Recent hard or no start when warm E85
 

Flex fuel E content has been between 50-63. Car starts fine when cold, if I drive somewhere car sits for a couple hours then it cranks fine but wont fire or stumbles after cranking and dies, stumble and almost run, and I have to play with the gas a little when its stumbling to get it to slowly idle like normal. Its been hot here 90+. This weekend I drove it to work after driving around about 25 miles car sat for 3.5 hrs and I had to deal with trying to get it to start and probably had to hit the start button about 6-7 times to finally get it to run. I have only ever had this happen on a very very rare occasion twice maybe in the last year and it seemed to be when it was cooler weather before I replaced my failed fuel pump. Any ideas? thnx

With the higher temps. Your E-85 is going from a liquid to a vapor. You're vapor locking.

Would this still happen with a fuel return system? I don't get why it would vapor lock after sitting for 3 or 4 hours and after the sun goes down. Would increasing fuel reg pressure a tad help? I think at idle it's around 48/49psi

In cold, yeah that is normal. In the heat, it is not normal. Check your fuel pressure. You may have a tune issue. It's hard to say.

I been driving daily in the OKC heat as well.

Never had a starting issue, unless there was some cheap 87 E10 in the tank, along with my regular E70, diluting it way down.

As long as the yellow gas is 65% or better, mine starts fine in the heat. If it’s below 65% I have to feather the pedal etc..

I don’t have a flex fuel sensor, so I doubt mine would start at all at 50%. It’s tuned for 70-80% Ethanol, or 91 Gas on a different map.

I have the fuel pressure right at 52 psi at the fuel block.

I can drive it all day with E70 in the tank, on the 93 gasoline map, it just runs lean. Still makes good power too! NA motor, so knock is the risk here.

It wont run at all with 91 in the tank, on the E70 map. Way too rich apparently.

So, check your AFR and see if it’s in line with what you expect. I know my AFR will be way off if the E content is off, since I don’t have the flex sensor.

If the AFR looks ok, then probably something else is going on. Maybe your flex sensor is bad?

Would this still happen with a fuel return system? I don't get why it would vapor lock after sitting for 3 or 4 hours and after the sun goes down. Would increasing fuel reg pressure a tad help?

It's not vapor locking. If it was, it would be if your ran into a store and ran back out or if you stopped to get fuel.

Log it and send it to your tuner. Map sensors are known to go bad. That may be your problem.

Are you running an Omni 4 bar map sensor?

I believe so has to be a 3 or 4 bar

Not sure what your fuel pump assembly set up is, but I had this EXACT issue with the OE fuel pump assy. (everything that hangs from the hat). My system was all OE and running gasoline. I replaced the pump and had same issue. After I replaced the entire assembly the problem was solved. The fuel pressure regulator is located within the plastic assembly somewhere so I believe it was the problem.

If you still have the assembly and the regulator contained therein I'd lean toward that. I didn't see any notes about testing your fuel pressure so that may be your first check.

FWIW, I had a return E85 system on a previous roots blower + nitrous V8 platform in S. Florida heat and NEVER had the issue you're experiencing. I'm not saying it's not possible, I just didn't experience that in heat. Additionally, if it's happening "all of a sudden" and not during previous heat spells, I'd look beyond the weather.

Check your fuel pressure since you have a return system and pull some logs when this is happening. Omni 4 bar Maps fail quite a bit especially if they are mounted on a metal intake manifold. You will need an Ecutek Bluetooth dongle to be able to log it with your phone.

I have all that just havnt had a chance to get to it or find where the map sensor is located at, assume its on the back side of the stillen manifold somewhere. I dont really have a "tuner" but did have Eugene look at some logs last year and he didnt see anything that really needed attention. But this issue wasnt happening then.

Fuel wise I have cjm top hat, aero fuel return set up, jms powermax, an almost new 450 pump

Does that use an aftermarket fuel pressure regulator and delete the OE intake one?

Yes has the adjustable aero that comes with the fuel return kit.

The map sensor is on the back of the stillen manifold, omni 4 bar 3 pin. I still havnt had time or not raining to take it out and try to log the issue.