Tuning out hot start issues

[SnakeBoostE85]

During the winter I didn't have any issues, but now that's its pretty hot out, my hot start issues have returned. When I'm cruising around for a while in hot weather and totally heat soaked, I tend to have a hard time with start ups. Its starts eventually after a couple cranks, but I will eventually get a P0190 FRPS code for fuel rail pressure.

I think what's happening, when its so hot, is that the ethanol is vaporizing. My crank lambda's are VERY rich to help with cold start ups in general, so I don't see how much richer I can make them in this case.

I'm running e85, on a return fuel system with a fore regulator and rails.

Don LaSota's book has a section on hot start problems - I haven't bought the book, was thinking about picking it up, but if anyone has any obvious tips that would be cool. Thanks!

 

[cj428mach]

How rich of a Lambda are you commanding at startup?

If while its trying to start does hitting the gas pedal help? hurt? or leave it the same?

 

[SnakeBoostE85]

I'll have to see what happens with some pedal in that situation and report back. In general, my concern is piston washing and dropping fuel down into the crank case if I go richer. The cold side made a considerable difference at start up. I think I added 20% more fuel to the entire table originally and that cured the cold startups during the winter here. So what does it mean if adding pedal helps? Does adding pedal add air or fuel?

Here are my tables for crank lambda and spark:

 

[cj428mach]

The pedal adds air, so if it fires right up then you could try subtracting fuel or see if there are some adjustments to increase the IAC at startup.

I'm rich in the cold start up area than you are but in the upper temps I think I'm leaner. I think I'm like .799 but I'd have to check.

 

[txcharlie]

LaSota's book says later PCMs use crank lambda and aircharge. Looks like yours uses crank lambda. He stated that later PCMs usually don't have this issue, but if it does, you should adjust aircharge first, then crank lambda.

 

[SnakeBoostE85]

Awesome - thanks guys. I'll play with it. There is a table called "Air charge during crank" and "ISC Duty Cycle" which are all currently set to stock AMZ1 values.

 

[Mach828]

Sure you aren't over fueling it on startup? What happens if you take it closer to lamba on the higher coolant temps. Makes sense to add fuel when its cold out on a cold start, but you don't need as much if its warm.

 

[xtreme_exploder]

Bringing this back, I currently have a hot start issue and use SCT PRP to tune my car. Ever figure this out? If I tap the gas after I crank it, it'll stay running. Otherwise it just stumbles and stalls out.

 

[SnakeBoostE85]

I was going to start playing with this again this summer, now that its hot out. When its cold in the winter it starts right up every time.

However after today, I am having either a failing fuel pump or clogged fuel filter, so I have to get it up in the air and fix that first.


When I get it running again, I will probably just try adding mad crank fuel. Anyone else, had any luck with that?

 

[oxfordgt]

I actually pulled 15% fuel during cranking. Maxed out cranking spark table and used start up enrichment to add fuel depending on ECT. No problems while starting at 20* or 90*

 

[xtreme_exploder]

How did you pull fuel, crank lambda?

 

[oxfordgt]

I think the table in mine is actually called "crank fuel" I'll have to take a look tomorrow to be sure. If hitting the gas pedal helps it start easier then you need to pull cranking fuel. Your crank lambda is way to rich across the board. If you have trouble getting an idle when cold you need to add fuel after startup not during cranking.

 

[SnakeBoostE85]

I think the table in mine is actually called "crank fuel" I'll have to take a look tomorrow to be sure. If hitting the gas pedal helps it start easier then you need to pull cranking fuel. Your crank lambda is way to rich across the board. If you have trouble getting an idle when cold you need to add fuel after startup not during cranking.

so I just switched to E70 from E85 because that's all I can get right now. Funny thing - its starts much easier when hot on E70 then E85

 

[xtreme_exploder]

Ethanol fuels do not like even the slightest heat. Return style fuel systems make it worse. The fuel gets heated and recirculated back to the tank. That's why ideally you'd do a deadhead system so that the returning fuel sees little to no engine heat (not sure how yours is set up).

 

[SnakeBoostE85]

Ethanol fuels do not like even the slightest heat. Return style fuel systems make it worse. The fuel gets heated and recirculated back to the tank. That's why ideally you'd do a deadhead system so that the returning fuel sees little to no engine heat (not sure how yours is set up).

Nope mine is a fully circulating system. I've heard dead heading the rails is not a good idea either.

 

[xtreme_exploder]

I'm not quite sure why people say deadhead is bad, from an engineering perspective it's superior. I've seen some silly theories out there on this stuff lol

 

[SnakeBoostE85]

Alright this is driving me nuts... I've tried lots of things and nothing seems to help and if anything it gets worse. Here's the deal... if the car is heat soaked on a hot day and lets say you park it for 5 minutes to run into the store, come back out and try to restart it, its a bitch. It eventually starts, but it takes about 2-3 tries. What I have found is that priming it about 2-3 times without attempting to start it, seems to make the most difference. When I'm priming it several times, I'm probably cooling down the runners and cylinders with fuel making it easier to fire or perhaps I am just circulating more cooler fuel through the rails. Obviously the fuel under pressure sitting in the rails is reaching 230+ degrees when its sitting there. So perhaps that circulation of fresh fuel at a cooler temp allows it to start easier...

So having said that, what can I do with my tune to help this? I know some guys bypass the FPDM with return fuel systems and have the pump run full time at key on... I didn't want to do that because it bypasses your enertia switch in case of an accident or rollover. There is also no way to lengthen the prime in the tune.

Any ideas, please... And if you have an idea of what to do using PRP, PLEASE, say EXACTLY which table to edit... A few guys above just throw half cocked suggestions out like... oh "add air" or "add fuel"... Lets try to be more specific on that. There is the IAC table, air charge, crank lamba, enleanment, enrichment... please be specific.

also take screen shots of your tables if possible!! Thanks.

 

[xtreme_exploder]

Its probably not the tune since I'm sure there's tons of people running the same setup without issues. I found out that my issue was an electrical problem. Heat adds resistance to a circuit, so if there's a problem somewhere, it may not show up until it's hot. My car has a lot of extra things wired in, and it turned out it was causing issues with the 5v reference line that goes to many of the sensors.

 

[SnakeBoostE85]

Its probably not the tune since I'm sure there's tons of people running the same setup without issues. I found out that my issue was an electrical problem. Heat adds resistance to a circuit, so if there's a problem somewhere, it may not show up until it's hot. My car has a lot of extra things wired in, and it turned out it was causing issues with the 5v reference line that goes to many of the sensors.

Appreciate the reply, not sure that makes sense though in this case, because it started fine on Gas before the ethanol swap.

temps in the engine bay would be the same. This is a very common issue on ethanol swaps unfortunately its more popular on the ricer forums. i.e., subaru, mitsubishi, supras

 

[SnakeBoostE85]

maybe someone could tell me this... The tables for air charge and ISC duty cycle... they look like lambda numbers i.e. .89 .79 etc... can someone tell me if increasing these adds air or remove air during crank.