Fixed head, now wont start! E320
 

I am working on my Girlfriends 94 E320. It has the HFM mangement. I had the head milled, cleaned the block mating surface installed a new gasket, and all associated hardware. I marked everything when I took it apart and am sure that the wiring and vacuum lines are all correct.

However, the engine turns over but does not start. I checked the compression with a crappy old gauge and it was reading a little low, but not bad. I think this was from the gauge.

ANyway, the engine has spark on at least three of the plugs. I believe the car is getting fuel (its pressurizing the fuel rail).

I don't know what else to do!

Thanks,
Rob

I think we need Arthur Dalton.

He's our resident expert on 124.032's..... :D

I spoke w/ Steve Brotherton
 

The guy that wrote the Head gasket replacement article on www.continentalimports.com. He said that becasue the compression is a little low, I might still have the mechanical timing off a bit. Anybody have any thoughts on this? Thanks,
Rob

Steve Brotherton might have been referring to either the M103 3.0 liter engine, or the early 3.0 liter M104 engine with the mechanic fuel injection.

Your M104 engine has the HFM-SFI fuel injection system (hot-film mass air flow sensor), with integrated electronic ignition and sequential fuel injection. This system combines fuel injection and ignition control in one module.

HFM fuel injection systems are designed so that idle speed can't be adjusted. Idle speed is completely controlled electronically.

What SB is referring to is that a little low on compression is a red flag indicator to the Tech that the mechanical valve timing is off , resulting in improper valve /piston relationship for full compression.
..and if this indicator proves to be the case , then the cam position sensor is not in sinc with the crank sensor . So HFM module has incorrect fuel/ignition inputs..and no start
So, incorrect mechanical timing chain spec is suspect. You may be off when you did the chain..

what now?
 

Now that I figure the timing is off, how do I get it back to where it shuold be? Is it simply a matter of lining up the 4mm holes in the cams, getting the crank "OT" aligned with the standoff on the front of the motor and getting the intake cam in the retarded position?

I did check the compression earlier in my troubles, and it was reading around 100 psi. I then noticed that when I rotated the assembly, the intake cam was off a little. I believe that I set the timing in the advanced position. Anyway, I haven't checked the compression since then.


If the compression is above 150 psi now, does that mean that the rotating assembly is correct?

Thanks,

Rob

Also, if you somehow got the #6 piston aligned at TDC with the cams, wouldn't it still run? THe HFM management fires two sparks per cylinder, 180 deg. apart. Wouldn't it run just fine?

anybody?
 

I'd hate to take this whole thing apart again, and then find that I just did nit wrong again.

If I have the crank at "OT" can I just align the cams with this position? what's a good way to check to see if I'm at TDC #1 and not #6?

Thanks,

Rob

TDC has to be lined up when # 1 is on the top of the COMPRESSION stroke , so .. you look at the valves when the balancer says OT.. If the valves are BOTH closed , you are on compression.. if not, you are 180 degrees OUT/OFF.
The old fashion way was to put your thumb in the plug hole and feel for pressure as the piston was coming up on compression, then just line up the OT mark..

Either way....

There are two sections in the M104 service manual that show 1. how to check if the cams are in the proper position and 2. how to adjust them if they are not in the proper position. I'd be happy to send them to you if you email me.

I'm not sure if you'll be able to adjust the cams w/o taking the front cover off. You definitely need to remove the chain tensioner. Perhaps you can caterpillar the untensioned chain on the sprockets while rotating the camshafts to avoid removing the front cover.

Timing is right!
 

Okay, the timing is right. I checked it again today. it is dead on!

But the compression is still reading right at 100 psi. on number 1 piston. I was told by a local shop that if the car was overheated alot (it was) that the piston rings could actually be broken causing low compression. Has anybody ever witnessed this?

THanks,
Rob

Do a compressiom leak-down test on that cylinder...

Are you sure the cam/valve timing is correct? I would think even with low compression in 1 cylinder the thing should run.

Mike

Maybe the engine wire harness is toast.

I can say without any doubt that the old harness in my '94 E320 never would have survived the handling and movement required for a head R&R.

Was that one of those biodegradable ones?

MP

Yes ...Slit it open

.. might as well give the OVP a tap and check the fuse on top , too...

won't solve you comp. problem but if that is the only bad one, still should run.. Do you have the other readings..??
..and , did you set the gap at the cam sensor ?

Where is the OVP?
 

Also, the harness looks okay, still flexible and the car has spark.

I don't know about the gap at the cam sensor either. I am not sure how to do this. I was under the impression that it would start without the cam sensor plugged in. (It is plugged in) Because the cam sensor only deals with the variable cam timing.

How do I do a compression leak down test? Is that when you leave the guage connected and allow it to sit at TDC and see how much it drops off?

Thanks,
Rob

<<Because the cam sensor only deals with the variable cam timing.>>


That is the intake cam advance magnet . Nothng to do with the cam sensor.
The cam position sensor times the fuel injection in sinc with the engine timing/ignition module.

The OVP is behind the panel behind the battery..

Are you going to give the other comp readings???

don't have the readings yet.
 

The car is about half an hour from where I live.

I didn't think this car had a cam sensor. With the HFM management, the car gets its spark timing from the computer with reference to the crank. If I'm wrong on this, I have made a bunch of bad assumptions.

Thanks,
Rob

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1D00YU6RY1DR0LX0TC&year=1994&make=MB&model=E-320-001&category=A&part=Camshaft+Position+Sensor

cam sensor
 

where is the sensor located.

Just so we are on the same page, you are saying there are two cam sensors? One for the timing advance, and another for the fuel injector timing?

Thanks,

Rob

Ok..

Well, here is the page I am on....

The cam sensor is L5/1. It is just to the left of the thermostat housing and goes into the head .. It is a pick-up that identifies the positon of the cam.. It has a gap adjustment/clearance spec. to the cam segments of .4-.6mm. This is the Gap clearance for it to work properly and is set with shim washers..The signal it sends to the ECU is an a/c sig of .5-1.5 volts.
There is only one of these . It sincs the injectors [among other things]

The cam magnet [which I assume you think is a sensor] is in front of the cam and it advances the intake cam when the ECU mapping decides to do it... this will be determined by various ECU load/air volume/ temps/etc .
This device does not send a sig to the ECU, it recieves a sig from the ECU.. so.. it is an acuator, not a sensor..
I have been trying to help in your diagnosis, but you write back such things as No cam sens. or this is HFM , so this does that , etc..
I assure you I am familiar with the HFM/SFI particulars and can only advise possible solutions if my questions are answered without the assumptions..
The reason for my question of the compression on the other cylinders
is to help verify to me if you have a valve chain timing problem or just bad comp on that one jug..so, we are still down to that question.???????

I understand.
 

I realize that the compression is important to determine if it is a single cylionder problem, or a timing issue.

I was unaware that the vehicle had a cam sensor. I made some assumptions early on in my personal troubleshooting about the timing because I did not know it had a cam sensor. I meant nothing negative about it towards you or anybody else on this forum. I merely meant that I may have screwed myself by not having complete knowledge.

I would have checked the cam sensor first if I knew it had one because that seems to be the likely culprite.

What kind of a plug does the cam sensor have on it? I now believ that the cam advance actuator is on the right side of the timing cover just in front of the timing chain.

I will check the compression tonight across all cylinders.

I appreciate the help!

Rob

Checked compression
 

I checked the compression and it is not good!

The number one cylinder has about 90psi
#1 90
#2 60
#3 45
#4 45
#5 50
#6 60

I am not sure what this means now!

I checked the timing again, and the holes (with Drill bits) sit flat on top of head, and the standout on the block is directly above the O T mark.

I don't know what to think now.

Rob

I haven't read much of this but that compression su*ks. Big guess is the cam timing is wrong. Sub guess is it is so wrong thevalves touched things they shouldn't.

If it is wrong, I don't know how to fix it!
 

THe cams line up with the outsides of the cylinder head (4mm drill bits resting against head) and the OT is lined up with the standout from the block. I don't know how it could be off. I have rotated the motor several times to ensure that it is all correct, and it lines back up every time.

I don't know how the valves would be bent (not saying they aren't) but I only had the timing off the first time I had it all together by the amount of the cam advance. (I had the variable valve timing rotated the wrong direction).

Unless when I got the head milled, they took off too much and now the valves are hitting the pistons. How possible is this?

Thanks,

Rob

In your initial post, you'd mentioned that your gauge was crappy. Do you think the readings you are getting are accurate?


While removing/installing the head, was the crank set at 30 degrees before TDC? It think its at that setting where the camshafts can be rotated without risk of the valves touching the pistons.