Cranks but won't start, no RPM movement

bravobob

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2000 Bravada, Upon cranking, the engine made a misfire sound and then nothing, fuel pump primes, good burst of fuel comes out of schrader valve but don't have pressure gauge to verify actual pressure. Good spark at coil, distributor and plug. All fuses good. On thing caught my attention..while cranking the engine the RPM gauge does NOT move at all, it should move a little while cranking on this vehicle right?
A little more info: She usually starts instantly, then the last few weeks the time it took for the engine to fire up increased a lot. Then then last time she did fire up, I almost gave up as the battery was getting weak, then she misfired as engine started running, then to keep her from stalling I had to floor it a few times, the engine smoothed out but surged to 3000 RPM by itself, stayed there for 10 seconds then dropped to normal.
Also, when driving, the engine would hesitate cruising at 2000 RPM only and eventually throw a P0300 "multiple engine misfires detected". And most times trying to accelerate quickly from a stop the engine would rev up accordingly with pedal depression but the vehicle would just slooowly gain speed like the brakes were being applied. Then after flooring it a few times she would take right off normally. So, I'm sending out an SOS, I'm disabled vet (disabled, not dead!) with nobody to help me in person so any help to to get this thing running would be greatly appreciated.
 

bravobob

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Update: scan tool shows 120 RPM when cranking,
NO codes present.
Something is preventing battery voltage to half of the pink wires going to the injectors,
I read all off them should have battery voltage in run..what is causing this?
 
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Cutlass350

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New England! :-)
Unfortunately, I don't see any DEALER service manuals for your SUV on ebay. Imho, you really want/need a DEALER service manual if you want to repair any newer vehicle.

I found an EFI schematic for a GM 1999 4.3L engine. Yours is likely very close, but not exactly the same.
Still, it should be similar.

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So

1) We see that GM uses the PCM to ground the injectors, to turn them on.
2) We see that there is one fusible link for all 6 injectors. And, all 6 injectors should have power at the same time, through a single wire.


That means that there is likely a broken between the injectors. A simple test is to use a wire, and jumper from the wire from the working set, to a wire on the bad set. See if all of the injectors get power. You can leave the jumper. But, it's better to find the broken wire in the wire loom, and replace it there.
SOLDER any connection. Crimps are infamous for making cr*p connections, especially in engine environments.


Good Luck!


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bravobob

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Thank for the schematic, in light of how the engine was "acting up" recently...Hesitation, surging, P0300 code misfires, stumbling, no start now, BUT since I have spark, fuel pressure is spot on, and injectors are not firing, I'm backtracking the wiring and right in line between the PCM and the injectors is the CKP sensor. I have read everywhere that if you have spark then your CKP sensor is working...Well, I pulled it and checked it out, it did not have any rubbing wear, so I checked it's resistance with a digital ohm meter and did NOT get any reading across all 3 pins so the sensor has an OPEN condition. I ordered up a new sensor and we'll see if If this fixes the no start. Hmmm.
 

bravobob

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No go replacing CKP sensor. I guess there is no help for this no start, it defies logic, how can you have good spark, spray starting fluid directly into intake and a cylinder, crank engine and you don't even get a sputter or even a hint of the engine wanting to start?
 
G

G-993738

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No go replacing CKP sensor. I guess there is no help for this no start, it defies logic, how can you have good spark, spray starting fluid directly into intake and a cylinder, crank engine and you don't even get a sputter or even a hint of the engine wanting to start?
What was the issue?
 
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