Hi I am having a no start condition with my 93 Audi 90 with 12v V6. I have already confirmed I have the basics. I pulled a plug wire from each bank and had spark, and I pulled fuel rail and confirmed I had fuel spray from each injector. Brand new plugs, plug wires and injectors all around. The engine cranks very fast and seems like it has very little resistance, although this 12v engine doesn't have a lot of valve tension so I'm not sure what to think about that. I just tried a compression test but I couldn't get any reading. Not sure if that's because I literally have zero compression or if it's because it's a cheap tool. I can hear the bassy exhaust pulses as I crank the engine with the plugs in so that leads me to believe I have at least more than zero compression.. I had also replaced the timing components with the proper procedure.. crankshaft at TDC and camshafts parallel to each other. I have rechecked timing numerous times since replacement and it has remained the same. I think I may have flooded the engine while replacing the injectors and while attempting to start the engine, so that could have something to do with the fast cranking speed, but it also cranked at this speed from the first attempt at starting. I've let the engine sit with spark plugs removed to help fuel dry out and I've also added oil to cylinders to try to regain compression but it hasn't helped. The car has been sitting for a year or so and gas was never removed but when I pulled the injectors the fuel that came out was of normal color and normal smell so I wouldn't think gas is the problem, I also added a bottle of ISO-HEET water remover just incase I had put ethanol gas into it. I can see the tach needle bounce as I crank so I will have to assume the crankshaft position sensor is working.
Stumped with no start engine
- Thread starter ruston
- Start date
Maybe try testing your compression tester on a different engine to verify function? Even a lawnmower would work if nothing else is available.
The fast cranking as well as no compression reading made me think first of a broken timing belt.
But given that you've got spark, that may rule out a TB problem. (I'm making several assumptions here - that the engine has a timing belt, that it has a distributor, and that the distributor is driven off a camshaft.)
If there is a distributor, did you have it out of the car? It's easy enough to reinstall them a tooth, or even 180°, out.
If you put a timing light on it, is the timing in the ballpark?
But given that you've got spark, that may rule out a TB problem. (I'm making several assumptions here - that the engine has a timing belt, that it has a distributor, and that the distributor is driven off a camshaft.)
If there is a distributor, did you have it out of the car? It's easy enough to reinstall them a tooth, or even 180°, out.
If you put a timing light on it, is the timing in the ballpark?
I am reminded of the Camry distributor that had an ignition module that would cause that issue, missed out on a good one I could have got cheap but I wasn't enlightened back then.
Timing belt is good, I just replaced it and I can see it as the engine is missing top timing covers. I tried spraying starting fluid through the throttle body and got nothing. I just confirmed gauge does hold pressure on a different engine. I couldn't get the gauge to even move a single psi on the audi. Only thing I could think of is zero compression or the o ring maybe isn't sealing on the spark plug hole. I have all the other spark plugs removed as well but I wouldn't think that would be an issue as if I'm not mistaken that's the proper procedure for compression testing?
Can you reach a finger to the sparkplug seat to see if you have any pressure that way?
Hate to say it but it sure sounds like you have have the timing set installed incorrectly
It started and ran before I replaced engine parts, but not that well. I noticed timing belt was replaced earlier with mark and pray method, so I decided I would redo it with proper procedure and new parts. I can't see how the timing would be wrong, but I suppose it could be off by just enough to disallow compression...
I would pull the timing cover(s) at this point to check the alignment of the timing marks - the crankshaft and both (or all four) camshaft marks. (Sorry, I am not at all familiar with this engine - don't know if it's DOHC or DOHC.)
If the timing marks are all good, check the distributor to ensure the rotor is pointing at #1 when it should be.
If the timing marks are all good, check the distributor to ensure the rotor is pointing at #1 when it should be.
Quick way to check flooding, pull the plugs, crank a few times, let it air out.
Plugs in, pedal to the floor, crank till it hiccups to life. The throttle to the floor should shut off the fuel flow till it finally fires.
Excess gas just grounds the sparkplugs. : l Your cranking time should be 15-30 seconds if it was truly flooded out.
Plugs in, pedal to the floor, crank till it hiccups to life. The throttle to the floor should shut off the fuel flow till it finally fires.
Excess gas just grounds the sparkplugs. : l Your cranking time should be 15-30 seconds if it was truly flooded out.
Well I guess I will redo the timing job and go over the procedure again and make sure I've not missed anything. I guess I am too bull-headed to admit I did the timing procedure wrong but it seems I have no choice lol. I am just hoping it wasn't off enough to bend valves. I don't think it was, reading on forums about these engines, it seems like the camshaft timing has to be absolutely perfect for proper operation.
It is hard to tell from your single paragraph, but did you ever see it run after the timing belt replacement? It not, and if it ran before, pretty much a timing issue. Maybe 180 degrees off? Do you have cam and crank signals such that the sensors weren't left unplugged?
Yes it ran before replacement. The more I think about it it really only makes sense that the timing is incorrect. The timing was set with locking bar on camshafts and crankshaft at TDC so there's no way it could be 180 degrees off but I think it could be off a tiny bit which with these engines seems like that's enough to prevent compression.
Maybe a cylinder leak down test?
Did you use the cam lock tool when you did the belt? It sounds like the belt is installed wrong. Pull the valve covers and measure the spring installed height they may be bent.