mundane ABC 2.6 David? Well you do indeed learn something everyday.

[ottawa coupe]

Check for spark. I find it hard to believe all 3 coils (batch fire) would die more or less at the same time, i guess it's possible. The other possibility could be a common wire to either the coils or the ignition module has gotten corroded.

As the coffee gets into my system more...if you have spark, then you could have said common wire issue for injectors too.

And ya, timing very unlikely as that woulda been a bang at 60 not gradualy over a mile. And it wouldn't be very happy to spin right now?

[John.]

.....over about a mile lost power and stalled.

Regardless of engine configuration I'm thinking an air or fuelling issue like a blockage or leak ?? When you say fuel pump primes, you can hear it yes or have you checked the pressure at the engine ?

Hedgehog in the air intake no !?

[SteveH]

I would guess fuel delivery issue if it got worse over time. Most of the ignition system will be either working or no spark. Could be the hose in the tank split if it sounds like it's priming but you have no fuel to the engine. As already mentioned, crack a fuel hose and see if you are getting pressure to the injectors.

[cgharibo]

Here is an exciting follow up. I checked the timing belt on the 12V. The passenger side bank looks OK, the driver side bank timing belt is shredded by 25%! Yikes! How do I tell if I jumped a tooth and would that be enough to damage the engine or cause a no start? The car is driven rather gently.

What's the advice here and truly thank you! My plan is to just get it towed and get the belt replaced. Prior to today, the engine cranked nicely and I dont believe anything is damaged.

[K Simmonds]

You need to try and set the engine on it's timing marks by turning it clockwise until piston No one is on the compression stroke to see if they still line up...

However I'm a little confused as the V6 engine only uses one timing belt so it should be equally shredded all the way around unless something very odd has happened.

You can normally get away with a timing belt jumping up to three or four teeth, anymore than that and it depends on the engine, some motors are non interference and the belt can snap completely and the engine still be fine, the V6 is not one of them.

As long as the belt is still tight it should be okay, if it's slack then you've probably got problems but no way of knowing without doing a compression test. If it's jumped teeth that could possibly cause a non start as the cam position sensor will be out of sync with the crank sensor.

It's going to need a complete timing belt kit and water pump as something must have failed to shred the belt, most likely a the tensioner, an idle roller or the water pump.

[cgharibo]

The belt still seems pretty tight. Hoping for the best.

[K Simmonds]

In that case if you don't have the tools required to do the job I'd get the car to a trust worthy workshop and I expect you'll be fine, if it's shredded the belt and not lost tension you've probably dodged a bullet. Disconnect the battery as a safety measure and don't try and start the car again just in case it does let go, it needs immediate attention even that's not what causing the non start.

Got my fingers crossed for you.

[JayCab]

If the timing belt is shredded and suspect jumped, any troubleshooting without first having a complete timing belt service risks writing off the engine…

I wouldn’t crank that car any more in that situation with a 30 odd year old AAH.

I would sort the timing belt next with no other diagnostics and no further mechanical engine rotation until the timing belt/water pump/tensioner roller/idler roller are all renewed and the engine re-timed.

[GazzaG60]

Guys
Not been here in years. I'm getting back on the road.
Sounds like an issue I had. Is the tank Im the boot. Even if fuel flows and all seems good in the tank on the end of the flow out is a mesh filter bag. I could do so many miles then it would conk and not start again for. Few hours. Basically till all the crud had dropped from the filter.

[cgharibo]

I changed the timing belt on the 12V and it started right up.

[K Simmonds]

That's a result.

Did you you fit a complete kit inc water pump and workout what had damaged the previous belt? You got pretty lucky there!