I have a 96 sonoma 4.3l with csfi. It cranks but won't start. I've checked
fuel pressure 60lbs, timing tdc and rotor button are lined up on number 1,
has spark on several cycinders, and checked a few sensors for 5 volts.
Even tried to get it to run by spraying starting fluid at the air intake
while cranking it. Could the csfi system poppet valves need replaced.
Anyone had this problem?
First have you checked for spark at all 6 spark plugs? which means
pulling the wires from the plugs and looking for spark to arc?
Have you checked that you coil is putting out the correct injector
Give us a list of what YOU haved tested and how you tested each item.
Then people on here can respond with a bit less guessing.
Ok here's what I've done.
1.Checked fuel pressure 60psi
2.Has spark on #1 and 2 cycinders wires with a extra plug grounded.
3. Ohmed out the crank sensor compared to haynes manual and was ok.
4.Replaced spark plugs gaped 60 thousands.
5.Replaced fuel filter.
6.Looked at computer errors found low reading for the map sensor but don't
think that would not let it start.
7.Tried cranking with sraying starting fluid at the air intake with
throttle wide open ( wouldn't try to fire).
With all this I assume,either the csfi system or the PCM must have a
problem, I wish I had a spare PCM to plug on it and might try local scrap
yards. I know it has a fuel regulator and injectors and I going to take
the csfi apart to look it over. Either of these are expensive just to
guess at. That's why I posted here to see if anyone has had this problem,
Is there a way to see if the injectors are getting pulsed? By the way this
happened suddenly just quit running (dead).
Checking spark like that can be decieving, the spark may look ok, but no
strong enough to fire in the cylinder, one of those testers that uses an
adjustable gap is a better test of actual kv, it should at least try to
start when sprayed.
There is a three wire plug:
It goes through the plenum, I forget the wire colors to back probe. But,
that's where you test for injector pulses. It sounds to me, since you used
silly juice, and it still didn't start.
You have something more sinister than a fuel delivery problem. Have you
checked for timing chain alignment> Check that, and also check compression
and for uniformity between cylinders.
Then get back to us. Because with spark and silly juice, it should have
fired for atleast a few seconds!
I hope this helps?
Six injectors, two wires per injector= 12 wires going into the
The wires are laid out in to rows of six, like this:
Pick any pair of wires and use a noid light or a 12 volt
automotive test light to see if the PCM is commanding an injector
We checked the timing second mark to the rotor button and it was pointing
to number one electrode in the dist cap. Also to get the timing marks
lined up we took number one plug out and with finger in the hole cranked
the engine over until compression pushed out. WE haven't measured actual
pounds of compression but it appears at least the crank and cam are
connected. Also the rotor rotates when cranked. Next thing I'll try is
measuring the amount of kv on the plug wires and see if the PCM is pulsing
the injectors. Thanks for the ideas.
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