Emergency help needed:

[wolfox]

Ladies and Gentlefolk...

I am 1073 miles away from home and my shop manuals. I have a problematic crank position sensor I suspect. (Engine sputters and dies when hot, cranks and starts after sitting for an hour to cool) I cannot find the dad-blamed sensor for the life of me. There is a blank spot on the crank boss on the front of the engine where the new sensor would fit perfectly - but there is nothing there. Later revisions of the VIN-W 4.3 used this spot I am guessing. Where is the crank sensor hiding on this '95 CPI fired beast, anyone know? Thanks in advance folks.

[OverBoardProject]

I'd like to help you wolfox, but I don't have any books here.
There's a chance that your truck didn't have 1 instaled though, how about telling us what's happening and we might be able to help you figure it out.
you know as well as any of us do that if the sensor wasn't there in the first place it isn't required.
And I know what it's like to troubleshoot when your stressed out. Shall I say that it's almost impossible.

I've got a full sized book lying around here somewhere that I'll try to dig up later. It might have somthing that can help. I'll look after breakfast.

Good Luck

[goser]

"The crankshaft position sensor is located on the passenger side of the engine block below the coil pack and is accessible when the vehicle is raised and supported with jackstands" Hope that helps... It should have an oval connector you could trace from the Ignition control module.

[blazes9395]

The crank sensor is located on the front of the crankshaft, behind the balancer, on the timing chain cover. Its on the passenger side of the cover, close to the bottom. It will have three wires coming from it. Do you have your PCM inside or outside under the hood? How about your distributor, is it a top or side plug cap? If your PCM is outside under the hood, and side mounted distributor, then you will have a crankshaft position sensor. If you PCm is inside the truck, and top mounted distributor, then you don't have a crankshaft position sensor. Good Luck!, hope you get it figured out.

[wolfox]

Thanks for the input one and all. Here is what I managed to figure out and do:

I compared a '94 and previous (1st Gen.) repair manual with one that covers '95 and on in the shop. The gang over at a nifty Advance auto shop let me read them and take them out of the wrap. I quickly found out that it seems that the '95s like mine, with the vertical cap and mising sensor in the crank boss by the timing cover derive their timing from the reluctor inside the distributor. Exactly like how the origional High Output option package in '93 or so in the first gen. Blazers work with the MEMCAL unit under the dash. (My MEMCAL is under the dash and glove box inside the truck too, though it has an OBD-II plug under the knee bolster and requires a non-standard scantool to read) After yanking the distributor up and out, sure enough I found a nearly totally trashed pickup coil. (Some units of this same vintage saw a hall effect Camshaft position sensor with little spiked towers protruding up and around the rotor - these use a small, flat hall effect sensor called - again for redundancy's sake, a Camshaft Position Sensor - and when that goes out or looses signal, the OBD-II system simply switches to a default, limp-home mode. Those that use a magnetic coil for a pickup (like mine, a simple HEI with vertical towers on the distributor) generally stall, stutter and then just drop dead, crank but no start/spark condition) Anyway, I missed the pickup bobbin when I replaced my ignition module because it is hidden inside of a brass assembly that houses the rotating magnet under the rotor bug. After popping off the snap-in ring that retains the works assembled at the ends of the distributor I found a crufty, nasty, decomposed pickup bobbin. Replacement parts were secured for $16, the guys cut me a great break after the trouble I was going through at the parts shop.

Now onto problem #2:

I have established TDC, even the distributor rotor is properly aligned for TDC, Cylinder #1 - and the blighter won't drop the extra 1/4" so I can place the retaining bolt and clamp everything into place. I figured that I may have accidentally assembled the rotor's gear at the end of the shaft 180 degrees out. I popped the roll pin out, rotated the gear 180 degrees and set the pin. Same problem. I took meticulous notes and used a sharpie marker to make certain that everything went back together in the distributor shaft, gears, rotor, etc..etc... in the proper way. So swapping everything back to what i have marked, I went to try to set the distributor over an hour and a half. Yet try as I might, even after engaging the distributor gear and getting dead on alignment with TDC, cylinder #1, it will not sink that last 1/4" - almost like it is not engaging the slot for the oil pump at all.

And yes, I even gently and slowly turned the engine by hand through several revolutions by the main crank to attempt to set the distributor completely against the block - just no dice. The old gal's beat me up while I was doing this, having once slipped and slid as I fell out of the nose of the truck's engine compatment, severely gouging myself here and there. So unless someone has a great idea or insight into what I am doing - the old gal's going to get towed to a local service shop for repairs. I am NOT going to get myself hurt working on this beastie again.

[OverBoardProject]

Wish that I could help you, but I've never har the problem.

I think that the biggest factor is the stress that you must have.

Just a sugestion but how about asking for some help in the AF off topic forum (not just the Blazer) There's hopefully someone living close bye that can help you
Here's the link and good luck
http://www.automotiveforums.com/vbul...play.php?f=715

[MT-2500]

Originally Posted by wolfox

Ladies and Gentlefolk...

I am 1073 miles away from home and my shop manuals. I have a problematic crank position sensor I suspect. (Engine sputters and dies when hot, cranks and starts after sitting for an hour to cool) I cannot find the dad-blamed sensor for the life of me. There is a blank spot on the crank boss on the front of the engine where the new sensor would fit perfectly - but there is nothing there. Later revisions of the VIN-W 4.3 used this spot I am guessing. Where is the crank sensor hiding on this '95 CPI fired beast, anyone know? Thanks in advance folks.

PCM or VCM
PCM =computer behind glove box does not have a crank sensor.
The dist module in dist trigers ign.
On th the pcm the dist mdle or computer coluld mess you up.
If it loses fire when it acts up check dist module /coil and dist pickup.
Another test on PCM is the old tap test or twist test.

If VCM the computer under the overflow tank the crank sensor is on front of engoine and cam sensor in dist.
If you can make it to a auto zone get a free code check and or rent a fuel pressure gauge and check that fuel pressure.
On getting the dist in get it set tdc compression and rotor to no 1 piston.
And on that last 1/4 drop in stay out of the road and fan blade and belts while holding down on dist while someone cranks the engine over.
Some are a pain but they should drop on down in there.
Good Luck And let us all know how it goes.
MT

[blazes9395]

Originally Posted by MT-2500

PCM or VCM

On getting the dist in get it set tdc compression and rotor to no 1 piston.
And on that last 1/4 drop in stay out of the road and fan blade and belts while holding down on dist while someone cranks the engine over.
Some are a pain but they should drop on down in there.
Good Luck And let us all know how it goes.
MT

Yeah, MT's method works for sure, I've seen it done. Get it on TDC, throw the distributor on there, pointing to #1. Use one hand to hold the distributor body, other to wiggle the actual shaft a little, it will go, just make sure its straightdown, so the gears will mesh. If its the same that came out, it will go back in.

[wolfox]

Originally Posted by MT-2500

PCM or VCM
PCM =computer behind glove box does not have a crank sensor.
The dist module in dist trigers ign.
On th the pcm the dist mdle or computer coluld mess you up.
If it loses fire when it acts up check dist module /coil and dist pickup.
Another test on PCM is the old tap test or twist test.

If VCM the computer under the overflow tank the crank sensor is on front of engoine and cam sensor in dist.
If you can make it to a auto zone get a free code check and or rent a fuel pressure gauge and check that fuel pressure.
On getting the dist in get it set tdc compression and rotor to no 1 piston.
And on that last 1/4 drop in stay out of the road and fan blade and belts while holding down on dist while someone cranks the engine over.
Some are a pain but they should drop on down in there.
Good Luck And let us all know how it goes.
MT

Good info MT, and I appreciate it. Yeah, I found out in my case, it's a pickup coil, IGN module and a PCM. I will try your suggestion of getting an assistant to crank engine (My little brother) while pressing on the dist. backplate/flange. I will yank the ECM-Batt, ECM, and engine fuses after also removing fuel pump relay. That should make sure that the engine is dead. If this does not seat it, I guess I will think again seriously about dragging it into a shop. I am more positive thinking on the matter knowing I am not doing anything wrong just yet - just hitting a slightly sticky point of re-assembly. For the record, the truck's getting a new distributor cap and rotor bug too. The IGN module and now the pickup coil is brand new. Wiring between IGN module output and coil has been checked, cleaned and put back into place. The IGN coil is a new (less than 9 motnhs old) Bosch OEM component. It was replaced back when chasing previous sputter/mild stumble problem at launch from standstill. The coil pack was producing a weak, orange-yellow spark through new wires when last tuned up. Got a strong, blue, hot spark after replacement but - well, now you know my current troubles.

The old ignition pickup coil was tested with a Digital VOM, and found to be horribly out of spec. It was literally a high open condition, over 6x more than factory spec. I surmised that as this component heated, electrical resistance increased too far and completely attenuated the already weak signal flux causing my stumble-stall/crank & no start condition with no spark at the plugs. I am crossing my fingers at this point, I shopped for a new PCM and got a little sticker shock. By far the more expensive repair when compared to a $16 part but will be critically looked at and checked by the twist test if still having trouble. If nothing, it would be good to just reseat the unit and the electrical harnesses I can reach for good measure. Wouldn't it be a hoot to find a partially unplugged VCM under the dash? It happened to my Oldsmobomber before and is a possibility too.

Oh, and there are no codes stored/pending or showing. When the engine dies, it simply dies. Sometimes with a sputter, sometimes with a bump - but never did it throw a code during this new ordeal. It just stops producing a spark and when left to cool for 10 minutes to an hour, starts right up again. Once running again, she will keep going as long as there is sufficient aiflow/speed to cool the under-hood area.

Again, thanks for your help guys. I am going to clean and re-dress deep cuts on my legs and get to bed. When my bro and I try again in the morning, I will let you know if the short taps of the key while pressing on the dist. worked or not.

[wolfox]

Well, it's going to the shop. Try as I might and without climbing atop of the engine, I got my "assistant" to crank the engine for me whilst I wiggled, pushed and even slightly drew up and then pressed down on the shaft assembly. Short taps, to sustained cranking for up to 2 seconds and at least 2-3 complete engine revolutions at a go didn't seat the distributor. I am going to let the pro's get a look at it. When I called them and described the situation in detail he said, "A-yup, sometimes it can be problematic setting those properly." He'll do it for me and set the base engine timing for me @ $55/hour + towing. This situation didn't work out like I wanted, but at least the old gal's getting a god look over by the pros with GM/Goodwrench certification - so they know the truck.

[MT-2500]

Originally Posted by wolfox

Well, it's going to the shop. Try as I might and without climbing atop of the engine, I got my "assistant" to crank the engine for me whilst I wiggled, pushed and even slightly drew up and then pressed down on the shaft assembly. Short taps, to sustained cranking for up to 2 seconds and at least 2-3 complete engine revolutions at a go didn't seat the distributor. I am going to let the pro's get a look at it. When I called them and described the situation in detail he said, "A-yup, sometimes it can be problematic setting those properly." He'll do it for me and set the base engine timing for me @ $55/hour + towing. This situation didn't work out like I wanted, but at least the old gal's getting a god look over by the pros with GM/Goodwrench certification - so they know the truck.

Sounds like you got a problem one there.
Good Luck and we hope them Goodwrench people take good care of you.
Not bad for dealer labor rate.
Let us know how it goes.
MT

[Markgc]

I had the same problem with the distributor on my 89 4.3l. I was working in my shop so that was a lot easier. I took photos and everything was aligned right. Sometimes the distributor would go all the way in but with the rotor arm pointing at the wrong plug lead. I just kept on trying and trying and then SUDDENLY it went in after maybe 2 hours of fiddling around. I had torn the little gasket by then but I wasn't going to take that distributor out again.

I wonder if you can put a screwdriver down there and wobble the slot at the end a little bit. It is a real pain to get the distributor in - just keep trying is all I can suggest.

You will have to unplug the timing wire to strobe the engine - mine was timed at TDC with the timing wire (hidden behind passenger footwell carpet) open circuit.

Send me a pm if I can be of any more help. It will go in in the end. I even had trouble getting the original distributor back in even though nothing in the engine had been rotated. I tried that as a test 'cos I couldn't figure why the new distributor wouldn't go in.

By the way my distributor pickup coil fell apart too but I had 240,000 miles on the engine.

Mark


Mark