No start after head gasket replacement; "chuffing" sound instead
 

Put the car back together after doing head gasket.

Originally there was a plain old "no start" situation. Found that I had failed to reconnect one of the sensors back toward the firewall atop the clutch housing.

Now I get nothing but a "chuffing" sound, and still no start. Sounded like I had a couple of good explosions (heard a backfire), but after that, there's only chuffing.

Any thoughts on what could be wrong?

Thank you.

Spark plug wires out of order, ref/speed sensor plugs reversed, ref/speed sensors or wiring faulty.

Turns out it's 1-3-4-2

WRONG

4 - 1

center lead from coil

2 - 3

This is the way it should be per the discussion in this thread:

4 - 2

center lead from coil

3 - 1

Hello there:

First and foremost, the firing order on the 944 is 1-3-4-2

If you are looking at the distributor cap from the front of the car, the number 1 plug wire is LOWER RIGHT.

Now, moving clockwise the next plug wire is number 3, so that would be lower left side position on cap. Then, number 4 is next which is on the cap as upper left.
Of course, the last plug wire is number 2...upper right side of cap.

Most importantly, be sure to line up all your timing marks. First, ensure that the OT mark is showing on top of the flywheel housing opening...rear of engine on bellhousing. Then, with cap removed ensure you are pointed at the number 1 position mark on the cam housing, and last ensure that the timing mark on the cam wheel is showing through the opening and lined up with the associated mark.

Hope this helps and good luck.

From this description, you have 4 and 2 in wrong location. This would cause a backfire. IMHOSmileWavy

Thank you for the comments. I've corrected my earlier post.

Correct on the car too but still no start. Have horsed around with the connectors at the firewall too.

I will double check timing but it was correct when I buttoned everything up.

Any further suggestions? Obviously it's a no spark situation, but I can't seem to even get close to firing now.

Could try to start looking into whether the ECU/DME signals are getting to the injectors. This would be done via NOID light testers.

If you are sure compression and fuel delivery are proper, electrical signals and voltages should suffice for the "brain" (ECU/DME) to provide good information for the functioning.

However, in view of the fact this car overheated at one time, have those issues and potential problems been addressed? If yes, then you can eliminate that for now. IMHO

Another thought...how is the battery voltage? Condition; new versus older?

Did you swap the ref sensor connectors over as previously mentioned. Common mistake, they are not keyed differently.

I did a teardown of everything above the block. Put a rebuilt head on; torqued it correctly per Clark's garage instructions in three steps with a recheck after 24 hours.

Seems that it's a spark problem, but I'll take your suggestions. Battery should be fine; has been on charger for a couple of days. I'll look at that too.

My gut tells me that I just put something back together wrong. May dissemble some stuff and put it back together to be sure.

I'm having what sounds like the exact same issue, after doing a top-end rebuild, just like yourself.

What is your tachometer doing when you crank it?

Mine doesn't do the little normal bounce, but will shoot up all over the place. I think I might have the reference and speed sensors connected backwards, so I'm going to try that today.

mikey, you really ought to put your model and year in your sig line.

what year is the car, anyway?

also, the firing order is stamped right on the cam tower. zundfolge, 1-3-4-2.

your problem could be a large vacuum leak.

Still troubleshooting.

-have spark
-have fuel to the rail
-timing is correct

I believe I'm getting fuel to the cylinders as there's a good smell of fuel coming out the tailpipe, but I cannot get the damned thing to start.

Checked the speed/reference sensors using the instructions at Clark's garage (procedure IGN-02). Found that my resistance is about right.

Next step is to test compression, I guess. Going to get a compression tester at the parts store now.

Okay, now we know the DME/ECU is working properly since all of the basic requirements are met. I think it is good news.

However, early in your statement above you say "I believe

The fact that there is a "good smell of fuel coming out the tailpipe" suggests to me that the fuel mixture is too rich at this time.

Your compression test will provide some good data next. Keep us all posted.

Keep on it.

I know it's been asked twice before but you have not confirmed that you have dine this.

The two speed/ref sensor connectors at the back of the engine, did you swap the connectors over to check you didn't assemble them wrongly?

Excellent point, 9FF!!!

Good luck.

Sorry; yes, I did that. Certain that they are in the right places.

Compression test complete.

Dry readings (rounded to nearest 5)

1-145
2-140
3-140
4-0

As in a goose egg at the 4 cylinder. Needle didn't even move.

I would think that even with bad rings the needle would move a little bit, so I can only assume that the valves somehow got screwed up during my install.

#4cyl valve retainer off, good news there is way of replacing it without taking the head off. Bad news, the valve (whichever one on #4) will be touching the piston so don't crank anymore. Probably no damage as the piston is pushing the valve in the guide with no spring resistance as the retainer is off.

I would take the cam cover off, pressurize the cyl with compressed air through the spark plug hole and try and compress the valve spring and refit the retainer. I've seen it done but not on a 944 and not done it myself. Hardest part is you need to figure how to compress the spring without access to the valve head. I do hope you didn't bend the valve or damage the guide, have my fingers crossed for you, GL.

If I have to pull the head again, do I have to put on yet another new head gasket/cam tower gasket?

yes.