Crank No Start

[evalegacy]

Hello! Looking to the community for some much needed help.

I apologize for the VERY LONG post! This is an overload of info since I've done quite a few things; not sure what might be related or not, so I'm including every potential thing I can think of to hopefully help towards next things to try before bringing car to a shop (again). Already brought it to a shop once before; they realized it was not stock/tuned and refused to continue working on it.

Car is 2000 S4 - K04 Stage 3. Will provide additional specific details requested as it may pertain to issue.

Immediately after installing 034 carbon intake last year, car frequently got code (can't recall code #) think it was seeing unmetered air after MAF; 034 intake is before MAF, never changed anything after MAF, clamps are tight confirmed by boost testing; no leaks. When MAF unplugged car runs perfect, ran car with MAF unplugged since; car is not my daily and honestly don't really care about mpg anyway.

About 5 months ago started getting intermittent hard starts; most times car would start immediately other times would take a few cranks before it starts (only an issue on cold starts). At that time, all hard start instances car did start, never bad enough that car wouldn't start and car never stalled or ran rough after start, car idled and ran great, pulled hard. Never got any codes except for unplugged MAF. Never investigated further.

Fast forward 1-2 months (around July) while driving to in-laws, got stuck in stop/go traffic about 15 minutes; engine temp gauge would climb slightly (next notch above halfway at most) and fall back down, repeatedly. This went away soon as traffic was back up to speed. I pull into driveway and notice smoke coming from hood. It was coming from under aluminum MAF sensor housing and back of engine (near CTS and exhaust to turbo). I noticed this once before arriving at work, never came back until this time (several weeks apart). After briefly inspecting visually, didn't see anything out of the ordinary; thought maybe exhaust leak forming but car performance never degraded (was going to look into it another day).

Next morning attempted to start car and would just crank but not start. This is the start of a never-ending headache to my entire summer! It rained heavily the night prior and some rain managed to leak in, making the back foot wells a bit soaked but not standing water. I've been battling this issue for a while, clearing drain plugs all over (under battery, back trunk, sunroof, etc). The front floors were dry and back trunk was also dry. I pulled the back bench seat out and pulled carpet back to confirm I didn't see any wet electronics or broken/cracked/corroded wires. Even in the past when rain leaked into car, I've never had any starting issues. Let car dry for a few days while I wasn't able to work on it; tried to start car again, still no luck; solid cranking but no start. Scanned with scan tool and VCDS; initially no codes at this point. When I turn key on, I get EPC and check engine so ECU should be good and I can communicate with ECU via scan tools and VCDS. Assume I can rule out bad ECU or fubar ECU tune. Very few times in between cranks car will seem to start for a split second, stumble, but immediately die. Eventually got P0321 code (CPS) from cranking attempts but read code will get thrown after about 30 cranks and no start; I replaced it anyway, no change. Replaced front passenger camshaft position sensor, no change.

Other things I’ve done/checked so far (in order to the best of my memory):
Verified all fuses are good. Verified I'm getting fuel; all spark plugs get wet. All plugs were pretty black and fouled; car always ran very rich; literally guzzles gas even when stock airbox was installed and MAF was connected! Replaced all spark plugs with NGK 4644 BKR7E gapped to .028 (same exact plugs and gapping used before when car was running flawless). While plugs were out I pulled fuel pump fuse and tested compression (145psi on one cylinder which I read was normal and 160-170 on the rest - should be between 150-180psi and no more than 10% variance) used endoscope and couldn't get good view of valves but pistons looked fine; no marks on top from hitting valves. Highly doubt timing belt broke/jumped or cam tensioner failed since car ran fine until parked, didn't stall while driving and compression is good (assume no bent valves) and several cranking attempts. Although it's getting fuel, couldn't hear pump ever prime anymore; thought maybe pump on it's way out, maybe not sending enough fuel to start but over several crank attempts, flooding the engine. However, through further testing seems like getting too much fuel or not enough air/spark. Initial inspection after replacing plugs, they were clear wet as if there was no spark; tested spark with each coil/plug and results seemed odd to me. On every coil/plug car would crank several times before they would finally start to spark and some times spark seemed erratic/intermittent even at times weak. Replaced fuel pump with previously purchased Bosch 044 sitting around already planned to install anyway. Pump primes, tested good flow from pump out hose before connecting, verified proper hose direction when installing, and plugs getting wet again trying to crank. Let sit for few hours to dry up fuel, removed fuel pump fuse, cranked a few times to burn leftover fuel then tried a bit of starter fluid, no change. Pulled plugs and noticed carbon so they were burning residual fuel/starter fluid. Still no codes, except occasionally P0321 after several crank attempts. Installed 034 coil conversion/ICM delete I had laying around on standby in case of future ICM/coil death. Immediately got P0321 repeatedly after just a couple cranks and clearing code. Replaced CPS again, knowing some people have had issues with DOA CPS. Then start getting codes P1355 and P1364, checked coil wiring and looks fine but didn't actually check voltage with meter; read online someone resolved this by replacing driver side camshaft position sensor. Replaced it since I bought two anyway; P1355 and P1364 disappear and now no codes again. Also replaced the battery over the weekend as it was weakened from constant cranking and jumping.

The issue definitely seems to be too much fuel, or timing off but given the circumstance and how car ran fine then won't start next day leads me to believe it's not timing, at least not internally/mechanically (timing belt, cam, tensioner). Every time I inspect plugs after cranking, there is some burned fuel (definitely carbon, not oil) and are super wet with fuel.

Someone suggested I check CTS wiring, also didn't think to measure blocks in VCDS; I believe 004 - 3 and coolant temp should be in Celsius?
Supposedly, if ECU reads coolant is super cold (bad sensor) system will dump tons of fuel and flood the engine.

What I find interesting is the car ALWAYS had MAF unplugged code, even if I cleared the code, it would come back almost immediately. However, that code has never come back since the no start issue. Do I have the engine running and/or drive the car for that code to show up?

Car is currently parked at in-laws 40 miles away, so unfortunately I've really only been able to work on weekends as weather permits and time permits (also have 10 month old).
Will try to check coolant reading in VCDS after work tonight, or guide someone over the phone lol since laptop is with car.

Any additional suggestions and help appreciated. Thanks everyone!!

[evalegacy]

The wife went to visit the parents; had her connect laptop with VCDS. Coolant temp reading while engine cold and no crank attempts was 11 Celsius (51 Fahrenheit) which matches outside temperature, so CTS is good.

[evalegacy]

Nothing?

[Silverex]

I’d start with checking the CPS wiring and replacing sensor then go from there.
FWIW I’ve had issues with mine and never threw a code for it.

Also I’d double check all your grounds and make sure they have clean contact surfaces…including the one on pass side frame rail -> block ground.

[Monty23]

Check the crank sensor and or wiring. Make sure to pull the rubber boot back from the connector and verify the insulation isn't cracked and shorting.

https://www.sepautoproducts.com/prod...g-and-pig-tail

[JunkB5]

My plug was messed up for a while on my MAF and it had a hard start issue until I fixed that, don't know if it would cause a no start issue but it may be worth looking into, as I over looked it for months not even thinking it would be my problem. I'm sure you have tried this already, but have you tried un plugging the MAF and then try starting it without the MAF? In most cases if you have a major vacuum leak the car would still run with the MAF plugged in, but there's a chance it wouldn't.

Also, years ago on a customers car, the customer had broken his o2 sensor somehow and it was causing a no start issue with no faults, it was very visibly bent so try to get eyes on them and see if one is bent some how.

As far as timing goes, its easy enough to verify so id double check mechanical timing just to be sure. You were saying your spark could potentially be random, as someone else said, I'd check over your grounds as well.

I'll try to think of more things, its been a while since I last worked on these cars outside of my own.

[VR6Bomber]

Did you swap in a known working MAF sensor..?

[evalegacy]

I’d start with checking the CPS wiring and replacing sensor then go from there.
FWIW I’ve had issues with mine and never threw a code for it.

Also I’d double check all your grounds and make sure they have clean contact surfaces…including the one on pass side frame rail -> block ground.

Check the crank sensor and or wiring. Make sure to pull the rubber boot back from the connector and verify the insulation isn't cracked and shorting.

https://www.sepautoproducts.com/prod...g-and-pig-tail

I've replaced the CPS sensor three times as I've heard they can be DOA or just really finicky, but no change or difference noticed with each replacement. The connector itself and coating around wires appears to be in good condition, no cracking or melting, but I'll try inspect it closer.

I know the one ground location on driver side is fine. I found another forum post showing all the ground locations, I will definitely check those thoroughly.

My plug was messed up for a while on my MAF and it had a hard start issue until I fixed that, don't know if it would cause a no start issue but it may be worth looking into, as I over looked it for months not even thinking it would be my problem. I'm sure you have tried this already, but have you tried un plugging the MAF and then try starting it without the MAF? In most cases if you have a major vacuum leak the car would still run with the MAF plugged in, but there's a chance it wouldn't.

Also, years ago on a customers car, the customer had broken his o2 sensor somehow and it was causing a no start issue with no faults, it was very visibly bent so try to get eyes on them and see if one is bent some how.

As far as timing goes, its easy enough to verify so id double check mechanical timing just to be sure. You were saying your spark could potentially be random, as someone else said, I'd check over your grounds as well.

I'll try to think of more things, its been a while since I last worked on these cars outside of my own.

After installing an 034 intake last year I was constantly throwing a code for unmetered air after MAF but I've done several boost leak tests up to 15psi (replaced TBB that kept popping off after a few months and then installed an XS-Power aluminum TBB and Bi-pipes) and found no leaks each test. Since then I was explicitly running with MAF unplugged, car ran perfect. A bad MAF may effect performance and fuel economy, unplugged MAF (running this way for almost a year) will cause it to run rich but it certainly shouldn't cause a no start issue.

The o2 sensor suggestion, that's an odd one for sure; I would certainly imagine you'd get a code for something like that. I can check mine but I don't think a bad o2 sensor can cause a no start issue; if I understand correctly, car is in closed loop when starting and doesn't rely on o2 sensors at all until open loop to adjust fuel trims while driving.

Did you swap in a known working MAF sensor..?

No, if MAF was bad then unplugging MAF as mentioned would allow car to start and run fine assuming no major boost/vacuum leaks. Considering the car was running fine when I parked it and not start the next day would likely rule this out.

[dannyn424]

Try using a fuel pump check valve like this https://www.ecstuning.com/b-bosch-pa...893906093~bos/ it worked for me

[JunkB5]

Do you have a spare MAP sensor laying around? if your running without MAF then its forcing a revert to MAP, in theory it shouldn't need it to start but I've seen weirder things.

[evalegacy]

Try using a fuel pump check valve like this https://www.ecstuning.com/b-bosch-pa...893906093~bos/ it worked for me

I'm running a Bosch 044 racing fuel pump; it has a built-in check valve. It's getting plenty of fuel.

[evalegacy]

Do you have a spare MAP sensor laying around? if your running without MAF then its forcing a revert to MAP, in theory it shouldn't need it to start but I've seen weirder things.

I do not have a spare MAP but I never checked it either. I will visually inspect it and maybe spray some carb cleaner on it as well.

I could also check the Intake Air Temperature Sensor, haven't looked at that either.

However, both of these sensors if bad should throw codes; if wiring issue it would make the car run poorly but not cause a no start issue.

I also found the measuring blocks in VCDS: 007 (MAP) and 006 (IAT). I will see what readings I get to verify sensors are working.

[evalegacy]

Does anyone know what the MAP sensor should read in VCDS/Vagcom when engine is either off or while cranking? I tried searching and couldn't find an answer. My MAP sensor in VCDS reads 980 mbar and it doesn't change at all even when cranking; I don't know if this is normal or not. I pulled the sensor; looks clean; no dirt, sludge or oil vapor. I did spray just a bit of carb cleaner, wiped it and let dry for a few minutes. Tried starting again, cranks but won't start. I am still highly confident a bad MAP sensor wouldn't cause a no start issue but I'll order a new one.

On the plus side, the IAT and speed sensor (CPS) both appear to be reading correctly when measuring their blocks in VCDS.

I checked grounding on firewall and frame rail; both are good.

[Silverex]

There’s also a ground on back of engine that’s for the ICMs. I believe it gets bolted to the coolant hard pipe behind coolant sensor on passenger side. That ground gets beat up over time also.....did you verify your getting spark? Getting fuel? My thinking is if you have both of those and an rpm reading the car should start.

Just curious what was your RPM readings during cranking?

[evalegacy]

There’s also a ground on back of engine that’s for the ICMs. I believe it gets bolted to the coolant hard pipe behind coolant sensor on passenger side. That ground gets beat up over time also.....did you verify your getting spark? Getting fuel? My thinking is if you have both of those and an rpm reading the car should start.

Just curious what was your RPM readings during cranking?

I didn't notice a ground there when replacing the coolant temp sensor, I'll look again. When looking online, I did see depending on model year, some only have two grounds where-as other years had three; mine is a 2000 which I think only has two. Also, installed an 034 coil conversion and ICM delete if that matters.

I do get spark and fuel but it seems like I'm getting too much fuel. I don't recall the exact reading of the CPS but the number was changing while it was cranking and it is a new sensor, so I assume good.

[Monty23]

FYI, a number of 034 coil conversion kits were wired incorrectly causing no start issues (at least in the past, not sure how old your kit is). Have you verified spark since you installed the 034 coil conversion kit? Take the TBB off and spray some engine start in there and see if it wants to start for a few seconds... If it does, its most likely a fuel issue like you suspect, if not its probably something else (or multiple issues).

[Silverex]

I didn't notice a ground there when replacing the coolant temp sensor, I'll look again. When looking online, I did see depending on model year, some only have two grounds where-as other years had three; mine is a 2000 which I think only has two. Also, installed an 034 coil conversion and ICM delete if that matters.

I do get spark and fuel but it seems like I'm getting too much fuel. I don't recall the exact reading of the CPS but the number was changing while it was cranking and it is a new sensor, so I assume good.

There actually 2 wires going to that ground point, one for ICMs, other for EGTs. If you have ICM deletes I guess it doesn’t matter tho. Grounds come out of main harness and should be on of these locations


How are you checking for fuel? What makes you think you are getting too much?

FYI, a number of 034 coil conversion kits were wired incorrectly causing no start issues (at least in the past, not sure how old your kit is). Have you verified spark since you installed the 034 coil conversion kit? Take the TBB off and spray some engine start in there and see if it wants to start for a few seconds... If it does, its most likely a fuel issue like you suspect, if not its probably something else (or multiple issues).

Any of the PnP kits are wired “wrong” since they tied both of the grounds together. For whatever reason some guys don’t have issues and others do but I havnt heard of anyone having a no start situation from it.

I might be wrong but if you have spark, fuel, and CPS reading it should start with no other sensors hooked up. Might need the oil psi sensor also but you’d be throwing a light on LCD display for that.
Have you done a compression test?

[evalegacy]

FYI, a number of 034 coil conversion kits were wired incorrectly causing no start issues (at least in the past, not sure how old your kit is). Have you verified spark since you installed the 034 coil conversion kit? Take the TBB off and spray some engine start in there and see if it wants to start for a few seconds... If it does, its most likely a fuel issue like you suspect, if not its probably something else (or multiple issues).

I was actually running stock ICMs and coils when the car exhibited the no start issue. I did check spark and was getting spark on all coils but seemed weak and inconsistent, and my plugs were always wet. If you read above, you'll see I mentioned pulling the fuel pump fuse and plugs to let them dry, then sprayed starter fluid; no change. Since I was already working on plugs and coils, I installed the 034 coil conversion kit and ICM delete I already had laying around (not sure how old; I bought used from user on here) tested for spark, no change, no codes.

[evalegacy]

Any of the PnP kits are wired “wrong” since they tied both of the grounds together. For whatever reason some guys don’t have issues and others do but I haven't heard of anyone having a no start situation from it.

I might be wrong but if you have spark, fuel, and CPS reading it should start with no other sensors hooked up. Might need the oil psi sensor also but you’d be throwing a light on LCD display for that.
Have you done a compression test?

I haven't heard of "wrong" wiring issues but I've heard of people have issues with the 2.0 coil conversions and not wiring grounds correctly. I'm not using the 2.0 coils, I'm using Beru bolt-down from the RS6 which get ground from the connector. If I'm getting spark, then I assume wiring is working. However, I guess it's possible there could still be a ground issue and it's not strong enough??

Yes, somewhere buried in my initial post I stated I performed a compression test: 145psi on one cylinder (cylinder 1 or 3 pretty sure cylinder 1) which I read was normal and then 160-170 on the rest of the cylinders. According to my research, they should be between 150-180psi and no more than 10% variance, aside from the one cylinder at 145psi.

[Monty23]

I was actually running stock ICMs and coils when the car exhibited the no start issue. I did check spark and was getting spark on all coils but seemed weak and inconsistent, and my plugs were always wet. If you read above, you'll see I mentioned pulling the fuel pump fuse and plugs to let them dry, then sprayed starter fluid; no change. Since I was already working on plugs and coils, I installed the 034 coil conversion kit and ICM delete I already had laying around (not sure how old; I bought used from user on here) tested for spark, no change, no codes.

Ok sorry for not seeing that. It is a lot to read through. What does no change mean?
- Does the engine crank and there is no signs of life?
- Does the engine crank and will the engine cough "at all" like there is some minimal amount of combustion happening?
- Something else?

Yes, somewhere buried in my initial post I stated I performed a compression test: 145psi on one cylinder (cylinder 1 or 3 pretty sure cylinder 1) which I read was normal and then 160-170 on the rest of the cylinders. According to my research, they should be between 150-180psi and no more than 10% variance, aside from the one cylinder at 145psi.

That compression is fine and not the issue.

Have you verified fuel pressure with a pressure gauge in the fuel feed line?

[Silverex]

I haven't heard of "wrong" wiring issues but I've heard of people have issues with the 2.0 coil conversions and not wiring grounds correctly. I'm not using the 2.0 coils, I'm using Beru bolt-down from the RS6 which get ground from the connector. If I'm getting spark, then I assume wiring is working. However, I guess it's possible there could still be a ground issue and it's not strong enough??

Yes, somewhere buried in my initial post I stated I performed a compression test: 145psi on one cylinder (cylinder 1 or 3 pretty sure cylinder 1) which I read was normal and then 160-170 on the rest of the cylinders. According to my research, they should be between 150-180psi and no more than 10% variance, aside from the one cylinder at 145psi.

The plug adapters for coils have both grounds tied together instead of one going to engine and one going to chassis…that’s what I ment by “wrong”. I’ve had multiple customers with miss fires using them and once they switched to one of my harnesses that is grounded correctly miss fires went away….none of them had no start issues tho. So I agree it’s probably not your issue if you confirmed spark

Compression numbers are fine.

[CELison]

Make sure you have good fuel pressure when cranking. You can make a gauge easy with some home depot fittings and a cheap oil pressure gauge. With stock fuel lines, I would disconnect from the firewall, small piece of fuel line, T, then the factory fuel line on the other side of the T. Some tubing and you're good to go.

[evalegacy]

Ok sorry for not seeing that. It is a lot to read through. What does no change mean?
- Does the engine crank and there is no signs of life?
- Does the engine crank and will the engine cough "at all" like there is some minimal amount of combustion happening?
- Something else?

No worries, I know I posted a lot of information. It will crank strong but not start. As long as the car has sat long enough for fuel to evaporate or I pull plugs to wipe them dry, there are times within the first few cranks it will "cough" as if it's making combustion and will stumble for maybe a split second then die. Thereafter, it will just crank because it seems that plugs are too wet at that point. If I pull plugs they have some carbon but are very wet.

Have you verified fuel pressure with a pressure gauge in the fuel feed line?

No, I do not have a fuel pressure gauge and haven't tested fuel pressure. Are you thinking PFR or injectors? I have seen other posts, although rare, where injectors took a crap/plugged after some bad/dirty gas. However, in all of those cases they had idle/running issues, the car stalled and then they had hard starting issues. I've never once has issues with idle or stalling at all, car ran perfectly the day before.

[evalegacy]

Make sure you have good fuel pressure when cranking. You can make a gauge easy with some home depot fittings and a cheap oil pressure gauge. With stock fuel lines, I would disconnect from the firewall, small piece of fuel line, T, then the factory fuel line on the other side of the T. Some tubing and you're good to go.

I'm using stock FPR, is that would I should see (about 50psi)?

If plugs are getting wet, you still think fuel pressure is an issue?

[CELison]

I'm using stock FPR, is that would I should see (about 50psi)?

If plugs are getting wet, you still think fuel pressure is an issue?

That's 4bar with the vac line attached at idle. I think stock is 4 bar so you should see around there.

[Monty23]

That's 4bar with the vac line attached at idle. I think stock is 4 bar so you should see around there.

The engine needs compression, fuel (in roughly the right amount), and spark (at the right moment) in order to start and run. You need to rule each of these out to find your problem.

1) Compression has been confirmed to be good
2) You visually verified spark (hopefully on all cylinders) - we can assume it is happening at the right time as long as the correct spark plug wiring is going to the correct cylinder
3) Fuel - you need to confirm the pressure is correct
- Either rent a gauge from the auto parts store or buy an inline gauge and install it. (https://www.ecstuning.com/b-ecs-part...BoChpgQAvD_BwE)
- Fuel pressure regulators adjust fuel pressure both positive and negative with manifold pressure (so at 10psi boost, you should see base fuel pressure + 10 pis or 58psi + 10psi = 68psi) or at idle and high vacuum is about negative 10psi. So 58psi - 10psi = 48psi. If you pull the vacuum line off the regulator - then it should read a straight 58psi.
- If fuel pressure is good, then verify none of your injectors are partially clogged. (2 of my injectors clogged after sitting only 3 months with E85, this gave me a no start and coughing situation also.) Pull the fuel rail and injector assembly off the intake manifold and put a towel down on the intake manifold. Crank the engine over and verify each injector is spraying roughly the same amount. It should be obvious if there is an issue.

[belms4]

Once you do have it running again just be aware running rich from an unplugged maf will keep fouling plugs and eventually clog up catalytic converters if you have them.

Do you have a video with decent audio of it cranking and not starting? Might be worth grabbing and uploading to have some folks on here give a listen and see if there's anything odd we can pick out.

Sent from my SM-F721U1 using Audizine Forum mobile app

[LJS]

That's 4bar with the vac line attached at idle. I think stock is 4 bar so you should see around there.

Not to be a pain in the ass but it's 4 bar(58 psi) with the VAC line off..it will drop to approx 3.6 bar when the line is attached
4 bar is BASE pressure per Audi- Base Pressure is measured with the reference line off.
That comes from an Audi Tech (not me)

[CELison]

Not to be a pain in the ass but it's 4 bar(58 psi) with the VAC line off..it will drop to approx 3.6 bar when the line is attached
4 bar is BASE pressure per Audi- Base Pressure is measured with the reference line off.
That comes from an Audi Tech (not me)

Right, so 4bar base with the vac line on will get you in the real world around 50 psi which is what the gauge in my picture was showing. "That" was referring to my picture. Base pressure is what the fuel pressure would be with the pump running and injectors closed, motor off.

[evalegacy]

The issue ended up being a bad tone ring; it was corroded. Sorry for the late update... had car at a shop for the past 1.5 years for big turbo build and upgraded to JHM Aluminum flywheel and Stage 5 clutch.