My rebuilt engine won't start....

[pjo046]

Hi folks

I have just completed my rebuild (1986 944 Turbo).

When trying to start the engine, it sputters, misfires and backfires, and simply refuses to start. I got it started for a minute or two today, but had to use the Accelerator to keep it running. It poured out black smoke (But I have used thermal coating on both inside and outside of the catback system, so some of the smoke was probably just paint curing.

I have checked that I have spark on all plugs, and that I have fuel from all injectors.

I have renovated the entire engine wiring harness. So I am wondering if there might be a wiring related problem(Bad connection somewhere, wires swapped, or similar)?

Furthermore, I have installed a Rogue Tuning A-tune chip together with the accompanying MAP-sensor. I have also installed the required 3-bar FPR that is needed with this chip. The injectors are rebuilt by Witch Hunter. They have sat for a while before being installed (Bought them of a fellow Porsche enthusiast because he didn't need them for his Project after all), but the injectors had been treated with some sort of lubricant to prevent them seizing upon Storage.

I have renovated/checked both the AFM and TPS according to online-instructions, and rebuilt the entire TB. The turbo is a professionally rebuilt K26/8.

Any thoughts? Could the ignition timing be off? There is no adjustment possible that I am aware of. I have tripple checked that the firing order is correct.
I have tried swapping the flywheel sensors, so have confirmed they are installed correctly. As mentioned I have verified spark and fuel on all cylinders. But all brand New plugs had Heavy black deposits after the starting trials...

So far I am clueless as to what to check NeXT..

[zedsn]

It could be one or many things. You probably should have got it running and then rebuilt or replaced one thing at a time and gone from there. You are going to have to make sure that you put the timing belt back on the correct way if not you have bent some valves and who did the head work and what did they do? Do you have fuel and spark? There is a way to see if your injectors are pulsing like they are suppose to with a noid light. I would go to Clarks garage do some reading and eliminate components one at a time and narrow it down for starters. My 2 cents.

[pjo046]

Thank you for your feedback! :-)

I have spark on all four cylinders. Verified both with a check-light between plug wire and plugs, and also with plugs detatched from head with plug wires attatched, lying on intake manifold, and all four were firing when I cranked the engine.

As the engine startet for a short moment and was held running for nearly a minute with the accelerator, the engine is receiving fuel. Looking into the cylinders through the spark plug holes it did seem that cylinders 1 and 4 got more fuel than 2 and 3.

Btw, it is 11:40 PM here in Norway now, but I will continue to search for solutions in the garage tomorrow. But the more help and hints I can get untill then, the easier it makes it to hopefully locate the problem.

A reputable machine shop did the head rebuild. They are known for their head-work, although not specifically with these engines. Mostly Ford Cosworths and BMWs. But they seemed very competent. The head has been resurfaced. The exhaust valve guides have been replaced, while the intake valve guides were ok. The valve seats have been re-cut with a multi angle method that is to be superior to the stock design. The valve stem seals have been replaced.



I double and tripple checked my work when installing the timing belt. So I am fairly sure I did it correctly. I used ArnWorx's belt tensioning tool. I rotated the engine by hand several times after installing the belts, and there were no intereference issues between valves and pistons. Marks ligned up again after manual rotation.

Just to eliminate two things without having to try it tomorrow: If speed and reference sensors were installed into the wrong connectors, the engine wouldn't even try to start, right? I should see no spark or fuel if I had reversed those connections?
And if I had reversed ground and signal on the coil, should I then see any spark at all?

Btw, my DME-relay is also new.

[pjo046]

Could an air-leak cause problems like these? I have changed every hose on the engine, so I really don't think the problem lies there.

[zedsn]

Looks like they did a nice job on your cylinder head. Any idea how much it was decked? I would next make sure you are getting proper fuel pressure by puting a gauge on the end of your rail or using the hose into jug method to rule out a fuel pressure issue. You installed new intake gaskets etc right? Are you sure that you have the plug wires going to the correct plugs? I would next get a noid light or send your injectors out to make sure that they are working properly or put your old ones back in next. If you had the sensor wires swaped the car would not even fire and are you sure that you have the correct adjustment for the reference sensors to begin with? You said that you rebuilt your TPS and there is adjustments to make on that as well with an ohm meter. Go to Clarks garage and do some reading as it might help you out.

[pjo046]

Yes, I followed the procedures on Clark's garage for both the TPS and the AFM. I checked and verified correct operation with a multimeter.

Not sure how much the head was decked, but I think not much. Hopefully tomorrow a mechanic friend of mine will bring a fuel pressure gauge so we can check the fuel pressure at the test port on the fuel rail. I installed new intake manifold gaskets, exhaust manifold gaskets, new silicone couplers for the intercooler, with T-bolt clamps everywhere. I am absolutely certain that the spark plug wires have the correct lay out. We even tried the reverse combination plus a few other combinations just to make sure the problem didn't lay there. We made sure to get the correct adjustment for the reference sensor as it was installed prior to the clutch housing coming on. So we could use a feeler gage to ensure the gap was within spec.

If the fuel pressure turns out ok tomorrow, I can try to put my old injectors in tomorrow to see if they work better than the rebuilt ones.

One question, can anything make the ignition timing get thrown off spec? It feels as if the misfires are caused by wrong ignition timing. My father was inside the house when I was trying to get the engine to start. He came out after a while and insisted that this sounded like a ignition related problem. His experience is only with old Jaguars though. :-)

[zedsn]

As you know there is no distributor for timing adjustment and if you have installed the rotor correctly and plug wires then the DME takes care of the rest. Coils don't seem to ever go bad but did you check the ohms reading and are you getting 12 volts to the coil with the ignition switch on?

[Techno Duck]

Sounds like your running excessively rich which would explain the black deposits on the plugs. Just how dirty are the plugs, it's possible they are so fouled it is continuing to miss fire.

[pjo046]

They are quite dirty, but they did all fire when we "bench tested" them on top of the intake manifold. We cleaned them before putting them back in the engine.

I tested the fuel pressure off the fuel rail now. When the ignition is turned on, there is no pressure buildup. Not untill I start cranking the engine does the pressure start to build. And then it builds steadily to 3 bar which is correct for my current chip and FPR-combo. But after turning the ignition of, the pressure quickly goes away.

Could reversing the supply and return fuel lines cause this behavior?

[Techno Duck]

Look into the cylinders through the spark plug hole, I think you may have a leaking injector. You might see fuel pooling in the cylinders. The pressure should not bleed off immediately.

The fuel supply line (hose) should go to the damper, the return comes from the FPR. It is not possible to mix them up due to the difference in fittings.

[zedsn]

You should get fuel pressure when cranking over the motor and not just turning on the key but I would think that the pressure should stay there when you off the ignition. There is a check valve at the fuel pump but you are getting pressure so that would be a different issue to your non start I would think. your AFM is plugged in to the harness right?

[pjo046]

Yesterday we found more acummulated fuel in cylinders 1 and 4 compared with 2 and 3. So maybe injector 1 and 4 is leaking.

I think the next step now would be to reinstall my old injectors to see if that rectifies the problem.

AS for the fuel lines, I have made new custom lines using twist lok hose and AN fittings. I have used compression fittings from LR on the cut fuel hard lines, from the inner fender area. So I found have swapped those two connections. But I guess I wouldn't have been able to build correct fuel pressure then.

[pjo046]

Someone on the Norwegian Porsche-forum mentioned old fuel as a problem. My car has been sitting for just over a year because of the rebuild. It has under a quarter full tank. Could bad fuel cause such start difficulties and also symptoms with sooted spark plugs?

At the moment I think Techno Duck has the most promising solution when mentioning stuck injectors. These injectors are however cleaned and flow tested at Witch Hunter. But have after that sat for probably two years.

[pjo046]

Btw, today I verified that the rotor is firmly mounted with the set screw. I furhter verified that the coil has the proper primary and secondary resistance, and also that both terminals see 12V when the ignition is turned on.

Should I then rule out ignition as a problem source? All plugs fire, the coil is in good working condition, the rotor and cap are new and firmly mounted, and the firing order is correct.

Could the DME send totally whack signals that distorted the ignition timing so much the car won't start? And if so, caused by a malfunctioning chip, a problem with the wiring harness or similar? I will of course check the injector hypothesis first chance I have, but it is nice to rule out things meanwhile.

[pjo046]

Is it likely that a stuck open injector can cause hydrolock? Just got scared I might have ruined something when "forcing" the engine to run yesterday.

[zedsn]

I would find it unlikely that you would cause a hydrolock condition with your injectors and you could drain your oil and see if you can smell fuel mixed with the oil.

[commdiver]

I would say that 99% route cause of this no run condition is your work performed! I would rule out the hard components like coils, injectors, computers etc.........
It's most likely a intake manifold just off the gaskets and a huge vacuum leak, a missed hose somewhere with a huge vacuum leak, a wiring problem in your harness fix, ie they weren't soldered back together exactly right? Or worse and your cam timing is off and you either have a few teeth off problem or it's badly missed and you have bent some of the valves in your head?

Remove all spark plugs then in the #1 spark plug hole stick a screwdriver down that hole, turn the engine over by hand with 24mm wrench until this piston is at top dead center as high as it goes! Then make sure your cam gears notch is right at the TDC mark which should be easily seen through view port......

If your cam is timed right, check that you have good compression in all 4 cylinders. Once both these things are ruled out and your sure you have no vacuum leaks then it's on to triple checking all your wiring?

Side note the rear reference and speed senders have to be adjusted perfectly off the reference set screw and starter ring gear in order for the computer to run engine right? Check height of the bracket and use an old sensor or one of yours bye gluing a washer that's the right thickness to it and inserting while adjusting bracket down till it hits.

[mreid]

This is exactly the symptoms of a distributor installed 180 degrees out. When you get it to true TDC on cylinder 1 as commdiver says above, verify that the valves for cylinder 1 are closed and the distributor rotor is pointing to plug wire #1.

[Techno Duck]

It is not possible to put the ignition rotor on 180 degrees off, it is keyed to the cam snout with a bolt.

[mreid]

Right. And if you have the crank at TDC, but not on the compression stroke, can you install the distributor with the rotor pointing at cylinder 1 plug wire?