My W203 / M271 will not fire. Engine cranks fine but the engine tries to start but will not fire (see movie file attached). It sounds to me like a spark or timing issue because once i turn the key off there is the slightest cough from one of the cylinders. I am wondering if it is possible for the crank and cams to be out of sync by 360 degrees? I say this because this starting issue has only started after i have put the cylinder head back on the car after i had checked the valves after the timing slipped due to worn intake cam gear.

While conducting the repair of the cam gears i don't remember turning the crank more than a quarter of a turn at any one time but yet i can't figure out why the engine will not start again.

While lining up the cams and crank i rotated the engine a number of times and everything moved easily and there was no fouling of valves and pistons
There is definitely fuel getting to the engine because when i first tried to start the engine there was the smell of fuel and i did have a fuel leak where the injector seals had not seated correctly
I will check the spark plugs to be sure i have a spark but at this time of writing i can't see why the plugs should suddenly need replacing when they worked fine before i stripped down the head

Is it possible that for some reason the crankshaft and camshafts can be out of sync. I'm presuming not because the crank position sensor can only be on one place of the crankshaft and even if the engine had been turned 360 degrees the sensor would still be in the same place. The same must be true for the camshaft sensor as it can only be in one place and if all of my timing marks line up, then what else could be the reason for not starting.

Does anyone have an ideas?

Thanks.

 

From the sound of your cranking it does sound like the valve timing is out. But not like you think.
send pics of how you set the timing show us the marks. Crank on OT and both inlet and exhaust cams must line up with their marks. Then the timing is correct.

 

Thanks Russell, I'll strip the cam cover off again and look at the timing. marks. I thought they were spot on when i put it back together, although the exhaust and intake never quite seemed to be exactly lined up. They always seemed to be the slightest fraction away from the exact marks but when i moved them one tooth either way, they seemed to be out the same distance the other way. No matter what i did they always seemed to be out a fraction. I'll take a picture tomorrow morning and post here so you can see.

 

Being out a fraction is not a problem. Also remove cyl 1 spark plug and make sure the piston is infact at TDC when the crank shows OT.

 

Hi Russell,
So, here are the photos this morning. The crank is at TDC and the #1 piston is at the very top of its stroke. The cam lobes on #1 cylinder are both pointing upwards.

As you can see the intake cam mark is a few degrees past centre but if i try and move the gear over one tooth then it goes about the same degrees before centre. However, when you look at the cam adjuster it gives the impression of being a bit further past centre. What do you think, should i move the intake camshaft back one tooth and put it all back together and try it? Could this amount of error in timing make that much of an issue starting?


TDC

Exhaust Cam Lobes

Intake Cam Lobes

Exhaust Cam Mark

Exhaust Cam Adjuster

Intake Cam Mark

Intake Cam Adjuster


Thanks.

 

Hi Russell,
I've posted photos of cam positions as promised. Would appreciate your input.

Thanks,
A

 

Definitely looks like intake cam is too advanced..
yes shift intake back 1 tooth.
Always remember when checking valve timing.. rotate the crank until inlet cam lines up perfectly with its marks then take a reading as to where the crank position it. It should be on OT or slightly after OT but never before OT. Do the same with the exhaust cam line marks up perfectly and take a reading of crank position. Maybe take a reading before and after you jump the inlet cam.
Good luck

 

Okay, Update!
I successfully moved the intake and exhaust cams back a tooth and now when they line up on the cam marks the crank pulley is at about 1/2 degree before TDC. I put everything back together and unfortunately the engine still doesn't start. It is still trying to start similar to the sound file in the earlier thread. It sounds marginally better, as if it wants to start but just can't fire on all four pots. I have taken out the plugs and cleaned with electrical cleaner and used a multimeter to check for any shorts. All plugs are fine and returning 4.5k to 5k ohms. I also hooked up the ODBII scanner but no codes are being reported.

I'm completely at a loss now as to what the issue may be. I have fuel and i have a spark, but i can't tell if they are happening at the correct time.

When i took the head off a couple of weeks ago the valves seemed to be in good condition because i was expecting to see bent valves since the intake cam had jumped a few teeth.I filled the intake ports with water and didn't have any leaks through the intake valves. Therefore i didn't replace any valves as i didn't want to have to buy a valve spring compressor and new valves etc as i just want to get the car going to last me 6 more months when i will scrap it or trade it in for a new car. Could a slightly leaking valve cause the engine not to start? I guess it is possible, but from my water test, i would find this hard to believe.

Any further ideas as to what the hell may be stopping it from firing? Would the AA be able to see anything with their limited resources because i could call them out as part of home start.

Thanks,
A

 

half a degree is nothing. So valve timing is now correct!
no faults.. you have fuel pressure and spark?
remove the plugs and do a compression test
If its low pump some oil down the plug hole. About 4 to 5 squirts from an oil can. If the compression comes up then refit the plugs and try to start.
water is not the best test for leaky valves.
Rather use petrol or similar fill the combustion chamber and watch for any leaks into the both ports

 

Hi Russell,
I purchased a compression tester yesterday and carried out a test as follows:

Took all plugs out and turned engine over with gas pedal full to the floor. Results are as follows:

Each cylinder gave out an initial pressure of 90 psi on the first crank, and then they all ended up with the following pressures

Cylinder 1 - 180 psi
Cylinder 2 - 150 psi
Cylinder 3 - 180 psi
Cylinder 4 - 150 psi

I'm reasonably pleased with those results as they seem to show that the valves didn't get bent when the chain moved a few teeth on the inlet cam.

However, I'm still perplexed as to why it won't start. I guess the nest steps are as follows:

1) I'll now check if i have sparks at the plugs even though a multi tester told me the plugs were fine
2) I guess i'll need to look at the injectors too. Is it enough just to put them into a plastic bottle and see if they provide a reasonable spray? I really don't want to have to spend more money on an injector tester to see if pressure is satisfactory
3) Would either the crank or cam shaft sensors stop the engine firing?

That's all i can think of because the car was running prior to the chain jumping a few teeth.

Alan

 

Compression looks fine. Although it doesn't always indicate a leaky valve. Best test is a cyl leakage test. If you have spark or inj pulse then sensors are fine. Check for any major airleaks in the intake tracked

 

Hi Russell,
Final update!!!

I tested all coil packs with a multimeter and all seemed good. I then placed the same plug in each coil pack and got my 10 year old to urn the engine over for me and each pack and each plug sparked fine. I assumed from this that sparks were fine and crank sensor etc was working okay. That led me to look to the fuel injectors where i planned to take them all out still attached to the fuel rail and turn the engine over to see if they all sprayed.to a reasonable standard. After taking off the air filter i was pleasantly surprised to see that only one injector had the electrical connector attached, and i hadn't fully connected the other three electrical connectors for some reason. I must have got distracted after i attached the fuel rail and trying to find out the torque setting. That now explains why the car was only firing on one cylinder.

So injectors connected and it fired up first try and i'm delighted.

I just wanted to say a big thank you Russell for all your comments and support. These forums are such a great place for sharing support an knowledge. Your support over the last couple of weeks has made a huge difference and given me the courage to continue and work out what the hell was wrong. I now have a working engine after jumping three teeth, replacing cam adjusters and stripping the engine down to remove the head and inspect all valves. Thanks very much fo ryour support

Alan

 

No problem. I am glad you found the problem. Maybe you need to invest in a scan tool. Because it would have triggered a fault for sure.
Enjoy!

 

I have a foxwell scanner but codes never came up - strange!!

 

I now have an engine misfire when hot.

• Engine runs smooth on idle and drives fine while cold
• One engine gets up to full temps it develops a misfire and throws engine light code for cylinder 4 misfire. It has also shown a misfire on cylinder 1
• I have changed over the coil packs and plugs to see if misfire follows them but it doesn't
• If i leave the engine to cool and restart then the engine runs smooth again until it gets up to full temp and then misfires again
• The Short term fuel trim reads around 2.2 and Long Term fuel trim reads a constant 0.8
• The O2 B1 S1 sensor reads 1.5v and goes upto 2.2v when the misfire begins
• I have sprayed engine start around the intake to see if misfire disappears but it doesn't change the engine note at all so i don't think it is an air leak near the intake manifold or air box

I have searched high and low to find out if an upstream O2 sensor reading 2v is a sign it is faulty and about to fail but i have found nothing on this forum or on Google anywhere. Any ideas?

I am thinking of taking the o2 sensor out and cleaning it with electrical cleaner to see if it makes a difference

Thanks

 

Short term trim of 2.2 sounds like a lean mixture. Check the complete intake for leaks. Usually I pressurize the intake then check for leaks.