1998 blazer 4.3l 4wd crank/ no start after engine swap.

Asked by Apr 24, 2017 at 11:56 AM about the 1998 Chevrolet Blazer LS 4-Door 4WD

Question type: Maintenance & Repair

1998 blazer 4.3l engine.
Old engine blew out a rod bearing so i replaced with a 4.3 out of a 98 blazer
that had been rear ended. Engine is hooked up.
I have a Crank but no spark condition.
After futzing with it for about a month I've gave up tracing the problem with a
vom and test probe being that i have no O-scope to test for a signal.
I have Done  the following:
Checked ECM1 15a fuse and all fuses---Good.
New Computer flashed with my vin number
Ign control Module  New
Distributor w/cam positioning sensor New
Crank positioning Sensor  NEW
Coil New
Tested Ignition switch at the wire block pink w black stripe as i tried to start.  
Got power to that wire when i put into start/run position

Still have a crank no spark condition.
I do have power going to all of the components.
I also have power going to the injectors and am smelling fuel when i try to

To verify i have power to the components i tested the pink wire going to the
coil, ICD, CMP, CKP.  They all show 12v

Tested continuity on wires i could not test signals.
Coil was tested for resistance and is within specs.
Coil tach sig wire white/black stripe has continuity no signal from ICD
ICD ign timing wire white going to est output sig on computer chip c2 has
continuity no signal from ecm
Ground wire black/white stripe has continuity
CMP sensor pnk has 12v, pn/blk has continuity to the pcm chip c1. brn/white
wire has continuity to pcm chip1
CKP sensor has power to pink wire.  Yellow wire has continuity to ecm chip
c1  Purple wire has continuity to ecm chip 1

Computer is new.  Flashed with vehicle vin
This car according to gm does not have passlock or any security to prevent

I am a mechanic but am 100% disabled and rely on this car to get to my
heart doctor and medical treatments. Sure need to find out what is wrong.  
IT ran before i swapped motor.
I'm at a loss on what to check now. It ran before i swapped motors now i
don't get any spark. IF i could solve the no spark issue i believe it would fire
up and start running.

Any ideas?

19 Answers


This thing should start, everything sounds like it is checking out. So ideas...Was the distributor out of the engine? If so how did you put it back in, just interested at where the rotor was pointing when the engine was on TDC on the compression stroke. And what is ICD? And is the coil grounded good at the mounting points?

Yes the distributor was replaced. I set the rotor at the arrow on the base of the distributor Approx 7oclock position. The ONLY thing and i just thought of it is that it is very possible that i wasn't TDC number 1 spark if i happened to be 180 deg off I was using a comp gugage to tell me when i was hitting the cyl. Sorry ICD should be ICM ignition control module. On the coil grounded. It should be, its mounted to the original studs but i'll check it and see.


Sorry I wasn't getting my responses. So, Yes, the rotor pointing at 7:00 o-clock is what I was getting at, since the #1 contact is not at the #1 tower in that distributor cap. And yes still, you need to be on the compression stroke at TDC. Let me know what you found.

1 people found this helpful.

Rotated the distributor got a po336. code. did not have any code prior to that. as it is i do not know if i am tdc on number 1 or not. guess i am going to have to pull the valve cover to check for sure. Cannot test the signal wire til i get my 1/2" drive tools back. I do have another connector for the ckp coming in. I am hoping its just a bad connector.


So your waiting for some tools...when you know your coming up on the compression stroke just get a ratchet, strong arm and put on the end of the crankshaft bolt and just turn the crank until the timing mark on the pulley is on "0" of the timing pointer. Take the spark plug out, lot easier turning the engine over by hand.

yeah i know thats right. I do that.

went under, could not get a definitive answer on voltage off of the ckp. I rotated it but never saw a fluctuation. Going to wait on a connector to come in, i'll replace and go from there.

Update I tested circuit. I have a new connector wired in, soldered in. I left my shrink wrap tubing loose so that yellow and purple wire solder is exposed so i can test. I connected connector to the CKP. I took a voltage source and tapped the yellow wire at the solder and fuel pump engaged and i heard injectors fire and relays activate. I then tested voltage while cranking on yellow. Got 2-3v highs on yellow. Got .03v on the purple Still get no spark on the coil. Not sure why. Timing is correct. I removed valve cover watched exhaust open and close and intake open and close then moved the balancer mark 180 deg. its sitting no 1 tdc. Distrib is sitting on its triangle mark on the edge so its in time. I get po336 on the scanner. So something isn't working right. I dont' know why the computer would report this when i have a 2- 3v voltage on the sig wire.


I'd feel a lot better if you watch this video on how to install this distributor... https://youtu.be/LOR-9JZUUI0

yep Thats how i installed it. I use either that dimple or you can point the tab off of the cap nut about 1/4 inch and it achieves same result. Usuallly if i am not dead on i lift it enough to turn the rotor one tooth either way and set back down to get dead on.


I don't know what to think on this other than we're missing something simple.

well hopefully it will dry up tomorrow and i can get out there. i'm at a loss. po336 means computer cannot see a signal from the ckp. SO that means either its not working or the wires are bad. IF it were the reluctor wheel it would throw a 337,338, or 339 code. The computer must be good in that it sees no signal. So that leaves only wiring. I may just tool down to the junkyard and buy some computer connectors from them and replace the deteriorated ones that are on mine. Maybe even get some wires connected to the ones. I wish i knew where to find the pins that are on the connectors i would just go get the wire and remake the wire.

Unfortunately still a no spark situation. BUT when i connected that broken groundwire i rerouted to a bolt hole on the block where the spark plug loom bolts in, i got different readings on the sensor. while cranking 1.07 on the yellow wire. Yellow wire to ground. .002 on the purpe wire Purple to ground 1.17 on the yellow wire with ground lead on purple wire. Wires ohm'd out around .012 resistance Which is normal and shows no breaks I'm trying to find a car with the same oem sensor in it thats running and test with that ckp sensor

Hmmm I worked on it today, for now i do get a singal through the computer. Its not much though but i am limited to my vom. On the ignition timing signal wire. (white one going into ICM from c1 pin 9 on the PCM) i'm getting around 2v when cranking. So that does tell me that something is getting through the pcm from the CKP. But it still gives me a 336. I do know that i can ground wire d on the icm plug which is tach signal going to the coil and i get a spark. The problem is i bought a icm a while back and put on before i started this thread so its a new one. I can't keep throwing money at parts hoping to get a good one though. Sigh. Now one problem i saw is this. On the ICM connector b pin is ground. I did a cont test but got no tone. So i hooked it up directly to the ground on battery and got no spark either. That wire goes direct to the left side head and bolts on with another ground wire. Those wires i had to rerout and put a new connector on and ground to the block where i could reach the bolt. I'm not getting tone on continuity. I got some numbers on the continuity test but no tone at all.


You know, I wounder if the reluctor is damaged at the crankshaft. I know the air gap is important between the crankshaft sensor and the reluctor. Any broken teeth on the reluctor, or grease, dirt would interfere with the signal.

this reluctor has 3 lobes. i felt up in there with my finger and did not detect any damage on the leading edge of one lobe. I was also wondering the same thing. But to replace it which i do have another on in another motor here, i have to get a timing chain cover and gasket set. They say you can't reuse the plastic ones as they will never seal due to heat baking it from the engine. I don't have the money yet but i think i am going to buy me a newer ODB2 scanner. the one i have only reads p0 codes not p1 p2 or p3 codes. From what i am reading about newer scanners it reads the live data from the ckp sensor and icm


Your engine needs to be running to collect the live data. I have the Actron CP9690 Elite AutoScanner. It would read live data but just for a short time, and when viewing the data, you need to print it out in-order to get a continuous graph, otherwise it just shows you frame by frame views of the data in the time it recorded.

Took car to a shop. They tilted the motor forward by lifting the transmission to see behind it and found a ground wire disconnected and found the icd connector was not making contact with the icd. Its getting spark now, but now we have a fuel pressure problem. He said it may be from sitting for a year.

You crack oils sending unit?

Your Answer:


Looking for a Used Blazer in your area?

CarGurus has 739 nationwide Blazer listings starting at $900.


Chevrolet Blazer Experts

  • #1
    Andrew Olsen
  • #2
  • #3
View All

Related Models For Sale

Used Chevrolet Tahoe
646 Great Deals out of 37,769 listings starting at $1,995
Used Chevrolet Silverado 1500
1,837 Great Deals out of 155,600 listings starting at $1,799
Used Chevrolet S-10
5 Great Deals out of 906 listings starting at $995
Used GMC Jimmy
152 listings
Used Chevrolet Camaro
306 Great Deals out of 26,931 listings starting at $2,500
Used Chevrolet C/K 1500
717 listings starting at $2,200
Used Ford F-150
2,266 Great Deals out of 187,689 listings starting at $495
Used GMC Yukon
326 Great Deals out of 23,849 listings starting at $2,000
Used Jeep Wrangler
218 Great Deals out of 14,764 listings starting at $3,800
Used Ford Explorer
933 Great Deals out of 71,647 listings starting at $495
Used Chevrolet Suburban
304 Great Deals out of 21,330 listings starting at $1,988
Used Jeep Grand Cherokee
1,148 Great Deals out of 80,317 listings starting at $1,500

Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. Please refer to CarGurus Terms of Use.