Hot/Warm start issues

[beast02]

I have a bit of an issue I have discovered. I can get the car started fine cold, fires up easily. I can do this from what i've tried in the 40F up to 75F outside with the coolant at relative room temp. I'm still in the earlier testing/tuning stages, so most all of my drives are fire it up, go for a drive and datalog, come back shut it down and then check out the log.

The other night I went for a drive to meet my Dad, turned it off so I could load a different tune, and when I went to fire it back up, it wouldn't start. After quite a bit of cranking I started to get worried I was flooding it. I pulled the plugs and they weren't wet. It sat for a while while my dad got the sockets so I could do this.

Once it cooled a bit to more like 120F coolant, it still wouldn't fire up. I was suspecting the battery V was low and had been having my Dad jump me as well, but looking at logs later it looks like the battery is charging fine.

The next day I fired up cold, and if fired up just fine. Took it for a drive to get the coolant up to temp, parked it, turned it off and then tried to fire it up. Wouldn't start. I tried bumping to Cranking PW up from what it was at like 110 or 120 in 10 increments up to about 170 180 and it still wouldn't fire up. So, I am stumped and need a little help from here on what to look for or what to change.

I have attached the tune, the cold start which was fine (dated 6/30) the warm start that wasn't fine (6/29) and the tune.

Thanks,

Bryan

[DaveEFI]

One thing it might well be is vapour lock. Which would explain no firing and dry plugs. If you have the normal fuel return rail to the tank, rig up a switch so you can run the pump manually before attempting a hot re-start. If you can hear the pump running when the engine is stopped, you might well hear it slow down as gets rid of the vapour and gets the fuel pressure up. Normally only perhaps 20 seconds or so should be more than enough. You also might need to open the throttle a bit when starting.

If this works, you'll need to investigate insulating the fuel rails, etc.

[grom_e30]

i found that when hot my car wanted less fuel to start reliably somewhere about 70% for cranking pw. you could try opening the throttle on a bad warm start and see if it helps. there is 'flood clear' as well if you open the throttle past 70% (default setting) when cranking it turns off the injectors may save you pulling the plugs out to let them dry off.

[beast02]

I definitely tried opening the throttle while cranking with no effect on helping. When I first had the issue, I also tried cranking for quite a while (off and on) and it still wouldn't start (assuming the vapor would clear in 20 seconds per the one comment).

-Bryan

[turbo conversion]

Have you physically checked to see if you are getting spark at the plugs when this happens?

If you have spark then get some starting fluid and try spraying some in the throttle body when cranking.

If you have spark and it try's to fire with the starting fluid it is either to lean or the fuel is going away on hot start.

David

[beast02]

I have not validated the spark because if you look at the one log I have posted, the car is catching and slightly firing up a little.......which, as I think about this and write this, I think I need to look in to my after start enrichment's for this temperature range as this could be the issue.

[beast02]

I am so freakin stumped it's not even funny. It fires up so easily cold! I just had it out again tonight to try stuff after it is warmed up. I am posting my start up attempt (after the drive) log so hopefully someone can see something I am not. I checked spark after doing this, there was spark.

I'm not sure how you test vapor lock, but I am currently running around hoodless and I live in the PNW, so it's about 68 out while I was driving, hardly hot enough conditions to cause vapor lock I would think.

[slow_hemi6]

So ambient is 68f and your MAT is reading 101.2f. That sounds like heat soak of the MAT sensor. Do you have the "ignore Mat during ASE" box set to ON? If not give that a try.

[billr]

I'm of the opinion that vapor-lock is not the problem. The vapor pressure of fuels is much lower than normal EFI fuel pressures, even if the fuel is quite hot. Even back in the carb days, when FP was about 5 psi and the pump was mounted on the engine, there was rarely much problem with vapor-lock in the (hot) pressure line from the pump to carb; problems were in the suction line from the tank to the pump, where pressures would go below atmospheric.

Post your tune as a native MSQ, maybe I will see something that is an issue.

[DaveEFI]

I am so freakin stumped it's not even funny. It fires up so easily cold! I just had it out again tonight to try stuff after it is warmed up. I am posting my start up attempt (after the drive) log so hopefully someone can see something I am not. I checked spark after doing this, there was spark.

I'm not sure how you test vapor lock, but I am currently running around hoodless and I live in the PNW, so it's about 68 out while I was driving, hardly hot enough conditions to cause vapor lock I would think.

Vapour lock is pretty well never a problem on the move. It's heat soak when you stop the engine hot. (not saying this is your problem, though)

[Dennis930]

If your fuel pressure regulator has a port for a pressure gage I would install one. Fuel pressure should be present for at least 20 minutes after engine shut down. If not you get vapor lock. You can not purge enough fuel to clear out the vapor by just cranking the engine. Maybe if you change your cranking pulses to the that for 0* at the high temperature to see if that will clear it out and the engine may start. My car had Bosch CIS injection before I converted to efi. If fuel pressure was not maintained after hot shut down, 15 - 20 minutes later it would not start. Had to remove the air cleaner, override the fuel pump, and manually position the metering flap to purge fuel through the injectors, then it would start. Currently I have a pressure gage installed on my engine at the regulator. It maintains pressure for 20 minutes. Never had it not start after hot shut down. I did have heat soak issues affecting how smoothly the engine ran, but I have corrected this with more ASE at hot temperatures.

Another thing you can try is at shut down, clamp off the return line somewhere were there is a rubber hose and then later unclamp it and see if that helps it start. This assumes that the fuel pump is holding pressure and the regulator is leaking through.

As mentioned previously, ensure that MAT correction is disabled for ASE.

[DaveEFI]

Thing I've found is many after market adjustable regulators do not hold pressure with the engine stopped as well as fixed maker's ones - if at all. The same may apply to after market fuel pumps. With the engine running, this doesn't much matter. But can make a big difference to starting time, especially when hot if all that is left is vapour.
The best fix would be to sort this. But arranging for a longer pump run at switch on and waiting till the pressure builds before attempting a start may be a work round.

[beast02]

Thanks guys. I'll be trying it with the ignore MAT setting set to ON tonight (this was set to off). I'll post logs if this does not work (hoping this IS the issue. Googling found someone with a similar issue and it looked like this fixed it for them). Crossing my fingers!

-Bryan

[beast02]

Welp, bad news, changing the ignore MAT setting didn't make it any better. Attached is the latest tune Plus the start up attempt 30 seconds after shutting it down after a 13 mile drive.

No change in behavior.

-Bryan

[DaveEFI]

Your AFR reading in MV doesn't seem to be reacting as I'd expect. Is your wideband O2 sensor system working properly?

[beast02]

The wideband seems to be working for my normal drives where it fires up and runs fine. I'd post one of those logs but they are really big.

[turbo conversion]

Your AFR reading in MV doesn't seem to be reacting as I'd expect. Is your wideband O2 sensor system working properly?

I agree, the o2 reading is very strange through out the log.

I also noticed there are 8 lost sync counts, whats up with that?

Not sure what problem this will create but the baro correction should be set to 100 not 0.

David

[beast02]

I am assuming the lost sync count is from turning the key on/off, I don't think it's loosing sync while i'm actually cranking.

I'll check the barro correction and try and post a snap of one of my fire up logs where it does work.

[turbo conversion]

Look at the log, it is loosing sync while cranking.

Look at counter number 214621.297 rpm drops to 0 while cranking, this is not a key cycle.

This happens several times through the log, it should not be happening.

David

[beast02]

I'll look in to this....POT tuning or signal noise issue?

I disregarded this as it does it as well when it does fire up and run (when the engine and everything is cold), so I assumed it was ok/normal