Help! Car won't start
 

I need some help diagnosing my car's no start condition.

Last fall, I drove my car around the block and parked it in my driveway and ever since then it won't start. There's fuel and there's spark, but it won't start, it doesn't even sound like it wants to start. It gives me no trouble codes, so I'm taking that as evidence that there's no problems with the harness. I replaced the spark plugs and wires. I've replaced the computer and both the leading and trailing ignition coils and igniters. I've checked the fuel pressure and it's ok as is the hold pressure. I adjusted the TPS and it reads ok. I checked all the ECU related input and output devices (sensors, BAC, etc) and came up with everything within specs, or only ever so slightly outside of them. I've ordered a new intake air and water temp sensor, just because they weren't crazy expensive, not that the old ones didn't test fine.

Just before it died, I swapped in a TII transmission, but drove it around a few times afterwards and it was ok. I bled the clutch after parking it, but have looked extensively around the slave and I can't see any wires or vacuum hoses knocked loose.

It wasn't 100% trouble free before, but it always started well. Here's some issues it had before: Sometimes when re-started hot, it won't stay running without a bit of throttle until it's been on for a minute or so and it doesn't happen all the time. The hot idle makes a sort of ticking/popping noise coupled with a momentary drop in the idle speed, mostly it's just annoying. It had a tendancy to buck slightly when getting back on the throttle below about 2000 rpm or so, but it has good driveline mounts. It ran just fine at higher rpm.

What could it be? I'm thinking my next move might be to change the CAS and BAC. Any helpful advice would be appreciated.

if u parked it and didnt touch anything then it started doing this i doubt its your CAS have u done all the de-flooding procedures? and then tried to start it? also made sure you havent tossed a seal lol. alot of times if the engines flooded it will crank but not even try to fire

if u havent already try this and get back to us
take out your fuel injection fuse
crank the engine for 15-30 seconds
re-install fuse
try to start it but dont give it any gas

if that doesnt work try the same process but crank it for 15-30 seconds with all 4 spark plugs and injection fuse out, clean plugs and put it all back together and go for it

I tried de-flooding it first, with the built in S5 full throttle fuel cut and with taking out the injectors. I also disconnected the MSD early on, thinking that might be the culprit, but nothing.

I haven't checked the compression yet, since I can't immagine how it'd loose enough compression in both rotors to not start after such a short, low stress drive.

It's so strange because I've checked everything and there's no smoking gun, so at this point I'm reduced to throwing parts at it until it works unless someone's got a better idea?

It sounds like the starting mixture is too rich, though that is not certain.

Some things you could check that might be causing this kind of a start problem:
1. Water thermo sensor. If the sensor is disonnected, or failed as an open, the ECU interprets the high resistance (infinity) as an extreme cold temp and runs the mixture up too high, making a start impossible. Check and see that the connector to the themo sensor is connected; double check the voltage at the ECU from the thermo sensor.
2. BAC valve. If the BAC valve is not operating, there is not enough air to start, particularly when hot. Sometimes it will start and then die after a couple of seconds. Check the BAC valve connector, and if that is ok, check the BAC valve operation per the FSM.
3. If these two checks are ok, try the flooded start procedure again with the fuse out, but make sure you crank it for a long time (30 sec?) with the throttle full. If it fires at all during that process, it is probably flooded.
4. Does the check engine light come on for a few seconds after you turn the key to run (before start)?

I just re-read my last post, I de-flooded it by removing the spark plugs, not the injectors.

I've checked the water temp sensor through the harness and it seemed ok.
I'm somewhat suspicious of the BAC, but it seems ok.
The check engine light comes on, then goes off. I've checked for codes and got none.

I'll check the compression, get a spark tester, thoroughly de-flood it, swap in the new water and air temp sensors and fuel filter that should be here tomorrow and give it another go I guess.

In your 91, it should automatically cut of the injectors if you crank it with the throttle full.


What was the resitance value, and at what temp?

You should be able to put 12v onto its terminals and hear it click.

Good, thats what it should do, it says the ECU is powered up.

That helps narrow things down.

Have you checked the voltages at the ECU on the pins from the various inputs and outputs vs. the values in the FSM? If there is a bad sensor it should show up there.

You try roll starting it?

I tried that first, then repeatedly with each new attempt at starting.

It was about 3.5k at about 15C, the FSM says 2.5k at 20C, then increasing resistance from there.

I think I did that last fall, but ìt was on my radar of things to look at next.

I haven`t gone that far yet, but I`ve checked all the resistances.

I don`t want to try roll starting it, since then the car`s down at the end of the street and I`ve got to push it or tow it back up to my place to work on it. It`s in my driveway now and it will stay there until it decides to start on its own.

Well, I got the car started. I swapped my old computer back in, with the new coils and after lots of cranking without fuel to check spark and compression and to de-flood, and after swapping out the air temp and water temp sensors it works again.

There's still an issue though, the idle sucks and when I drove it around the block to put it in the carport it wasn't very smooth, bucking and generally not being very driveable. I checked the timing and it seems to be advancing and retarding with the engine as it surges up and down. Now I'm not sure how much would be as a result of the idle issue vs. a cause, but it's still not driveable yet. There weren't any trouble codes. Suggestions?

Adjust your TPS while the car is running and up to proper operating temp as opposed to a car which is cold and not running. Also , you might need to jumper the initial set connector and adjust the idle adjust screw on top of the thottle body. Setting the TPS would be done after dealing with the the idle adjust screw.