So I'm seeking a bit of help as I am not good with EFI and tuning. About 4 months ago I installed an HEI distributor and a Hedman Hedder. Long story but with a 80 dollar chinese carb it ran perfect while it was installed. This month my offy DP intake was finally delivered after a few month wait. So I installed it along with the Max-EFI 500 from Summit. Back when I put the hedder and HEI on I had to get a new side tank as mine was rusted bad and clogging filters. So as it sits now there is a brand new tank and sending unit. I have a quick connect to -6 AN fitting on the sending unit and from there to the throttle body it is -6 fittings with nylon braided hose. There is a 40 micron filter before the new in-line fuel pump, and a 100 micron after the pump. Under the hood it connects to a fuel pressure regulator that provides 58psi as the system calls out for with a return back to the tank.

Now I made a dummy mistake and fiddled with it for a few hours before realizing after a good nights sleep that I forgot to plug one of the ports on the intake so I had a huge vacuum leak. Fixed that though. The first time I felt confident taking it out on the road it ran like a hot damn for the first 15 minutes, I could not believe how much power it gained from the intake and EFI. After 15 minutes though it started sputtering with any input on the gas pedal. Limped it home and reset all the learning, fired right up and took it out again. This time it was not running perfect but it seemed to be heading in the right direction. The next day I decide to take it to work, didn't make it 5 minutes out before it lost just about all power, so I limped it home again. Did some more trouble shooting on it and did a run around the county roads and again it seemed to be on the way to sorting itself out. Today I drive it to work in the morning, and same thing, about 5 minutes into my drive it started the sputtering crap again. Seems like the damn thing is playing tricks on me haha. Oh we are just going out for a short drive? Here burn the tires! Oh you want to go to work? NOPE

Things I'm sure of:
No vacuum leaks as it runs great sometimes and always shows 13+ on the handheld.
No leaks in the fuel system

Starting to wish I had went with a 4-barrel carb.

EDIT: forgot to mention that there are no fault codes pinging... I also have a hot thermostat installed but it never overheats.

 

The fact that it's running good for a few minutes right after you start it up is the first thing that stands out. I'm not sure how this unit handles startup enrichment. It's conceivable that you have a vacuum leak somewhere and for the first little while, startup enrichment keeps it running nicely. It looks like you're missing a few intake bolts(?) from the photo, but it's hard to tell for sure.

Where is the fuel pump mounted? Those need to be gravity fed to the inlet side, meaning it needs to be mounted below the fuel level you're trying to get to, and as close to the tank as possible. You want the pump pushing, not pulling. Pumps can get hot and not be able to keep up with demand.

Speaking of, what pump do you have? It needs to be up to the task in the first place. I have had failing pumps work fine and show rock-steady pressure at idle, then the car fell on it's face when driven (and left me on the roadside a couple times, though it always made it home after I let it cool down).

What regulator are you running and where? How is the regulator plumbed into the unit? I'm a little unclear on that. Is it Filter->Pump->Filter->EFI Unit->Regulator-> Return?
Be sure to verify that there are no excess restrictions on the return side and that the return is sized adequately for the application. When the fuel doesn't have anywhere to go, it builds up and pressure increases, richening the mixture. The EFI should adjust for it, but it'll be a longer-term adjustment.

Go back to the basics. Be sure to check the plugs; if the engine is running richer than it needs to while learning and tuning, they can be fouling out.

If I have learned anything fiddling with EFI and engines in general, it's that usually I forgot to do something or made a little error somewhere. Not always. But more oft than not. Once you get the bugs worked out, though, you won't regret going EFI over the carb imo.

By the way, this is probably unrelated to your actual issue, but you have the filters backward. The 100-micron filter should be on the inlet side of the pump. The 40-micron filter should be on the outlet. This goes back to the need to keep restrictions low on the inlet side so that the pump doesn't have to "pull" the fuel. This can burn up the pump in the long run.

 

I'm not sure what sort of software the Summit unit has available, but are you able to log your driving? Those logs can tell you nearly everything that's going on.

Things to keep in mind. When the engine is cold (usually below 160°), the system will be running with learning turned off. During this time, it's simply going to go by what it's programmed to do. So if it likes the tune, your engine will be happy.
Once it warms up, it's going to readjust based on what it sees from the O2 sensor and recalibrate itself.

So if you have a good tune while it's cold, and then a messed up tune once it warms up, it's seeing bad data and readjusting incorrectly.

This is usually caused by a vacuum leak. And as cstephens said, it looks like you're missing intake/exhaust manifold bolts. I can see a few that are not present. This is going to definitely cause a leak, and EFI is much more susceptible to vacuum leaks than a carb. This is also true on the exhaust pipes upstream of the O2 sensor, since air can seep in. If air sneaks in, even if your engine is running 100% perfectly, the O2 sensor is going to see extra air in the exhaust and "think" your engine is running extremely lean. To fix this, it's going to dump in more and more fuel until it looks right, which will make it run really rich and poor.


A test you can do is to turn off learning mode. I don't know how to do this on the Summit unit as I've never seen/used one. But on the Holley Sniper, it's under the advanced features on the handheld unit.

If you rerun the wizard and turn it back to the original tune, then turn learning off, and the engine STAYS running really nicely, then you know the unit is working fine and you have something messing up your learning mode (like a leak messing with the O2 sensor).
If it starts out running okay and then still gets worse, it's more likely you have something else going on that's more heat related.

 

The fact that it's running good for a few minutes right after you start it up is the first thing that stands out. I'm not sure how this unit handles startup enrichment. It's conceivable that you have a vacuum leak somewhere and for the first little while, startup enrichment keeps it running nicely. It looks like you're missing a few intake bolts(?) from the photo, but it's hard to tell for sure. The bolts are all there, I think that one hole that looks empty is just for an alignment dowel? I know the head was not threaded for that hole. I know the computer is reading around 16 HG vacuum at idle, that is pretty good right?

Where is the fuel pump mounted? Those need to be gravity fed to the inlet side, meaning it needs to be mounted below the fuel level you're trying to get to, and as close to the tank as possible. You want the pump pushing, not pulling. Pumps can get hot and not be able to keep up with demand. I struggled with this due to the tank layout and having to put a filter before the pump, I put it as low as feasible without having it below the framerail.

Speaking of, what pump do you have? It needs to be up to the task in the first place. I have had failing pumps work fine and show rock-steady pressure at idle, then the car fell on it's face when driven (and left me on the roadside a couple times, though it always made it home after I let it cool down). It is a summit in line fuel pump, I'm wondering if that might be the issue, it is brand new. I have an in line fuel pressure gauge showing up tomorrow so that should be able to help me.

What regulator are you running and where? How is the regulator plumbed into the unit? I'm a little unclear on that. Is it Filter->Pump->Filter->EFI Unit->Regulator-> Return?
Be sure to verify that there are no excess restrictions on the return side and that the return is sized adequately for the application. When the fuel doesn't have anywhere to go, it builds up and pressure increases, richening the mixture. The EFI should adjust for it, but it'll be a longer-term adjustment. The layout is filter>pump>filter>regulator/filter combo(return goes from regulator)>EFI unit. I mounted the regulator on the inside drivers side fender, I figured if the pump was getting adequate fuel it was ok if the regulator was elevated beyond the pump?

Go back to the basics. Be sure to check the plugs; if the engine is running richer than it needs to while learning and tuning, they can be fouling out.

If I have learned anything fiddling with EFI and engines in general, it's that usually I forgot to do something or made a little error somewhere. Not always. But more oft than not. Once you get the bugs worked out, though, you won't regret going EFI over the carb imo.

By the way, this is probably unrelated to your actual issue, but you have the filters backward. The 100-micron filter should be on the inlet side of the pump. The 40-micron filter should be on the outlet. This goes back to the need to keep restrictions low on the inlet side so that the pump doesn't have to "pull" the fuel. This can burn up the pump in the long run. Son of a diddly you are right! I looked at fuel system layouts for hours but for some reason I brain farted this one. Thanks! I could see this maybe causing an issue that it is trying to suck fuel through the more restrictive filter? Part of this is me being a dummy, I thought the higher the number was the smaller particulate.

Here is a parts list

Summit Racing SUM-251000 - Summit Racing™ Inline Fuel Pumps(60PSI)

Summit Racing SUM-230150 - Summit Racing™ Universal LS Fuel Filter Regulators (5 Micron, 58psi)

Summit Racing SUM-230118-B - Summit Racing™ Inline Billet Fuel Filters (100 micron)

Summit Racing SUM-230102 - Summit Racing™ Full Flow Fuel Filters (40 micron)

 

A little bit of new info since yesterday. I reset all of the learning and started over. I warmed it up and took it for a drive, the AFR is sitting at 13.1 at idle, with any throttle input it goes up to almost 20! I'm thinking fuel starvation? I went through all the vacuum hoses and all seems to be great, and took another look at the intake and throttle body and it appears there is nothing obvious that would cause a leak. What do ya'll think of my plan?

Install the fuel pressure gauge tomorrow, swap the filters to the correct orientation and reset all of the learning again. I can have my better half look at the gauge as I rev it, it was leaning out really bad while revving it stationary.

 

Ah. I was looking at that one. With the way the headers are shaped, it looked those were ears with no bolt. I looked at some pictures of mine and there isn't one there.
As long as you have 13 on a carb'd head, you have them all.

 

What are all of your other settings?
What's the AFR at cruise? And if you hold it at WOT, what is it?

If it just "blips" up to 20 and then richens back up as you accelerate, that could come down to tuning, and you might need to richen up the acceleration table.
As much as they sell the "self learning", that only means it learns how to calibrate itself to your settings. If the settings aren't correct and need to be tweaked to fit your engine better, that has to be done manually.


Then again, if it's going really lean when you accelerate, yes, you simply might have fuel starvation. Get your filters in order, and get the fuel pressure gauge installed. That should help. You should barely have a wiggle on the needle no matter what you do. If it drops way down when you accelerate then that's an issue.

Keep at it. After fussing with carbs for years, no matter what issues I've had with my EFI kit, I'll never trade it for another carb.

 

At cruise with very light throttle it is at about 14. With any input on the throttle it jumps way up to the point it sputters to the point it will die.

 

I will report back tomorrow but I'm about 99.9% sure the filter orientation was the issue. I swapped them around and it idles fine. Will have to wait until the morning to take it out on the road. One huge difference I notice other than the smooth idle is that the fuel pump no longer has a high pitch noise, just a deep noise like it is pumping fuel.
*edit* just drove about 20 miles with no issues! Confident in saying it was the filters. Thanks so much guys, both problems I've had were user error haha

 

Ah, you're right. The third one back looked empty, but it's because the washer was blending into the header below. Sorry about that!

The layout you have there is perfect. And, yes, totally fine to have the regulator anywhere you want it. Anything after the pump, you don't really need to worry about too much. Even the return line, just a little bit of pressure will return the fuel fine as long as there aren't any kinks or other restrictions.

That's a common confusion point with the filters. I caught it, but I still had to look it up to double-check before I posted lol.

Good plan. That should help you narrow it down to a supply issue (pump) or a demand issue (EFI).

Could be related to the filter deal, I guess. You may want to look into acceleration enrichment as well. Though, on a 300, I would think you would be shooting to the rich side with the Holley auto-tune, not the lean side.

What happens if you give it gas really slowly, keeping it out of the AE tables? Does it still shoot way up?

Good to hear...I'll be surprised if the filter orientation made that much of a difference, but happily so!

Pay attention to the noise the pump is making, so that you notice any changes down the road. One plus of having to listen to the annoying whine that inline pumps make is that you DO get some feedback on the pump's health.