Warm restart backfire

SC Spyder

Registered User
Howdy all.

We now have close to 4K miles on the the Spyder and I am very happy with the SC engine. Love that low end torque...

Anyway, on a couple of occasions after the engine is all warmed up, if I stop to run into a store for example, when I go to restart it, the engine will crank then it will backfire and not start. It acts like it is flooded. I can hold the pedal to the floor and it will not start but if I wait for 10 or 15 minutes the engine will start. There is no smell of gas and there doesn't seem to be any black smoke when it does start.

Anyone have any thoughts?

Tks.
 
Bad DIS...`Hummmm

I'll check to see what sort of voltages I should see and if/when it happens again, check to see if they are correct.

Thank you.
 
Are you running a Motorcraft DIS module or an aftermarket DIS module?

These modules get pretty hot and you can sometimes smell them when they overheat....
 
I say the ECT sensor could be bad. If the wrong coolant temperature parameter is given to the PCM on a warm soak restart. The wrong fuel mixture could happen. Specifically a lean condition...if it is backfiring. But it could go either way. I have seen ECT's go bad and cause a no start due to the mixture being too rich (since the sensor was bad it thought the engine was cold, cold engines require richer starting conditions).
 
Etc

I'm thinking that Lean is the proper thinking .... The motor will backfire only once, the fuel pressure gauge on the rail doesn't lose pressure, there is no smell of raw fuel and no black smoke when it does finally start. I am running a K & N filter on a 15" long x 3" intake, the blower is being overdriven by 5% and the exhaust is true dual 2 1/4".

The it ETC is new and the thermostat is a 180 degree unit and the coolant temp is in the 180 - 190 degree range.

The EEC does not have a chip yet either.

It will pop only once then it doesn't try to fire no mater how long I crank it. If I wait a few moments it will seem like it trys to start (like a flooded engine but still will not start.

After about a 15 minute wait, it starts like there was never anything wrong.
 
Im not calling you an idiot here, just trying to help. But, are you sure you replaced the ECT and not the coolant temperature sending unit. Ect has several wires in the connector, Temperature sender has just one. Next time it happens, try push the gas pedal to the floor to cut off the injectors while its cranking. If it then fires or trys to fire, you will have your answer. That being that it is getting too much fuel.
 
Quite a few us have this unusual problem from time to time alot say its fuel vaporization at the rail from the heat. But no one really knows for sure. I had this issue, I remember David Neibert also had this issue at times.

http://www.sccoa.com/forums/showthread.php?t=101129&highlight=hot+start

Having chased Vapor lock issues myself. They usually come down to fuel delivery issues. Meaning the Pump has enough pressure to supply the rail, but not enough volume. I say usually. This is not always the case. Especially in the old Vein Air Meter system's and Bosch Dashpot(Japanese and German) systems that the Manufacturer's used to love to use...They were Vapor Lock Prone...
 
Last edited:
fdlvr30,

I appreciate your help and wouldn't have thought you would call me an idoit even though I have a tendency to be one.

You are correct in this instance, I thought ETC stood for Engine Coolant .... T(for something else).

Having admitted to being stupid, I will tell you that each time I after it refused to fire, I did hold the pedel to the floor but nothing happened, no change in how it cranked over. It dosen't even try to fire.

I do have a pressure gauge on the rail and it shows good pressure (mid 30 psi). It didn't drop to 0 while cranking but I didn't note what the cranking pressure is.
 
Pedal to the floor will cut out fuel to the engine, the injectors will not engage, you will still have fuel pressure since the pump is still activating.
This is a great feature when you are trying to clear out the engine after your have flooded the car. Bottom line is the car is not meant to start with the pedal to the floor. Just an FYI.
 
Pedal to the floor will cut out fuel to the engine, the injectors will not engage, you will still have fuel pressure since the pump is still activating.
This is a great feature when you are trying to clear out the engine after your have flooded the car. Bottom line is the car is not meant to start with the pedal to the floor. Just an FYI.

I gathered that you understood what Recardo is saying here already. Crank the car, then push the pedal to the floor while still cranking, then let up. I did not specify, sorry.
I would verify that it is getting spark while acting up before trying to diagnos anymore fuel delivery issues. Buy yourself a spark tester and check that next time. If it is getting spark, you know its a fuel delivery issue. If not you have a DIS, Crank/Cam sensor problem...
 
Backfire update.

Took the Spyder out this afternoon and it did it again. Low 80's and just couldn't resist any longer. Sorry if it is cold where you are. Wish I could send you some.

Sequence of events;

1st try - Engine spun like normal than one pop and not start.
2nd try - Engine spun and immediately sounded like the timing was advanced too much.
3rd try - I held the pedal to the floor to clear it out.
4th try - No fire
5th try - Sounded like it wanted to start
6th try - Tried to catch
7th try - Engine fired, I didn't touch the pedal and after a few seconds died.
8th try - No fire
9th try - No fire
10th try - Fired like there had never been an issue.

Wait time between the first 4 trys was about 30 seconds
Wait time between 9 th and 10th try, about 5 minutes during which I opened the hood to check the fuel pressure and all was well. I also wiggled all assessable connectors.

Still no real odor of fuel or cloud when it does fire.

I will pull and clean all connectors before I try to drive it again.

Any thoughts?
 
>2nd try - Engine spun and immediately sounded like the timing was advanced too much.

>10th try - Fired like there had never been an issue.


Classic signs of the DIS & EEC not getting a reliable CID off the camshaft sensor and then switching to FMEM where a guess is made as to which cylinder(s) should be fired. Could be sensor, module and/or harness/ground path issues. Have any spares of those on hand? Pulled codes yet?
 
I have a spare crank sensor.

I will be checking codes after dinner and cleaning as many contacts as possible to reach.

Tks.
 
>2nd try - Engine spun and immediately sounded like the timing was advanced too much.

>10th try - Fired like there had never been an issue.


Classic signs of the DIS & EEC not getting a reliable CID off the camshaft sensor and then switching to FMEM where a guess is made as to which cylinder(s) should be fired. Could be sensor, module and/or harness/ground path issues. Have any spares of those on hand? Pulled codes yet?

I second that. If the cam sensor is bad the computer will try to guess the firing sequence until it get its right.
 
Some facts that need to be cleared up.

- The failure of the CID signal going to the EEC will not cause an FMEM. IF the EEC-IV goes into FMEM mode, timing is automatically set to 10 degrees advance only and a fixed rich AFR which you will notice the difference immediately. There is no if, and, but's about this and it is right in the code for all 4 strategies our SC"s use, and the mustangs and so on and so on etc......

- The EEC does not control what cylinder is firing, the DIS module does that.

- If the DIS can't see the CID signal but has a proper PIP signal it tries the random firing order, not the EEC. The CID signal's only purpose in life is to identify #1 cylinder.

- If the loss of a PIP signal is encountered, the DIS will not even attempt to run the motor. The PIP signal is also used to set the fuel injector timing.

- At the loss of the spout signal which is the only signal from the EEC to the DIS, timing is locked to 10 degrees. Spout is used to set dwell and spark advance.

- The other signal to the EEC from the DIS is the IDM which is the high voltage kickback signal from the coil pack and is used for diagnostics purposes for the EEC as it will compare the PIP, CID and IDM signals for a "regular" pattern.

Erratic signal behaviour between the 3 signals in respect to timing etc over so many PIP events could cause an "FMEM" mode, with the exception of the CID signal on its own if the other 2 are fine as the car will run with no issues without it. As I mentioned, you will know it if the car goes into limp home mode, which is the FMEM mentioned.

The DIS module is the heart of the spark control system in our cars, not the EEC.

Check your wiring harnesses as mentioned, but I believe you have more of a problem than just a cam sensor. I'd be looking at the DIS, especially since we're talking heat related. Remove the DIS, clean all of the gunk off it, and reapply a very thin coat of heat transfer compound and hand tightened it back down.

Fraser
 
Live by the code!

Finally got a chance to read the codes.

KOEO

2 KOEO - 565 Canister Purge circuit failure. I don't have the canister any longer!
542 Fuel pump secondary circuit failure control module to ground. Not sure where to start looking for this other than at the EEC and tracing the circuit back.

3 Memory - 212 Loss of ignition diagnostic monitor input to Spark Output circuit grounded. No clue!
214 Cylinder Identification circuit failure. No clue here either!
542 Fuel pump secondary circuit failure control module to ground.

KOER - 111 System pass.

After warming the engine for only about 10 minutes and with a water temp of barely 180, when the code reader instructed me to restart the engine, it did the same thing again. This time, I didn't wait long between each try and it started on the third or fourth try.

So, next opportunity, I will take a look at the BHJ balancer & sensor to see if anything looks suspicious. I will change out the Cam Sensor and check all the connectors for clean and tight connections.
 
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