96 Riviera SC not running

Hey Guys,

My 96 Series II, SC with 170,500 miles, won't start. It was running good when my daughter overheated the engine, which cracked a head. I replaced both heads and the car ran fine for a few months. Then it developed a miss which progressively got worse until it finally just won't start. Now, it hasn't been running for 4 or 5 months.

Recently I have installed and gapped new spark plugs, replace both O2 sensors with new ones, cleaned the mass air flow sensor, replaced the plug wires and air filter. I also have a set of spare coils which I changed out.

All of this work had no affect on helping the situation. When I try to start the engine, it would sound like it is trying to start every once in a while, usually when the throttle is near wide open. I think I can detect some coughing back through the air intake system.

What should be my next step? Would a sensor reader work if the car won't start? Any help would be greatly appreciated.

curt

have you tried starting it with starting fluid? 4-5months is plenty of time for gas to go bad, or the engine to collect water from our humid weather.
you may be able to read a code if the car wont start, may not. depends on if it is active or pending code and if it happen the last time it cycled.
does it have spark? can you hear the fuel pump turn on? how about fuel pressure at the schrader valve?

not to belittle your daughter, but most females (especially younger one) dont know jack about cars. They will drive them until it completey kills over.

That being said, are you sure she didnt do anymore damage after the overheating incident? I mean, she cracked a freaking head! thats big time damage. I wonder if you have further internal damage as well.

Yes, I have tried the starter fluid and it didn't help at all. The spark looked pretty good with the old plugs but the new plugs have a much skinner electrode and a much skinnier looking spark but I assume they are ok. I should have mentioned I can hear the fuel pump cut on but I have not check the pressure at the value. I will do that.

In regard to further engine damage I don't believe there is any. The car ran very strong for several months after I replaced the heads. and,.... yea, your right about young females not having a clue. She has one now! LOL

What kind of plugs did you use?

Curt, you asked what's your net step and will a code reader work.

What's your next step? Diagnosis.

Will a code reader work? Yes but that won't give complete diagnosis.

Around the number of miles that you have, the crank sensor on my Riv went bad and at the same time the fuel pump went bad. The problem showed up as an occaisional miss, and one day while driving my wife home from school the car missed and quit, I could not restart it.

Towed it to the dealer. Doug (one of the mechs) at the dealership used a Tech II (GM's handheld computer interface to vehicle systems) to watch and 'freeze-frame' operations as he tried to start the car. He found that the fuel pump was not coming on, even if he told it (via the tech II) to turn on.

So the first thing he checks is the wiring - there is a chance that road debris of corrosion takes out the wires to the fuel pump module (which contains a pressure sensor, a pump, and a level sensor, all asembled helocopter-style (bunch of lo-spec parts assembled by the lowest bidder... if your fuel pump goes I recommend you buy the Bosch replacement module wiht improved sensors and pump. Partsamerica has them... ) Anyway, Doug found that the wiring was OK (GM had a bunch of these things where the wiring went bad at the pump connector) in spite of several years of road dirt and dead leaves piled on top. He replaced the pump and as well replaced the locking ring, and re-sealed the works with brush-on rustproofing (I uppose cosmoline would have worked, too).

So I get the car back and it runs alright, then starts missing again. I figure maybe Doug got a bum pump module - so back to the dealer. Doug checks - car starts and runs OK - he racked up a few miles test-driving it. So I tell Doug, "replace the crank sensor. That is, I am not asking you if, I am telling you to. " Did that basically because of the failure pattern. Crank sensors are Hall effect sensors. Very reliable, But they are a primary sensor in the engine controls, and whn they quit the car's computer and the Tech II diagnostics will *NOT* detect the failure. If the ECU does not get a crank sensor signal, it quits so far early in the starting sequence that no fault is recorded.

See http://www.tec-help.com/TXT_GM_3800.htm, http://www.asashop.org/autoinc/feb2000/techtips.htm, or ust use Google or some such to search on "GM 3800 crank sensor problem" for more.

One problem is that no noe can guarantee that the crank sensor is the prolbem. It may be the ECU (one of he Riv's five computers) or PCM (anohter one). (the other three, by the way - the BCM, MALL, maybe AA remembers the other one unless it's the radio...) But based on my personal experience I'd guess either the crank sensor wore out (when you read the posts you'll see that they go around 150K miles or more) or theECM cooked when the engine over heated and got flaky.

Another problem is that when they fail they go intermittenly. Actually this is somehting that tells me it might be the ECU and not the sensor.

Your problem sounds like the crank sensor is involved but maybe not the only problem. I could be wrong. If you can get the crank pulley off you can replace the thing for less than $50. If you have a mechanic do it, maybe $100 - $150. Thing abouthaving a mechanic do it is that if it does not fix the problem (and the re is a chance it won't) the mechanic thinks you are going to blame him or her for the error. Just the same, I'd replace it or get it replaced if only because I know they crap out around 150K miles, plus or minus a wide margin. The cam sensor is up top, you could replace it yourself for under $40 or have the mechanic do that at the same time.

The other thing I would do is swap the ECU you have in with a known good one and see of the car starts and runs OK. Not sure how to go about that - maybe get one from Ed Morad (check his EBay store, moradparts, or search on web).

Hopefully the above will help. It is way too long - kind of like asking someone what time is it and then they tell you how to build a watch. But I hope it helps, and I don't have time to edit it down right now so here it is.

Hey AA, the plugs are AC-Dleco's ITR4A 15 12568387. Th electrode is very thin when compared to the standard electrode found on the typical spark plug. I don't know if the plug has any advantages over the typical plug. My wife purchased them and this is what the parts guy recommended to her.

Albertj, Wow, thanks for all the information. I can hear the fuel pump running but I need to check the fuel pressure in the lines as mentioned earlier in the tread. You have given me some work to do. I happen to have a spare engine/supercharger setup that I pulled the heads from which may still have the crank and cam sensors.

I really appreciate all the information you have provided me. It will take me a couple of weeks to work through all of this but I will post the results as soon as do.

Many many thanks!

curt

The plugs aren't the reason for your car not running, but they aren't my first choice for our engine. The reason the electrodes are so thin is they're made of iridium. It's one of the hardest known elements, so it will stay in a sharp point for many thousands of miles with little or no wear. In contrast, older style copper plugs used wider electrodes, so the spark jumps from a different part of the electrode each time.

The problem with the spark being focused in the exact same point each time is, that tiny iridium point gets hotter than if the spark randomly jumps from different parts of a large, flat electrode. This, in theory, makes a possible hot spot in a high-compression supercharged engine, which could cause increased knock or preignition. It's only theory, but I believe in extreme situations, it does come into play.

Don't change the plugs out yet (I know they weren't cheap), but down the road if you decide to take you car to the next level, you may consider a cheaper, copper plug in a lower heat range.

Best of luck with your problem.

AA, thanks for the information and the education on the plugs. When I get this thing going again I might just drop to a copper plug with a lower heat range.

thanks, curt

UPdate to chollis:

The crank and cam sensors are pretty cheap, actually. Getting to the crank sensor is a pain due to location. Using the ones pulled from your spare engine is not a bad idea, but is problematic in that do you really know the used sensors are good? I'd bet the ECU is OK

You may want to get a copy of Alex Peper's "Car Code" along with his dongle for GM cars to read the sensors. Software is free; I strongly recommend buying his dongle rather than making your own due to cost/time tradeoff. See http://www.obd-2.com/. Do not be put off by the plain text web page - Peper is just a no-frills kind of guy. Car code will give you freeze frames and actual sensor readings, in addition to allowing you to pull and re-set fault codes et cetera. I use it.

If you hear your fuel pump running, I would not mess with it right now. As you know, there is a Schrader valve on the fuel rail to check pressure. I bet the pressure is fine.

And about those plugs - AA is right enough, however I use the Delcos and have had no problems. They are specified for the car because of the long (100,000 mile) interval called for between plug changes. When I pulled my first set (after a bit more than 100,000 miles) they looked good and the gap had widened consistently but not much. I got mine from gmpartsdirect. If I am not mistaken they are made for Delco by NGK.

If your car's like my car (it is and it isn't, natch...) I'd bet the problem is that one or another of the primary sensors (crank, cam, hey AA what are the other ones that quit but don't throw a code?) has died. Luckily the sensors are pretty cheap - so consider using a good line like Delphi or Bosch for the replacements.

And if it is any consolation, new crank sensor may improve mileage a little bit because the ECU will no longer have to interpolate soem of the control data.

All the best, and keep us posted.

Albertj

Hey Albertj,
Thanks for the update. I plan on checking the fuel pressure anyway as it is pretty easy to do. I think I will take your advance on using new sensors too! The AC-Delco plugs I used did have "NGK" stamped in the metal base so you are correct on who makes them. I will go ahead and order the crank and cam sensors and probably the other ones if AA chimes in on what they are.

Thanks again!
curt

[quote="albertj"
It may be the ECU (one of he Riv's five computers) or PCM (anohter one). (the other three, by the way - the BCM, MALL, maybe AA remembers the other one unless it's the radio...) But based on my personal experience I'd guess either the crank sensor wore out (when you read the posts you'll see that they go around 150K miles or more) or theECM cooked when the engine over heated and got flaky.

Another problem is that when they fail they go intermittenly. Actually this is somehting that tells me it might be the ECU and not the sensor.
.[/quote]

When you say ECU, are you referring to the ignition module? (mounted with the coils)

and then 2 more quick questions:

Where is the BCM?

and What is MALL?

quick tidbit - a bad cam sensor will not cause a no start condition.

Sorry guys, having never experienced any sensor problems, I'm not the one to ask.

AA wrote:

Sorry guys, having never experienced any sensor problems, I'm not the one to ask.

to me, you are lucky as a leprechaun.

turtleman wrote:

AA wrote:

Sorry guys, having never experienced any sensor problems, I'm not the one to ask.

to me, you are lucky as a leprechaun.

i've never heard of MALL or BCM on our cars before either. assuming the bcm is the body control module, how would that make the car not start?

the crank position sensor and the vats key seem to be the 2 most common no start problems with our cars.

I had a similar problem about a week ago with my 96. Granite, my engine is in tip-top shape, but it would not start. I had a bad fuel filter that was clogged with gunk. Might want to try that. 10 minute fix and it ran great. Good luck

ECU is the spark unit under the coil pack in engine compartment.
PCM is the transmission control box, inside the car.
ABS (brakes) has a computer.
MALL is the body/lock/remote controller, under the rear deck lid between one of the stereo speakers and the CHMSL (center high mounted stop lamp)
BCM is the body controller, monitors seat belts and position memory and such, is under the drivers seat.

If you do not have a used ECU ( I don't ) try Ed Morad to get a used ECU, GTPED@msn.com or ebay, "Morad Parts Company."

ALSO news flash be sure to check the grounds, especially the ground strap on the front passenger side frame rail. Before you do anything else. If that ground has gone bad it will stop your car. For some reason all this talk about computers in the car made me remember, this happend to me once.

Finally sorry about the cam sensor, I think turtleman is right. I think the ECU compensates for a missing cam signal to a certain extent. Someone else please chime in here.

If I was you, I would check that ground first before I did ANYTHING else. I really wish I put that in my first post. A quick and dirty check is to use a booster cable to clamp from the ground wire (NOT the post) to a clean ground on the car somewhere else like the engine. Then try starting car.

Second, I probably don't need to tell you this but please please please disconnect battery (detatch the ground line off the battery under the back seat, if you don't much stuff stays live) before you mess with the control computers. AND before you disconnect battery, turn OFF the theftlock on the radio otherwise it will quit working, too.

best of luck again and I hope this gets you going.

Reflecting on this, what do you want to bet the problem is that &$^#*&$^ ground line?

If the ground is bad try some PB blaster to loosen it, you will have to go behind the inner fender to spray the bottom of it. If you bust it, just dril it out and use a tap to rethread for a stainless steel bolt - cut the head off the bolt and use a pair of nuts (one to set depth and the tther to jam) to put it back together. Cut a slot in the bolt so you can screw it in with a screwdriver, get it in about an inch then spin a nut on to hold it on the frame. Put the terminal back on adn spina second nut on to jam the works and hold the terminal. If you do happen to get it apart clean it real good & use battery terminal grease/tune up grease to coat it so it does not corrode so fast on you next time.

All the best and as usual hope this helps.

Albertj

[/i]

Aside to Mr Riviera - BCM won't give you a no start. That was just me overexplaining -- sorry.

Albertj

Wow, I'm getting quite an education here! I was going to order the sensors this evening but I will check that ground wire as you suggested first.

He is one thing I don't get. If a sensor is giving off a no-start would I still have spark at the plugs? Because I do have spark at the plugs. Kinda makes me want to check the fuel pressure at the injector rack. What do you think?

Hopefully, I can get these things checked out on Thanksgiven day.

curt

I am away from my manuals so I can't check order of operations, but I think you get spark w/o crank sensor. Riv has a 'waste spark' setup that fires 2 cylinders at a time. Someone please check me on this.

A seonsor won't give a 'no start' signal. If a signal is not proper, typically the next event in the sequence won't happen. If cam sensor is reporting rotation & you get sparks, is different from crank sensor is reporting rotation & then ECU turns fuel pump on. I can't answer this one.

I see no reason not to check fuel pressure. I also see no reason not to check the grounds.

Albertj

I hoped to check them Thanksgiven day but it rained so I will check these out this weekend.
thanks for the help,
curt

So, Curt - what happened?

Albertj

Hey Albertj,
I have plenty of fuel pressure so that checked out OK. The ground wire was good and that checked out OK. I ran two jumper wires just to double check it and still no start.

I started on removing the crank sensor, pain in the a$$, but I will have to finish it sometime this week after work.

I appreciate all of your help,

curt

All the best, hope the crank sensor change fixes it.

You can verify the crank sensor is bad by heating it - boiling water works. Use 'gator clips to connect it to an ohmmeter. If completely dead it will be open circuit. If it is going bad, when it's that warm if it is bad it will open, and then when it cools back off it will go back to normal.

You know, before you pull it you might want to pull the connector and read it with an ohmmeter. I think the factory manual says what it is supposed to read, and if it is just open then you have found your criminal.

Albertj