Any mechanics in the house?

1997 5.7 Vortec 350 with about 55,000 miles on it. Truck died a few weeks ago while sitting at idle at a stop light. No warning, no previous symptoms, just died as though someone had keyed the motor off.

I have a “no spark” scenario that I’ve had a bear of a time fixing. The fuel pump primes, 60 psi at the rail, and the motor turns over but no spark. So far I’ve replaced the fuel pump, coil, ignition control module, cam position sensor, plugs, wires, cap, rotor and crank position sensor. Still no spark..

Having said all that, my question revolves around the crank position sensor. Is this normal wear? Something to worry about or do I just need to shim the new one?

Ask REALKILLER

He just positioned his crank at Walmart

I have no clue, texaslefty might.


fyi, I would not use that terminology anywhere in east Texas, you may be mistaken for a narc. just sayin.

That crank sensor causes some concern for me......

Did you check and make sure the distributor is turning?

Besides the CPS you’ve replaced all the typical suspects....

Feel free to PM me.

Where did you buy the parts from?

Retest all the parts you replaced.

Just a thought, have you checked the fuses? Since you have replaced the most common suspects that would be my next step.

Timing chain?

Have you checked the fuses in the engine bay fuse box?
Have you checked for codes / DTC's? Even if the engine light didn't come on it is common to get P0300 PO335 codes with crank sensor problems.

No, the crank sensor shouldn't be worn or scratched.
I think the air gap spec is .030+ so if the new crank sensor contacts the reluctor wheel I'd use a shim.
Check or replace the wire/harness & connector while you're at it, common they go flaky too.

Also all parts are not created equal, one of those parts I'd get from a GM dealer or a supplier that doesn't deal in foreign made domestic car parts.

Get a new one, it's a common problem on the 5.7 Vortecs. I washed my Tahoe one day and killed the dam thing. Put a bit of silicone around it when you reinstall. DO NOT BUY FROM THE BOX STORES, trust me. Get it from the dealer or OEM from NAPA.

Thanks for the advice and help! This truck is a bit of a Frankenstein. This engine and transmission was transplanted into my Studebaker several years and is on a stand alone harness. The original owner swapped the original 1997 black box ECU for a newer generation “411” ECU with custom tune. This requires re-pinning the connectors over to the newer ECU. The truck has been running great for months and several hundred miles since the swap so I feel fairly confident that the ECU swap was done correctly.

I have checked every fuse, relay, wiring harness, tested for voltage at all sensor inputs/outputs and all other troubleshooting that I can do with my limited knowledge. Everything seems to be in order. My primary concern now is that the Crank position sensor has somehow fried the ECU. I do have an OB port and there are no DTCs. Unfortunately, I unplugged the battery to test wiring continuity on several sensor circuits and didn’t know it would erase DTCs. I thought they were stored until manually erased. Now I know better..

I believe the distributor is turning as I had to “bump” it over to line the cam position sensor for removal.

I’ve bought most of the parts from Orileys and NAPA, always opting for the higher quality parts they offer.

He’s right

Unable to help until we see PHOTOS!

Not the best pics but what I have..

Sharp looking ride, hope you find out what is wrong and get it back on the street.

Now that is a REAL truck. Reminds me of a guy I went to high school with, same truck, painted bright yellow, his dad worked for the North Dakota highway department, we accused him of using highway center stripe paint. Chevy 348 with a 4 speed transmission.

With dissimilar ecu/pcm swaps especially dealing with older vehicles improper or insufficient grounds are often the cause of electrical gremlins.

Can you check voltage going into & out of crank sensor while cranking the engine with what you have?
Texaslefty probably knows the actual spec, I think the range is 9.2v - 7.2v in ~ 6.2v - 5v out.

I doubt the crank sensor itself can fry the ecu. Their wiring harness & connectors are famous for malfunction.
It isn't uncommon for pins to 'drop out' when you do a dissimilar ecu/pcm conversion, or have a situation like going from any 2 - 4 pin sensor from old ecu to a 3 - 5 pin pin sensor on new ecu.
But that's a stretch if you've already checked everything out & everything is okay.

The newer ecu probably controls/triggers the alternator charge & voltage regulation, any mistake in wiring / pin over conversions like above from old to new can jack stuff up.
They'll run a while, maybe 10 minutes, maybe 20 hours then poof electrical feedback fries circuit(s) in the ecu.

Some places can test the ecu for full function off the vehicle you may be at that point.

Rustler has given some good advice. Never heard of a CPS affecting an ECU as it's just a pickup, not energizing anything. Ground would be a very good culprit for sudden loss of spark, but so would a bad CPS...

The obvious contact on the CPS is a troubling problem as it shouldn't contact anything... I'd try to get some light on it and a pic of the crank reluctor, that's more than just a little contact.

Charlie

I can't help but say that's a beautiful truck and I'd own it even if I had to push it everywhere. Nice ride Misfire, I hope you get it figured out.

I’ve gone over the CPU re-pin quite extensively and have found two ground leads called out in the wiring schematic for the new CPU that are not installed. There is only one ground per connector terminated and the schematic calls for two. This is due to the old harness not having wires to go to the second ground positions. I did not notice this until after the truck quit running. (Really paid no attention to the conversion because the truck was running great.) this could easily be the root of my problems. I have already spoken to the “tuner” and he has a newly programmed CPU on the way along with extra pins so I can add the two additional grounds.

I had read somewhere that if the Crank Pos Sensor picked up metal filings enough to make contact it could “short a circuit.” That may be total nonsense which is why I was asking here.

If running additional grounds and installing a new CPU doesn’t fix the motor I’m going to have to find someone to take the truck to. I’m about as far as I can go with my limited knowledge and abilities.

Again, thanks for the help and advice guys!

Ground problems usually show up fairly quick, you'll notice odd unexplainable electrical gremlins, intermittent / temporary glitches in almost any part of the elec systems.
If they go unnoticed it leads to bigger problems.
Anything from a light that flickers for 2 seconds, to a slight miss or an occasional stumble on acceleration, taking a few crank longer to start, any noise in audio systems, alternator that buzzes, clicks or has a intermittent whir, really almost any little random funkyness.

If you find the ecu is damaged at all, I would pay very close attention to the alternator connections & compatibility with the new ecu.
An ecu expecting to see inputs from and being able to control outputs going to an alternator mis wired or going to an incapable / older alternator will wreck a new ecu also.

This is a big stretch of the imagination, the only way I can see a crank sensor causing any ecu damage is from a large 'static' build up due to contact between the crank sensor & reluctor causing a harmonic discharge feed back in an amount of voltage capable of damaging the ecu..

Right up there with the one & only time you buy a lotto ticket you hit the 20 million jackpot. Not totally impossible, but.

Again, no the crank sensor should not be scratched, eat up, ground against, have much more than very light swirls almost as if made by dust or 400 grit emory.
The last one I bought came with 2 shims.

Consider the reluctor has been grinding on your CPS for some time, you've had direct contact with the reluctor for some time. The above is not the issue.


So just as I was about to hit post.... How did that CPS wear like that? I don't see how it could have even been installed, if that much has been eaten away as it appears? It certainly wouldn't get slowly chewed on over time. as the reluctor and CPS are in fixed positions, assuming the reluctor isn't loose or broken.

Did someone by chance grind that to make it fit? Something isn't right with this....

Charlie

Surprised no one has asked if you have tried dry humping a spinnerbait whilts you were in the truck ? Asking for a friend.

I would take it to a hot rod shop. I'm sure they could track it down fairly easy. I've done a engine swap and full rewiring myself. When you put something into some where doesn't belong you can't follow regular troubleshooting format because of all new variables added to the equation. The fact that it ran and then stop as if you turned off the key could possibly be from the ECU. Get the ECU pin diagram and trace the signal all the way back to the plugs. To save time, you work from the ECU out. Man it could be anything from a ground that got loose, a wire rubbing and getting frayed and making contact with the chassis, to a Pin backing out, a wire getting fried from the exhaust, and on and on it goes. Good luck.

I agree, has me worried too. This is the OEM sensor. What I read online is that with regular wear and tear bearings loosen up and things move ever so incrementally (Crankshaft, reluctor, etc..) and could cause some contact. The directions that came with the sensor say to use shims, if necessary, to achieve .030” clearance. This may not address a more sinister underlying problem but it seems common enough for them to supply shims with the sensor.

I have no way of measuring the contact groove depth so I used .060” shim when I reinstalled.

.

Shouldn't be any crankshaft walk with only 55,000 miles on it. Something you'd see on a high mileage, severe duty or abused engine.

Now if someone rebuilt it at some point easy to do a crappy job and end up with stuff like that.