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.....

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

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.

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

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..

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?

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.

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

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

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

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

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 ?