ksuxtc

I have a 305 TPI 91 Formula with 90k miles. Everything is stock. The problem is that once the car gets warm, it intermittently won't start. The starter engages, the engine turns over, but it won't fire. Since the starting problem began, it's also stalled out a couple times while driving once it warms up. Another thing I just noticed last night is that when the starting problem is occurring, with the key in the on position, the radiator fan randomly kicks on and off, abruptly like there's a shorted wire. On top of all of this, it's not throwing any codes.

A little history. Tuned up about 1000 miles ago, plugs, wires, cap, rotor, air filter, fuel filter. Had an injector fail just after the tune up, tested < 2 Ohms hot, replaced. 500 miles later a different injector failed, also < 2 Ohms hot. Also found that four other injectors tested < 10 Ohms hot, the new injector and two others tested OK at around 16.8 Ohms hot. Replaced all eight injectors with a matching set and it runs great...when it starts.

I've been reading alot on this forum and warm start problems seem to plague TPI's and from reading other threads it seems it's never the same culprit twice. Alot of threads point towards the ignition module. I'm fairly certain we didn't replace the ignition module when we replaced the cap, so it is likely the original. This car does have VATS, and I'm a little unclear about what the symptoms would be for a VATS problem. Some threads suggest that the starter wouldn't even engage if it was a VATS problem. Also the security light turns on when the key is in the on position and goes out quickly.

If anyone has any suggestions, any help would be greatly appreciated.

ksuxtc

Stalled again on me today on the way home from work. This time the engine was not warm though. I noticed a bit more detail about what's going on with the radiator fan too. When the car is operating normally, I turn the key to the on position, I hear the fuel pump prime, no radiator fan. When it won't start after stalling, I turn the key to the on position, I hear the fuel pump prime, the radiator fan is running, the radiator fan kicks off when the service engine light comes on, then kicks back on when the light goes out. I also noticed that when the fan goes off (while the service engine light is on) there are several clicks from around the engine. One is definitely from the fuel pump relay, another sounds like the MAP sensor or nearby, and the other sounds like it's from somewhere around the distributor. Letting the car sit for a couple hours seems to resolve the issue at least temporarily.

After it finally started it ran extremely rough the mile or so home, lots of bucking and surging. Once home I let it idle for a few minutes, still running rough and idling at a much higher RPM than usual, it started at about 1200 and after a few minutes it was about 2000, with no interaction from me. I went ahead and shut it down because the temp was spiking and getting close to 260. I don't know if that means my thermostat is stuck. Could a stuck thermostat possibly cause some of these other symptoms?

I know there are some really knowledgeable people on this forums. Does anyone have any suggestions? Even just some tips on where to begin looking?

Once again, thanks for any suggestions.

LambOfGod

check the distributor, i had the same problem with a mustang i almost bought, hopefully that will be it, it's not an expensive fix. I think it also had a problem with the ignition coil. so check those areas out.

Pukka

Check your fuel pressure - sounds like your pump has gone bad.

ksuxtc

Thanks for the suggestions, I will check the fuel pressure and take a close look at the distributor this weekend.

I've been really puzzled by how the radiator fan has been acting through all of this. The more I think about it, I'm really beginning to wonder if it might be the Coolant Temperature Sensor. I've read that a faulty CTS can cause the ECM to disable the fuel system to prevent engine damage if it thinks the engine is overheating. Is it possible that the CTS could be sending a faulty signal and the fans are kicking on because the ECM thinks the engine is overheating?

Anyone else ever seen their radiator fan act like this in a no-start condition?

vetteoz

iTrader: (13)

Possibly , worth changing for the $15 cost

If the ECM is not seeing the correct inputs from the sensor(s) it goes into "limp home" mode where it runs the engine off a preset program; not from the sensor inputs.
When in "limp home" mode the fan runs full time ; key on

Have you pulled the codes to see if anything is showing?

Pukka

A faulty CTS can give you a high idle if it is sending a low reading, so its possible it could force a shut-off if it is sending an extremely high reading. The only way you will know if the CTS is running properly is to plug in a scanner.

The fan is strictly electrical, no sensors connected to it. If its wired stock, a single fan will only turn on when the fan temp switch reaches 220 degrees or if you turn on the A/C.

ksuxtc

When jumpering A&B on the ALDL it only gives code 12. Kind of a related question. I took it to the local az and they hooked up their scanner, and the car would not start with the scanner hooked up. As soon as we'd remove the scanner it would fire up as usual. The az tech was surprised and said he had never seen a car that wouldn't start with the scanner hooked up. Should it start with the scanner hooked up?

Being in limp mode would explain the fans, but it should start in limp mode right, it just wouldn't be running optimally?

During the no-start condition both radiator fans turn on.

After I got it home after the no-start issue that I documented the other day, it's started every time I've tried. Granted I haven't driven it anywhere other than around my block because I don't want it to strand me again, but regardless it starts and runs great. I just checked this weekend, and during a normal-start normal-run the radiator fans did not kick on until the temp was around 230. It's hard to get a precise reading and determine what each tick mark is on that 100-220 & 220-260 gauge. Then at around what I would guess is 240 the radiator fans either kicked into a "high" mode or the second fan kicked on, I'm not sure as it looked like both fans were spinning at the 230 mark.

Thanks again for the suggestions.

ksuxtc

I think I've got this problem finally figured out.

So my car was nice enough to finally crap out on me while it was sitting in the driveway instead of out on the road so I could do some troubleshooting. It did the whole thing where the fans would spin, the SES (Service Engine Soon) light would flicker randomly, and crank but no-start. Sitting there watching the SES flash randomly I noticed that a couple times it looked like it started to flash a code, but it wasn't doing it right, it would flash one code extremely fast then nothing then something different. By extremely fast, I mean I couldn't count how many flashes it was doing to determine the code. I've read that when the car is in diagnostic mode (sockets A&B jumpered on the ALDL) the SES is supposed to flash a code 3 times, then move on to another code if it exists. This got me to thinking, that it's kind of acting like it's in diagnostic mode, except I didn't have the ALDL jumpered, so why would it think it's in diagnostic mode. I started looking for a shorted wire somewhere thinking that maybe sockets A&B on the ALDL were shorting each other somewhere before the connector. Everything looked fine under the driver's side of the dash. I moved over to the passenger's side under the dashboard. I pulled the ECM down out of the dashboard to get a better look at the wires and it was so hot that I couldn't hold it for more than a couple seconds. This struck me as odd because the car had not been run at all that day, it had been sitting out in the sun, but other metal components inside the car were not nearly as hot as the ECM. I had been turning the car over, maybe 10 tries, which I guess could have generated some heat, but it should not have been nearly as hot as it was. I took a look at the wires around the ECM, and they were fine.

I took the ECM out, took it inside to see if there was anything obviously wrong with the board. Everything looked pretty good, nothing discolored, but some of the solder points looked kinda strange under the coating. Not finding an obvious problem, I put everything back together, and installed the ECM in the car. First try it fires up and runs great. So it's starting to come together now, it starts and runs great when the ECM is cool, but it doesn't when the ECM is hot. So instead of an engine hot scenario it's more of a time of the day/ambient temperature affecting the ECM scenario.

Just to make sure I wasn't hallucinating, I waited until the next day and tried to recreate the scenario. 3PM, 93 degrees, car has been sitting in the sun all day, turns over, won't start, fans running, SES flashing. I take the ECM out, let it cool inside in the air conditioner for 10 minutes, reinstall it in the car, it starts up first try, second try, third try, run it for 10 minutes, I turn it off, it starts for a fourth try.

While looking for a replacement ECM, I noticed that one of the retailers had a description saying that the remanufactured ECM corrects a problem with the O.E. ECM coating. Apparently the O.E. coating on the ECM can cause the resistors on the board to lift when it gets hot. The remanufactured ECM has the O.E. coating removed and replaced with something better that is stress tested in extreme hot and cold conditions.

Picking up the replacement ECM this week and hopefully no more of this intermittent crap.

ksuxtc

Thought I'd post an update in case anyone else ever has these symptoms.

Replacing the ECM resolved all of the issues I had been seeing. It's been starting reliably and running great as my daily driver for the past 5 months. Thanks again for everyone's suggestions.