91 Buick Century 3.3 no start

starting
buick
century

#1

Alright. Here’s where I’m at and losing my mind
Car was running uber rich, so bad that even driving with the windows down exhaust was still strong enough to burn the eyes.
While on a short drive car began to lose power then just quit.
So things that have been replaced in order
Plugs /wires
coils, all 3
crank sensor
battery

Fuel pressure is good
ICM is good
it cranks like a champ but only on occasion will it seem one cylinder fires
When cranking for more then 20 seconds you can smell fuel from the exhaust

Is the timing chain shot? am I even looking in the right place?
should I just look for black market c4 and make it disappear?

60k on on it. It was bought from what I consider a shady shop owner who said it was a old lady single owner. When he inspected it he knew about emission issues so to get it to pass he used PA exempt clause for having driven less then 5000 miles since prior year inspection. Only work he did was an oil change.


#2

If that much fuel is getting in must mean a leaking injector or two. Pull the plugs and see which ones are wet with gas. That is the easiest way to find a leaking injector. All of them leaking, and I’d be concerned about the ECM. That’s assuming you actually measured the fuel pressure and it is between 28-40 psi. If the regulator is bad, fuel pressure could be much higher. I’ve seen a bad regulator let the pressure go up to 100 psi, severely flooding the cylinders.


#3

Fuel pressure regulator leaking fuel into the vacuum hose could cause the car to be flooded. Remove vacuum hose from fuel pressure regulator and see if there is fuel present.


#4

My first assumptions are those given - leaky injectors and/or fuel pressure regulator. Saying “Fuel pressure is good” by the way, doesn’t tell car people anything. For a lot of people, checking fuel pressure means popping the stem on the valve to see if fuel squirts out. But if it does, that doesn’t tell you much. The only way to check fuel pressure is with a gauge, and it has to be within the specs (given above).

If you do eliminate the above, then look at the coolant temp sensor. A scantool is the easiest way, but if you find the resistance specs, an ohmmeter is a good substitute.


#5

I have to go grab a pressure gauge because yes, I don’t know if it falls into spec. Else wise, checked the pressure regulator and vacuum line is dry. Do have some wet injectors so I’m working on pulling them. It looks like 3 of 6.
Is it normal for the plugs to get light carbon deposits just from cranking the engine? Since I replaced them the car has never actually ran.
I don’t have a scan tool, but I’ve tried to pull error codes from the OBD 1, but its clear :confused:


#6

This car is old enough to have thrown the timing chain. Compression test maybe?


#7

yeah, I’m thinking that too. Just because of the way it quit. Ran rich but didn’t hesitate or anything then lost power and finally we are where we are - no start.


#8

So here we are. Compression and fuel pressure are within spec. Timing chain looks brand new, “remanufactured” the cat and she fired up!
so took it out drove a few miles and then I went WOT and it died. Threw it in neutral, cranked it, started, gave a little gas and low side tps error and died immediately.
got it towed home cranked it and it fired up then just quit like the ignition was shut off. Now its just intermittently starting and running. Replaced the icm and still starts when it feels like it. Starts when hot, starts when cold. Just won’t start consistently.
When it is running its idling on the rough side. It’s also showing o2 sensor is bad.
so do I cut the line or try and track down the gremlin ?


#9

What do you mean by “reman’d” the cat? If you have a super rich mixture that can damage the cat enough to impede the flow of exhaust gasses, so when that happens the car won’t run or even start. Like putting a potato in the tail pipe. Have you tried removing the cat entirely, just for purposes of testing the theory that a plugged cat is causing this? There are back pressure tests that can test for this too, and don’t require removing the cat.


#10

It’s been gutted. After we removed the timing chain and it was pristine, clogged cat made sense. that was the first time it started. Ran ok. Started like it should have. Then I took it out, put gas in it and it died on the way home just as described above.


#11

Ok, you knocked the guts out of the cat and removed all the internal debris so it is now just a through pipe. Well, that eliminates the cat as the cause. Since it ran ok after that, but then clammed up, I wonder if there is still something impeding the flow of exhaust gasses? Debris from the cat got into the muffler maybe?


#12

I don’t know. I guess its possible. Issue with that is when it does fire up, it runs pretty good. Throttle is dead on, no hesitation and while in park, it doesn’t bog out. I say in park because I dare not put it back on the road till I know it will start and not just crank. Had the thing running for a few minutes each time.


#13

I like George’s idea about the debris . . . because I’ve seen it actually happen


#14

You mentioned showing an O2 sensor was bad. I assume that means you have an error code or two. There’s no code that can tell you that an O2 sensor is bad, so report the exact code. Does it maybe say the sensor indicates a rich condition? Or perhaps an O2 circuit issue? If it’s about being rich, then you’re still just running too rich. did you check the coolant temp sensor yet? If it’s an O2 sensor circuit problem then you should correct it as the PCM is flying blind on managing the A/F ratio.


#15

O 2 sensor reported lean condition error 44 which makes sense as the exhaust would burn with the Windows cracked at 40 but I have very dark vapor, not blue.temp sensor - when pulled fan kicks on.
If it helps, the car first threw the o2 code while sitting in standstill traffic for 5-10 minutes. Since the cat was gutted the exhaust hasn’t been as acidic.


#16

I don’t know what it means on the temp sensor to say “when pulled fan kicks on.” Do you mean if you unplug it the fan kicks on? That doesn’t tell you much except that the PCM can tell if it’s got a complete circuit. The coolant temp sensor works by electrical resistance. Resistance goes up with higher temps and down with lower temps. At lower temps, the A/F ratio is richer. At higher temps it is leaner. Problems happen when the resistance is off. Maybe it’s 70 out but the CTS tells the PCM it’s 20 - or vice versa. The former case will make you too rich and the latter lean. The PCM won’t set an error code because, while the reading is “wrong” it’s not outside of possible spec. You can check the resistances with a voltmeter at various coolant temps.

Your 44 code does not make sense with smoke out the exhaust. Smoke out the exhaust would mean too rich, but the code is reporting lean.

Elaborate on you check of compression. Were all of the plugs removed what it was checked? Was it held at WOT for the cranking? What were the specific numbers cylinder by cylinder?

How often do you have to add oil, if at all?

I would probably start checking the crank sensor circuit (wiring) as well as the other stuff.


#17

Cig, believe me, I know it doesn’t make sense but that’s where I am with this. I had a local shop do the compression test so I don’t have the specific return but I was assured it was good. Also if there was an issue, wouldn’t it show when it did turn over?
crank sensor was tested, replaced and tested good. Icm was changed out as a, “well maybe its going bad”.
I’m pretty much looking at this like its a short somewhere at this point but at 23 years old I feel like I should just redo all the harness if I’m going to check it all. I’m already 700 in the hole on what was a $1200 purchase and I haven’t even gotten 700 miles out of it in the 7 months I’ve had it. Sorry, just ranting. So even if these sensors were out of spec the car should still start, just run like pop right?


#18

I know it seems like a bad thing, but it is actually a good thing the car won’t start. That makes it easier to diagnose. Engine tech is 100+ years old. You need just five things for the engine to start and run: spark, fuel, compression, free-flow of air in and exhaust out, and timing. There must be something amiss in at least one of those five. Ask your mechanic to take a guess and rule out one item on the list, and then the next, etc, eventually you’ll have to find the cause of why it doesn’t start.


#19

Yeah, that’s kinda why I’m here. The educated guesses haven’t been working out. It’s been in the shop for a week. I’ve been keeping tabs on it since the shop is only a 3 minute walk from my house but I’ve also got to get the car back to put my other car out of commission to do a tranny rebuild. I guess I’m just hoping for someone to have that eureka moment.
tomorrow were getting an odb1 scanner to see if there are any hidden errors beyond the dash codes.