94 Lesabre starts then stops; crank sensor?

[cliffw]

94 Buick Lesabre 3800. Starts, then stops immediately. Fuel pressure seems good. I've had conflicting theories on the function of the crank sensors. One mechanic says if the car starts it can't be the crank sensor, others say it probably is . Check engine light has been on for some time. Any ideas? Thanks.

[buickmastermind]

Test to see what codes are present. I think the 94 still has the ALCL connector, right? If it does, go to this website, and it will tell you how to read the codes.

http://www.geocities.com/dann8785/s...enginesoon.html

Thank pirho451 for this link.

[avatar307]

The data from the crank sensor is not read until the engine is at operating temperature.

I've seen several post of people with cars that will run fine until the engine warms up to operating temp. The crankshaft sensor usually is to blame.

There was one test that was proposed. I believe letting the car come to operating temp and die. Then pouring water over the crankshaft sensor to cool it down, and attempting to restart the engine.

[rustbucket]

In 87 manual, it says below 400 rpm. the spark is controlled by the crank sensor and ICM. Above 400 rpm, the ICM yeilds control of the spark to the ECM, so it can do things like retard spark.

[cliffw]

Originally Posted by rustbucket

In 87 manual, it says below 400 rpm. the spark is controlled by the crank sensor and ICM. Above 400 rpm, the ICM yeilds control of the spark to the ECM, so it can do things like retard spark.

Thanks for the input. The car has a 16 pin connector, can I manually get the codes? Another thing the alternator gauge shows no charge, but a meter shows about 14 volts at the battery when it momentarily runs. I checked all grounds -seem ok.

I have always have Chrysler products - have rebuilt several and know them inside out, but have very little knowledge of GM's, this is actually my daughters car. The Haynes manual is limited. I really appreciate your help. Where are the ICM and ECM located?

[avatar307]

Below 400 RPM? So... the only time that would occur would be when you're starting the car right? I don't think I've ever seen a car idle at 400 RPM... then again, my LeSabre doesn't have a Tach.

I need a Tach. I also want one of those neat little displays that caculates instant MPG, avg MPG, range, etc, etc. Too bad I haven't been able to find an aftermarket version... you'd think someone would make one.

[rustbucket]

My 87 idles at 725 RPM in park. Again I dont know a 94, but on 87, the ICM is under the coils packs the whole assembly is above the rear valve cover. The ECM is in behind the glovebox and is about 7" X 4" X 2".

[cliffw]

Thanks. Is an ECM from a 93 3.4 compatible with 94 3800. I have an olds with the 3.4 Are any other sensors compatible?

[rustbucket]

I am guessing not compatible.

[avatar307]

Is any portion of the engine and powertrain diagnostics and driveabilty system from a 1993 3.4L engine compatible with a 1994 3.8L engine?

No. Absolutely not. Do not even attempt it. 1) The sensors won't fit. 2) There will be different sensors on each engine. 3) The wiring harness will not connect to any other sensors or diagnostic module, and if it does the wires will likely be in the wrong places. 4) If the sensors do fit, they will be calibrated with the wrong values and resistances. 5) The PCM/ECM/engine and powertrain diagnostic module is programmed to operate a 3.4L engine and associated transmission, not a 3.8L engine.

[avatar307]

To get the error codes from a 1994 pre-OBD-II car, equipped with an ECM, but pinned on a 16-pin connector instead of a 12-pin ALDL....

1) Ignition off.
2) Short pins 5 and 6.
3) Ignition on (don't start the car, just switch the car on).
4) Diagnostic read out should begin via flashing the Sevice Engine Soon, Check Engine, or similar light.
5) First code flashed will be 12. 12 is simply the "handshake" code to basically confirm the code readout is functioning properly.
6) All codes will be repeated 3 times, including code 12.
7) When code read out finishes, turn off ignition and remove jumper wire. To clear diagnostic codes, remove power from the ECM for at least 30 seconds. I.e. Disconnect the negative battery cable or remove the ECM fuse.

If you do not have a pin 6, your car does not conform to the non-standard GM pin out. The diagnostic codes are likely not manually retrievable. Send me a picture or list of the pins you have, and I'll reference the materials I have compiled on GMs use of the 16-pin OBD-II type connector in non-OBD-II cars with non-OBD-II pin outs.

View my recent post about this phenonmenon here.

http://www.automotiveforums.com/vbul...d.php?t=307153

[buickmastermind]

In general, but NOT always, GM mid-sized and full-sized sedans with the v6 have the exact same O2 sensor. Some have the same coolant temp sensor, and also the MAT sensor. If these sensors, all of which are on my '86 (3.8), are the same as the ones on a '94 Grand Am (3400), I am pretty sure that I can safely make that statement.

Interesting fact. The MAS from an '87 3.8 is not compatable with the one on the '86. The '87 has about 140 hp and gets 31mpg (non-asparated) and the '86 has about 150 hp and gets 30mpg (also non-aspirated).

[cliffw]

Thanks everyone. I ckecked the sights you referred to AVARTAR301, should be very helpful. I'll check the connector tonoght and get back

[avatar307]

Right, but how do you know if they are compatible? You have to check the part numbers on ever sensor. The O2 sensors might be compatible, they are both likely non-heated. The crankshaft and cam shaft sensors most likely are not, as they are from two different sized engines. The MAS, MAP, MAF sensors most likely will not even fit, because the engines likely use two completely different intake styles. The EGR might fit, but it's best not to mess with the EGR systems.

1994 is the year a lot of changes started happening as far as engine sensors and diagnostics. It's more likely that the sensors from a 1995, or 1996, engine would be more compatible. Then again, there are a lot of things about 1994-1996 Buicks/Olds that are completely different from other Buicks/Olds. Even within the same model year there are huge variations.

My 1995 is more compatible with 1996 parts than it is with 1995 parts. There was a huge shift mid-year 1995, and a lot of the new design for the 1996 was implimented on the 1995 to test it, as it had to be incorperated by 1996.

This is mostly due to the requirement that all cars be certified OBD-II complient by 1996. OBD-II goes beyond a standardized plug and pin out for diagnostics. It involves a huge amount of sensors and engine/powertrain diagnostics. All relating to emissions control, monitoring, and making efficent repairs of cars possible to emissions problems caused by cars needing hard to diagnose repairs.

We all think of a PVC valve as that thing that screws up the idle. In fact, it's one of the first emissions control measures. Now, it's another thing that has to be monitored. Starting in 2004, all cars must use the CAN protocol for diagnostic communication... that means no more of this 4 different adapters depending on which car you have.

Anyway, the general rule is, never mess with anything that has wires coming out of it unless you know eactly what you're doing (and have a multimeter).

Some parts will migrate between years, many parts will migrate between models of the same years, but it's very touch and go. Most sensors are related to emissions, there was a huge federally manidated emissions control systems change in 1996, manufacturers started changing in 1994. I've begun to see parts compatibility falling into these groups: 86 to 93, 94 to early-95, late-95 to early-96, 96 to 2000, 2000 to 2003, 2004.

I think one thing we can agree on is the answer to the question that was actually asked. "Thanks. Is an ECM from a 93 3.4[L] compatible with 94 3800 [3.8L]?"

Even if they use the same model and part number ECM/PCM/computer, they would be programed for two very different engines. At the very least, they use two different fuel loads, thus MOST of the sensor varibles will be different.

[cliffw]

Here's an update. The car is OBD1. 16 pin connector, pins 4,5,8,9,14,16 used. I tried the cooling down with water trick. Seemed to work first time, but second time nothing. Let it sit overnight. Started this morning and ran quite a while 10-15 min. Did not stall. Finally turned it off. Something else is happening. The gauges are going crazy. The tack goes from 0-about 5000, temp shows red , ammeter shows 0, red light is on. Fuel gauge seems ok. I tried all fuses- ok. The under dash fuses are not labelled. The two banks under the hood benieth windshield ok. Are there any others? From what has been posted I'm thinking crank sensor, but the problem with the gauges worries me. How long to change CS? Thanks.