rebuild complete, but engine won't start...
 

Hello,

I finally finished rebuilding and installing my 3.0 today. However, I can't get it to fire up.

I have spark...I checked a couple of plug wires with a timing light. I'm pretty sure I'm getting gas back there, because I can faintly smell it. CD is plugged in, I can hear it whining.

So far, it has barely caught a few times. I let it set still for a while, and on my next attempt, it backfired pretty good...it actually blew the relief valve out.

A bit later, I took the cover off the air box and tried again, and it came closer to starting than ever, but once again with no success.

Finally, I started running out of battery, and quit.

I'm grateful for any suggestions anyone might give me.

Thanks.

My $.02 would be to double check the timing.

AM

Try to static time it using a 12 volt lamp. Make sure that the distributor is installed correctly. If it is 180 out of sync, the spark plug will be sparking out of phase with the piston at the bottom of the stroke. Check that the spark plug wires are installed correctly.

Good luck!

Triple check the plug wires - look at the caption in the book - the 911SC ones are reverse from the picture...

-Wayne

Thanks for your replies...

I checked the timing, and it seems to be okay. I put it at top dead center, turned on the ignition, hooked up a timing light, and found that it would spark when I rotated the base of the distributer. I then set the timing as best *I could with the engine turning over.

I checked all the plug wires, and as best I can tell, they're in the proper order, as is shown in Wayne's book, with the neccessary adjustments between 5&6, 2&3.

I turned the ignition on, and fiddled with the fuel sensor plate, which meowed as it was supposed to.

I gopt it to start for a brief moment, but then it quit...and white smoke poured out the tail pipe. On other tries, it has backfired again, twice. Scared my dogs.

As best I can tell, it's getting spark, gas, and air. I think the timing is right...I can't figure it out.

Thanks for any suggestions.

It might need more fuel...try to start it with sensor plate pushed slightly down.

Can you turn the crank without binding? Are cams timed correctly?

I had almost exactly the same symptoms after I rebuilt my '69 911E. turned out the distributor was 180 degrees out, and in the year it took to do the rebuild, the gas in the tank had turned to varnish. fresh tank of gas and a correctly set distributor, and it ran like a top. good luck!

I forgot to hook up the ground wires that attach to the intake manifold which cured my problem......couldn't believe I missed that.

I'm truly grateful to all who have replied.

I think I have all the grounds in place, but I'll check again.

I drained all the old gas I could as a precaution, and added eight gallons of fresh gas before I originally tried to start it.

I began re-checking everything this morning. The plug wires are in the proper order. I'm fairly certain the distributor is in the right position...the rotor lines up with the mark on the distributor case when the crank pulley is at TDC. I guess it could be 180 off, but I'm not certain how...and besides that, I hooked up a timing light while the starter turned the engine, and it hit the proper mark.

And just to be certain, I also took out plug #1 and noticed that manually turning it to #1 tdc required little effort, compared to the other five cylinders. But I'm not all that experienced at this...and I'm open to suggestion about the distributor.

While I had the plug out, I checked the spark, which was good.

I pulled #4 injector, and checked it, which worked fine.

I did get it to run for about thirty seconds, but I had to lift the air sensor plate in order to start it and keep it running. It ran kind of rough, and backfired through the pop-off several times, so I turned it off. More white smoke out the tail pipe, and this time out the vents in the dash. I assume that has to do with too much gas when I lifted the air sensor plate.

No oil on the ground underneath, yet...that's kind of a relief.

And still it won't start on its on. Any suggestions where to head next? My step-father thinks I ought to check the adjustment on all the valves...

I appreciate all the help.

If the engine did run, the distributor is probably installed in the correct orientation.

I would try shifting my attention to fuel delivery and ignition timing.

I think at this point since you actually got combustion, I would try to keep it running. Unless there is a danger of fire or any weird sounds I would get it to run, then, if possible try to check out the ignition by pulling plug wires etc., and investigate fuel system troubles.

get out the k-jet tester and be sure you are at the right pressures for your system.

I typically don't talk so infatically, but I am 99.99% sure that this is a timing problem. Backfires when you try to start the engine after a rebuild are almost always caused by timing problems. It sounds like when you got it to run for 30 seconds, it sounds like it was correctly firing on only a few cylinders.

Take your cap off, and rotate your engine 720 degrees. Verify that the firing order matches the rotor as it rotates around the distributor. I have made this mistake many times, even after checking it a few times (it's easy to get confused). Double and triple check the plug wires, and make sure that they are going to the correct cylinders.

Pull the top valve cover off and verify that the valves are closed when the rotor is at TDC. This will confirm that your distributor is installed correctly...

-Wayne

Wayne,

I appreciate your emphasis...But I have checked, double checked and triple checked.

The plug wires are in the right order. And just to be certain I wasn't 180 degrees off with the distributor, I put it tdc for #1, pulled the distributor, turned the crank 360, and then put it back, with the rotor pointing toward the mark. It was worse than before...absolutely nothing a few weak backfires. So I put it back.

I'll pull the cover off the 1-3 intake, just to be dead certain.

I'm wondering if there is some bad thing going on with my injection system, but I don't know too much, or have a tester...yet.

Thanks

If you had a fuel problem, then it most likely wouldn't misfire. Is your distributor turning backwards, as expected?

-Wayne

Hi Wayne,

My distributor is okay...I checked it out this morning, and re-checked all the plug wires...

What I think is going on is a pretty good sized vacuum leak...I think that maybe the connection to the auxiliary air valve and auxiliary air regulator has somehow come loose from the back of the engine, where it hooks up under the decellertion (sp?) valve. I can't see it clearly, even with a mirror, so I'll have to partially drop the engine. I'm going to look into it as soon as I can clear up some time from work, hopefully by Thursday or Friday.

Do you think a really bad vacuum leak would cause such problems?

Thanks

Lee,
What I didn't hear you say was that the #1 piston was at TDC ready to fire (both valves closed) when the rotor was pointing at the notch and crank pully marks were at TDC.

If the distributor is installed with the engine out of the proper firing order, the rotor can still point to the notch with the crank pulley marks at TDC.

The #1 piston must be at TDC, both valves closed. Wayne suggested looking at the rockers; that means removing top and bottom covers. You can also remove #1 spark plug, insert a hose from a compression tester as an extension, then feel for compression as the crank rotates toward TDC. At that point, the rotor should point toward the notch.

Hope this helps eliminate this area from your diagnosis,

Sherwood

Absolutely

Another option to check that #1 is at TDC, (and not out of phase with the distibuto) is: when the distributor rotor points to the mark on the distributor case AND the crank pulley is a TDC; Remove the number 1 spark plug and put a lenght of hose in the cylinder. Check to see if the piston is at the top of its stroke. If it is the timing is in the correct orientation for combustion. This way, no removing of the of the valve covers is required. At this point you can now double check the spark plug wire orientation. IE, make sure the number 1 cylinger wire is going to number i spark plug.

Hey y'all,

Thanks for so many good replies.

I haven't taken the upper vavle covers off, but I'm 99% certain that the distributor is in the proper position. Just to be certain, yesterday, I lined the distributor up at #1 tdc, removed it, rotated the crank 360, and then replaced the dist. in the same position. Absolutely nothing happened. So I repeated the process (back to the original #1 tdc position) and got the original results.

However, I did take my air boot off, and feel around down the back of the engine...somehow the hose that connects the aux. air valve and aux air reg to the block below the decellerator valve has come off.

I tried to put it back, but can't get to it in a meaningful way. I needed practice at dropping the engine some more, anyway. I probably won't have time to get to it until at least Thursday...I'll put up a new post after that.

Thank you all for your help...this is such a great BBS!