D-jet April fools

[norustscott]

Well, It has been two week since I put the 914 back on the road after my year long resto. Very nice day here in Maryland so I thought I would take the 2.0l to work. I have put about six hundred miles on it so far.

April Fools hit early this am. About 10 minutes from home she dies at a stop sign with a lot of sputtering and missing. I mean perfect one second and crap the next. The T-stat had just reached open position...every thing looks good ( no leaks and every still connected) but she will only run with 3/4 throttle or better and then under protest. Lots of missing and back firing through the throttle body.

No black smoke. No white smoke. No blue smoke. Just missing and way down on power.

BTW all injectors fire via the Throttle body test.(BRRRP TEST) 1/2 and 3/4. Fuel pressure is unknown but I doubt it is a problem. Has to be temp related. Sounds like the head temp sensor?


Other than going through the complete Ohm meter dance on each of the D-Jet componenets can you think of anything? A possible starting point. Has this ever happen to you? please share?

Stock 1973 2.0l D-jet...very stock.

Thanks, lsg

[pbanders]

First thing I'd suggest is to check the ignition before checking the FI. If the ignition is OK, the next three things I'd check would be:

1. Fuel pressure and supply - you said it's running at 3/4 throttle, so I'm assuming the fuel pump is running. You make have sucked up something that is restricting fuel supply (e.g. clogged filter, jammed pump, etc.).

2. Resistance of the head temperature sender,

3. Make sure the MPS vacuum hose is intact, that the MPS holds vacuum, and that the coil resistances check out.

Resistance values for these components are in my D-Jet parts table:

http://members.rennlist.com/pbanders/djetparts.htm

[Dave at Pelican Parts]

If the head temp sensor gets unplugged, it will result in similar symptoms.

--DD

[norustscott]

Good points...

1. Pump runs, Tank is very clean in side and out from restoration, new filter.

2. I will check for spark and timing. Points my have slipped too?


3. I have this strange feeling that when I get home tonight and fire it up it will run fine




Thouth that if this mirrored another experience I may find a ggod starting piont.

[JP Noonan]

When I had points, if I let the car sit for too long or after a tropical storm or hurricane the points would rust up. The car would only run at near full throttle.

Maybe use some 320 grit to clean them, or put on new ones.

[bowlsby]

Do the dance...its the only way you will know for sure. It could be several items...MPS, TS2, TPS, bad grounds, clogged fuel lines, bad fuel pump, and on and on...

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[CoolTool]

Timing maybe ??? I know that on other vehicles it is possible to not get the distributor tightened down all the way and the timing will retard itself. May not be the problem, but it is a thought!

[Jim Smolka]

Cracked Distributor cap?
Failed open fuel cold start valve?
Points or worn out dizzy?

[norustscott]

So, I got home from work, stressed out as usual, I started the process of diagnosing the D-jet. Long story short. Not electrical. Not Fuel injection. Would you believe mechanical? It seems that the intake push rod on #3 fell out of the rocker arm pocket and wedged on the endge of the arm. This caused the intake on three to never close, causing a major vacuum leak in the system which is why the engine would run at 3/4 to full throttle and miss like crazy.
I took the rocker arms off and deburred the end and reassembled and ajusted all valves.

The vavle was not "way" out of adjustment( maybe .008) and the rocker assembly was torqued correctly. The only thing I can think of is that the valve stuck slightly open or was slow to close allowing the push rod to fall out and wedge on the end of the rocker arm?

Just came back from a 30 mile test loop. everything checks ok.


Any thoughts why and how?

I have had this happen years ago on a 1200cc 40 hp type one only that the clearance on the T-1 is enough to miss the rocker arm completely.


lsg

[pbanders]

Originally posted by norustscott
So, I got home from work, stressed out as usual, I started the process of diagnosing the D-jet. Long story short. Not electrical. Not Fuel injection. Would you believe mechanical? It seems that the intake push rod on #3 fell out of the rocker arm pocket and wedged on the endge of the arm. This caused the intake on three to never close, causing a major vacuum leak in the system which is why the engine would run at 3/4 to full throttle and miss like crazy.

I gotta laugh, I didn't follow my own rules when I made my suggestions, and if I had, it would have been the right advice.

ALWAYS check for problems in the following order:

1. Basic mechanical condition of the motor
2. Ignition
3. Fuel system

[norustscott]

I am with you...but all of the symptoms would have lead you to believe it was not a mechanical problem. No clanking, rattle, It just happen...

Perfect for the 1st of April.

[norustscott]

Thought I had the problem licked.

Well after about 30 miles of test drive last night...I started the car for a drive to the office this am and after about 3 minutes of very smooth idle I eased off down the road...plop. the same thing has happened.

This time noisy did not make it to the end of the block.

The engine is a very fresh top end rebuild. heads have new exhaust valves, valve job. New pistons and cylinders and rings...

I have put 600 miles on the engine will all kinds of driving.

What is allowing this excessive clearence to allow the push rod to become unseated from the rocker arm?

I am sure I am seating the lifter end and the adjuster is in line hieght wise with the others. Nothing bent. Rocker assembly studs are tight. The push rod tesion springs are in the correct location I.e. not pinched under or in the valve train.

One thought I have had and maybe someone can substainiate...Is it possible that the geometry is allowing the adjuster to slip off of the stem of the valve during operation? Too much side motion allowed by the center spring? Any more thoughts?

I will hand turn a cycle to watch.

back to it tonight I guess.

[Dave at Pelican Parts]

Well, you're on the right track it sounds like!

First, are you aboslutely certain that the pushrod is seated all the way in the lifter? Are the rocker stand bolts torqued correctly? (10 lb-ft, but you hafta do it when the cylinder is at TDC so the rocker arms aren't putting any load on the shaft.)

How's the lifter itself? Tough to see without removing it--you might wanna pull the pushrods & tubes on that cylinder so you can look at the lifters; both the "problem" one and the "normal" one to compare them. Even the solid lifters do come apart occasionally. Or mushroom--that happened to Jim Thorusen; he couldn't take the lifter out without completely disassembling the motor.

If there's any reasonable way to check the valve spring tension, try it. At least try to compare the intake and exhaust on that cylinder; I think they should be the same. Check for wear on the adjuster and the valve tip. Check for valve rock. Inspect the lifter for wear. A cam lobe problem would show on opposite cylinders, since those share a single cam lobe. Check the pushrod for straightness and length, especially against its "non-problem" neighbor.

I'm guessing that the above will show up your problem.

--DD

[Joe Ricard]

While you are at it roll the push rod on a piece of glass. could be bent. I have a couple of good spares. I say sticky valve because you just did a top end and the tolerance might be to tight in that one guide only shows up when the head gets warm.

[norustscott]

Dave,

Is it possible to take out the push rod on # 3 intake with the engine in place...and without disturbing teh very dry tubes next to it? Exhaust #3 and Intake #4?


Would it be easier to just drop the engine to clear the suspension. I have read the tech article on tube replacemetn in the car...Still not clear on how to get the rod and tue out.


Do you end up pulling the tub free from the case and then going down and out in the direction of the case? If so is there enough room to pull the P rod out and then have it follow in the same path as the tube?


thanks for the input...scott

[Dave at Pelican Parts]

You've got it right. You slide the tube outward so that the middle of the tube is "hanging" from the head. Slide the pushrod out that far, too. Then swing the tube downward with the pushrod. You might not be able to swing it far enough to completely remove it--I don't think I've done that--but all you need is for the tube to be out of the way so you can poke a magnet into the lifter bore and fish out the lifter.

I recommend pulling two--probably both of the #3 valves--just so you have a basis for comparison.

--DD

[norustscott]

final chapter...

It appears that my problem is cam related. The intake lobe for 1 and 3 appears to be wearing rapidly. However, the problem valve is intake on #3. Intake on 1 appears to be unaffected at this time as it runs on the pully end of the lobe.

Per the above text from Dave, I have removed the pushrods and lifters from #3. The push rod is fine as well as the rocker assembly. The lifter from the exhaust side checks ok. The Intake lifter shows signs of wear most alarming is the ragged edge around the cam side of the lifter.

If this is the case, it is wearing fast! 1/16th" off lift every 25 miles....No metal in the sump screen though??????

This from a cam that 600 mile ago showed zero wear or hard coat penetration. The cam has about 80k miles on it. This is hard to believe this but it appears to be the only reason that I can adjust the valves and after 30 minutes of operation have 1/16" valve lash on exhaust #3.

Jake, ever seen anything like this before?

Oh well, there is an NOS cam in a box in the basement. Looks like the car won't make Hershey @ this rate I will be lucky to the Blind Rally. Bummer.


Scott