Fuel Injection, Cold Start

[airborn_ranger]

In a cold start scenario, what do the injectors do?
Does each squirt once into each cylinder just before TDC, then the engine keeps cranking until combustion occurs?

Thereafter, do the injectors squirt once per cycle?

Reason: I can't start my V-6. I pulled the fuel rail off the manifold and watched the injectors squirt as the engine was cranked over several revolutions--enough to get each cylinder to pass through TDC. Only two injectors (passenger side) squirted. Pressure in the fuel rail is proper.

Most sensors have been replaced, except knock-sensor. Will bad knock-sensor prevent engine from starting?

Crankshaft-position sensor is suspect also...if it is bad, is it true that the ECM/PCM will not know when/where to send fuel nor spark?

 

[Earl43P]

http://oldfuelinjection.com/?p=64

http://oldfuelinjection.com/?p=82

My understanding is that the Crank sensor times the spark and the Cam sensor times the injectors. Is there any chance that your injectors are clogged? Simply relocate the two squirters to another position and try the crank again.

 

[mp3deviant721]

Bad knock sensor probably won't affect anything. Check for a signal coming from the PCM to the other injectors. Otherwise, your injectors may be clogged, which I think is a little unlikely for 4 injectors to clog up all at once.

 

[LearjetMinako]

Kind of noticed a longer start time on my 4 banger this winter. I'm thinking fuel pump isn't building pressure high enough or injectors not squirting fuel. And I use fuel injector cleaner every 5k miles.

 

[adsm08]

I think you have a wiring or computer problem. The injectors don't fire directly into the cylinder as you seem to think they might. They don't "prefire" either.

The injectors should squirt once per cycle, which would be every other revolution. I think they were sequential fire by 96. Older Fords used a batch-fire system for a while where it would fire all the injectors on one side of the engine at a time.

Check each cylinder for spark while cranking. That will eliminate the crankshaft signal as a suspect.

Next would be to hook a 194 bulb into the injector sockets and see if they are all being fired. The light won't flash so much as flicker and the faster the engine spins the brighter it will get. If all are being fired, then the other 6 are probably clogged or bad.

At that point I'd get some BG 44k, let them soak in it for a weekend and then try it again. A can of 44k is a lot cheaper than 4 injectors.

 

[airborn_ranger]

the thick plottens...

Thanks, guys!
All plugs spark.
I forgot to mention that OBDII scanner shows "0" or no codes.
Interesting thing: The scanner flashes 8888 until I place a grounded wire on the aluminum body of the ECM, then it reads normally, but shows no codes. It seems I should have a few. With the ECM grounded as explained it still will not start. One cylinder ignites once in a while, but I never get a series of combustions.

I'll try the 194 bulb in the injector sockets next--great suggestion!

 

[airborn_ranger]

Better late than never? Fixed!

It ended up being a ground wire @ passenger side, rear, near bottom of engine, in a bundle of wires. My landlord with a magic Fluke and a lot of patience found it. Thanks for your most excellent help! TheRangerStation and its BROS Rock!