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Crank but no start

saturntech95

saturntech95

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The truck listed in sig (96 Suburban). While I was pulling into the parking lot at my truck stalled out and wouldn't restart. SES and wait to start light both come on. Lift pump runs and has pressure, fuel filter is good. All fuses OK. Tried unplugging the optic sensor to start it, nothing. Now here is what I can't remember, is the tach supposed to read while cranking. Cause right now it doesn't read anything just stays on 0. Cranking speed sounds fine. So I am thinking crank sensor?

So am I barking up the right tree here? Or should I check somewhere else?
 
Yes already tried my spare pmd. Sorry forgot to mention that. Other than this there has been no drivability or starting issues.
 
even if your CPS was bad it should still start. Maybe you could probe your pmd and see if your getting power to it.
 
possible but not probable that both CPS and OS are bad, also possible bad PCM but pretty rare. How long since you did your grounds?
 
IIRC if it were your CPS, you could unplug it and it should run in limp mode. It may take extended cranking.

Fuses may be good but are they making contact? Wiggle the ecm and fsos fuses to make sure there is contact.
 
I wiggled the heck out of everything, I thought if the optic sensor was bad you could unplug it and it would run but I didn't know it would work the other way. Grounds were done when motor was rebuilt about a year ago. I'll have to probe the PMD tomorrow, which terminal is it?
 
I copied this from one of buddy's posts


Those wishing to see if the PMD is outputting control signals to the injection pump, perform the following:
You will need to access the red wire in position "B" of the PMD connector with the PMD plugged in. This can be challenging with the intake manifold installed if using an IP mounted PMD. Straighten out a small paper clip and push one of the pieces of paper clip into the BACK of the PMD connector right alongside the wire to pin B. Push the piece of paper clip gently between the rubber seal and the wire. Wiggle the paper clip and push gently until about an inch of the paper clip is no longer visible. The paper clip is now touching the back of the bare metal terminal connected to the wire. Use your ohmmeter on the continuity test setting to ensure that the paper clip is indeed making contact with the respective wire. If you have wire piercing probes they can also be used for a more reliable connection (be sure to repair the wires later). You can also strip sections of the wire and attach short sections of wire as "test leads."
Now, plug the PMD connection back in. Connect your volt meter to the pin B wire and the ground on top of the IP, with the meter to measure AC volts. Be sure not to let the paper clip short against engine ground or the PMD will be destroyed!
Crank/Run the engine and observe the voltage. You should observe at least 1.0 VAC while cranking, up to 1.3VAC. If the engine will not start and this value is lower then the PMD is likely bad. If the engine will not start and your voltage value is higher than 1.3VAC then the connections to the IP's Fuel Solenoid (FS) under the rubber boot probably have broken loose. You can ensure the connections are good by measuring the resistance from PMD pin B to pin F (or FS ground), which should read approximately 0.4ohms on a healthy FS.
While idling you should observe approximately 1.6VAC. The voltage will rise with RPMs, up to 5VAC around 4000rpm. If your PMD is outputting a constant 1.6VAC, but the engine is revving uncontrollably then the IP is faulty.

This does NOT mean the PMD may not later cause stalling or other issues, but it should bring the engine to life and operate.
 
The tach wont read anything while cranking because it starts at 500rpm

That FSOL fuse is a likely culprit, but if not, make sure the FSO/ESO solenoid is actually working. With the igntion it should pull up the plunger that you can feel/hear it click. Or you can take it off and test it, or just remove the plunger with a snap ring pliers.

The PMD test above will tell you if the injection command isnt happening or if the IP just isnt following orders. Checking the resistance through the FS is good, and easiest thing to do, just to make sure the wires under the intake didnt break off the IP.

Before anything you could unplug the CPS with the OS plugged in. In either scenario, either one unplugged, it could take 10 seconds of cranking to start.

The all of a sudden stall and no restart sounds like a hot IP maybe, pour water on it perhaps, or a blown fuse. But the ESO could suddenly fail I suppose.
 
Fuel shutoff solenoid is gutted do to that being the no start culprit last time. I seriously have to doubt ip since it has never acted up before. It is a dirt road I was driving on when it stalled so possibly a wire chafed through but I didn't see any blown fuses?
 
Well resistance is way out on the FS... So I geuss it's time to pull the lower intake and check the wires. I have a spare one of those harnesses so atleast if it is broken I won't have to f with it I can just replace it. This atleast makes some sence since I was on a really bumpy dirt road when it died? Fingers crossed it's not a IP problem cause I gave my spare away.... Dumb move on my part!
 
It just kept climbing, went into kilo and mega ohms. Checked it a couple times just to be sure I had a good connection to the wires.
 
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