iansane

iTrader: (1)

So I was having a cold start issue that was progressively getting worse if the car sat for a few hours or more. I'm *assuming* it's related to my currant problem but I don't know for sure. I had thought the fuel pump was going out but got around to checking pressure and it's ~55psi key on, engine off and ~60psi while cranking.

I pulled a plug and it's covered in fuel so again I'm *assuming* that I'm not getting spark. The car cranks and cranks and cranks and sometimes will hiccup out the exhaust. I pulled a coil connector and I get 12v pink, ground on black and the others I get nothing but I don't have a person here to crank while I check with the DVOM. Nor do I have a scanner to look at the sensor outputs. I checked locally on LSxnation and LS1tech to see if anyone had a scanner to help me but no.

Any ideas guys?

one92rs

iTrader: (5)

you dont have an extra cam or crank sensor around do ya?

iansane

iTrader: (1)

Actually I did have an extra crank sensor but I don't know if it works? I had another 5.3 I picked up awhile ago for another project, slapped in that motor's sensor and it didn't change anything. However, I don't know if it was a functioning sensor because I got that motor off craigslist.

BlueZee28

iTrader: (30)

I'd buy a new crank sensor, it's around $50-60 and try that. My motor was a pullout on craigslist and I had the exact same issue and when I replaced th crank sensor it fired right up.

Pocket

iTrader: (24)

Crank sensor is the biggie for LSx engines, but Id check that the plugs are not firing before buying one

No fire and your grounds are good, then buy the sensor. You may have to do a crank relearn

From the coil connector, your only testable points are the IGN and ground pins. The low ref wire is to the PCM testing a return voltage when a coil fires. No voltage when expected is part of how a PCM determines a misfire occurs. Each of the colored wires driving the coils gets a very brief (think miliseconds) 12v signal to fire. Its so fast your meter wont read this. Only way to test these is to unhook the red connector and do a continuity test across the 8 wires. An O-scope will pick this up, but most places dont have them anymore

If your crank and coil circuits check out, try testing for leaky injectors fouling out the plugs. Unplug the injectors, pop the rail out and prime the pump. If fuel dribbles out, those injectors are bad

LSx engines will fire in nearly every circumstance. I once forgot to plug in 4 of my injectors (whole pass side bank) and it still fired up. It ran like crap, but it ran. The only sensor it absolutely cannot run without is the crank

iansane

iTrader: (1)

Grounds are good. I had a problem with those when I first got the motor in. Only had one and almost burned it away.

I pulled a plug and put it to the strut tower bolt and got nothing so I'm "presuming" no spark.

Crank relearn? Is that a necessity? I remember not doing one with the initial fire up last year.

This confuses me a bit. Which connector? You mean check continuity from the pcm connector out to the coil connector?

While I was still ruling out fuel issues I yanked the fuel rail out of the manifold and pressurized the system and got no leaks overnight.

Thanks for the help guys. I really appreciate it. I think first I'm going to make sure the wiring to the crank sensor is kosher and then replace the sensor itself with a new one.

Pocket

iTrader: (24)

Do a continuity test from the coil connector wires to the PCM. You can use a scope across the wires you just tested to see if a signal is being sent

The STB isnt the best place to ground a plug because its either painted or PC. Hold it next to the cyl head, header or a bare bolt head

GM states a crank relearn is required when you change PCM, engine, crank sensor, cam sensor, or disturb the balancer. If the code is not set it generally is not required, but not always like with my engine. If you've ruled everything else out, then do a relearn

Crank sensor wiring is often burned against the header, but is quite obvious if this is done. Hope its just a dead sensor

iansane

iTrader: (1)

With key on, engine off; what do the pins on the CKPS see? One obviously 12v but is it like the others that get 5v and ground?

iansane

iTrader: (1)

Wish I still worked at the dealership right about now. The coil connector>pcm wires are good.

I've always had great luck using the bolt but you're right, the block/head are probably better choices!

Everywhere I've read you have to have a scanner hooked up to do a relearn. Is there another way?

The wires looked good. I tried to make sure I routed them so they wouldn't get hit by the headers. The continuity test looked good too. I'm leaving now to go get a new sensor as it looks like that's the culprit. Hopefully.

Edit; I'm actually a little perturbed that I get help within a few hours here at TGO. And on LS1tech I got almost nothing in a few days. Meh. Just show how much better this subforum is.

BlueZee28

iTrader: (30)

For what it's worth, I never did a crank relearn on mine, and I got the ECM from ebay with a reflash off a VIN I got on Ebay.

To me it sounds like the crank sensor is bad. I hope that's the case for you because it's probably the easiest fix at this point.

one92rs

iTrader: (5)

most if not all sensors will run a 5v reference.

Pocket

iTrader: (24)

Crank sensor has a 12v pin, 5v signal and low reference

iansane

iTrader: (1)

Aaaaaannnndddd, it was the crank sensor. You guys were right, thanks Blu and Pocket. Haven't driven my bird in days. I feel like a heroin addict that missed his last few fixes. Just give me the juice man!

When I pulled the connect there was one pin that had sunken a bit into the housing? I don't know if that made a difference but it still had enough material there to be making contact (it looked like).

ericjon262

congrats on getting you're bird back, I'm wanting to drive my RS so bad I'm looking at buying another one!

BlueZee28

iTrader: (30)

Glad we could help. If it makes you feel any better I haven't driven mine in over 3 weeks. And it probably won't see the road this weekend like I had hoped.

Pocket

iTrader: (24)

Pop the rear lock cap off and give the wire a light tug. If it comes out the locking finger needs to be reset. If it doesnt budge, then dont worry about it

iansane

iTrader: (1)

Well...I enjoyed driving while it lasted. Went into town this morning and came out of the pet store to a no start situation again. Crank and crank. Went back inside for 5 minutes, came out and after a few hiccups and sputters it started up unwillingly. I knew I should get home quickly but I barely made it out of the parking lot before the car just died. Coasted into an O'Rielly's parking lot and tried warrantying out the crank sensor. At the same time I pushed the wire back into the connector body. One terminal *looks* off. It's at the same level as the others but rotated a bit in the housing. The car won't start at all now. I pulled the pcm in the parking lot and check continuity again between the pcm and connector and it's good. It's no spark again. I think I need to replace the connector? If I yank on the wire I'm sure it'd slide right out the back.

Pocket

iTrader: (24)

Most FWD econo cars use the same MAF connector as the LSx crank sensor. Grab one from a JY or I can send you one

If your terminals are still in good shape then depin the old and push them into the new, otherwise cut and solder

iansane

iTrader: (1)

Thanks for the heads-up. I'll try to get to a yard tomorrow and find a connector. Are we talking like 90s cars? The pullaparts around here never really get anything newer than 98 or so. And for some reason, a ton of saturns.

Pocket

iTrader: (24)

90's work fine

Saturns may be a bad apple, most of their stuff is wierd, I avoid them when shopping for wiring