85 rebuild but no re-start
 

I have just finished rebuilding my engine. A novice, I did it myself. I turned the key for that first start with great anticipation and no small amount of anxiety. The result was…. nothing happened. The battery and starter are fine – it cranks, but it won’t fire at all.

The issue appears to be at the injectors, whether electrical or injectors themselves, I cannot say. Here's what I know:
1. i have a good strong spark. We took a plug out, grounded it, and watched a nice spark.
2. I have strong fuel flow at the rails. I didn’t however measure the actual pressure.
3. the injectors don't make any clicking noise, and the plugs seemed dry after attempting start. We turned it over with one injector pulled out to see if any fuel came out - negative.
4. I checked power at the injector – positive, 12V
5. I used a noid light to test pulsing and strength – there was a pulse, but it was very weak lighting of the noid. The element turned orange, not white. The light dimmed further after a few seconds of cranking.
6. Suspecting a weak/bad ground, I re-cleaned and re-tightened the grounds on the no. 1 intake runner
7. The engine-transmission ground strap looks fine, although it was not replaced. To eliminate doubt, I used jumper cables to create two additional “ground straps” from the engine case to the frame.
8. i put in a new ECU
9. I followed Ingo Schmitz’s advice to another Carrera no start issue. Disconnected all the injectors. Checked voltage at the conncectors (12v, affirmative). Confirmed noid light does not light when ignition on. Confirmed with ohmmeter that pin 14 is connected to 1,2,3 bank and pin 15 is connected to 4,5,6. Confirmed infinite resistance across each FI connector when all unplugged. I could NOT check the resistance across the injectors themselves as my ohmmeter was not sensitive enough.
10. As a last WTH measure, I took the jumper cables that were my makeshift ground straps and tried to jumpstart from my Cayenne, thinking that maybe a weak noid light was indicative of a 12v, but weak battery. No joy.

So, I’m left with two technically possible, but seemingly unlikely causes. 1) I have a weak battery AND a bad ground strap, and my jumper cables were only addressing one at a time. 2) All six of my injectors went bad while sitting on the shelf as I rebuilt the engine.

What am I missing? Any ideas are greatly appreciated. And, I promise to share the results once resolved, no matter how simple or embarrassing.

You have strong fuel at the fuel rails, and you have nice spark. That leaves timing or injectors it would seem.
I read somewhere and then tried this myself last year on a full set of injectors out of my daughters hemi dodge, worked great.
Take a 12 volt car battery and affix wire from both poles, some injector cleaner, 1ft. of rubber hose. Slip the rubber hose over the injector, spray cleaner into the hose to create a pool. Ground on the injector body and tap the positive on and off. It was amazing to me at how the cleaner came out in drops to start then eventually in a stream. We didn't have to buy a single injector,(100.+ ea.) and her truck is running fine now.
I have a 85 carrera and the engine is down now on it but I haven't even looked at the injectors to know if the hose would work on these. My clutch fork broke and just now getting the parts installed.
Anyway, that's my 2cents and probably not worth 2.

Stop by autoparts store, pickup starting fluid. Have a helper spray it in the intake while you try and start the car.

My guess is the battery is low. There is enough juice to turn over, but the draw does not leave enough for the injectors to fire.

Just a WAG from the shade tree.

Make sure the ground wires on the #1 intake runner are tight.
Switch the flywheel sensors as they are the same but do different things that won't start If reversed.
Bruce

Sage advice +1

PMH sensor , perhaps..........

Thanks everyone.

I had already redone the ground on the no. 1 intake runner. I cleaned all the leads. Also, the threads in the manifold were a little stripped, so i used a through bolt and tightened from both sides to make sure.

Since I posted, I got some off line feedback suggesting it was clogged injectors (they sat for nearly two years). So, I've removed the injectors and i'm sending them off for cleaning and testing.

Will let you know what happens.

What's a PMH sensor?

Did you check the flywheel sensors as flatpac6 recommended?

The flywheel sensors are new. My understanding is that they are more or less "on/off" switches that control both fuel pump and injectors (and maybe ignition?). Since I have good fuel pressure and the noid light was showing some light, I didn't think that was the issue.

I had 3.6 four years in garage and when i put it in car all injector were clogged. The engine had 35k.

One is a reference sensor pulse for the injectors (DME) the other position sensor for (spark) tdc if reversed the engine won't start. Try reversing the sensor connections.

He has a spark so the sensors are good.

Best case is your injector refurb comes back with one shorted injector.

If you need to shell out money with 3 digits for a single injector read through this.

http://forums.pelicanparts.com/porsche-911-technical-forum/327832-alternative-fuel-injectors.html

had the same prob. ck all the brown wires inside engine bay I missed one
that did the trick. oh flatsix is also correct. just sayn good luck.

regards

Looking over this again it looks promising that one injector is bad.

It is always the one thing you didn't check. Just like you find everything in the last place you look :)

A good possibility! Try disconnecting all the injectors and as was mentioned previously,
use some starting fluid or carb cleaner sprayed into the intake. If the engine starts
and runs briefly, that checks the distributor timing, ignition wiring and the DME ECM
with the exception of the injector output. While doing this, have a noid light plugged
into an injector to check for an injector pulse.

Got it. It was the injectors sitting for 22 months. I had them all tested and cleaned (RC Engineering in Torrance) and it started right up.

Meant to include that I got great advice from Walt Watson (Competition Engineering) and Tony Callas.

The 3.2 injectors are known to stick when sitting for a while. You can shock them open by connecting them to 12V or by tapping them with a screwdriver handle while cranking. Cheap and works all the time.