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1994 Buick Lesabre won't start


jimwalker
12-03-2005, 07:07 PM
This is a tough one. I have 94 buick lesabre with 170K miles my brother gave me. He had taken it to the dealership and they scanned it and said that the intake and valve covers were leaking and wanted $1100 to fix it. He decided it wasn't worth it and gave it to me. The symptoms were missing badly at anything except idle and smoking under the hood. It would barely do 40 floored. I replaced the intake manifold gaskets, plenum (seperate part on this engine) gaskets , injector O-rings, and the valve cover gaskets. When the repair was complete the engine was much better, not smoking under the hood and did 80 no problem on the hiway. As I continued road testing I noticed that as it warmed to normal operating temperature power would fade and the transmission would refuse to backshift even with the peddle to the floor. The repair manual I am working from suggested fuel delivery problems or vacuum problems. I replaced and then pinch tested every vacuum line there was with no improvement. During more trouble shooting and test driving it became clear that the problem was temperature related. The car ran fine cold then as it warmed up the power and shifting problem got worse and worse and the engine would lope during idle slightly. With more test driving the car began to die at stop signs after warming up. The last time I drove it and it died at a stop sign, I had to crank for a long time but it did finally start. I parked it a week ago intending to continue trouble shooting this weekend but now it refuses to start at all after sitting for a week. I checked for spark and was getting good fire so I moved to the fuel system. I listened for the fuel pump to spool up and it does. I checked the fuel filter and it was flowing. I checked for pressure at the injector fuel rail by pressing in the needle at the valve for testing fuel pressure and gas sprayed out spiritedly. I pulled out the injectors and cranked the engine and the injectors did nothing. To rule out that there might be some catastrophic mechanical failure I squirted some fuel into each injector port, plugged the injectors back in, and cranked the engine. It fired right up for a second or two and then died.

Sorry for all the background, but now at last here are my questions....

Are all these problems possibly related?
The manual I'm working from doesn't say anything about why the injectors might not be firing except for checking manifold ground wires, which I see none of. I don't really know where to go from here, thanks for any help.

Jim

maxwedge
12-03-2005, 07:39 PM
This is a tough one. I have 94 buick lesabre with 170K miles my brother gave me. He had taken it to the dealership and they scanned it and said that the intake and valve covers were leaking and wanted $1100 to fix it. He decided it wasn't worth it and gave it to me. The symptoms were missing badly at anything except idle and smoking under the hood. It would barely do 40 floored. I replaced the intake manifold gaskets, plenum (seperate part on this engine) gaskets , injector O-rings, and the valve cover gaskets. When the repair was complete the engine was much better, not smoking under the hood and did 80 no problem on the hiway. As I continued road testing I noticed that as it warmed to normal operating temperature power would fade and the transmission would refuse to backshift even with the peddle to the floor. The repair manual I am working from suggested fuel delivery problems or vacuum problems. I replaced and then pinch tested every vacuum line there was with no improvement. During more trouble shooting and test driving it became clear that the problem was temperature related. The car ran fine cold then as it warmed up the power and shifting problem got worse and worse and the engine would lope during idle slightly. With more test driving the car began to die at stop signs after warming up. The last time I drove it and it died at a stop sign, I had to crank for a long time but it did finally start. I parked it a week ago intending to continue trouble shooting this weekend but now it refuses to start at all after sitting for a week. I checked for spark and was getting good fire so I moved to the fuel system. I listened for the fuel pump to spool up and it does. I checked the fuel filter and it was flowing. I checked for pressure at the injector fuel rail by pressing in the needle at the valve for testing fuel pressure and gas sprayed out spiritedly. I pulled out the injectors and cranked the engine and the injectors did nothing. To rule out that there might be some catastrophic mechanical failure I squirted some fuel into each injector port, plugged the injectors back in, and cranked the engine. It fired right up for a second or two and then died.

Sorry for all the background, but now at last here are my questions....

Are all these problems possibly related?
The manual I'm working from doesn't say anything about why the injectors might not be firing except for checking manifold ground wires, which I see none of. I don't really know where to go from here, thanks for any help.

JimFirst check for power at the injectors, get a " noid" lite. Plug it into an injector or 2, see if it flashes when cranking. If not that is one problem, if so, check fuel pressure properly at the rail. The pcm grounds the injectors from the signal from the crank sensor and ICM.
Try and get a scanner on it and see if you are reading rpms when cranking, also.

jimwalker
12-03-2005, 11:31 PM
First check for power at the injectors, get a " noid" lite. Plug it into an injector or 2, see if it flashes when cranking. If not that is one problem, if so, check fuel pressure properly at the rail. The pcm grounds the injectors from the signal from the crank sensor and ICM.
Try and get a scanner on it and see if you are reading rpms when cranking, also.

Maxwedge,

Thanks for the reply! I asked for some help on another web site as well and a guy responded with very similar advice to yours. He also mentioned a noid light and the PCM. Did you mean the PCM or is the ICM something else? I found a noid light for $6 so that's not a problem, but what is the PCM and/or the ICM? He said that I should check the throttle position sensor first. According to him it had to be the TPS or something to do with the PCM. If the TPS checks good but no joy at the injectors with the noid light then he said the PCM. What kind of scanner are you referring to, is it something one could buy? Do you think the earlier symptoms when it was still running are related to it refusing to start now?

Thanks again,

Jim

stuzman
12-04-2005, 09:42 AM
Maxwedge,

Thanks for the reply! I asked for some help on another web site as well and a guy responded with very similar advice to yours. He also mentioned a noid light and the PCM. Did you mean the PCM or is the ICM something else? I found a noid light for $6 so that's not a problem, but what is the PCM and/or the ICM? He said that I should check the throttle position sensor first. According to him it had to be the TPS or something to do with the PCM. If the TPS checks good but no joy at the injectors with the noid light then he said the PCM. What kind of scanner are you referring to, is it something one could buy? Do you think the earlier symptoms when it was still running are related to it refusing to start now?

Thanks again,

Jim

PCM would be the power control module and ICM would be ignition control module. Yes, you can buy a scanner to monitor the RPM's as Maxwedge said. If you see RPM's on the scanner, it would let you know that the crankshaft sensor was developing a voltage that the ICM was seeing. It's just one more thing that you can get out of the way in diagnosis. I can't see how the TPS can create a no-start, but the scanner could quickly get that out of the way also. You can also check this sensor with a DMM.

jimwalker
12-04-2005, 03:43 PM
PCM would be the power control module and ICM would be ignition control module. Yes, you can buy a scanner to monitor the RPM's as Maxwedge said. If you see RPM's on the scanner, it would let you know that the crankshaft sensor was developing a voltage that the ICM was seeing. It's just one more thing that you can get out of the way in diagnosis. I can't see how the TPS can create a no-start, but the scanner could quickly get that out of the way also. You can also check this sensor with a DMM.

Thanks for the reply Stuzman!

Well the other guy was right and so were you. The TPS was bad and I envision that it was causing some of the problems I was having while the car was still running. However it didn't solve the problem of no-start. I did some more trouble shooting and here is the additional information.

Fuel pressure tested with guage at the fuel rail and was within factory specs. No one in town has a noid light for sale so I couldn't use one to test. From what I read last night on the internet about "noid lights", they are just an LED circuit that flashes if a pulsed signal is going to the injector. It doesn't tell you if the pulse width is correct for the timing just if you're getting any kind of signal at all. Since no one in town had one and I dabble in electronics, I used an onhand 12v LED and resistor to make my own. I first checked the connectors voltage with the key on and saw battery voltage. Next I plugged in my LED circuit with the key on and the LED came on. Finally I had someone crank the engine and the LED did not flash in any way but was solid.

The other guy said that the only two components that deal with telling the injectors to fire are the TPS and the PCM. Do you agree? I called around town to find a scanner that would tell me RPM's and confirm that the crankshaft sensor was functioning but everyone kept trying to sell me a code reader. Could you be more specific on what kind of scanner I need and where to connect it?

Thanks, Jim

maxwedge
12-04-2005, 04:24 PM
You need a scanner that gives data, not just a code reader. You should not have a constant lite on when checking the injectors, the pcm grounds/pulses them based on demand, the tps is only one source of analog input to the pcm controlling this. You are trying to do this with tools/instruments not designed for proper diagnosis. A scanner that will give you data starts at about 300.00.

jimwalker
12-04-2005, 05:17 PM
You need a scanner that gives data, not just a code reader. You should not have a constant lite on when checking the injectors, the pcm grounds/pulses them based on demand, the tps is only one source of analog input to the pcm controlling this. You are trying to do this with tools/instruments not designed for proper diagnosis. A scanner that will give you data starts at about 300.00.

Thanks Maxwedge, it sounds like I've gone as far as I can go on my own. $300 is beyond the scope of what I can spend on this project. It would be cheaper to have it done so off to the shop it goes for a scan.

Thanks to everyone who offered help!

Jim

stuzman
12-05-2005, 06:45 PM
Thanks Maxwedge, it sounds like I've gone as far as I can go on my own. $300 is beyond the scope of what I can spend on this project. It would be cheaper to have it done so off to the shop it goes for a scan.

Thanks to everyone who offered help!

Jim

Jim, keep us posted on the outcome of your vehicle and hope that the repair isn't too expensive.

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