New guy with a few questions - Car shuts off

Hey there everyone. I am the proud new owner of a pearl white 1997 supercharged Riv. I bought the car with a problem, though. Car shuts off randomly for apparently no reason. Did some searching and sounds like a bad crank sensor, right? What about a bad PCM? Maybe some kind of ground problem? No codes on PCM and previous owner was told by reputable repair outfit that it needs a PCM. What can I do to find the culprit before I go buy parts? Any help is appreciated greatly.

Thanks!
Tom

When you say, "shuts off" do you mean all electrical accessories and the engine? Or just the engine? And welcome to the site, very informational.

welcome here!
give a little more info if you can.
these guys/this site is great.
we/they will help every possible way.
my (ex)wife had a le sabre w a 3800 that would randomly die for no aparent reason, untill i tightened the battery connections- solved that problem.
congrats on ur riv... u'll get it worked out soon.
good luck

Welcome. The PCM should be fairly inexpensive, and it's easy to swap out, but I doubt it's the problem. Very rare to see a bad PCM. I would suspect the crank sensor too.

Engine shuts off but electrical stays on. I think I will go the crank sensor route. Seems most likely. I saw a write up on removeing harmonic balacer. Anyone do a good writeup on replacing the sensor start to finish? I have done this type of thing before, just not on this car. Any helpful tips? I didn't really find what I was looking for by using search.

Thanks again!

Sounds like you got a bad crank sensor.

If you have removed/replaced a harmonic balancer before you are alll set. You already know how to use a puller. So the only thing I can think of that you need to think about, I think, is having some way to hold the engine in place if you remove the front engine mount. Might want to get your hands on a service manual (for almost anything with a GM Series II 3800 engine) to check me on this. When I had mine replaced at the Buick dealer I think they charged me $120 - $150.

By the way while you are at it with the balancer, you might want to replace the front engine crankshaft seal and the idler pulleys if that has not yet been done. Might want to get the Timken Viton seal, along with a quik-sleeve in case you need it - if your seal is not leaking yet you might not want to bother and you almost certainly won't need the quik-sleeve, BUT those seals fail before 200,000 miles (mine failed bad at about 180,000) and if you're thinking keeping the car that long, you can slip the sucker in there and avoid the hassle later. Check RockAuto.com or NAPAOnLine.Com.

The goofy thing about the crank sensor problem is that it sets NO codes, and many mechanics have never seen the problem before. Have to recognize crank sensor from the failure pattern (engine quits/accessories on). A medical doctor would likely call it a 'diagnosis of exclusion' because there's no code or other symptom that points to the problem. Anyway - for whatever reason, the crank sensors on these cars tend to crap out after so much age (~10 yrs) or mileage (~150,000 although I have heard of ~80,000). I would not be surprised to find that many of the ones that have been traded in/junked were dumped for this reason alone.

And oh by the way - I was told once don't get the cheapest sensor - get a good one, a Delphi or a red-box or blue-box Standard, or an Echlin, because the cheap ones quit quickly.

Albertj

You can do this without needing to use the crank sensor alignment tool but you need to be able to get your head in there to look for clearance as you're installing the balancer. There are two rings on the back of the balancer, they need to fit in between the teeth on the new sensor without interference. As the balancer starts to slide onto the crank, have a look at the rings and the sensor to make sure there's no contact. Doesn't hurt to turn the crank by hand to make sure.

And handle the balancer with care so you don't bend the rings - that'll eat your new sensor before the car even fires.

My $.02. Remove right (pass. side) wheel/tire and plastic inner fender well for better vision and work area.

Check fuel system. Filter first cause it is cheap and then the fuel pump which isn't.

sburch23 has a good point!

If your 'random' shut off occurrs at any time (like, sometimes it won't start adn sometimes it will run all day) another typical problem is either the fuel pump goes (and for some reason they are really cheap on the aftermarket right now, try Google Shopping) or the wiring gets corroded (more likely than you think, you'll understand when you take a look at it). There is an access panel under the trunk carpet, fore of the rear axle, that you can remove to get to the pump. The ring that holds the pump in is usually corroded beyond hope - you will need to order a new one thru the dealer, the pumps do not come with. The dealer and the parts store RockAuto.Com both sell wiring repair kits. Kit is just a new connector with wire pigtails haning off it that you splice in with weather tight crimp on connectors (a walmart or auto part store item).

The crank sensor thing is that it's a Hall Effect sensor, and it changes size a little from the heating and cooling of the engine. The changes are minute, and if everything else is normal don't make a difference. Problem is - after enough of this'thermal cycling' it gets to the point where when it heats up the elements in the sensor no longer stay positioned to work properly. Typically what you see is it starts when stone cold, you drive for a while and it is fine, you stop for 20-40 minutes and then it won't start for an hour or more. Sometimes what you see is you're just driving along and it quits.

By the way - what happened to me is my crank sensor and fuel pump were failing at the same time. That was tough to figure out. FIxed the fuel pump first, had to tell the mechanic to replace the crank sensor 'customer request' because there was no code showing and the failure was not consistenly repeatable.

Albertj

I really appreciate the info you all have given me so far. I have not yet been able to really try to do any troubleshooting with the car. The day I bought it, the car shut off after about 10 minutes. I let it sit for roughly 5 minutes and it restarted and has not shut off on me since. I let it run in my shop for an hour and watched the cooling fan cycle. It got plenty warm but did not stall. I drove approximately 20 miles to a friend's shop and it never shut off on me then, either. We messed with it a little (jiggled wires, visual inspection, scanned for codes) all with no results. I will check wiring for fuel pump and replace crank sensor. I am just kind of hesitant to start driveing this thing until I find the problem and fix it. Thanks again for the help and I will post findings.

Crank sensor in, loose battery cables tightened, oil changed, sway bar end link replaced. Car no longer seems to have a problem. Thanks again for the help! These cars rock!

By the way, there is a decent article about crank sensors at

http://www.mightyautoparts.com/pdf/articles/tt64.pdf

And good call on your part to check/clean/tighten battery cables. The riv has I think 5 computers and NONE of them like low voltage or intermittent/spiky power. As long as you are at it, be sure to check the starter grounding post - it is in the front of the engine bay on the frame rail, passenger side, below and fore of the positive terminal post in the engine compartment. If it ain't corroded you might not want to mess with it but if the post or the cable is corroded, pick a day to get in there to disassemble and clean it before it starts to give you headaches. I actually replaced mine with a stainless steel bolt a couple years ago - was having a problem with starting that the dealers' techs could not find (gee it tests OK?!?!). A half-hour with the wiring diagram and asking "what did they tell you in school about how teh startup sequence works?" helped me figure out what in general was wrong - and one look at the post did not help. When I disassembled it I found that the connection on the frame, which is hidden when it's all screwed together, had corroded. So I busted the old bolt out and drilled/tapped the opening to accept a new one. Heated the corroded area to get the oxygen out of the rusted area then used a torch and some solder to plate the contact area (with rosin-core solder). This gives you a connection that has negligible additional reisstance, but won't corrode from engine compartment conditions because it's not steel. And so won't turn into a nightmare later.

As they used to say, 'happy motoring...'

Albertj

Well, bad news. Drove it to do some Xmas shopping for my daughter today and it shut off on me again. Will not restart. I am not sure which way to go on this now. Fuel pump maybe? Computer? I don't have access to a fuel pressure gauge until tomorrow. Is the pump supposed to prime before starting? If so, I think it's dead because I don't hear anything. Grrr!

yes,,, when you turn the key, you should hear the pump kick on

Hmmm....

You did look at the fuel pump wiring, right?

At a dealer or well-equipped independent mechanic they can "command" the pump on using a Tech II scanner. I remember getting a Check Engine light while traveing in Pittsburgh, going to a Firestone out in Pleasant Hills on a Sunday and being Very Surprised to see that they had several GM-trained mechincs no staff (there is/was a GM training center in Pittsburgh area). Point is the trained mechanic can use that device to tell pretty quick if the fuel pump is bad, as long as the fuel pressure and volume sensors in the car are OK (they most likely are).

As for yochecking it yourself, actually, if the car is in a quiet environment and the engine is off, the fuel pump is pretty loud. When car is cold and you turn the key to ON it will whirr. If car is cold and you turn key to ON and you either hear no Whirr, or a Whirr that wavers, odds are your fuel pump and/or the wiring to it are bad.

By the way, one way to toast these fuel pumps is to run the car with less than 1/4 tank of gas. A dealer mechanic told me (we were BSing not replacing my pump) that people who run their cars near empty frequenlty are almost certain to cook a fuel pump, because the way the OE pump is designed it depends on the fuel for cooling.

Albertj

Hopped in it last night, turned on the key, fuel pump primed just like it should, started right up. I have not bought the pump yet. I just want to be sure I've checked everything before plopping sown the cash for the pump. Any thoughts?

Next time the car dies, check the fuel pressure. There should be a schrader valve on the fuel rail that you can connect the gauge to. If you have over 30 PSI and the car won't start, you can start looking at electrical.

Solid state components like the ECM usually don't have intermittent problems - they're either fried or not. Since your fuel pump primed, it sounds like your ECM and fuel pump relay are fine but that doesn't mean the wiring in between them are fine too.

When it wasn't starting before, could you hear the fuel pump priming?

I wonder if it is a problem with the theft deterrent system? Is your "SECURITY" light active?

Albertj

When it died the last time, it would not restart at all. I had it towed home (ouch) and tried to start it after leaving it sit for 4 hours. Pushed the schrader valve and had no fuel at all. That's when I noticed no fuel pump prime when I turned on the key. After the car sat for an additional 2 days, the fuel pump primed at key on and car started normally. I have not had an "active" security light. It will come on when doing the key on self test, but goes out and stays out. I sure hope a fuel pump takes care of it. I want to start using and enjoying this thing! Thanks again for the help.

Sounds like either:
VATS (ignition switch?)
Fuel Pump Relay
or
Fuel pump

But usually, when the fuel pump dies, it's dead. So it's most likely the relay or the security system.

I agree with Deekster.

Albertj

I was thinking VATS/loose key too but he said he scanned it and VATS should throw a code.

Fuel pump prime is part of the ECM diagnostics, it should prime when powered up regardless of VATS signal. Vats will not stop the car from firing initially but only runs for a half second until the priming pressure runs down. I could be wrong here, based on my data being from OBD1.

Find the fuel pump relay and probe the green (?) wire while it's still plugged in. I had an ECM once that would show 12V at the relay when not connected to the relay but only 0.7V when connected - not enough to close the relay and turn on the pump. The only way to start that car was to crank until the oil pressure switch closed the fuel pump relay. Not fun.

Based on your last post, I would say your problem definitely lies between the ECM and the fuel pump. VATS may still be a player as I'm not positive how OBD2 VATS functions exactly. I'm leaning toward a bad fuel pump relay or insufficient voltage to the relay.

Next time it won't start, check for voltage at the relay - both on the ECM side and the fuel pump side. This will narrow it down a lot. Does your fuel gauge seem to work properly?

I don't know if they still call it VATS, but if the key 'chip' isn't reading correctly, it won't enable the fuel pump relay. I have dealt with a few cars where the ignition switch was the cause.

I replaced the fuel pump relay and car still starts and runs normally. Battery cables were loosish again. Not sure how that happened. I can now hear the relay closing and the fuel pump priming. Started it and drove around the neighborhood. Shut it off and restarted about 50 times. No problems. I started it after driving the first time and it would chug. I gave it some pedal and it came right out of it. Only did it the one time. This is getting troublesome. The more I mess with it, the less convinced I am that it needs a pump. Runs hard at wide open. I am confused.