No start 2002 Buick Century 3.1

Jim Davis

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#1
Background, 2002 Buick Century limited, 3.1. 120k miles, recent new starter, battery, crank sensor on back of block, fuel pump approx 2 years ago. Only codes are P0135 both in codes and pending. Fuel pressure reads 50-51 koeo, when I do get it started, 52lbs. The car will take run fine for days, then a no start. Will crank fine, seems to spin fast. Good spark. I Cannot get to the injectors to check for pulse, or at least I do not know how. I can pull the intake hose from the throttle body, open the throttle plates and a quick shot of starting fluid and it will start right up and run fine and start for days. I could sure use some fresh eyes on this.
 

billr

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#2
Since it starts with a quick blast of starting fluid, then keeps running normally, I suspect the ECT circuit. Have you checked ECT in live-data during one of those "no start" episodes?
 

kev2

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#3
everything I thought of was a dead end-

I think billr has another great idea... only thing makes sense.
 

Jim Davis

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#4
No, I did not think and check that, and as luck will have it, this thing will probably start and run fine now for who knows, a few days or a couple weeks. Though I guess I could go ahead and get a hold of it and check the data with it cold and hot anyway, may tell me something. Thanks for giving me something to go on.
 

mony0_8

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#5
Might want to check the crank sensor behind the harmonic balancer, had the same problem with '96 lumina w/3,1 engine.
 
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#6
GM has been known to kill the injector circuits with the anti-thief circuit. Older ones used a point contact relay for this that could have dirty contacts. Have to get a circuit diagram to learn this.

Got a good deal from a fellow Cruze owner on a brand new set of shop manuals. Was interested in learning the ABS pump relay location. Is a three volume set with just bits and pieces of the ABS circuit scattered over all three manuals. Just showed a line on one page from the ABS module electronics in volume one, going to the pump in volume 2. So have no idea if this is a relay or not. Sure didn't make tracing a circuit easy. Haven't looked at the anti-thief circuit yet to learn what is killed.

Couldn't even write down the connector pin number on the circuit diagram for this pump. Had to thumb through over a hundred pages to find this ABS pump connector diagram the finally showed the pin number. I am suppose to be good at tracing circuit diagrams, this practically drove me nuts.
 

nickb2

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#7
Ok, here is my $.02 In hot days like this, after all you have replaced, look to ignition module. You say you have good spark, but is it enough. Do you have a spark tester??

These models need to deliver at least 40kv's. :idea: Do a crank relearn since you did replace the crank sensor,

To check for cam sensor activity, I really recomend you check to see if the cam shaft gear has not lost it's magnet. I have seen this often and is a known issue with gm of these years. This was a large with the 3.8l and 3.1l

Easy way is to remove the cam sensor, and just rotate engine till you see the plastic tang that holds the magnet. With a morroir try to look into the hole, do you see it, or just grab a stubby screw driver and feel if it sticks if you can see right with the mirroire. :idea:

Sorry had to modify, not the same as the older versions before 99. Forget it if you do not have a balance shaft, not the system, but the same block :thx
 

Gus

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#8
What do ICM's, security systems, and crank sensors have to do with this problem, if a shot of starting fluid starts the car?
 

nickb2

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#9
@gus, again here is good question. I always have a can of brake cleaner and carb cleaner in my trunk. But never ETHER!!! We did a post on this before here long ago.

I see that this is an intermittent problem, but who wants to always use starting fluid when the intermittent comes around. Better to check basics, spark, fuel and air.

Best thing when no codes show up, is to go to the basic three rule, air, fuel, spark 8) I know you know this gus, but many clients don't.

So just trying to educate and rule out possible problems. Sometimes we here just get a question and no specifics, such as what has been the maintenance schedule, was the client assiduous or just went with was written in the driver manual, and also age of car, etc, etc!!

That is why I get pissed off at service writers, they don't ask enough questions. We as techs don't that kind of access to clients. Makes are job harder with the new tech coming out.

However, these old school 3.1l have been around for century's :ROFL Easy to fix. My $.02
 
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#10
I missed this:

I can pull the intake hose from the throttle body, open the throttle plates and a quick shot of starting fluid and it will start right up and run fine and start for days.
Must have been tired, injectors do not have a choke, but still require an extra rich mixture to start.

One vehicle had an erratic EGR valve that wouldn't fully close so could crank all day and wouldn't pop. Another with a vacuum leak, another with fowled injectors, another with dirty fuel pump relay contacts, also erratic. What about carboned up intake valve, compression would be low.
 

mony0_8

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#11
My thought is the crank sensor behind the balancer is part of the circuit to fire injectors. Don't have a schematic to check.
 
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#12
Would think that would also mess up the ignition, injectors fire at least 90 degrees ahead of the spark plugs.
 

nickb2

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#13
Nobody is listening :mad:

The crank sensor was replaced. :eek:

Ok, had to modify.

I have been reading this magazine since trying to work work this trade in my favor.

Here is a link to this great mag!! http://www.canadiantechnician.com/mag.cfm

It is free if you are a licensed tech!!

the article in question is this one.

The ford missfire article was most honest.

Damn, link did not work. Anyways, if there any licensed techs here, check this out 8)
 

gpcorcor

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#14
These cars were notorious for shorted injectors. If one injector is shorted it will cause a no-start condition (this condition can be intermittent). The shorted injector will cause a high amperage condition and result in the injector driver in the PCM to shut down to protect itself. There should be a harness coming out from under the intake with the injector power, ground and pulse wires (you will need a wiring diagram to identify). There should be 2 injector signal wires, 1 for front bank and 1 for rear bank (they are both driven in the PCM by the same transistor). With the harness disconnected, you should be able to check the resistance of the front bank and rear bank and compare them (or take an amp reading while cranking) - each inj should draw just less than 1 amp.
Good Luck
Gene C.
 
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#15
In 1948, Dumont came out with a scope they claim you needed to check your plugs, followed by the likes of Snap-on, Sun, Marquette, and Allen with wall sized test equipment using modified TV sets. Do you really need all this to check out a 35 cent spark plugs? Yes, a spark plug use to be 35 cents. Now you need a scanner?

Was given a Dumont, would take a half a day playing with those trigger controls to get a stable waveform, for a six, should get six even spikes, high, excessive gaps causing a misfire, lows, the plug was fouled. Was far easier and quicker to pull all the plugs and look at them. Course with some vehicles can be an all day job.

Breaker point ignition was actually better than using solid state, that condenser as it was called, actually a high voltage capacitor would resonant with the coil inductance to give several decaying pulses for a much longer duration spark. With solid state, only get one such pulse. When GM came out with the HEI, some idiot decided to use a 63 mil gap, energy is fixed, so with high voltage, would get a very weak current. Just regapped at 35 mils that was a job to reform that ground electrode.

What has not changed in the last 60 years I have been doing this is carbon problems, after all these years, still a problem.