Tune issues with a new 6.4 Hemi swap in a 64 Dart

[Andyz]

Hi all
I recently got a new 6.4 with a Mopar ECU that comes with the crate engine. When first installed it ran really rough but auto tuned to drivable but runs rich based on the smell of the exhaust and running issues. It also runs hot now that the weather has warmed up. The ODB2 scanner says all is fine though. What I need is a shop on NC that can look into the tune in the ECU. I suspect the ECU may not be new as advertised but when I purchased the engine from a dealer. If anyone can recommend a tuner in the Greensboro area I would appreciate the help.

 

[Syleng1]

I’m by no means a “tuner.” But having said that, double check your fuel pressure. I know when I was playing with the FI Tech system in my 66’ I had the exact same condition I could not rectify. I sent it to a “tuner.” He said my fuel lines especially the return was too small and the pump was flowing too much pressure. I put an inline gauge on it and sure enough it was higher pressure than the one that goes on the schrader valve. That did clean up the exhaust some once the pressure was measured correctly.
Sorry if your past this knowledge wise. Typically I go back to the basics but forget and get tripped up. Good luck.

 

[DionR]

I’m by no means a “tuner.” But having said that, double check your fuel pressure. I know when I was playing with the FI Tech system in my 66’ I had the exact same condition I could not rectify. I sent it to a “tuner.” He said my fuel lines especially the return was too small and the pump was flowing too much pressure. I put an inline gauge on it and sure enough it was higher pressure than the one that goes on the schrader valve. That did clean up the exhaust some once the pressure was measured correctly.
Sorry if your past this knowledge wise. Typically I go back to the basics but forget and get tripped up. Good luck.

That's a great point.

@Andyz, what is your fuel system setup? How are you controlling fuel pressure? It wouldn't happen to be the Corvette FPR/filter combo would it?

I helped my brother with his '71 Demon build with a cammed 6.4 and we initially built the fuel system with the Corvette FPR/filter setup. He has a big fuel pump (I forget the size) and thankfully a fuel pressure gauge, and the first time we pressurized the system the fuel pressure went to 100 psi (or more) and would take a day or more to bleed off. He reached out to someone and the response was that the Corvette part is way too small for the pump he was running and couldn't return enough fuel to regulate his pump resulting in maxing out the pressure. We had to swap to an adjustable FPR and separate filter.

 

[Andyz]

That's a great point.

@Andyz, what is your fuel system setup? How are you controlling fuel pressure? It wouldn't happen to be the Corvette FPR/filter combo would it?

I helped my brother with his '71 Demon build with a cammed 6.4 and we initially built the fuel system with the Corvette FPR/filter setup. He has a big fuel pump (I forget the size) and thankfully a fuel pressure gauge, and the first time we pressurized the system the fuel pressure went to 100 psi (or more) and would take a day or more to bleed off. He reached out to someone and the response was that the Corvette part is way too small for the pump he was running and couldn't return enough fuel to regulate his pump resulting in maxing out the pressure. We had to swap to an adjustable FPR and separate filter.

I am running 3/8” line from a Tapped Performance fuel pump in the tank. The return line is also 3/8”. The fuel regulator Summit brand I believe. The pressure does fluctuate a bit but usually lower than 55ish. I have not monitored it during hard acceleration.

 

[DionR]

Ok, so no Corvette FPR/filter to trip you up.

For what it's worth, the instructions I have for the crate motor say fuel pressure is supposed to be 58.5 psi +/- 5 psi. Sounds like you are a bit low, no idea how that would cause an over-rich condition so not saying it is related. It's within the tolerance though, unless it fluctuates too much while running.

You don't have the FPR hooked to vacuum do you? They aren't supposed to be.

Looks like a stick car too? Cool build!

 

[TT5.9mag]

Contact FRP

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[Andyz]

I will check the FPR and get back to you.
Yes, it has a TKX and it is a lot of fun for sure. All new QA1 full front and rear with new k member as well. 3:91 lsd gears.

 

[Andyz]

Hi all,
Thanks for all the help!
When you had the issue with the fuel pressure being high with your gen3 hemi, did the computer log a fault? I get no reports of issues with the setup as it is. I thought it was an exhaust leak, but that wasn’t the issue.
The overheating is a concern too. This is a new engine, new radiator and pretty much new everything. I am now thinking the timing may be off due to some previous tune that may have been in the ECU before I got it. It was supposed to be new but…

 

[DionR]

Hi all,
Thanks for all the help!
When you had the issue with the fuel pressure being high with your gen3 hemi, did the computer log a fault? I get no reports of issues with the setup as it is. I thought it was an exhaust leak, but that wasn’t the issue.
The overheating is a concern too. This is a new engine, new radiator and pretty much new everything. I am now thinking the timing may be off due to some previous tune that may have been in the ECU before I got it. It was supposed to be new but…

The computer has no way of knowing what the fuel pressure is at, so the only feedback it could give is that the O2 sensor readings are off. No idea if it would be off enough to throw a code though.

I assume you left the 6.4 stock? The PCM you have should have run it as if it was in a Scat Pack, so (I would guess) the issue is somewhere else. There is a chance the PCM missed a step and didn't get flashed by the factory or something, or maybe the flash was corrupted, but beyond that I can't see how the PCM would be the source of your problems. Unless the PCM wasn't new? Where did you get it?

 

[Andyz]

PCM and engine came from a Mopar Performance distributor and tuner shop.
I understand the ECU cannot sense fuel pressure but the pressure is very close to the 58.5psi setpoint.
It runs obviously rich but no indication from the scanner feedback, so I thought it was an exhaust leak, which it had, but has been fixed with new cast iron exhaust manifolds. I would like to bring this to a recommended tuner shop in NC and have them check the tune. Maybe check the O2 sensor too.
So if anyone can recommend a Mopar shop in the Greensboro NC area, I would appreciate any help.
Thanks all!

 

[DionR]

I understand the ECU cannot sense fuel pressure but the pressure is very close to the 58.5psi setpoint.

I agree, 55psi should be close enough. And it feels like the wrong end of the scale to make it run rich.

Wasn't trying to say it was a source of your problem.

It runs obviously rich but no indication from the scanner feedback, so I thought it was an exhaust leak, which it had, but has been fixed with new cast iron exhaust manifolds.

Have you tried to reset the PCM after fixing the exhaust leak to clear the tweaks the PCM made while it had the leak? Not sure how on that PCM, just an idea.

I would like to bring this to a recommended tuner shop in NC and have them check the tune. Maybe check the O2 sensor too.
So if anyone can recommend a Mopar shop in the Greensboro NC area, I would appreciate any help.

Good luck, and please update us when you get it figured out.

 

[408 swinger]

You say it's overheating, but, no actual numbers. As you are probably already aware, these engines run at a bit higher operating temp than the old engines did. The thermostat opens at 205 and maintains around 215.